Note: 1 feet(‘)=30,48 cm.=0,3048 m.
Note: Meaning of glossary term of ’kcmil’: MCM is an abbreviation for thousands of circular
mils, an old measurement of wire gauge. 1 MCM = 1 kcmil = 0.5067 square milimeters. A mil is
1/1000 inch. A wire 200 mils in diameter is 40 MCM.
MCM is generally used for very large-diameter wire. Most wire uses AWG.
kcmil—In the North American electrical industry, conductors larger than 4/0 AWG are generally
identified by the area in thousands of circular mils(kcmil), where 1 kcmil = 0.5067 mm². A circular
mil is the area of a wire one mil in diameter. One million circular mils is the area of a rod with 1000
mil = 1 inch diameter. IT IS NOT ADDED TO THE OTHER TECHNICAL DOCUMENT.
Note: 1 horsepower=0,746 kW IT IS NOT ADDED TO THE OTHER TECHNICAL
DOCUMENT.
Note:
Electrical
Parameter
Measuring
Unit
Symbol
Description
Voltage
Volt
V or E
Unit of Electrical Potential
V=I×R
Current
Ampere
I or i
Unit of Electrical Current
I=V÷R
Resistance
Ohm
R or Ω
Unit of DC Resistance
R=V÷I
Conductance Siemen
G or ℧
Reciprocal of Resistance
G=1÷R
Capacitance Farad
C
Unit of Capacitance
C=Q÷V
Charge
Coulomb
Q
Unit of Electrical Charge
Q=C×V
Inductance
Henry
L or H
Unit of Inductance
VL = -L(di/dt)
Power
Watts
W
Unit of Power
P = V × I or I2 × R
Impedance
Ohm
Z
Unit of AC Resistance
Z2 = R2 + X2
Unit of Frequency
ƒ=1÷T
IT IS NOT ADDED TO THE OTHER TECHNICAL DOCUMENT.
Frequency
Hertz
Hz
Not: Metrik birimi civa, somun, dübel(çap) gibi malzemelerin ölçülendirme boyutudur(mm.).
~1~
Parçaları birbirine sökülebilir şekilde bağlamaya yarayan, gövde kısmına vida dişi açılmış, başı
altıgen, dörtgen veya değişik biçimlerde şekillendirilmiş bağlantı elemanlarını açmaya ve
kapamaya yarayan anahtar ölçüleri
Metrik – cıvata ve somun anahtar ölçüleri.
Note: Minimum size equipment grounding conductors for grounding raceway ‘kablo kanalı’
and equipment.
~2~
Table 1– Minimum size equipment grounding conductors for grounding raceway and equipment.
Earthing conductor to the earth electrode must be clearly and permanently labelled ‘SAFETY
ELECTRICAL CONNECTION – DO NOT REMOVE’ and this should be placed at the connection
of conductor to the electrode.
For protective conductors of the same material as the phase conductor the cross-sectional area
shall be the same size as the phase conductor upto 16 mm2. IMPORTANT: When the phase
conductor is above 16 mm2 then the protective conductor may remain at 16 mm2 until the phase
conductor is 35 mm2, after which the protective conductor should be half the size of the phase
conductor.
The protective conductors previously known as earth continuity conductors must also comply
with BS 7671(the IEE Regulations) and in general for phase conductors of less than 16 mm2; this
means the protective conductors must be the same size as the phase conductors. When the phase
conductor is above 16 mm2 then the protective conductor remains at 16 mm2 until the phase
conductor is 35 mm2, after which the protective conductor should be half the cross-sectional area of
the phase conductor.
~3~
Note: Isolated Grounded Systems: As permitted by NEC250.146(D) and NEC408.40 exception,
consider installing an isolated grounding system to provide a clean signal reference for the proper
operation of sensitive electronic equipment.
Isolated grounding system for branch circuits.
Isolated grounding is a technique that attempts to reduce the chances of “noise” entering
the sensitive equipment through the equipment grounding conductor. The grounding pin is not
electrically connected to the device yoke, and, so, not connected to the metallic outlet box ‘çıkış
kutusu, priz kutusu’. It is therefore “isolated” from the green wire ground.
A separate conductor, green with a yellow stripe ‘renk’, is run to the panel board with the rest
of the circuit conductors, but it is usually not connected to the metallic enclosure. Instead it is
insulated from the enclosure, and run all the way through to the ground bus of the service
equipment or the ground connection of a separately derived system. Isolated grounding systems
sometimes eliminate ground loop circulating currents.
‘Note that the NEC prefers the term isolated ground, while the IEEE prefers the
term insulated ground.’
i
Note: The substation and electrical network shall be earthed adequately. This is to avoid overvoltages in the system and to limit harmful step and touch voltages(Power transformers and
reactors). The selection of neutral earthing method shall be defined in consideration of the grid
structure, protection concept and desired service security.
IP KORUMA SINIFLARI VE IP KODLARI(IEC VE EN 60529 STANDARTINA GÖRE)
Kullandığımız birçok ürünün üzerinde yer alan ve o ürünün hangi dış etkenlere karşı korunaklı
olduğunu belirten “IP” kısaltması literatürde iki farklı açılımı olsa da; iki açılım da aynı anlamla
karşımıza çıkmaktadır. Bunlardan birincisi giriş koruma kodu anlamına gelen “Ingress Protection
Code”, diğeri ise uluslararası koruma kodu anlamına gelen “International Protection Code” dur.
Tüm dünyada aynı anlama gelen ve evrensel olarak nitelendirilebilen IP kodları; merkezi
Brüksel’de bulunan “European Committee for Electromechanical Standardization” tarafından
yayınlanan IEC-60529 nolu standartına göre belirlenmiş ve tüm dünya tarafından kabul görmüştür.
IP kodunda yer alan 1’inci rakam katı cisimlere karşı koruma
~4~
sınıfını belirtmektedir. IP kodda yer alan 2’nci rakamın anlamı ise ürünün sıvılara karşı koruma
sınıfını temsil etmektedir.
IP kodunda yer alan 1’inci rakamın anlamları şu şekildedir: 0: Ürünün toza karşı korumasız
olduğunu belirtir. Ürünün tehlikeli bölümlerine temas edilebilir. 1: Çapı 50 mm yani 5 cm ve
üzerindeki katı cisimlere karşı korumalıdır. Çapı 5 cm ve üzerindeki cisimlercihazın içerisine
giremez. 2: Çapı 12,5 mm yani 1,25 cm ve üzerindeki katı cisimlere karşı korumalıdır. Çapı 1,25
cm ve üzerindeki cisimler cihazın içerisine giremez. 3: Çapı 2,5 mm yani 0,25 cm ve üzerindeki
katı cisimlere karşı korumalıdır. Çapı 0,25 cm ve üzerindeki cisimler cihazın içerisine giremez.
4: Çapı 1 mm yani 0,1 cm ve üzerindeki katı cisimlere karşı korumalıdır. Çapı 0,1 cm ve üzerindeki
cisimler cihazın içerisine giremez. 5: Toz girişine karşı korumalıdır. Toz girişi tamamen
engellenememiştir ancak ürüne zarar vermesi söz konusu değildir. 6: Toz geçirmez. Ürüne toz girişi
tamamen engellenmiştir.
IP kodunda yer alan 2’nci rakamın anlamları şu şekildedir: 0: Cihazın sıvılara karşı herhangi bir
muhafazası yoktur. Ürün sıvılara karşı korumasızdır. 1: Cihazın muhafazası düşey sıvı damlalarına
karşı korumalıdır. Düşey su damlaları cihazın çalışmasına herhangi bir zarar vermez. 2: Cihazın
muhafazası 15º’ye kadar eğiklikte düşen sıvı damlalarına karşı cihazı korumaktadır. Cihaza 0º-15º
aralığındaki açılarla düşen sıvı damlaları cihaza herhangi bir zarar vermez. 3: Cihazın muhafazası
sıvı püskürtmelerine karşı cihazı korumaktadır. Cihaza 0º-60º’lik açıyla püskürtülen sıvılar cihazın
çalışmasını etkilemez. 4: Cihazın muhafazası sıvı sıçramasına karşı cihazı korumaktadır. Cihazın
herhangi bir bölgesine herhangi bir yönden sıçrayan sıvı cihazın çalışmasını etkilemez. 5: Cihazın
muhafazası fışkırtılan sıvılara karşı cihazı korumaktadır. Cihaza herhangi bir yönden fışkırtılan sıvı
cihazın çalışmasını etkilemez. 6: Cihazın muhafazası yüksek şiddetle fışkırtılan sıvalara karşı cihazı
korumaktadır. Cihaza herhangi bir yönden yüksek şiddette fışkırtılan su cihazın çalışmasını
etkilemez. 7: Cihazın muhafazası geçici olarak sıvıya batırılması durumunda cihazı korumaktadır.
Cihaz kataloğunda yer alan basınç ve süre değerlerinde sıvıya batırıldığı takdirde çalışmaya devam
edecektir. 8: Cihazın muhafazası kalıcı olarak sıvı altında kalması durumuna uygun şekilde cihazı
koruyacak şekilde tasarlanmıştır. Cihaz kataloğunda yer alan değerlerde sıvı içinde çalışmaya
uygun şekilde tasarlanmıştır.
Elektrikçi eldivenleri(yalıtkan eldivenler) voltaj dayanım testlerine göre class00, class0, class1,
class2, class3, class4 olarak sınıflara ayrılır.
Sınıf
Maksimum Çalışma Gerilimi V AC
Test Gerilimi V AC
Dayanım Gerilimi V AC
00
500 V AC
2.500 V AC
5.000 V AC
0
1.000 V AC
5.000 V AC
10.000 V AC
1
7.500 V AC
10.000 V AC
20.000 V AC
2
17.000 V AC
20.000 V AC
30.000 V AC
~5~
3
26.500 V AC
30.000 V AC
40.000 V AC
4
36.000 V AC
40.000 V AC
50.000 V AC
Çizelge 1- Elektriksel değerler.
Sınıfına göre eldivenlerde kayıtlı gerilim değerleri aşağıda açıklanmıştır:
1- Maksimum Çalışma Gerilimi: Şebeke nominal gerilimidir.
2- Test Gerilimi: Testlerde eldivene uygulanan gerilimdir.
3- Dayanma Gerilimi: 3 dakika ıslak test gerilimine maruz bırakılan eldivenlere 16 saat boyunca
kurutulduktan sonra uygulanan gerilim testidir.
‘What Is a Good Ground Resistance Value?’ The goal in ground resistance is to achieve the
lowest ground resistance value possible, that makes sense economically and physically, when
contacting the earth, also known as the soil/ground rod ‘çubuk’ interface.
Ideally, a ground should be zero ohms of resistance, but…
Unfortunately, there is not one Standard ground resistance threshold recognized by all certifying
agencies.
The NFPA and IEEE recommend a ground resistance value of 5 ohms or less while the NEC has
stated to “Make sure that system impedance to ground is less than 5 ohms specified in NEC 50.56.
In facilities with sensitive equipment it should be 5 ohms or less.”
The telecommunications industry has often used 5 ohms or less as their value for grounding and
bonding while electric utilities construct ‘inşa etm.; oluşturm.’ Their ground systems so that the
resistance at a large station will be no more than a few tenths ‘onda bir’ of one ohm.
In general, the lower the ground resistance, the safer the system is considered to be.
Note: Factors Influencing Requirements for a Good Grounding System: In an industrial plant or
other facility that requires a grounding system, one or more of the following must be carefully
considered(see Fig. 8): 1-) Limiting to definite values the voltage to earth of the entire electrical
system. Use of a suitable grounding system can do this by maintaining some point in the circuit at
earth potential. Such a grounding system provides these advantages: a-) Limits voltage to which the
system-to-ground insulation is subjected, thereby more definitely fixing the insulation rating. b-)
Limits the system-to-ground or system-to-frame ‘şasi’ voltage to values safe for personnel. c-)
Provides a relatively ‘oldukça’ stable system with a minimum of transient ‘geçici’ overvoltages. d-)
Permits any system fault to ground to be quickly isolated.
Fig. 8: Typical conditions to be considered in a plant ground system.
~6~
2-) Proper grounding of metallic enclosures ‘muhafaza’ and support structures that are part of the
electrical system and may be contacted by personnel. Also to be included are portable electrically
operated devices. Consider that only a small amount of electric current — as little as 0.1 A for one
second — can be fatal! An even smaller amount can cause you to lose muscular control. These low
currents can occur in your body at voltages as low as 100 V, if your skin is moist ‘nemli’. 3-)
Protection against static electricity from friction. Along with this are the attendant ‘eşlik eden,
bağlı’ hazards of shock, fire and explosion ‘patlama’. Moving objects that may be inherent
‘doğasında olan’ insulators - such as paper, textiles, conveyor belts ‘taşıyıcı bant’ or power belts
and rubberized ‘kauçuklanmış’ fabrics ‘dokuma’ - can develop surprisingly high charges unless
properly grounded. 4-) Protection against direct lightning strokes ‘darbe’. Elevated ‘yüksek’
structures, such as stacks ‘baca’, the building proper, and water tanks may require lightning rods
connected into the grounding system. 5-) Protection against induced lightning voltages. This is
particularly a factor if aerial ‘havai’ power distribution and communications circuits are involved.
Lightning arresters may be required in strategic locations throughout the plant. 6-) Providing good
grounds for electric process control and communication circuits. With the increased use of
industrial control instruments, computers, and communications equipment, accessibility
‘ulaşabilirlik’ of low-resistance ground connections in many plant locations — in office and
production areas — must be considered.
Factors That Can Change Your Minimum Earth Resistance: We will discuss later what value of
earth resistance is considered low enough. You’ll see that there is no general rule usable for all
cases. First, however, consider three factors that can change the earth electrode requirements from
year to year: 1-) A plant ‘tesis’ or other electrical facility can expand in size. Also, new plants
continue to be built larger and larger. Such changes create different needs in the earth electrode.
What was formerly ‘eskiden’ a suitably low earth resistance can become an obsolete ‘artık
kullanılmayan’ “standard.” 2-) As facilities add more modern sensitive computer-controlled
equipment, the problems of electrical noise is magnified ‘büyütm.’. Noise that would not effect
cruder ‘daha basit’, older equipment can cause daily problems with new equipment. 3-) As more
nonmetallic pipes and conduits ‘elektrik tesisat borusu’ are installed underground, such installations
become less and less dependable ‘güvenli’ as effective, low-resistance ground connections. 4-) In
many locations, the water table ‘yeraltı suyu düzeyi’ is gradually falling. In a year or so, earth
electrode systems that formerly were effective may end up in dry earth of high resistance.
These factors emphasize the importance of a continuous, periodic program of earth-resistance
testing. It is not enough to check the earth resistance only at the time of installation.
Lazy Spikes: The latest designs of digital earth testers can operate with very high temporary
‘geçici’ spike resistances and still give reliable and accurate results. Because the current and voltage
are measured separately, it enables electrode measurements to be carried out with test spike
resistances up to 400 kΩ. The advantage of these instruments tolerating such high spike resistance
is generally that tests can be performed quickly on a green field site ‘kısım, bölüm’ because
electrodes do not have to be inserted too far into the ground. However, in urban ‘kentsel’ situations,
tests can be carried out using street furniture such as sign posts ‘yol işaret direği’, metal fences and
bollards ‘direkler’. Where this is not possible, results have been obtained by laying the temporary
electrodes on a wet patch ‘parça’ of concrete ‘beton’. Coiled metal chains or metallized ground
mats, with water poured over them, make an even better electrode because they conform ‘uyumlu
olm.; uym.’ more intimately ‘yakından’ to the earth’s surface than does a rigid spike ‘sivri uçlu
~7~
çubuk’. This technique has led to measured values of “spike” of less than 10 kΩ, well inside the
maximum value that will cause an error to the reading. With modern instruments, any problem with
the temporary spikes will be indicated on the display to show that a reading may not be valid. A
more suitable position for the spike may have to be used such as along the gap between paving
stones ‘kaldırım taşı’, a crack ‘yarık’ in concrete, or in a nearby ‘yakındaki’ puddle ‘su birikintisi’.
As long as warning indicators do not appear, sufficient contact has been made and a reliable test
may be performed. TECHNICAL DOCUMENT OF ‘A practical guide to earth resistance testing’
Note: Ground Testing Methods Chart
TECHNICAL DOCUMENT OF ‘A practical guide to earth resistance testing’
Note: How to Bond Metallic Piping. Step 6. Locate an open hole on your ground and neutral
bus and insert the ground wire. These holes are large enough to accommodate ‘yerleştirm.’ up to a
#4 awg wire(21.20 mm²), but it may be difficult at times ‘bazen’. If you’re having trouble pushing
the wire in, trim a little wire off the end and try with a clean cut piece. Secure ‘bir yere sıkıca
tutturm.’ the set screw ‘tespit vidası’ at the lug ‘bağlantı noktası olarak kullanılan çıkıntı’.
Replace the panel cover and turn the main breaker back on.
~8~
TECHNICAL DOCUMENT OF ‘https://electrical-engineering-portal.com/grounding-bondinghome-wiring-system’
Note: 6. Ground Ring: Ground rings made of copper are extensively used at substations and
commercial establishments ‘kuruluş’, such as apartments and supermarkets, etc. These ground rings
are often supplemented by grounding rods along with water piping encased ‘kılıfa koym.’ in metal,
structural steel and electrodes that are encased in concrete ’konsantre, derişinti’.
Installing ground rings around your building, a few feet away from the structural ‘yapısal’
blueprint ‘proje’ can ensure maximum protection of the household ‘ev ile ilgili’ electrical
equipment. In cases where the ground resistance is high, supplement ‘tamamlam., eklem.’ the rings
with deep-driven grounding rods to lessen ‘azal(t)m.’ the impedance. Generally, ground rods having
triplex ‘üç ögeli, üçlü’ configuration are to be used for such purposes, as per the code.
According to the standards set by the NEC, a minimum of 2 AWG(13.08 mm. çaplı, 67.2 mm²
kesitli, 95-130 A) sized ground rings are to be used at the apartments and the commercial sites. But
in practice, it is found that ground rings as large as 500 kcmil(253.4 mm², 19.7 mm. çaplı, 320-430
A) are used for grounding purposes, in an attempt to reduce the ground resistance in the future(?).
This can prove to be quite an effective grounding system.
Note: Ground rings serve as a great place to connect multiple grounding conductors, such as
lightning conductors, ufer groundings and vertically designed electrodes.
7. Grounding Electrode System: This is a single grounding system that can replicate ‘benzerini
yapm.’ all the other grounding systems such as: a-) Grounding of underground metal water piping,
b-) Grounding of the steel used to build apartments and other structures, c-) Grounding of the
~9~
electrode encased in concrete, d-) Grounding of the pipes and deep driven rod electrodes, e-)
Grounding of the plated electrodes, f-) Grounding of the copper rings, g-) Grounding of the entire
metal piping that cross the ground rings.
Using this single grounding electrode system, you can effectively bond all you domestic
electrical equipment that need grounding such as television, telephones, antennas and radio towers,
etc.
8. Lightning Protecion System: When installing grounding systems, for protecting the electrical
equipment during lightning strikes, make it a point to use a copper grounding system. This is
because, copper is far more superior compared to other metals and alloys, as far as ‘sürece’ the rate
of discharging the fault current into the ground is concerned.
This is also prove to be a cost effective alternative, because copper does not corrode quickly and
also needs less maintenance when compared to the other metals.
9. Surge Protection Device(SPDS): Using SPDs at critical equipment is always encouraged.
They can quite ‘iyice, tam, hayli’ effectively jolt ‘aniden etkinleştirm.’ down the fault currents
when properly connected to high quality, low impedance and robust ‘sağlam yapılmış’ grounding
electrodes.
TECHNICAL DOCUMENT OF ‘https://engineering.electrical-equipment.org/safety/9-bestrecommended-grounding-practices-for-safety-and-power-quality.html’ IT IS NOT ADDED TO
THE OTHER TECHNICAL DOCUMENT.
Note: Generally, a surge protection device should not be installed downstream from an
uninterruptible power supply(UPS).
NEUTRAL SYSTEM – SINGLE EARTHED OR MULTI EARTHED?
The Neutral System
~10~
In distribution system three phase load is unbalance and non-linear so the neutral plays a very
important role in distribution system.
Neutral system – Single earthed or multi earthed?
Generally, distribution networks are operated in an unbalanced configuration and also service to
consumers. This causes current flowing through neutral conductor and voltage dropping on neutral
wire. The unbalance load and excessive current in neutral wire is one of the issues in three phase
four-wire distribution systems that causes voltage drop through neutral wire and makes tribulations
'dert' for costumers.
The existence of neutral earth voltage makes unbalance in three phase voltages for three phase
customers and reduction of phase to neutral voltage for single phase customers. *
Multi-grounded three-phase four-wire service is widely adopted 'kullanm., kabul etm.' in modern
power distribution systems due to having lower installation costs and higher sensitivity of fault
protection than three-phase three-wire service.
The neutrals play an important role in power quality and safety problems. The multi-grounded
neutral system is the predominant 'üstün' electrical distribution system used in the United States.
i
It allows an uncontrolled amount of electric current to flow over the earth unrestrained
‘kontrolsüz, aşırı’, posing ‘sorun yaratm.’ The potential of harm to the public and to animals
causing electric shocks and is presumed ‘kabul etm., varsaym.’ responsible for undetected
electrocutions ‘elektrik çarpmasından dolayı ölüm’.
The protective grounding used in low voltage, 600-volt and below, applications will be
described and used to explain the hazards ‘tehlike, risk’ involved with the present day multigrounded neutral distribution system, used in the United States. This will allow the reader to see the
parallels ‘benzerlik’ between the safe low voltage distribution system and the dangerous medium
voltage multi-grounded neutral distribution system.
The reasons for the development of the three phase, four-wire, multi-grounded systems involve a
combination of safety and economic considerations ‘sebep, gözönünde tutulan önemli husus’. The
three-phase, four-wire multi-grounded design has been successfully used for many years and is well
documented in the standards including the National Electrical Code(NEC). It is crucial decisions to
adopt Multi Grounded Neutral System “save money” by the adoption of the multi-grounded neutral
electrical distribution system in the cost of the public’s safety.
~11~
Multi Grounded Neutral System(MEN)
Three-phase four wire multi-grounded neutral.
Figure on left shows the multi-grounded neutral systems commonly used by the electric utilities
in North America. The neutral grounding reactor 'reaktör' is used by some utilities to reduce the
available ground fault current while at the same time still maintaining 'sürdürm., korum., sağlam.'
an effectively grounded system.
The multiple earthed neutral(MEN) system of earthing is one in which the low voltage neutral
conductor is used as the low resistance return path for fault currents and where its potential rise is
kept low by having it connected to earth at a number of locations along its length. * The neutral
conductor is connected to earth at the distribution transformer, at each consumer’s installation and
at specified 'belirtm.' poles 'montaj direği, direk(telekom)' or underground pillars 'direk, sütun'. The
resistance between the neutral conductor of the distribution system and the earth must not exceed 10
ohms at any location.
NEC Article 250 Part X Grounding of Systems and Circuits 1 kV and Over(High Voltage)
1. Multiple Grounding: The neutral of a solidly 'iyice' grounded neutral system shall be permitted to be
grounded at more than one point.
2. Multi-grounded Neutral Conductor: Ground each transformer, ground at 400 m intervals or less,
ground shielded cables 'blendajlı kablo' where exposed to 'maruz bırakm.' personel contact.
Single Grounded Neutral
Three-phase four wire single neutral grounded.
Figure on left shows single grounded neutral which is different from multi-grounded system.
Figure shows the neutral also connected to earth, but the neutral conductor is extended along
'uzanm.' with the phase conductors. The configuration shown in figure allows electrical loads,
~12~
transformers to be placed between any of the three phase conductors, phase-to-phase and/or phaseto-neutral.
This connection, phase to neutral will force electric current to flow over the neutral back to the
transformer. So far, this electrical connection is acceptable, as long as 'sürece, şartıyla' the neutral is
insulated or treated ‘davranm.’ as being potentially energized, but modifications will be made in the
future that will negate 'hükümsüz kılm., çürütm.' safety for the public and animals.
The ground connection would typically be located in the distribution substation 'trafo merkezi,
indirici trafo merkezi'. This may appear insignificant, but the differences are significant.
Advantages of Multiple Grounded Neutral Systems
(1) Optimize the Size of Surge Arrestor 'parafudr':
 Surge arresters are applied to a power system based on the line-to-ground voltage under
normal condition and abnormal conditions. Under ground-fault conditions, the line-to-ground
voltage can increase up to 1.73 per unit on the two, unfaulted. *
 Application of surge arresters on a power system is dependent on the effectiveness of the
system grounding. The over voltage condition that can ocur during a ground fault can be minimized
by keeping the zero sequence 'ground fault' impedance low. Therefore, optimization in sizing the
surge arresters on the system is dependent on the system grounding.
 An effectively grounded power system allows the use of a lower rated surge arrester. The
lower rated surge arrester provides better surge protection at a lower cost. An effectively grounded
system can only be accomplished 'başarıyla tamamlam.' using a properly sized, multi-grounded
system neutral.

With single grounded neutral system require the use of full line-to-line voltage rated
arresters. This increases the cost of the surge arresters while at the same time reduces the protection
provided by the surge arrester. In addition, if the fourth wire neutral is not multi-grounded, it would
be good practice to place surge arresters at appropriate locations on that conductor(?).
(2) The zero sequence impedance is lower for a multi-grounded system than the single point
grounded neutral system.
(3) Freezing and arctic 'çok soğuk' conditions have an adverse impact on the zero sequence
impedance. * A multi-grounded system neutral will still lower the zero sequence impedance over a
single point ground. In fact, without the multi-grounded system, it is more probable 'olası,
muhtemel' that insufficient fault current will flow to properly operate the ground fault protection. *
(4) Cost of equipment for the multi-grounded system is lower.
(5) Safety concerns 'sorun, mesele' on cable shields 'kablo zırhı, koruyucu ekran'.

Medium voltage and high voltage cables typically have cable shields(NEC requirement
above 5 kV) that need to be grounded. There are several reasons for this shield:
o To confine 'sınırl., tutm.' electric fields within the cable
o To obtain uniform radial distribution of the electric field
o To protect against induced voltages
o To reduce the hazard 'tehlike' of shock
If the shield is not grounded, the shock hazard can be increased. With the shield grounded at one
point, induced voltage on the shield can be significant and create a shock hazard. Therefore, it is
common practice to apply multiple grounds on the shield to keep the voltage limited to 25 volts.
~13~
This practice of multi-grounding cable shields includes the grounding of concentric 'eş-aynımerkezli' neutrals on power cables thereby extending the need for multi-grounding of neutrals on
the power system.
Disadvantages of Multiple Neutral Grounding
(1) Less Electrical Safety in Public and Private Property.

With a multi-grounded neutral distribution system it is necessary to have an electrical
connection to earth at least 4 times per mile 'mil uzaklık ölçü birimi 1609 m' to keep the
voltage on the multi-grounded neutral from exceeding approximately 25 volts making it safe
for the linemen 'telefon ve elektrik taşıyan hatları döşemek ve onarmakla görevli kişi' who
come into contact with the neutral and the earth.
 As per NESC Rule 096 C in the section with the multi-grounded neutral conductor
connected to earth at least 4 times per mile and at each transformer and lightning arrester
'elektrikli cihazları yıldırımdan koruyan düzen' there are now multiple paths over and
through the earth that the hazardous electric current can flow over continuously,
uncontrolled.
 The path that this current flow takes through the earth cannot be determined. We cannot put
an isotope ‘izotop’ on each electron and trace its path as it flows uncontrolled through the
earth. It is irresponsible 'sorumlu olmayan' to permit stray 'başıboş' uncontrolled electric
current to flow into and over private property.
 The National Electrical Code(NEC) requires the neutral in the service disconnect and over
current panel board to be connected to the earth also. Now the secondary neutral is
connected to earth a second time. A parallel connection of the neutral to earth now exists
permitting hazardous electric current to flow continuously uncontrolled over the earth.
(2) Earth Fault Protection Relay setting is complicated.
Advantages of Single Grounded Neutral System
(1) More Reliable 'güvenilir' and Safe System.
(2) Protection Relay Setting is more easy in Single Grounded Neutral:
 Protective relays need to sense abnormal conditions, especially those involving a ground
fault. The single point grounded system, with or without a neutral conductor, current
flowing into the ground should be considered abnormal(excluding ‘hariç olmak üzere’
normal charging current). For sensing of ground faults are:
Ground fault relay at neutral
~14~


A current transformer in the location where the neutral is grounded can be used to sense the
ground fault(zero sequence) current.
A zero sequence CT enclosing ‘çevrelem.’ the three phase and neutral conductors.
CT residual circuit
Four CT residue 'artık' circuit(Three CT residual with neutral CT cancellation).
 Protecting against ground faults on a multi-grounded neutral system is more difficult than
the single point grounded system since both neutral and ground fault currents must be
considered.
 Neutral current and likewise 'benzer şekilde, ve de' ground fault current can flow in both the
neutral and the ground. So, we have must calculate both current as the amount of neutral
current which may flow in the circuit, and the ground fault setting must be above this neutral
current(?). This is self explanatory 'açıklayıcı' from the figure above.
(3) Sensing of Ground Fault current:
While the sensing of the ground fault current in the single point grounded system is less complex
than the multi-grounded system, the amount of ground fault current on the single-point grounded
system may be greatly limited due to the fact that all ground fault current must return through the
earth. This is especially true where the earth resistivity is high, the soil 'toprak' is frozen or the soil
is extremely dry.

Not: Yıldız noktasını, yani nötrü sadece yıldızdan topraklama yeterli değildir. Diyelim ki,
yıldızdan topraklayıcıya indirilen işletme topraklaması hattı(iletkeni, nakili) koparsa ya da bağlantı
yerinde bir gevşeme olursa o zaman koruma devreden çıkmıştır, can ve mal güvenliği kalmamıştır.
Bunu önlemek için tek bir yol vardır, o da şudur: Nötr iletkeninin birkaç yerden daha
topraklanmasıdır. *
INSPECTION AND TESTING OF ELECTRICAL INSTALLATIONS: RESIDUAL CURRENT
DEVICES
The correct device must be selected for the particular application. Choosing the wrong device
could have serious consequences and could result in electric shock or fire. The list in Figure 2 gives
examples of particular applications of RCDs and includes references to the relevant Regulations in
BS 7671:2008(2013).
Figure1- Examples of particular applications of RCDs.
RCD, IΔn
10 mA
Application
Regulation
A very sensitive device, sometimes
415.1.1
used to protect socket-outlets of
~15~
laboratory benches in schools.
30 mA
100 mA
300 mA
Adjustable ≤2000 mA
Mobile equipment used outdoors
must be protected by an RCD with 411.3.3(ii)
a rated residual operating current 514.1.1
not exceeding 30 mA.
In locations containing a bath or
shower, all circuits of the location
must be protected by the use of
one or more RCDs not exceeding
30 mA.
701.411.3.3
Note that the requirement is “of the
location”; in reality, this means
serving or passing through the
bathroom and is not limited to
circuits within the zones.
Socket-outlets for use by ordinary
411.3.3(i)
persons for general use.
Where an RCD is installed because
the earth fault loop impedance is
too high for fault protection, i.e.
411.5.3
disconnection time cannot be met
by the over current protective
device.
Fire protection purposes in
agricultural and horticultural
705.422.7
premises.
Devices with a residual operating
current of 2 A or more are
sometimes used in specific
31-02-10
industrial, distribution applications
or temporary supply supplies for
entertainment related purposes.
Advice must be sought from the
designer.
Any adjustment method or
531.2.10
mechanism should not be
accessible to ordinary, non-skilled
or non-instructed persons.
Note: Amendment ‘düzeltme, bir kanunu değiştirme’ 3 to BS 7671. Chapter 41 Protection Against
Shock. Reference to ordinary persons in Regulation 411.3.3 has now been removed. Regulation 411.3.3
now requires ‘gerektirm.’ RCD protection in accordance with Regulation 415.1 for socket outlets up to
20A(and for mobile equipment up to 32A for use outdoors) for all installations. However, there is an
exception for RCD protection(for socket outlets upto 20A) for a specific labelled socket outlet or where a
documented risk assessment ‘değerlendirme’ determines that RCD protection is not necessary. This
means that socket outlets up to 20 A in all types of installations, including commercial, domestic and
industrial, will need to be protected by a 30 mA RCD unless a risk assessment can determine that it’s not
necessary. TECHNICAL DOCUMENT OF ‘Amendment Number 3 of BS 7671 2008 WiringMatters’
Note: There are some instances where the use of an RCD should be considered to be obligatory. These
include:
1. In socket outlet circuits in TT installations;
~16~
2. In socket outlet circuits where it is foreseeable(önceden görülebilir) that the socket will be used to
power outdoor equipment;
3. Insituations where there is an increased risk due, for example, to the presence of water. This would
include the power supplies to power washers;
4. Where 240 V hand tools and power tools are being used. Especially in work environments such as
construction sites ‘inşaat alanı’ and workshops ‘atölye, fabrika’.
Note: There are a number of devices that may cause leakage. For example any thing that involves a
power supply, transformer, heating appliance.
Not: İnvertör, klima ve UPS cihazlarının kullanıldığı veya çok fazla harmonik yük üretilen yerlerde A
tipi kaçak akım rölesinin kullanılmaması elektrik kazalarının nedenlerinden biridir(?).
Note: Type F RCDs are used in the cases where the application may create composite ‘karma’ residual
current. For example, single-phase devices containing a motor controlled by a variable speed drive, like a
single-phase heat pump or an air conditioner.
Type B RCDs are used in cases where the application may create smooth DC residual current or
contain frequencies higher than 50 Hz. For example, three-phase devices containing a motor controlled by
a three-phase variable speed drive. This is the case for certain types of three phase air conditioners, or
pumps, or when supplying and electric vehicle or when medical equipment requiring a high precision
‘doğruluk, kesinlik’ of movement is used.
AG İLE ENERJİ ALAN TESİSLERDE YAPILAN SIFIRLAMA HAKKINDA BİLGİLER
Arıza sırasında nötr hattı geriliminin tehlikeli değerlere ulaşabileceği olasılığı düşünülerek, sıfırlamalı
tesislerde; nötr hattı, aynen faz hattı gibi izoleli çekilir ve kesiti faz hattı kesitine eşit alınır.
Sıfırlaması yapılmış arızasız bir tüketicide; şasenin nötr iletkenine bağlı bulunması sonucu bu nötrün
kopması ile koruma tehlikeye girmiş ve hata yerinde dokunma gerilimi, şebeke işletme gerilimine eşit
olmuştur.
Çizim 5- Sıfırlanan bir tesiste nötr hattının kopması ve yarattığı tehlike.
~17~
Peki, şekilde görüldüğü gibi, bir el, su musluğuna dokunmasaydı, o zaman(nötrün kopmasında) yine
bir çarpılma olur muydu? Elbette olurdu. Biz biliyoruz ki insanın çeşitli çarpılma durumları vardır: El-el;
el-ayak, ayak-ayak; vücut-el, vücut-ayak vs. gibi. O zaman el-ayak çarpılması olur ve akım gövdede kesik
çizgiyle gösterilen yolu takip ederdi. Buna göre sonuç şudur; bu kopma olayı sık sık olduğu için
kesinlikle önlem almak gerekir. İşte şimdi bu önlemleri sıralamak istiyoruz.
Çizim 6- Sıfırlamada tüketiciden dağıtım panosuna kadar nötr ve koruma iletkenlerinin birbirinden ayrılışı.
Öncelikle üzerinde titizlikle durulan ve artık uluslararası kabul edilmiş bir yolu izleyeceğiz. O da
şekilde görülen ve bir dağıtım şebekesinde uygulanan durumdur. Yani ana panodan sonra beş hattın
çekilişidir. Bunu biraz daha açalım.
Bir faz-toprak kısa devresinde; nötr iletkenin, faz iletkeni gibi, aynı değerdeki kısa devre akımını
taşıması sonucu Çizim 5'de görülen durum oluşacağı için koruma yapılmaz ve bu şekilde de can ve mal
güvenliği sağlanamaz.
10 mm² kesite kadar "kopma" söz konusu olduğundan ve bu arada dokunma gerilimi yükseleceğinden
bu kesite kadar nötr ve koruma iletkenlerini birbirlerinden dağıtım tablosuna kadar ayırmak ve tabloda
tekrar birleştirerek tek hat halinde nötr ile bağlamak gerekir.
Faz iletkenleri 10 mm²’den büyük kesitler için bu ayrıma gerek duyulmaz. Aşağıdaki çizelgede, sıfır
iletkenlerinin, faz iletkenlerine göre kesit değerleri verilmektedir.
faz iletkenleri(mm²)
1,5
2,5
4
6
10
16
25
35
50
70
95
120
150
185
240
300
400
boru içinden çekilen iletkenler(mm²)
nakil hatları ve bina içine ya da açığa döşenmiş iletkenler(mm²)
1,5
2,5
4
6
10
16
16
16
25
35
50
70
70
95
120
150
185
4
6
10
16
25
35
50
50
50
70
70
95
120
150
185
Çizelge 1- Sıfır iletkenlerinin faz iletkenlerine göre kesitleri.
Not: Sıfırlama, aslında pek tavsiye edilmeyen bir durumdur. Topraklamanın olmadığı binalarda
uygulanır. Kısaca, prizlerdeki toprak ucunun nötr hattına bağlanması şeklinde açıklayabiliriz. Bu
durumun tehlikeli olmasının en önemli nedeni, nötr hattına gelebilecek herhangi bir zarar durumunda,
nötr üzerindeki gerilimin boşalmamasından dolayı cihaz üzerinde akacak bir yer beklemesidir.
~18~
Not: TN sistemlerde(şebeke) koruma önlemi olarak genelde “Sıfırlama” olarak adlandırılan yöntem
kullanılır. Tanımı ise, tam gövde teması gibi bir yalıtım hatasında elektrik devresinin aşırı akım koruma
aygıtları ile açılmasını sağlamak için gerilim altında olmayan iletken tesis bölümlerinin sıfır iletkenine ya
da buna iletken olarak bağlanmış olan bir koruma iletkenine ayrı biçimde bağlanmasıdır.
Note: A TN-C-S system is a PME supply. PME stands for protective multiple earths which means that
the REC supply cable is earthed at mutiple points along the line to reduce the external earth fault loop
impedance.
MULTİMETRE GÜVENLİĞİNİN ESASLARI
Yeterince yüksek voltaj seviyeli bir multimetre seçtiğiniz sürece güvende olmayabiliyorsunuz. Multimetre güvenliğini analiz eden mühendisler, başarısız olan ünitelerin kullanıcılarının ölçtüklerini sandıklarından çok daha yüksek voltaja maruz kaldıklarını sık sık tespit etmişlerdir. Sadece nadiren meydana
gelen kazalarda düşük voltaj seviyeli metreler(1000 V ya da daha düşük) orta seviyeli voltajın ölçümü
için kullanılmıştır. Mesela 4160 V. Sorun hiç uyarısız gelip multimetre girişini vuran ani ya da geçici
voltaj yükselmesidir.
Ani Voltaj Yükselmesi, Önlenemez Bir Zarar
Dağıtım sistemleri ve yükler daha da karmaşıklaştıkça geçici voltaj yükselmesi olasılıkları da artar.
Motorlar, kapasitörler ve değişken hızlı sürücü gibi güç dönüşüm ekipmanları ani voltaj yükselmelerinin
en önemli kaynaklarıdır. Dış aktarım hatlarına düşen yıldırımlar da son derece zararlı geçici yüksek enerji
yükselmelerine sebep olur. Elektrik sistemlerinde ölçümler yapıyorsanız bu geçici yükselmelerin anlamı,
“görünmez” ve sık sık önlenemez tehlikelerdir. Düzenli olarak düşük voltajlı güç devrelerinde ortaya
çıkarlar ve binlerce voltluk zirve değerlere ulaşabilirler. Bu durumlarda multimetrenizde bulunan güvenlik payının size sağladığı korunmanın insafına kalırsınız. Cihazın voltaj seviyesi, tek başına size bu multimetrenin geçici voltaj yükselmelerinden hayatta kalabilecek tasarıma sahip olup olmadığını söylemeye
yetmez.
Ani voltaj yükselmelerinin sebep olduğu tehlikelerle ilgili ilk ipuçları, elektrikli banliyö trenlerinin
tedarik vagonlarındaki ölçümlerle ilgili uygulamalardan geldi. İtibari vagon voltajı, sadece 600 V’tu. Ama
multimetreler tren çalışıyorken ölçüm yaptıklarında birkaç dakikalığına 1000 V ölçtü. Daha yakından
incelendiğinde trenin durması ve harekete geçmesinin 10,000 V’luk ani voltaj yükselmelerine sebep olduğu ortaya çıktı. Bu geçici voltaj yükselmeleri, ilk multimetre giriş devrelerine hiç insaf göstermemişti. Bu
incelemeden multimetre giriş koruma devrelerinin geliştirilmesine sebep olacak dersler alındı.
Geçici Voltaj Yükselmesi Korunması
Multimetre devresi korunmasındaki gerçek sorun, sadece en yüksek kararlı durum voltaj aralığı değildir.
Hem kararlı durum, hem de geçici yüksek voltaj bileşimine karşı dayanabilme yeteneğidir. Geçici voltaj
yükselmesi koruması hayati öneme sahiptir. Geçici voltaj yükselmesi, yüksek enerji devrelerine
yüklendiğinde daha tehlikeli olur. Çünkü bu devreler, büyük akımlar aktarabilir. Geçici voltaj yükselmesi bir atlamaya(aşırı ark) sebep olursa yüksek akım, bu atlamayı devam ettirebilir. Bu da bir plazma
~19~
bozulması ya da patlama meydana getirebilir. Bu durum çevreleyen havanın değişerek iyonize ve iletken
olmaya başladığında gerçekleşir. Sonuç ise korkunç bir hadise olan bir atlama patlamasıdır. Bu hadise,
her yıl daha iyi bilinen elektrik şoklarından daha fazla elektrik yaralanmalarına sebep olur.
Aşırı-voltaj Kurulum Kategorileri
Yeni standartları anlamak için en önemli tek kavram, aşırı voltaj kurulum kategorisidir. Yeni standartlar,
kategori 1 ile 4 arasındaki kategorileri tarif eder. Bu kategoriler, sık sık kısaltılmış olarak CAT I, CAT II
vb. gibi belirtilir. Güç dağıtım sistemlerini kategorilere bölmenin temeli, şimşek gibi tehlikeli geçici
yüksek voltaj yükselmelerinin sistemin değişken akım direnci içinde yol alırken azaltılacağı ya da
bastırılacağı gerçeğine dayanır. Daha yüksek kategori numarası(CAT), daha yüksek güce ve daha yüksek
geçici enerji yükselmelerine sahne olan elektrik ortamlara işaret eder. Bu yüzden CAT III standardına
göre tasarımlanmış olan bir multimetre, CAT II standardına göre tasarımlanmış olan bir multimetreye
kıyasla daha yüksek geçici enerji yükselmelerine karşı dirence sahiptir. Bir kategorinin içindeki daha
yüksek bir voltaj seviyesi, daha yüksek bir geçici enerji yükselmesine karşı dirence işaret eder. Mesela,
bir CAT III-1000 V seviyeli metrenin koruması bir CAT III-600 V seviyeli metreye kıyasla daha
yüksektir. Gerçek yanlış anlaşılma, bir kişinin CAT II-1000 V seviyeli metreyi o metrenin CAT III-600 V
seviyeli metreden daha üstün olduğunu sanarak seçmesi ile meydana gelir.
Sadece Voltaj Seviyesi İle İlgili Değildir
CAT I konumunda ofis ekipmanı üzerinde çalışan teknisyen, aslında CAT III konumunda güç hattı
alternatif akım olan motor elektrikçisinin ölçtüğünden çok daha yüksek direkt akım voltajıyla karşı
karşıyadır ama voltaj ne olursa olsun, CAT I konumundaki elektronik devrelerde geçici yükselmeler,
hatırı sayılır bir şekilde çok küçük bir tehdittir. Çünkü, atlama için uygun olan enerji çok kısıtlanmıştır.
Bu CAT I ya da CAT II konumlarındaki ekipmanlarda elektriksel tehlike olmayacağı anlamına gelmez.
İlk tehlike, elektrik şokudur. Geçici yükselme ve atlama patlaması değildir. Şoklar, daha sonra
açıklanacağı üzere bazen atlama patlaması kadar ölümcül olabilir. Örneğin evden ayrı bir bina olan
atölyeye yüksekten çekilen bir hat, sadece 120 V ya da 240 V olabilir. Ama, yine de teknik olarak bir
CAT IV konumudur. Neden? Her dış iletken hattı, çok yüksek enerjili şimşek kaynaklı geçici yükselmelere her an için maruz kalabilir. Hatta yer altına gömülü iletken hatları bile CAT IV konumudur. Çünkü
onlar, her ne kadar direkt olarak şimşeğe maruz kalmayacak olsalar da yakına düşen bir şimşek, yüksek
elektromanyetik alanların var olması sebebiyle geçici bir yükselme yaratabilir.
Kablo akım taşıma kapasitesinde, kablonun tek ya da çok telli olması geçebilecek akımı etkiler mi?
Farklı kablo firmalarının aynı kablo için farklı akım taşıma kapasite değerleri vermesinin nedeni
nedir(VDE TSE standartları belirtilmesine rağmen)?
En ideal iletken solid iletkendir. İletken kesiti büyüdükçe, belli bir değerden sonra tek tel/solid iletken ile
kesiti sağlamak mümkün olmuyor, mecburen çok telli-örgülü yapılara geçmek gerekiyor. Akım taşıma
kapasitelerinin kaynağı standart yönüyle tektir. VDE 0298 ve IEC 287'dir. Tüm firmalar bu değerleri
referans değer kabul eder. Firma kataloglarında farklı değerler ile karşılaşılması, tercih edilen/önerilen
tesisat koşulları ve ortam şartları ile çok yakından ilişkilidir. Değişkenlikler beraberinde farklı düzeltme
katsayılarının kullanılmasını gerektirir, neticesinde de farklı akım taşıma kapasiteleri ile karşılaşılmaktadır.
~20~
ELECTRONIC TRIP UNITS OF THE MOLDED-CASE CIRCUIT BREAKER AND ONE OF THE
FUNCTIONS OF A CURRENT TRANSFORMER(CT): Electronic trip units typically consist of a CT
for each phase, a printed circuit board, and a shunt trip. The CTs monitor current and reduce it to the
required ratio for direct input into the printed circuit board, the brains of the electronic trip unit. The
circuit board then interprets current flow information, makes trip decisions based on predetermined
parameters, and tells the shunt trip unit to trip the breaker.
Not:
anma kaçak eşik akımı.
Not: 1- İşletmede oluşan harmonik akımları kaçak akım oluşturmaz fakat kaçak akım sistemlerinde
ölçümsel hataların oluşmasına sebep olur. Bu nedenle yüksek harmonik üreten kaynak hattı vb. yüklerde
kaçak akım sistemi kullanmak oldukça zordur. Harmonik akımlarından etkilenmeden ölçüm yapabilen
kaçak akım rölelerinin kullanılması bu sorunu ortadan kaldırır. Kaynak hattı vb. yüklerde bu kaçak akım
sistemi kullanılabilir. 2-Toroid mutlaka bağlı bulunduğu noktadaki tüm yükü ölçebilecek bir noktaya
bağlanmalıdır. Örneğin faz toroidin üstü kısmından, nötr toroidin alt kısmından alınmış bir sinyal lambası
vb. herhangi bir yük bile kaçak akım sisteminde gereksiz açmaya neden olabilir(?).
USE OF RCDS WITH VARIABLE SPEED DRIVES
Question: Is it possible to install a three-phase RCD between a VSD and a socket outlet supplying a
motor to provide RCD protection?
Could this result in nuisance tripping, or a lack of functionality ”işlevsellik” because of the waveform
of the drives output?
Answer: VSDs can cause nuisance tripping, depending on the level of harmonics they send to earth
and this depends on the products from the VSD manufacturer concerned.
In a variable-speed drive, the inverter section operating with a chopping frequency of, say, 4 kHz will
encounter ”rastlam.” Unbalance between phases and neutral thus giving rise to higher frequencies earth
loop current.
Likewise, transients ”voltaj veya akımda geçici dalgalanma” originating ”kaynaklanm.” upstream can
result in unbalanced earth loop pulses and thus cause nuisance tripping.
The selection of RCDs for variable speed drives, and other power electronics where EMC filters might
be employed, requires great care.
In general, for the protection of a motor circuit powered by an inverter, an A type should be selected.
The relay provides protection against a phase to earth fault for the inverter and for the motor.
Note that the existence of high frequency earth loop current returning via motor bearings “mil yatağı,
rulman, yatak” can cause bearing failure. An RCD will not protect in that situation unless it is capable of
tripping on high-frequency current components.
Note: Chopping frequency: The rate at which a chopper interrupts a signal. Also called chopping rate.
Chopper: A device which periodically interrupts a direct current, light beam “ışık huzmesi”, or other
signal. This may be done, for instance, to modulate, or to facilitate “olanak tanım., kolaylaştırm.” The
amplification of an associated quantity(1). A device which periodically interrupts DC in order to produce
AC(2).
Residual current protective devices of type B are used to detect smooth DC residual currents. Type B
RCDs are recommended for use with drives and inverters for supplying motors for pumps, lifts, textile
~21~
machines, machine tools etc., since they recognise a continuous fault current with a low level ripple
”küçük dalgalanma”. Tripping values defined up to 2 kHz.
Reduction of unwanted tripping: RD3M, RD3P and RCQ020 residual current devices perform leakage
current measurement through a frequency filtering that allows an increase dimmunity against highfrequency currents not hazardous to man that are typically generated by inverters and the main cause of
unwanted tripping of residual current devices. Moreover, some of the models of RD3 range and RCQ020
switchboard device feature a pre-alarm threshold adjustment that signals, through an output contact, when
a given residual leakage current is reached. This function indicates that the installation insulation level is
decreasing and therefore allows appropriate planning of the required maintenance operations. By
removing most of the unwanted tripping of residual current devices, a high degree of safety on the
systems can be reached, along with a high level of service continuity(one of the features of ABB’s
electronic low-voltage residual current devices for miniature and moulded-case circuit-breakers).
Frequency filtering: The measurement of leakage current provides an attenuation of high-frequency
components, which are especially due to the presence of inverters in the circuit and are the main cause of
unwanted tripping of residual current devices. This ensures a high degree of safety in the systems and a
high level of service continuity(one of the features of ABB’s electronic low-voltage residual current
devices for miniature and moulded-case circuit-breakers).
TOWER CRANE POWER SUPPLIES
Before the tower crane arrives on site, checks should be made to ensure that there is an adequate mains
electricity supply. Most tower cranes require a three phase supply and the tower crane manufacturer’s
instruction manual will specify the type and size of supply required. If a suitable mains supply is not
available on site, the alternative is to use an engine driven generator which must be adequately earthed
and sized to cope with the potentially high starting currents of the tower crane motors. The use of
frequency controlled motors on later designs of crane will reduce starting currents and consequently the
required capacity of the power supply, which is particularly beneficial when a generator is used.
Not: Otomatik sigorta: Koruma anahtarı.
PROTECTION OF INDUSTRIAL POWER SUPPLY SYSTEMS(FUSES, MCCBS AND
OVERCURRENT RELAYS SETTINGS)
Examples of Power Supply Protection
As industrial operations processes and plants have become more complex and extensive ‘geniş’,
the requirement for improved reliability ‘güvenilirlik’ of electrical power supplies has also
increased.
~22~
Protection And Control Of Industrial Power Supply Systems(Relay Schemes And Settings). - on photoMiCOM protection relays
The potential costs of outage ‘hizmet dışı kalma’ time following a failure of the power supply to
a plant have risen dramatically as well. The protection and control of industrial power supply
systems must be given careful attention. Many of the techniques that have been evolved ‘zaman
içinde gelişm., yavaş yavaş gelişm.’ for EHV(Extra High Voltage) power systems may be applied
to lower voltage systems also, but typically on a reduced scale.
However, industrial systems have many special problems that have warranted ‘gerektirm.’
individual attention and the development of specific solutions.
i
Many industrial plants have their own generation ‘üretim’ installed. Sometimes it is for
emergency use only, feeding a limited number of busbars and with limited capacity. This
arrangement is often adopted ‘benimsem., kabul etm., seçm.’ to ensure safe shut down ‘(fabrika, iş
yeri vb.) kapatm.’ of process ‘süreç, metot, işlemden geçirme’ plant ‘tesis’ and personnel safety.
In other plants, the nature of the process allows production of a substantial ‘önemli,
azımsanmayacak(sayı, miktar)’ quantity of electricity, perhaps allowing export ‘dışa aktarım’ of
any surplus ‘fazlalık’ to the public supply system – at either at sub-transmission or distribution
voltage levels. Plants that run generation in parallel with the public supply distribution network are
often referred to ‘değinm., adlandırm.’ as co-generation or embedded generation.
In this technical article, the following examples of protection & control of industrial power
supply systems are considered:
1. Fuse Co-ordination
2. Grading ‘sınıflandırma, ayırma; düzeltme’ of Fuses / MCCBs / Overcurrent Relays
a. Determination of relay current setting
b. Relay characteristic and time multiplier selection
3. Protection of a Dual-Fed Substation
a. General considerations
b. Motor protection relay settings
c. Relay B settings
d. Relays C settings
e. Comments on grading
1. Fuse Co-ordination
An example of the application of fuses is based on the arrangement in Figure 1(a). This shows an
unsatisfactory scheme ‘şema’ with commonly encountered shortcomings ‘kusur’.
~23~
It can be seen that fuses B, C and D will discriminate ‘ayırt etm.’with fuse A, but the 400 A
sub-circuit fuse E may not discriminate, with the 500 A sub-circuit fuse D at higher levels of
fault current.
Figure 1(a) – Fuse protection: effect of layout ‘yerleşim planı’ on discrimination. – In correct layout giving rise to problems in discrimination.
The solution, shown in Figure 1(b), is to feed the 400 A circuit E direct from the busbars ‘bara’.
The sub-circuit fuse D may now have its rating reduced from 500 A to a value, of say 100 A,
appropriate to the remaining sub-circuit.
This arrangement now provides a discriminating fuse distribution scheme satisfactory for an
industrial system.
Figure 1(b) – Fuse protection: effect of layout on discrimination. – In correct layout and discrimination.
Note: Discrimination is the practice of selecting protective devices and adjusting their settings
in order to limit interruption to electrical installations under fault conditions.
However, there are industrial applications where discrimination is a secondary factor. In the
application shown in Figure 2, a contactor having a fault rating of 20 kA controls the load in one
sub-circuit.
~24~
A fuse rating of 630 A is selected for the minor ‘tali, ikincil’ fuse in the contactor circuit to give
protection within the through-fault ‘baştan sona’ capacity of the contactor.
Figure 2– Example of back-up protection.
The major ‘asıl’ fuse of 800 A is chosen, as the minimum rating that is greater than the total load
current on the switchboard ‘dağıtım tablosu’. Discrimination between the two fuses is not obtained,
as the pre-arcing I2t of the 800 A fuse is less than the total I2t of the 630 A fuse.
i
Therefore, the major fuse will blow ‘sigorta atm.’ as well as the minor one, for most faults,
so that all other loads fed from the switchboard will be lost.
This may be acceptable in some cases. In most cases, however, loss of the complete switchboard
for a fault on a single outgoing ‘giden, çıkan’ circuit will not be acceptable, and the design will have
to be revised ‘değiştirm.’.
Note: Pre-arcing: Typically the fuse operation is as follows. When a fault current situation
occurs, the high level current implies ‘gerektirm.; anlamına gelm.’ the increase of the temperature
inside the fuse element due to Joule effect. Thus the electric resistance of the fuse element
increases. The temperature increase is especially high in the constrictions where ohmic resistance is
higher than in other parts of the fuse element. Due to the energy increase by Joule effect the fuse
element constriction is melted ‘erim.’ and hence vaporized ‘buharlaşm.’, thus leading to the ignition
‘ateşleme’ of an electric arc between the two parts of the fuse element. This time range is called the
pre-arcing period which ends in the sharp increase of the voltage across the fuse.
2. Grading of Fuses / MCCBs / Overcurrent Relays
An example of an application involving a moulded case circuit breaker, fuse and a protection
relay is shown in Figure 3.
A 1 MVA 3.3 kV/400 V transformer feeds the LV board via a circuit breaker, which is
equipped with an Alstom MiCOM P14x numerical relay having a setting range of 8-400% of
rated current and fed from 2000/1A CTs.
~25~
Figure 3– Network diagram for protection co-ordination example. – fuse / MCCB / relay.
Discrimination is required between the relay and both the fuse and MCCB up to the 40 kA fault rating of
the board. To begin with, the time/current characteristics of both the 400 A fuse and the MCCB are plotted in
Figure 18.19.
2a. Determination of relay current setting
The relay current setting chosen must not be less than the full load current level and must have
enough margin to allow the relay to reset with full load current flowing.
Note: The full-load amperes(FLA) is the current the motor draws while producing its rated
horsepower load at its rated voltage. FLC(full load current) is used when you size breaker size and
wire size for motors. Using the FLC tables is not only necessary when calculating branch circuit
conductors, the FLC tables are also necessary when calculating ampere ratings of switches, branchcircuit protection, feeder conductors, and feeder protection. *
The latter ‘(iki şeyden)sonuncu, son söylenen, sonuncusu’ may be determined from the
transformer rating:
i With the CT ratio of 2000/1A and a relay reset ratio of 95% of the nominal current setting, a
current setting of at least 80% would be satisfactory, to avoid tripping and/or failure to reset
with the transformer carrying full load current.
However, choice of a value at the lower end of this current setting range would move the relay
characteristic towards that of the MCCB and discrimination may be lost at low fault currents.
It is therefore prudent ‘tedbirli, sağgörülü’ to select initially a relay current setting of 100%.
2b. Relay characteristic and time multiplier ‘çarpan’ selection
An EI characteristic is selected for the relay to ensure discrimination with the fuse.
From Figure 4, it may be seen that at the fault level of 40 kA the fuse will operate in less than
0.01 s and the MCCB operates in approximately 0.014 s. Using a fixed grading margin of 0.4 s, the
required relay operating time becomes 0.4 + 0.014 = 0.414 s(?).
i With a CT ratio of 2000/1 A, a relay current setting of 100%, and a relay TMS setting(Time Multiplier
Setting) of 1.0, the extremely ‘aşırı derecede’ inverse ‘ters’ curve gives a relay operating time of 0.2 s at a
fault current of 40 kA. This is too fast to give adequate discrimination and indicates that the EI curve is too
~26~
severe ‘kötü’ for this application. Turning to the VI relay characteristic, the relay operation time is found to
be 0.71 s at a TMS of 1.0.
To obtain the required relay operating time of 0.414 s:
TMS setting = 0.414 / 0.71 = 0.583
Use a TMS of 0.6, nearest available setting.
The use of a different form of inverse time characteristic makes it advisable ‘tavsiye edilebilir’ to
check discrimination at the lower current levels also at this stage. At a fault current of 4 kA, the
relay will operate in 8.1 s, which does not give discrimination with the MCCB(?). A relay operation
time of 8.3 s is required.
To overcome this, the relay characteristic needs to be moved away from the MCCB
characteristic, a change that may be achieved by using a TMS of 0.625(?). The revised
‘değiştirm., gözden geçirm.’ relay characteristic is also shown in Figure 4.
Figure 4– Grading curves for Fuse / MCCB / relay grading example.
3. Protection of a Dual-Fed Substation
As an example of how numerical ‘sayısal’ protection relays can be used in an industrial system,
consider the typical large industrial substation of Figure 5 below. Two 1.6 MVA, 11/0.4 kV
transformers feeding a busbar whose bus-section CB ‘circuit breaker’ is normally open.
The LV system is solidly earthed. The largest outgoing ‘giden’ feeder ‘şebeke hattı, besleme
hattı, dağıtıcı’ is to a motor rated 160 kW, 193 kVA, and a starting current of 7 x FLC.
~27~
Figure 5– Relay grading example for dual-fed switchboard.
The transformer impedance is to IEC standards. The LV switchgear and busbars are fault rated at
50 kA RMS. To simplify the analysis, only the phase-fault LV protection is considered.
3a. General considerations
Analysis of many substations configured as in Figure 5 above shows that the maximum fault
level and feeder load current is obtained with the bus-section circuit breaker closed and one of the
in feeding ‘besleme, giriş’ CBs open. This applies so long as the switchboard has a significant
amount of motor load.
i
The contribution ‘katkı, destek’ of motor load to the fault level at the switchboard is usually
larger than that from a single in feeding transformer, as the transformer restricts the amount of fault current
infeed ‘besleme, giriş’ from the primary side.
The three-phase break ‘devreyi açma, akımı kesme’ fault level at the switchboard under these
conditions is assumed to be 40 kA RMS.
Relays C1 and C2 are not required to have directional ‘yön ile ilgili, yönlü’
characteristics(read more about it below) as all three circuit breakers are only closed momentarily
‘geçici olarak’ during transfer from a single in feeding transformer to two in feeding transformers
configuration.
This transfer is normally an automated ‘otomatikleştirilmiş’ sequence ‘ardıllık, art arda gelme’,
and the chance of a fault occurring during the short period(of the order of 1s) when all three CBs
are closed is taken to be negligibly small. Similarly, although this configuration gives the largest
fault level at the switchboard, it is not considered from either a switchboard fault rating or
protection viewpoint.
It is assumed that modern numerical relays are used. For simplicity, a fixed grading margin
of 0.3 s is used.
Application of Directional Relays
If non-unit ‘blok, takım, düzen; bir bütünü oluşturan parçalardan her biri’, non-directional relays
are applied to parallel feeders having a single generating source, any faults that might occur on any
~28~
one line will, regardless of ‘göz önüne almadan’ the relay settings used, isolate both lines and
completely disconnect the power supply. *
i
With this type of system configuration, it is necessary to apply directional relays at the
receiving end and to grade ‘ayırm.’ them with the non-directional relays at the sending end, to
ensure correct discriminative operation of the relays during line faults. *
This is done by setting the directional relays R’1 and R’2 in Figure 6 with their directional
elements looking into the protected line, and giving them lower time and current settings than relays
R1 and R2. *
The usual practice is to set relays R’1 and R’2 to 50 % of the normal full load of the protected
circuit and 0.1 TMS(Time Multiplier Setting), but care must be taken to ensure that the continuous
thermal rating of the relays of twice rated current is not exceeded.
Note: R₁' and R₂' are directional relays and R₁ and R₂ are non-directional relays.
Figure 6– Directional relays applied to parallel feeders.
Note: In electrical engineering, a protective relay is a relay device designed to trip a circuit
breaker when a fault is detected.[1]:4 The first protective relays were electromagnetic devices, relying
on(dayanm., bel bağlam.) coils operating on moving parts to provide detection of abnormal
operating conditions such as over-current, overvoltage, reverse power flow, over-frequency, and
under-frequency.[2]
Microprocessor-based digital protection relays now emulate ‘benzetm.; rekabet etm., yarışm.’
the original devices, as well as providing types of protection and supervision ‘denetim, kontrol’
impractical ‘uygulanamaz, yapılamaz’ with electromechanical relays. Electromechanical relays
provide only rudimentary ‘basit, ilkel’ indication of the location and origin of a fault.[3] In many
cases a single microprocess or relay provides functions that would take two or more
electromechanical devices. By combining several functions in one case, numerical relays also save
capital ‘para’ cost and maintenance cost over electromechanical relays.[4] However, due to their very
long life span ‘süre, müddet’, tens of thousands of these "silent ‘gürültüsüz’ sentinels ‘koruyucu’
"[5] are still protecting transmission lines and electrical apparatus all over the world. Important
transmission lines and generators have cubicles ‘küçük oda, kabin’ dedicated ‘tahsis etm.’ to
protection, with many individual electromechanical devices, or one or two microprocessor relays.
The theory and application of these protective devices is an important part of the education of a
power engineer who specializes ‘uzmanlaşm.’ in power system protection. The need to act quickly
to protect circuits and equipment often requires protective relays to respond and trip a breaker
within a few thousandths of a second. In some instances ‘bazı durumlarda’ these clearance times are
prescribed ‘bildirm.; belirtm.(şartları, kuralları)’ in legislation ‘yasa, mevzuat’ or operating rules.[6]
3b. Motor protection relay settings
~29~
From the motor characteristics given, the overcurrent relay settings(Relay A) can be found
using the following guidelines ‘önerge, kural’:
Thermal element
 Current setting: 300 A
 Time constant: 20 mins
Instantaneous element
 Current setting: 2.32 kA
These are the only settings relevant to ‘ile ilgili’ the upstream relays.
3c. Relay B settings
Relay B settings are derived from consideration ‘göz önünde tutma, değerlendirme, husus,
etmen’ of the loading and fault levels with the bus-section breaker between busbars A1 and A2
closed. No information is given about the load split ‘ayrılma’ between the two busbars, but it can be
assumed in the absence of definitive ‘belirli, açık’ information that each busbar is capable of
supplying the total load of 1.6 MVA.
With fixed tap transformers, the bus voltage may fall to 95% of nominal under these conditions,
leading to a load current of 2430 A.
The IDMT current setting must be greater than this, to avoid relay operation on normal
load currents and (ideally) with aggregate ‘kümelenme, toplaşım; bir araya getirilmiş, toplu’
starting/re-acceleration currents.
If the entire load on the busbar was motor load, an aggregate starting current in excess of ‘-den
fazla, -i geçen’ 13 kA would occur, but a current setting of this order would be excessively high and
lead to grading problems further upstream.
It is unlikely that the entire load is motor load(though this does occur, especially where a
supply voltage of 690 V is chosen for motors – an increasingly common practice) or that all
motors are started simultaneously(but simultaneous re-acceleration may well occur).
What is essential is that relay B does not issue ‘bildirm., yayınlam.’ a trip command under
these circumstances – i.e. the relay current/time characteristic is in excess of the current/time
characteristic of the worst-case starting/re-acceleration condition.
It is therefore assumed that 50 % of the total bus load is motor load, with an average starting
current of 600 % of full load current(=6930 A), and that re-acceleration takes 3 s.
A current setting of 3000 A is therefore initially used.
The SI characteristic is used for grading the relay, as co-ordination ‘düzenleme, uyumlu çalışma’
with fuses is not required. The TMS is required to be set to grade with the thermal protection of
relay A under ‘cold’ conditions, as this gives the longest operation time of Relay A, and the reacceleration conditions. A TMS value of 0.41 is found to provide satisfactory grading, being
dictated ‘zorla kabul ettirm., gerektirm.; belirlem.’ by the motor starting/re-acceleration transient.
Adjustment of both current and TMS settings may be required depending on the exact reacceleration conditions.
Note that lower current and TMS settings could be used if motor starting/re-acceleration did
not need to be considered.
The high-set setting needs to be above the full load current and motor starting/re-acceleration
transient current, but less than the fault current by a suitable margin.
~30~
A setting of 12.5 kA is initially selected. A time delay of 0.3 s has to used to ensure grading
with relay A at high fault current levels. Both relays A and B may see a current in excess of 25 kA
for faults on the cable side of the CB feeding the 160 kW motor.
The relay curves are shown in Figure 6 below:
Figure 6– Grading of relays A and B.
Note: A Centre Tapped transformer works in more or less the same way as a usual transformer.
The difference lies in just the fact that its secondary winding is divided into two parts, so two
individual voltages can be acquired across the two line ends.
Note: Generally, the over current relays are differentiating ‘farklılaşm.’ with their time of
operation. The most commonly used over current relays are IDMT(inverse definite mean time) over
current relays, DT(definite time) over current relays and instantaneous time over current relays.
They are designed to sense the over-current.
3d. Relays C settings
The setting of the IDMT element of relays C1and C2 has to be suitable for protecting the busbar
while grading with relay B. The limiting condition is grading with relay B, as this gives the longest
operation time for relays C.
The current setting has to be above that for relay B to achieve full co-ordination, and a value of
3250 A is suitable. The TMS setting using the SI characteristic is chosen to grade with that of relay
B at a current of 12.5 kA(relay B instantaneous setting), and is found to be 0.45.
The high-set element must grade with that of relay B, so a time delay of 0.62 sec is required. The
current setting must be higher than that of relay B, so use a value of 15 kA.
The final relay grading curves and settings are shown in Figure 7.
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Figure 7– Final relay grading curves.
3e. Comments on grading
While the above grading may appear satisfactory, the protection on the primary side of the
transformer has not been considered.
IDMT protection at this point will have to grade with relays C and with the through-fault ‘hata
yoluyla’ short-time withstand curves of the transformer and cabling. This may result in excessively
long operation times. Even if the operation time at the 11 kV level is satisfactory, there is probably
a Utility infeed to consider, which will involve a further set of relays and another stage of time
grading, and the fault clearance time at the Utility infeed will almost certainly be excessive.
One solution is to accept a total loss of supply to the 0.4 kV bus under conditions of a single infeed
and bus section CB closed.
This is achieved by setting relays C such that grading with relay B does not occur at all current
levels, or omitting relay B from the protection scheme. The argument for this is that network
operation policy ‘prensip’ is to ensure loss of supply to both sections of the switchboard does not
occur for single contingencies ‘olasılıklar’.
As single infeed operation is not normal, a contingency(whether fault or maintenance) has
already occurred, so that a further fault causing total loss of supply to the switchboard through
tripping of one of relays B is a second contingency. Total loss of supply is therefore acceptable. The
alternative is to accept a lack of discrimination at some point on the system.
Another solution is to employ partial differential protection to remove the need for Relay A,
but this is seldom ‘az, seyrek’ used. The strategy adopted ‘kabul etm., benimsem.’ will depend on
the individual circumstances ‘durum, koşul’.
WHAT IS TYPE 2 COORDINATION AND TYPE 1 COORDINATION
~32~
Type 2 coordination ‘bağlantı; düzenleme’ and type 1 coordination are IEC standard for
electrical machine starting equipment. Type-2 coordination is an advanced standard of type 1
coordination. While buying the starter materials, you should ensure ‘sağlam.’ the equipment’s
coordination. Let us understand what is type 1 coordination and type 2 coordination.
What is type 1 coordination: Type 1 coordination is nothing but a machine cannot be started
without any maintenance work and it should not create any damage for the installation and
personals.
For example, take a motor along with the starter ‘marş motoru; yolverici, motoru çalıştırmak için
ilk dönüş hareketini veren komponent’. During the short circuit condition, the motor or motor’s
starter equipment may get damage during the short circuit. Hence it cannot start immediately after
clearing the fault by resetting the starter. The starter material may need to be replaced with the spare
‘yedek parça’. Such a starting arrangement is called type 1 starter. It is an old standard.
But any industry wants to get continuous protection from their machine, but by using type-1
coordination starting equipment, may increase the downtime ‘arıza süresi’. In order to overcome
such things, type 2 coordination is created.
What is type 2 coordination: Type 2 coordination is nothing but an immediate start without any
work on the motor on starter under short circuit condition. It is applicable ‘uygulanabilir’ for both
moving and fixed contacts.
For example, a motor attains ‘elde etm., ulaşm.’ a short circuit; the relay commands the
contactor to open circuit. During this, the starter equipment such as contactor, relays, MCCB or
MPCB(Not Fuses-Motor Protection Circuit Breaker), Cable, bolts ‘civata’ should not get any
damage.
In this, only the relay rest flag shall indicate the circuit is opened, by resetting the same, the
equipment starts at no minute. Type 2 protective device, should clear peak current or fault current
within 8 milliseconds.
Why type 2 coordination is recommended?
 Increase productivity
 High Safety
 High initial cost but less maintenance cost.
Note: Section 715 Extra-low Voltage Lighting. Extra-low voltage(ELV) is used where the risks
are great: swimming pools, wandering ‘başıboş dolaşan’ -lead hand lamps, and other portable
appliances for outdoor use, etc.
The particular requirements apply to installations that are supplied from sources with a
maximum rated voltage of 50 V a.c. rms or 120 V d.c. BS 7671 already includes requirements for:
1) protection against electric shock(SELV);
2) protection against the risk of fire due to short circuit;
3) types of wiring systems, including special requirements where bare conductors are used;
4) the types of transformers and converters; and
5) suspended ‘ertelem.’ systems.
Amendment 3 will make a number of notable changes to align the latest IEC requirements with
CENELEC requirements, including:
1) the types of wiring systems permitted;
2) voltage drop in consumer’s installations; and
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3) requirements for isolation, switching and control.
TECHNICAL DOCUMENT OF ‘Amendment Number 3 of BS 7671 2008 WiringMatters’
COORDINATION PROBLEMS IN ELECTRICAL NETWORKS THAT LEAD TO NUISANCE
CB TRIPPING
Network Examples
There are a number of problems that commonly occur in industrial and commercial networks,
and some of them are covered in the following paragraphs. Coordination ‘koordinasyon, düzen’
malfunctioning ‘kötü çalışm., arızalanm.’ is leading to nuisance tripping of circuit breakers and
unwanted electrical effects.
Coordination problems in electrical networks that lead to nuisance CB tripping
Let’s discover some of coordination problems in networks:
1. Earth fault protection with residually-connected CTs
2. Four-Wire Dual-Fed Substations
1. Use of 3-pole CBs
2. Use of single earth electrode
1. Earth fault protection with residually-connected CTs
For four-wire systems, the residual connection of three phase CTs to an earth fault relay
element will offer ‘teklif etm., sunm.’ earth fault protection, but the earth fault relay element
must be set above the highest single-phase load current to avoid nuisance tripping. Harmonic
currents(which may sum in the neutral conductor) may also result in spurious ‘sahte, aldatıcı’
tripping.
The earth fault relay element will also respond to a phase-neutral fault for the phase that is not
covered by an overcurrent element where only two overcurrent elements are applied.
i
Where it is required that the earth fault protection should respond only to earth fault
current, the protection element must be residually connected to three phase CTs and to a
neutral CT or to a core balance CT.
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In this case, overcurrent protection must be applied to all three phases to ensure that all phaseneutral faults will be detected by overcurrent protection.
Placing a CT in the neutral earthing connection to drive an earth fault relay provides earth fault
protection at the source of supply for a 4-wire system. * If the neutral CT is omitted, neutral
current is seen by the relay as earth fault current and the relay setting would have to be increased
to prevent tripping under normal load conditions.
Figure 1– CBCT(core-balance current transformer) connection for four-wire system.
Not: cable gland: Kablo rakoru. Sheath: Kablo kılıfı.
When an earth fault relay is driven from residually connected CTs, the relay current and time
settings must be such that that the protection will be stable ‘sürekli, devamlı’ during the passage
‘geçiş, akış’ of transient CT spill ‘boşaltma’ current through the relay.
Such spill current can flow in the event of transient, asymmetric CT saturation during the
passage of offset ‘telafi etme; öteleme, kaymış’ fault current, inrush current or motor starting
current.
i
The risk of such nuisance tripping is greater with the deployment ‘konuşlanma,
yerleştirme’ of low impedance electronic relays rather than electromechanical earth fault relays
which present significant relay circuit impedance.
Energizing a relay from a core-balance type CT(CBCT) generally enables more sensitive
settings to be obtained without the risk of nuisance tripping with residually connected phase CTs.
When this method is applied to a four-wire system, it is essential that both the phase and neutral
conductors are passed through the core-balance CT aperture ‘açıklık, delik’.
For a 3-wire system, care must be taken with the arrangement of the cable sheath,
otherwise cable faults involving the sheath may not result in relay operation(Figure 1 above).
2. Four-Wire Dual-Fed Substations
The coordination of earth fault relays protecting four-wire systems requires special
consideration ‘göz önüne alma; dikkat; husus’ in the case of low voltage, dual-fed installations.
Horcher(Overcurrent Relay Coordination for Double Ended Substations. George R Horcher.
IEEE. Vol. 1A-14 No.6 1978.) has suggested various methods of achieving optimum
coordination.
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Problems in achieving optimum protection for common configurations are described below.
2.1. Use of 3-pole CBs
When both neutrals are earthed at the transformers and all circuit breakers are of the 3-pole
type, the neutral busbar in the switchgear ‘ana şalter; şalt cihazı’ creates a double neutral to
earth connection, as shown in Figure 2.
In the event of an uncleared feeder earth fault or busbar earth fault, with both the incoming
supply breakers closed and the bus section breaker open, the earth fault current will divide
between the two earth connections.
Earth fault relay RE2 may operate, tripping the supply to the healthy section of the switchboard
as well as relay RE1 tripping the supply to the faulted section.
Figure 2– Dual fed four-wire systems: use of 3-pole CBs.
If only one incoming ‘gelen’ supply breaker is closed, the earth fault relay on the energized
side will see only a proportion of the fault current flowing in the neutral busbar.
This not only significantly increases the relay operating time but also reduces its sensitivity to
low-level earth faults.
i
The solution to this problem is to utilise 4-pole CBs that switch the neutral as well as
the three phases. Then there is only a single earth fault path and relay operation is not
compromised ‘tehlikeli’.
2.2.Use of single earth electrode
A configuration sometimes adopted ‘benimsem., kabul etm.; kullanm.’ with four-wire dual-fed
substations where only a 3-pole bus section CB is used is to use a single earth electrode connected
to the mid-point of the neutral busbar in the switchgear, as shown in Figure 3.
i
When operating with both incoming main circuit breakers and the bus section breaker
closed, the bus section breaker must be opened first should an earth fault occur, in order to
achieve discrimination ‘selektivite(seçicilik)’.
~36~
The coordination time between the earth fault relays RF and RE should be established
at fault level F2 for a substation with both incoming supply breakers and bus section breaker
closed.
When the substation is operated with the bus section switch closed and either one or both of
the incoming supply breakers closed, it is possible for unbalanced neutral busbar load current
caused by single phase loading to operate relay RS1 and/or RS2 and inadvertently ‘yanlışlıkla,
istemeyerek’ trip the incoming breaker.
Figure 3– Dual fed four-wire systems: Use of single point neutral earthing.
Interlocking ‘birbirine bağlam.’ the trip circuit of each RS relay with normally closed
auxiliary contacts on the bus section breaker can prevent this.
However, should an earth fault occur on one side of the busbar when relays RS are already
operated, it is possible for a contact race to occur. When the bus section breaker opens, its break
contact ‘kapatma kontağı’ may close before the RS relay trip contact on the healthy side can
open(reset).
i Raising the pick-up ‘toplama’ level of relays RS1 and RS2 above the maximum unbalanced
neutral current may prevent the tripping of both supply breakers in this case. However, the best
solution is to use 4-pole circuit breakers, and independently earth both sides of the busbar.
If, during a busbar earth fault or uncleared feeder earth fault, the bus section breaker fails to
open when required, the interlocking break ‘devreyi açma, elektrik akışının kesilmesi’ auxiliary
contact will also be inoperative ‘çalışmayan; geçersiz’. This will prevent relays RS1 and RS2 from
operating and providing back-up ‘yedek’ protection, with the result that the fault must be cleared
eventually ‘sonunda’ by slower phase overcurrent relays.
An alternative method of obtaining back-up protection could be to connect a second relay RE,
in series with relay RE, having an operation time set longer than that of relays RS1 and RS2.
But since the additional relay must be arranged to trip both of the incoming supply breakers,
back-up protection would be obtained but busbar selectivity would be lost.
CURRENT AND VOLTAGE UNBALANCE-CAUSES
~37~
What is unbalance? Any deviation in voltage and current waveform from perfect sinusoidal, in
terms of magnitude or phase shift is termed as unbalance. In ideal conditions i.e. with only linear
loads connected to the system, the phases of power supply are 120 degree apart in terms of phase
angle and magnitude of their peaks should be same. On distribution level, the load imperfections
‘düzgünsüzlük’ cause current unbalance which travel to transformer and cause unbalance in the
three phase voltage. * Even minor ‘ufak, küçük’ unbalance in the voltage at transformer level
disturbs the current waveform significantly on all the loads connected to it. * Not only in the
distribution side but through the transformer, voltage unbalances disturbs the high voltage power
system as well.
Causes of unbalance: Practical imperfections which can result in unbalances are:
1. A three phase equipment such as induction motor with unbalance in its windings. If the reactance
of three phases is not same, it will result in varying current flowing in three phases and give out
system unbalance.
– With continuous operation, motor’s physical environment causes degradation ‘bozulum’ of rotor
and stator windings. This degradation is usually different in different phases, affecting both, the
magnitude and phase angel of current waveform.
– A current leakage from any phase through bearings ’mil yatağı’ or motor body provides floating
’değiş(k)en’ earth at times ‘bazen’, causing fluctuating current. *
2. Any large single phase load, or a number of small loads connected to only one phase cause more
current to flow from that particular phase causing voltage drop on line.
3. Switching of three phase heavy loads results in current and voltage surges which cause unbalance
in the system.
4. Unequal impedances in the power transmission or distribution system cause differentiating
‘farklılaşan’ current in three phases.
How to calculate unbalance: Unbalance is calculated in terms of maximum deviation of current in a
phase from the mean of three phases. To calculate the percentage deviation[1],
Where Im is mean ‘ortalama’ of currents in three phases(i.e. Im= (Ir+Iy+Ib)/3 Ir, Iy, Ib are phase
currents). % voltage unbalance = 100 x (maximum deviation from average voltage) / (average
voltage). This formula gives estimated values.
Besides ‘ayrıca, üstelik’, an unbalance can also be quantified ‘ölçmek’ by comparing the intensity
‘yoğunluk’ of negative sequence currents in comparison to the positive sequence currents. The
permissible limit in terms of percentage of negative phase sequence current over positive sequence
current is 1.3% ideally but acceptable up to 2%.[2]
Note: Maximum current unbalance limit is 10% and maximum voltage unbalance limit is 2%.
~38~
Note: To calculate unbalance of the system there is an example given below.
With phase-to-phase voltages of the system is 430 V, 435 V, and 400 V.
The average voltage= (430+435+400)/3= 421 V.
The maximum voltage deviation from average voltage= 435-421= 14 V.
% voltage unbalance= (14×100)/421= 3.32%
Note: Planning Limits for Voltage unbalance: In the European Standard EN 50160(1994)
voltage unbalance is measured in relation to the negative phase sequence component of the supply
voltage since this is considered the most relevant ‘konu ile ilgili; uygun’ with respect to interference
‘girişim, (radyo)parazit’ to equipment. This standard implies ‘anlamına gelm., ima etm.’ that if the
magnitude of the negative phase sequence component is within 2% of the positive phase sequence
component then the unbalance is acceptable.
In the supply system there may be a background ‘arka plan’ level of unbalance(normally less than
0.5%) and therefore the affect of any new load must be considered in the light of existing levels of
unbalance. The UK document Engineering Recommendation P29 states that unbalance caused by
individual loads should be kept within 1.3%, although short term deviations(less than 1 minute)
may be allowed up to 2%. In summary, the adopted ‘kabul edilen; uygulanan’ limits for unbalance
are: (a) unbalance at individual loads / connections: 1.3%, (b) unbalance at pcc(aggregate ‘toplam;
bütün; toplu’ affect of several loads): 2%
Note: Depending on the rating and impedance of the circuit, excessive current unbalance could
be either acceptable or a big problem. If the load current is close to the rated current for the circuit,
high level of unbalance can cauce nuisance ‘baş belası’ breaker tripping.
Effects of unbalance: 1. The unbalance decreases the motor efficiency by causing extra heating in
the motor. Heat generated also effect the equipment life by increasing the operating temperature,
which decompose ‘boz(ul)m.’ the grease or oil in the bearing 'rulman, mil yatağı' and de-rate the
motor windings.
2. In induction motors connected to unbalanced supply, the negative sequence currents flow along
with positive sequence current resulting in ‘sonuçlanm., yol açm.’ decreased percentage of
productive ‘verimli, yararlı’ current and poor motor efficiency. Any unbalance above 3% hampers
‘engellem.’ the motor efficiency.
3. Torque(and thus the speed) produced by the motor becomes fluctuating. These sudden changes in
torque cause more vibration in the gear box ‘dişli kutusu’ or the equipment connected to it. The
vibration and noise produced damages the equipment and also reduces the efficiency of equipment.
4. The variable frequency or speed drives connected to an unbalanced system can trip off. VFD
treats ‘davranm.’ high level unbalances as phase fault and can trip on earth fault or missing phase
fault.
5. Unbalances cause de-rating of power cables and thus increase I²R losses in the cable. For
distribution cables de-rating factor represents the part of total current giving fruitful ‘verimli’
outcomes ‘sonuç’.
6. UPS or inverter supplies also perform with poor efficiency and inject more harmonic currents in
case of unbalances in the system.
7. Negative phase sequence current flowing due to unbalance can cause faults in the motor,
resulting in, tripping or permanent damage of the electrical equipment.
Note: Some types of equipment are more sensitive to unbalance than others, in particular 3 phase
rotating machines, where the main affect of voltage unbalance is overheating of stator and rotor
~39~
windings. Also, rectifier and inverter equipment tend to generate more harmonics when subject to
an unbalanced supply voltage.
Quantifying 'miktarını/niceliğini belirlemek, ölçmek' the losses: An unbalance of 1% is acceptable
as it doesn’t affect the cable. But above 1% it increases linearly and at 4% the de-rating is 20%.
This implies that 20% of the current flowing in the cable will be unproductive and thus the copper
losses in the cable will increase by 25% at 4% unbalance.
1. For motors, an unbalance of 5% will result in capacity reduction by 25%. That means, the motor
current will increase to match the equipment’s torque needs which will result in proportional copper
losses in motor. The voltage unbalance of 3% increase the heating by 20% for an induction motor.
2. The resistance for negative sequence current is 1/6th of the positive sequence current which
means a small unbalance in voltage waveform will give more current and thus losses.
Effects on the distribution transformer: Transformer offers high reactance to negative phase
sequence currents and thus reduces the level of unbalance on the other side of the system.
– Ideally any distribution transformer gives best performance at 50% loading and every electrical
distribution system is designed for it. But in case of unbalance the loading goes over 50% as the
equipments draw more current.
– Following data represents the efficiency of transformer under different loading conditions:
1. Full Load- 98.1%
2. Half Load- 98.64%
3. Unbalanced loads- 96.5%
For a distribution transformer of 200 kVA rating, the eddy currents accounts for 'açıklam., izah
etm.' 200 W but in case of 5% voltage unbalance they can rise up to 720 W.
Control measures: 1. All the single phase loads should be distributed on the three phase system such
that they put equal load on three phases.
2. Replacing the disturbing equipments i.e. with unbalanced three phase reactance.
3. Reducing the harmonics also reduces the unbalance, which can be done by installing reactive or
active filters. These filters reduce the negative phase sequence currents by injecting a compensating
‘telafi eden, karşılayan, dengeleyen’ current wave. *
4. In case the disturbing loads cannot be replaced or repaired, connect them with high voltage side
this reduces the effects in terms of percentage and even controlled disturbance in low voltage
side(?).
5. Motors with unbalanced phase reactance should be replaced and re-winded 'çevresine sarılm.'.
VOLTAGE IMBALANCE(UNBALANCE) STUDY
What is voltage imbalance study? Electric voltage imbalance study is an activity to conduct
‘yürütm.’ a comprehensive ‘kapsamlı’ analysis of the voltage unbalance problem in an electrical
power system. Voltage unbalance analysis studies help utility and industrial managers to understand
the definition of a voltage imbalance, causes, effect or impact, and identify suitable mitigation
techniques.
Voltage imbalance can be very dangerous for electrical equipment. The source of the problem
must be thoroughly ‘derinlemesine, noksansız/mükemmel bir şekilde’ investigated and corrected.
~40~
Basic Knowledge
Definition of Voltage Unbalance
Voltage unbalance or imbalance is defined by IEEE as the ratio of the negative or zero sequence
component to the positive sequence component. In simple terms, it is a voltage variation in a power
system in which the voltage magnitudes or the phase angle differences between them are not equal.
It follows that this power quality problem affects only polyphase ‘çok fazlı, çok evreli’ systems(e.g.
three-phase).
In three phase systems, voltage unbalance or voltage imbalance occurs when the phase or line
voltages differ from the nominal balanced condition. Normal balanced condition is when the three
phase voltages are identical in magnitude and phase angles are displaced ‘yer değiştirm.’ 120
degree vectorially. The unbalance could be caused due to the difference in magnitude of the voltage
or the phase angle or both. From a reliability ‘güvenilirlik’ and power quality aspect having a good
voltage balance in the system is paramount ‘çok önemli’.
Causes of Voltage Unbalance
Following are some of the factors that could contribute to voltage unbalance:
 Electricity source voltage(either public grid or own generation) which is not balanced,
 The unequal impedance of a three-phase distribution system,
 Unbalanced loading of power factor correction capacitors[such as a blown fuse in one
phase],
 Uneven ‘eşit olmayan’ distribution of single-phase loads,
 The load is unbalanced even though it is connected in three phases(?),
 Incorrect transformer tapping ‘arabağlantı, bir sargının ara yerinden çıkarılan bağlantı ucu’.
Note: What is tapping of a transformer? Although power systems have a rated voltage, they
often operate at voltages slightly above or below this voltage. This deviation from the rated voltage
on the primary side of the transformer is seen on the secondary side of the transformer.
Transformers are normally provided with taps to adjust the turns ratio to compensate for this supply
variance ‘değişiklik’. This will allow the output voltage to be closer to the rated output voltage
when the input voltage is off rated voltage.
Effect of Voltage Imbalance
~41~
Like voltage drop, voltage imbalance is undeniable ‘yadsınamaz, kesin’. The problem is when
the difference of magnitude and the angle of the voltage exceeds the tolerance limits or allowable
percentage set by the applicable standards.
The effects of extensive voltage imbalances on power systems and equipment are broad and
serious. A severe imbalance might dramatically decrease the equipment life cycles, considerably
‘önemli ölçüde’ speed up the replacement cycle of equipment, and significantly increase system
operation and maintenance costs. Furthermore, for a 3 phase 4 wire system, voltage imbalance leads
to bigger neutral wire current and cause relay malfunction.
The major effects of voltage imbalance are described as follows:
 Extra power loss
 Safety deficiency ‘yetersizlik, açık’
 Motor failure
 Life cycle decrease
 Relay malfunction
 Inaccurate measurement
 Transformer failure
Why is Voltage Imbalance Study Important?
The impact of excessive voltage unbalance on power systems and equipment is extensive and
serious. Severe imbalances can dramatically decrease equipment life-time, greatly speed up
equipment replacement cycles, and significantly increase system operating and maintenance
costs(?). For 3 phase 4 wiring systems, voltage imbalance results in larger neutral wire currents and
causes relay failure.
Voltage unbalances will cause extra power loss, reduce system efficiency, reduce motor life
cycle, etc. Also some abnormal functioning and maintenance conditions also cause voltage
imbalance and result in negative impacts on equipment and systems. These conditions include
problems such as poor electrical contact, improper installation of capacitor banks, operation of
single-phase motors, etc. These operating and maintenance conditions may not occur frequently.
However, if it happens, it will cause very serious problems for the system or equipment.
Objective ‘amaç, hedef’ of Voltage Imbalance Studies

To determine the magnitude of the existing voltage imbalance and compare it with related
standards.
~42~


To determine the causes and consequences of unbalanced stresses ‘basınç; kuvvet; gerilme,
gerilim, gerginlik’ in distribution systems and user facilities ‘kolaylık; tesis’.
To identify mitigation techniques for distribution systems and for industry.
Mitigation of Voltage Unbalance
Making a zero voltage imbalance in a distribution system clearly impossible due to, (a)
randomness ‘raslantısallık’ of connection and termination ‘son verme, son bulma; sonlandırma’ of
single-phase loads (b) uneven distribution of single-phase loads over three phases and (c) inherent
‘doğasında olan’ asymmetry of the power system. However, there are utility system level mitigation
techniques as well as industry level(load) mitigation techniques that can be used to correct
‘düzeltm., doğrulam.’ excessive voltage imbalances.
Utility ‘kamu hizmeti yapan kuruluş’ Level Techniques

Redistribution of single-phase loads equally to all phases.
 Reduction of the system unbalance that arise ‘oluşm.’ due to system impedance ‘empedans’
such as those due to transformers and lines.
 Single-phase regulators have been suggested as devices that can be used to correct the
unbalance but care ‘bakım, özen’ must be exercised to ensure that they are controlled
carefully not to introduce further unbalance.
 Passive network systems and active power electronic systems such as static var compensator
and line conditioners also have been suggested for unbalance correction. Compared to
passive systems, active systems are able to dynamically correct the unbalance.
Note: A power conditioner(also known as a line conditioner or power line conditioner) is
a device intended to improve the quality of the power that is delivered ‘dağıtm.’ to electrical
load equipment. The term most often refers to a device that acts in one or more ways to deliver a
voltage of the proper level and characteristics to enable load equipment to function properly. In
some uses, power conditioner refers to a voltage regulator with at least one other function to
improve power quality.
Plant ‘tesis’ Level Techniques




Load balancing.
Use of passive networks and static var compensator.
Equipment that is sensitive to voltage unbalance should not be connected to systems which
supply single-phase loads.
Effect of voltage unbalance on AC variable speed drives can be reduced by properly sizing
AC side and DC link reactors. *
~43~
Standart 3 phase variable frequency drive(variable speed drive).
Not: Yüzdelik voltaj dengesizliğini 3 fazlı yükler(motor, 3 fazlı doğrultucu, transformatör) için
hesapla. Voltaj olarak faz-faz arası değerler hesaplamada kullanılır. *
VOLTAGE UNBALANCE STANDARDS
Unfortunately, there are different standards regarding the appropriate limits for voltage
unbalance. The American National Standard for Electric Power Systems and Equipment ANSI
C84.1 recommends that “electric supply systems should be designed and operated to limit the
maximum voltage unbalance to 3 percent when measured at the electric-utility ‘halka elektrik
sağlayan şirket’ revenue meter ‘sayaç’ under no-load conditions.”
Pacific Gas and Electric lays out ‘düzenlem.; planlam.’ its own requirements in Rule 2, which
states that “the voltage unbalance between phases will be maintained by PG&E as close as
practicable to 2 ½ percent maximum deviation from the average voltage between the three phases.”
*
The National Equipment Manufacturers Association ‘dernek, birlik’(NEMA), which represents
‘temsil etm.’ motor and drive manufacturers, only requires motors to give rated output for 1% of
voltage unbalance per NEMA MG-1-1998. By limiting voltage unbalance to 1%, this is more
stringent ‘zorlayıcı, bağlayıcı, uyulması gereken’ than either ANSI C84.1 or utility guidelines.
Furthermore, some motor manufacturers have tried to require less than 5% current unbalance for a
valid warranty. NEMA MG-1 states that 1% of voltage unbalance can create 6-10% current
unbalance; thus, these motor manufacturers have requirements that are potentially more restrictive
‘sınırlayıcı, kısıtlayıcı’ than even NEMA MG-1.
This inconsistency ‘uyuşmama’ can create disputes ‘anlaşmazlık’ between customers, motor
manufacturers, and the utility. Careful consideration should be made in each location to the utility’s
~44~
service guidelines ‘talimatname’ versus the motor manufacturer’s guidelines, to ensure a proper
understanding of the two.
International standards as EN-50160 and IEC 1000-3-series give limits for the unbalance voltage
calculated by the ratio of sequences method up to 2% for LV and MV systems measured as 10minute values with an instantaneous maximum of 4%. More detailed standardization can be found
in IEC 61000-2-x, as a part of EMC standardization, and EN 50160 describing the voltage
characteristic at the point of common coupling(PCC).[3]
Unfortunately there is no standard for current unbalance. But by attention ‘dikkat, uyarı’ to the
NEMA MG-1 standard the maximum standard limit of current unbalance due to 3% of voltage
unbalance can be advised as 30%.
Note: Synopsis ‘özet’:
Magnitude: 0.5% - 2.5%(typical)
Duration: Steady-state
Source: Utility or facility
Symptoms: Malfunction or overheating
Occurrence: Medium
Mitigating Devices: Voltage regulators
Note: NEMA definition(LVUR): The NEMA definition of voltage unbalance[5], which is also
referred to as the Line Voltage Unbalance Rate(LVUR), is used by motor manufacturers. It
calculates unbalance using the line-to-line voltage magnitudes Vab; Vbc and Vca:
.
To comply with the NEMA MG-1[5] and ANSI C84.I[18] standards, the maximum voltage
unbalance, as defined in (2), must not exceed 3% under no-load conditions. For voltage unbalance
greater than 1%, the induction motors should be derated by an appropriate factor[5].
TECHNICAL DOCUMENT OF ‘on the impact of different voltage unbalance metrics in
distribution system optimization’
GROUND FAULT PROTECTION
A ground fault is a condition in which electrical current unintentionally flows to ground.
Because ground faults can cause damage to equipment and can endanger ‘tehlike yaratm.’ lives,
ground fault protection is required in some situations.
For example, NEC®Article 230.95 requires ground fault protection of equipment for service
disconnects rated 1000 Amps or more on solidly-grounded wye services exceeding 150 volts-toground but not exceeding 600 volts phase-to-phase. Refer to the complete article for additional
information.
Keep in mind that ground fault equipment protection must open a circuit when ground fault
current reaches 30 milliamps. In contrast, ground fault circuit interrupters designed to provide life
protection must open a circuit at 5 milliamps(plus or minus 1 milliamp). When ground fault
~45~
protection is incorporated ‘katm., dahil etm.’ into a panel board, it is generally through use of
circuit breakers with ground fault protection.
One way a ground fault protector works is with a sensor around the insulated neutral bonding
jumper. When an unbalanced current from a line-to-ground fault occurs, current will flow in the
bonding jumper. When the current reaches a set level, the shunt trip opens the circuit breaker,
removing the load from the line.
Figure 1- Ground fault sensor around bonding jumper.
Another way a ground fault protector works is with a sensor around all the circuit conductors.
When current is flowing normally, the sum of all the currents is zero. However, a ground fault
causes an imbalance of the currents flowing in the individual conductors. When the imbalance
reaches a set level, the shunt trip opens the circuit breaker, removing the load from the line.
Figure 2- Ground fault sensor around all conductors.
TECHNICAL DOCUMENT OF 'basics_of_panelboards___Siemens'
Çizelge 1- Tesislerde karşılaşılabilecek güç kalitesi sorunları.
problem
hedef
Hangi verilere ihtiyaç var?
reaktif cezalar ve yüksek elektrik
faturaları
enerji tasarrufu(Elektrik faturası
ve cezaları azaltmak.)
tek-hat şeması
~46~
sıklıkla oluşan elektrik kesintileri
Teknik problemleri çözmek.
Teknik olaylar: sürücüler, sigortalar vb.
Kablo, trafo vb. ekipmanda aşırı
ısınma(Nötr iletkeni dahil.).
Genel verimliliği arttırmak(Bakım
maliyetleri, duruşlar, işletme vb.).
Uluslararası
standartlara
uymak(IEEE, IEC, GI4/5 vb.).
son birkaç aya ait elektrik faturaları
yük tipleri ve yüklenme durumları
bilgisi
ölçümler(güç kalitesi analizörü
cihazı ile)
Çizelge 2- Elektrik ile çalışan cihazların harmonik ve yük dengesizliğinden etkilenme düzeyleri.
cihaz
harmonikler
yük dengesizliği
sekron motor
asekron motor
kontaktör
değişken hızlı sürücü
UPS ?
bilgisayar
endüksiyon ısıtıcı ?
lamba(elektronik balastlı)
kompanzasyon sistemi ?
transformatör
kesici
kablo
yüksek
yüksek
orta
orta
orta
yüksek
yok
yüksek
yüksek
orta
yüksek
yüksek
yüksek
yüksek
yok
orta
orta
yok
yok
yok
yok
orta
orta
yok
Not: Tabloda endüksiyon ısıtıcılarında harmonik yüksek, yük dengesizliği yüksek olmalı. Çünkü
bölücüler(diyot, transistör, tristör, triyak ve CMOS devreler) çoğunlukla kullanılmaktadır.
Bölücülerin var olması harmonik doğurur. Bu devrelerde harmonikler çoğunluktadır, dolayısıyla
sinüs eğrisinde normalin üzerinde bozulmalar meydana gelir ve harmonik hat safhadadır.
Tabloda kompanzasyon sistemlerinde harmonik yüksek, yazılı. Kondansatörler harmonik
üretmezler. Yüklerden gelen harmoniklerden korunmak için kondansatörlerin önlerine pasif
filtre(reaktör) bağlanır. Bu sırada da maruz kaldıkları gerilimler yükseldiği için daha yüksek
gerilimlerdeki kondansatörler seçilir(L ve C seri bağlandığından bağlantı noktasındaki kondansatör
gerilimi yükselir.). Bu sebeple kondansatörün harmonik ürettiği anlamına gelmez.
UPS'ler en çok harmonik doğuran cihazlardır. Bunun için primeri üçgen, sekonderi ise çift
sargılı yapılmalıdır(Birisi üçgen, diğeri ise yıldız sarımlı olmalı. Fazlar arası gerilimleri birbirine
eşit olmalı.).
Note: What effects do harmonics produce?
~47~
IT IS NOT ADDED TO THE OTHER TECHNICAL DOCUMENT.
Not: Günümüzde harmoniklerin oluşmasının temel nedeni, modern enerji dönüşüm teknikleri
kullanan güç elektroniği cihazlarının sayısındaki hızlı artıştır. Örneğin artık birçok uygulamada
verimlilik ve kontrol olanakları gibi nedenlerle elektrik motorları, motor sürücüler tarafından
kontrol edilmektedir. Bir güç elektroniği cihazı olan motor sürücü şebekeden harmonik içerikli
akımlar çeker. Endüstriyel tesislerde ve işmerkezlerinde en yoğun olarak karşılaşılabilecek,
harmonik içerikli akımlar çeken cihazlar şunlardır: Motor sürücüleri(hız kontrol cihazları),
kesintisiz güç kaynakları, doğrultucular(redresörler) ve akü şarj cihazları, endüksiyon ocakları,
bilgisayarlar(yarı iletken elemanların kullanıldığı cihazlar), elektronik balastlı deşarj lambaları,
frekans çeviriciler. Ayrıca fotovoltaik sistemler, anahtarlamalı güç kaynakları, HVDC sistemleri,
kaynak cihazları, ark fırınları da harmonik oluşturur(ARAŞTIRILACAK VE ÖNEMİ AZ BİLGİ).
Harmoniğe Karşı Kompanzasyon Sistemlerinde Alınan Tedbirler: Harmoniklerin çözümü için
genellikle aşağıdaki yöntemlerden biri veya birkaçı uygulanır: 1- Kompanzasyon sisteminin filtreli
kompanzasyon sistemine dönüştürülmesi. 2- Aktif harmonik filtre uygulanması. 3- 3'üncü harmonik
filtresi gibi pasif harmonik filtre uygulamaları. 4- Elektrik tesisatında yük dağılımları değiştirilerek
yapılan çalışmalar sonucunda problemin çözülmesi. 5- Harmonik üreten yüklerde yapılacak çeşitli
çalışmalar ile problemin çözülmesi.
~48~
Not: Harmonik bozulmaların sonuçları: 3 fazlı rezonans sistemlerde, aşırı nötr oluşma
olasılığının artması; tüm kablo ve donanımlarında, elektrikli makinelerde, haberleşme sistemlerinde
hatalar sonucu verimlilik kaybı yaşanması. DOSYAYA KAYIT EDİLMEDİ.
Not: Harmonik filtre harmoniklerin neden olacağı rezonansları önler.
Not: Harmoniklerin en büyük bozucu etkilerinden biri de rezonans etkisidir. Sistemin rezonansı,
harmonik frekanslardan birine yakın bir değerde oluşursa, aşırı seviyede harmonik akım ve
gerilimleri ortaya çıkaracaktır. Harmonik seviyelerini etkileyen en önemli etkenlerden biri de
rezonansın seri veya paralel rezonans durumunda olmasıdır.
Rezonans Önleyici Tedbirler: a- Motor ve kondansatörler birlikte devreye girip çıkıyorsa,
rezonans olayı tehlike oluşturmamaktadır. b- Motorun ani olarak devreden çıkması, kondansatörün
devrede kalması hâlinde rezonans akımları meydana gelmektedir. Dolayısıyla merkezi
kompanzasyon yapılmış tesislerde, motorun devreden çıkarılmasında kondansatörlerin devrede
kalmasıyla rezonans olayı meydana gelebilecektir. Enerji kesilmesinde, tekrar enerji geldiğinde
kondansatörler direkt devreye girerlerse rezonans olayı meydana gelecektir. O halde kompanzasyon
devrelerinin projelendirilmesinde, her kondansatör grubu kontaktörü, start-stop butonu ile devreye
girecek şekilde projelendirilmelidir(?). c- Kısa devre gerilim yüzdesi büyük olan trafolarda,
rezonansın etkisi büyük olur. Bu tip trafoların kullanıldığı devrelerde, kompanzasyon tesisinin
projelendirilmesinde, rezonansa engel olacak tedbirler alınmalıdır. Bu tedbirlerin en önemlisi
kondansatörlerin trafolara yakın baralara bağlanmamasıdır. Bir ek kablo ile hatta paralel kablolar ile
kondansatörler bağlanmalıdır. ç- Kompanzasyonda az kademe tercih edilmelidir.
PRACTICAL DESIGN KNOWLEDGE IN HARMONICS DISTORTION AND POWER
FACTOR CORRECTION(PFC)
Harmonics And Network Design
Nowadays, if you do not consider harmonics distortion when designing a new network, you
missed the whole point of the network design. Yes, really. The sooner you realize that harmonics
problems are on the rise, the better. Modern power networks are already pretty dirty because of
mass ‘kitle, yığın’ non-linear loads installed without any prior ‘önceki, önce’ consultation
‘danışma’ with experts or power analysis.
This technical article will shed ‘ışık tutm., dağıtm., yaym.’ some light on practical ways of
looking at the problems with harmonics distortion. It will also refresh your knowledge in the basics
of harmonics and give you some good practical tips ‘taktik; tavsiye, öğüt’ in designing, installation
and protecting PFC(power factor correction) systems and measures.
1. Harmonics Facts And Questions
1.1 What Are Harmonics?
Modern low voltage networks increasingly have loads installed that draw non-sinusoidal
currents from the power distribution system. These load currents cause voltage drops through the
system impedances which distort ‘(biçimini) bozm.’ the original sinusoidal supply voltage. Fourier
~49~
analysis can be used to separate these superposed ‘çakıştırm., üst üste koym., bindirm.’ waveforms
into the basic oscillation(supply frequency) and the individual harmonics.
The frequencies of the harmonics are integral ‘tam’ multiples of the basic oscillation and are
denoted ‘belirtm., simgelem.’ by the ordinal number ‘n’ or ‘v’(Example: Supply frequency = 50 Hz
→ 5th harmonic = 250 Hz).
Linear loads are ohmic resistances(resistance heaters, light bulbs ‘elektrik ampulü-akkor
flamanlı’, etc.), three-phase motors and capacitors, and they are not harmful to the power system.
The most problematic loads that need attention!
Non-linear loads(harmonics generators) are:
1. Transformers and chokes ‘bobin’,
2. Electronic power converters,
3. Rectifiers and converters, especially when controlling variable-speed induction motors,
4. Induction and electric arc furnaces, welding equipment,
5. Uninterruptible power supplies,
6. Single-phase switched mode power supply units for modern electronic loads such as
televisions, VCRs ‘Automatic Voltage Regulator’, computers, monitors, printers, telefax
machines, electronic ballasts, compact energy-saving lamps.
Every periodic signal with a frequency f(regardless of the waveform) consists of the sum of the
following:
1. The sine component of the frequency f, known as the fundamental component or h₁.
2. The sine components of the integral multiples of the frequency f, known as the harmonics hₙ.
3. In some cases DC components can also be present.
y₍ₜ₎= h₁₍ₜ₎+ h₃₍ₜ₎ …
Figure 1- Analysing a periodic signal into its component harmonics.
Harmonics can be divided into three categories:
1. Even harmonics(2nd, 4th, 6th, etc.)
Even harmonics(2nd, 4th, 6th, etc.) as a rule only occur due to sudden load variations or faults in
converters.
2. Odd harmonics(3rd, 5th, 7th, etc.)
Harmonics divisible by 3(3rd, 9th, 15th, etc.) occur due to asymmetrical loads and single-phase
sources of harmonics. Typical sources are office buildings, hospitals, software companies, banks,
etc., factories with 2-phase welding equipment.
The problem they cause: The harmonic currents in the neutral conductor are cumulative ‘biriken,
gittikçe artan’.
~50~
Figure 2- Cumulative effect of the 3rd harmonic current in the neutral conductor.
3. Harmonics not divisible by 3(5th, 7th, 11th, etc.)
Harmonics not divisible by 3(5th, 7th, 11th, 13th, etc.) occur due to 3-phase sources of
harmonics. 5th and 7th harmonics: from 6-pulse converters, 11th and 13th harmonics: from 12pulse converters
The problem they cause: The harmonics are transmitted via the transformer! The total harmonic
distortion, THD, is the result of the vector addition of all harmonics present and is, as a rule,
expressed as a proportion of the fundamental frequency, thus providing a quick overview ‘gözden
geçirme, genel bakış’ of network power quality.
Each harmonic can be considered as an individual system with its own phase angle! This results
in a difference between cosφ(fundamental frequency) and PF(power factor, overall harmonics).
Harmonics are generated not only in industrial installations but also increasingly in private
households ‘konut’. As a rule, the devices generating these harmonics only feed in the odd ‘tek’
orders, so that it is only the 3rd, 5th, 7th, 9th, 11th, etc. harmonics that are encountered ‘raslam.,
karşılaşm.’.
Figure 3- Network current and voltage superposed with the following harmonics: 5% of the 5th harmonic, 4% of the 7th harmonic and 2.5% of the
11th harmonic.
~51~
1.2 How Are Harmonics Produced?
Harmonics are usually produced in a commercial facility’s own low voltage network, especially
when variable speed drives are installed. They are also generated in every household: in every
television, computer and in compact energy-saving lamps with electronic ballasts.
The sheer ‘tam’ number of these loads in the evenings with the currents in phase gives rise to
high levels of harmonics in some medium voltage networks.
1.2.1 Level Of Harmonics If No PFC System Has Yet Been Installed
a) In A Facility’s Own Low-Voltage System
The level of harmonics if no PFC system has yet been installed in a facility’s own LV system
depends on the power of the installed converters and rectifiers. If, for example, a large 6-pulse
converter is installed in the network and its power rating is 50% of the transformer nominal rating,
this gives rise to about:
a- 4% of the 5th harmonics(250 Hz) and
b- 3% of the 7th harmonics(350 Hz).
It is more usual, however, for several small converters that are not linked to each other to be
installed in a network. The fact that the currents to the individual rectifiers are not all in phase
means that the resulting harmonic voltages are less than in the above case.
If, for example, several rectifiers with a combined(toplam., bir araya getirm.) power of some
25% of the transformer nominal rating are installed, this gives rise to some:
a- 1-1.5% of the 5th harmonic and
b- 0.7-1% of the 7th harmonic.
These are approximate values to help in the initial assessment ‘değerlendirme’ of whether a
detuned ‘ayarını bozm.; ayarlam.’ PFC system needs to be installed.
Figure 4- Current of a power rectifier.
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Figure 5- Line current of a converter for induction motors.
b) In The Medium Voltage Supply System
Nowadays, most of these systems are affected predominantly ‘genelde, çoğunlukla’ by the
devices in private households(mainly television sets) that produce harmonics. This is readily
‘kolayca, güçlük çekmeden’ apparent when the daily curve for the 5th harmonic is examined:
Figure 6- Average and maximum levels of the 5th harmonic as %.
The level of harmonics in the medium voltage system of a municipal ’belediyeye ait, kentsel’
power supply with industrial loads on weekdays ‘hafta içi, iş günü’. In densely ‘yoğun ölçüde’
populated ‘nüfuslandırm.’ areas in the evenings, frequencies of about 4% 250 Hz and up to 1.5%
350 Hz can be superposed on the medium voltage supply system. The higher harmonics are usually
negligible.
1.3 What Effect Does A PFC System Have On A Network With Harmonics?
A PFC system with no detuning(Figure 7) forms an oscillatory circuit with reactive line
impedances. The resonant frequency is given by a simple rule of thumb ‘başparmak’:
~53~
Figure 7- A PFC system with no detuning.
fᵣ= 50 Hz x √ (Sₖ % Qc) where:
Sₖ- short-circuit power at the point where the correction ‘düzeltme’ system is connected,
Qc- correction system capacitor power rating.
The short-circuit power Sₖ at the point where the PFC system is connected is:
a- Determined essentially by the transformer(Sₙ/uₖ),
b- Reduced by some 10% by the impedance of the medium-voltage system,
c- Possibly greatly reduced by long lengths of cable between the transformer and the PFC system.
1.3.1 Example: a- Transformer 1000 kVA, uₖ= 6%.
b- Short-circuit power of the medium voltage system 150 MVA, Sₖ≈ 12.6 MVA.
c- PFC system 400 kVAr in 8 stages ‘kademe’, no detuned.
Table 1- Capacitor power ratings and resonant frequency.
When the capacitor stages of the correction system are switched in, the network resonant
frequency(fᵣ) changes considerably ‘önemli oranda/ölçüde’ and is repeatedly close to the frequency
of a network harmonic. If the natural resonance of this oscillatory circuit is near to a network
harmonic that is present, it is to be expected that resonance will increase the harmonic voltages.
“Under certain conditions, these may be multiplied by an amount approaching ‘yaklaşm.’ the
network Q-factor(in industrial systems about 5-10!):
Figure 8- Amplification factor for harmonic voltages in PFC system without detuning in the low voltage network.
~54~
1.4 When Can Dangerous Network Resonance Occurs?
From Figure 8 above it can be seen that it is possible to assess ‘değerlendirm.’ whether
resonance problems can occur with harmonics. Simple rules suffice ‘yetm., yetişm.’ for this:
1. If the resonant frequency is:
a- 10% below/above a network harmonic, the latter will be amplified in a network with a high Qfactor(e.g. in the evenings and at night) by a factor of up to 4.
b- 20% above a network harmonic, the latter will be amplified in a network with a high Q-factor
by up to 2.5.
c- 30% above a network harmonic, the latter will be amplified only slightly, by a factor of up to
1.7.
In a network with no harmonic generator of its own, but with pronounced ‘bariz, belirgin; telafuz
edilen’ harmonics present in the medium voltage system, the following can occur:
a- At a resonance frequency below 400 Hz- resonance peaks of the 7th harmonic,
b- At a resonance frequency below 300 Hz- dangerous resonance peaks of the 5th harmonic(250
Hz).
1.5 What Effect Does The Network Configuration Have On The Problem Of Harmonics?
The network short-circuit power determines the resonant frequency and, where harmonic
generators are present in that network, the amplitude of the harmonics in the network voltage. *
a- If the network short-circuit power at the point where the PFC system is connected is too low,
this causes problems.
b- If the short-circuit power is changed radically ‘tamamen, büyük ölçüde’ due to altered
switching conditions, this causes problems.
Example of large commercial facilies
In many large commercial facilities, continuity of power supply is achieved by connecting the
low voltage distribution points via a ring circuit. This network has a high short-circuit power even
with large PFC systems and heavy rectifier loads with hardly any harmonics problems arising since
the resonant frequency is high and the harmonic currents are dissipated with low voltage drops into
the medium voltage system.
If a break is made in the ring circuit, for example for maintenance work, the short-circuit power
can decrease considerably under certain conditions, so that the resonant frequency can fall below
300 Hz!
1.6 Voltage And Current Loads On PFC Systems Without Detuning
When resonance occurs, the network r.m.s. voltage only increases slightly, but the r.m.s. value of
the capacitor current increases considerably.
In the case of resonance with the fifth harmonic, this can reach a level of, say, 15% in which
case:
1. The network r.m.s. voltage increases by 1%,
2. The crest ‘tepe’ working line voltage increases by 10-15%(depending on phase angle),
~55~
3. The r.m.s. value of the capacitor current increases by 25%!
In the case of resonance with the 11th harmonic, this can reach a level of, say, 10% in which
case:
1. The network r.m.s. voltage increases by 0.5%,
2. The peak value of the mains voltage increases by 6-10%,
3. The r.m.s. value of the capacitor current increases by 50%!
i
For this reason, a high current-carrying capacity is one of the most important quality
characteristics for a capacitor! For example, FRAKO’s capacitors can withstand an overcurrent up
to 2.7 times the rated current as a continuous load.
2. Designing For Networks With Harmonics
What must be done if resonance is possible but rather ‘oldukça’ unlikely ‘olası olmayan’? A
considerable ‘önemli’ proportion of installations being designed today fall into this category, e.g.:
1. No internal harmonic generators installed in the network, no harmonics in the medium voltage
system, but a resonant frequency below 400 Hz.
2. If changes are made in the network configuration, for example, during maintenance work, the
resonant can fall below 400 Hz. Harmonics are present in the medium voltage distribution system.
3. It is planned to build installations with rectifiers at a later date.
i
To protect an installation without detuning from the occurrence of resonance, even if this
may only happen occasionally ‘ara sıra, bazen’, it is highly advantageous to use the Mains
Monitoring Instrument. This device monitors all three phases of the power supply system shuts the
installation down if a dangerous level of harmonics is exceeded and switches it automatically in
‘devreye girm.’ again when this level falls below the critical value. Figure 9 shows an example of
FRAKO’s mains monitoring instrument, type ‘EMA 1101’.
The peak values that have occurred are stored, however, and can be retrieved ‘düzeltm.’ via the
EMA 1101 bus interface ‘arayüz’.
Figure 9- Direct connection of Mains Monitoring Instrument, type ‘EMA 1101’ by FRAKO manufacturer to low voltage system.
~56~
Figure 10- Connection of Mains Monitoring Instrument to medium-voltage system.
For distribution systems that are symmetrically loaded, the Power Factor Control Relay can also
be installed. This instrument monitors the system to detect any resonance that may occur. For
example, FRAKO’s EMR 1100 power factor control relay determines the harmonic voltages in the
measured ‘ölçm.’ phase and calculates the r.m.s. current to the capacitors. If a programmed
maximum limit is exceeded, the installation is shut down and switched in when the level falls below
its critical value.
In cases of this description, PFC systems that can be retrofitted ‘sahip olunan donanımı
yenileriyle güçlendirm.’ with detuning are often installed.
Figure 11- Power Factor Control Relay, type ‘EMR 1100’ by FRAKO manufacturer.
2.1 Planning For PFC Systems In Networks With Harmonics
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The best information on the operational characteristics of a planned PFC system is obtained by a
combination of two planning activities:
1. Measuring the harmonic voltages and currents over several days with no PFC system
installed.
2. Theoretical calculation of the network resonance characteristics.
In the measured network, the following harmonic levels are to be expected with PFC: Maximum
value of measurement without power factor correction multiplied by the resonance factor from the
network analysis.
2.1.1 Example: An average-size low voltage system with a 1000 kVA transformer. The
installation, complete with the PFC system, is connected via two 20 m long cables laid in parallel
(equivalent to the impedance of a 10 m cable). Only purely ohmic loads may be taken into account
as equipment such as induction motors have no damping effect ‘sönüm/bastırma tesiri’ on
harmonics.
i
With a 400 kVAr installation and all capacitor sections switched in, the 5th harmonic(250
Hz) is amplified by a factor of about 3. At 250 kVAr the 7th harmonic is amplified by a factor of
about 4!
During the day, with increased network damping, these factors are lower, but in the evenings and
at weekends the amplification factor for the 7th can be higher.
Figure 12- Amplification of harmonic voltages as a function of the capacitor stages switched in FRAKO – Mains Analysis.
2.2 Measures to Counteract Expected Resonances
If harmonics with high voltage levels, such as:
1. 4% of the 3rd harmonic(150 Hz)
2. 5% of the 5th harmonic(250 Hz)
3. 4% of the 7th harmonic(350 Hz)
4. 3% of the 11th harmonic(550 Hz)
5. 2.1% of the 13th harmonic(650 Hz)
due to resonance induced amplification ‘kuvvetlendirme; zayıf sinyallerin seviyesini güçlendirme’
are anticipated ‘beklem., sezm., önceden görm.’ when planning a PFC system, serious disruptions
‘boz(ul)ma’ can occur in the low voltage distribution systems with:
1. Problems with IT systems and CNC machines,
2. Damage to rectifiers and/or converters,
3. Uncontrolled tripping of a variable capacitor bank and circuit breakers,
~58~
4. The shutdown of PFC systems without detuning,
5. Voltage peaks in the distribution system,
6. Increased eddy current losses in transformers and induction motors.
If the level of individual harmonics with no PFC system amounts ‘anlamına gelm.’ to more than
1.5%(7th and higher harmonics) or 2%(5th harmonic) and the resonant frequency of the network
can be close to these harmonics, then it must be assumed that these permissible limits will be
exceeded by resonance-induced amplification. In situations of this type, only detuned PFC systems
should be used in order not to jeopardize ‘tehlikeye atm.’ the reliability of the low voltage
distribution system.
Detuning reduces the resonant frequency to a value below 250 Hz. All harmonics above the
resonant frequency of the detuned system are attenuated.
Figure 13- Damping of harmonic voltages as a function of the detuned capacitor sections.
A detuned capacitor consists of a capacitor in series with a filter reactor. Its series resonant
frequency is adjusted by the appropriate design of the filter reactor so that it is below the frequency
of the 5th harmonic(250 Hz). This combination, therefore, has an inductive characteristic for all
frequencies above the series resonant frequency.
The resonance between the capacitors and the reactive network impedances is no longer
possible. A detuned system suppresses ‘bastırm.’ some of the harmonic currents. To prevent
overloads due to the 5th harmonic still present in the network, it is a present-day practice to adjust
the resonant frequency of the detuned circuit to 189 Hz or less.
The detuned circuit is characterized either by the capacitor-choke resonant frequency(fr) or by
the relative voltage drop(p) at the choke. These two parameters are related by the following:
fᵣ= 50 Hz x √ (1/p).
Example: p = 0.07 (7%) fr= 189 Hz.
Note: Choke: In electronics, a choke is an inductor used to block higher-frequency alternating
currents while passing direct current (DC) and lower-frequencies alternating current (AC) in an
electrical circuit. A choke usually consists of a coil of insulated wire often wound on a magnetic
core, although some consist of a doughnut-shaped "bead" of ferrite material strung on a wire. The
choke's impedance increases with frequency. Its low electrical resistance passes both AC and DC
with little power loss, but its reactance limits the amount of AC passed(1). An inductor that is used
to prevent electric signals and energy from being transmitted along undesired paths or into
inappropriate parts of an electric circuit or system. Power-supply chokes prevent alternating-current
~59~
components, inherent to a power supply, from entering the electronic equipment. Radio-frequency
chokes (RFCs) prevent radio-frequency signals from entering audio-frequency circuits. The printed
circuit boards used in virtually all electronic equipment such as computers, television sets, and
high-fidelity audio systems typically have one or more chokes. The purposes of these chokes are the
(1) attenuation of spurious signals generated in the equipment itself so that these signals will not be
transmitted to other parts of the circuit or beyond the overall system to other electronic devices; (2)
prevention of undesired signals or electrical noise generated in other parts of the system from
adversely affecting circuit performance; and (3) prevention of ripple from the power supply from
degrading system behavior. Waveguide chokes keep microwave energy from being transmitted to
the wrong part of a waveguide system(2, the term in electricity).
3. Installation Of Power Factor Correction
3.1 Current Transformer Location
A current transformer is necessary to operate PFC systems. This is not included in the scope of
supply but can be provided with the system after clarification ‘açıklığa kavuşturma, belirtme’ of
user requirements. The primary current in the transformer is determined by the user’s current input,
i.e. this unit is designed for the maximum current loading or the installed load connected to the
power transformer.
i
The reactive power control relay current circuit is designed for a …/ 1 to …/5 A current
transformer with a 5 VA rating and Class 3 accuracy. If ammeters are installed in series with the
control relay, the rating of the current transformer must be increased to suit ‘uydurm.’.
Figure 14- Correctly installed current transformer registers load current and capacitor current.
~60~
Figure 15- Incorrect! The current transformer only registers the load current: the capacitor bank is switched in but no out again. The reactive power
control relay gives the message “C=0”(No capacitor current can be measured.)
If further instruments need to be powered from the same current transformer, this must be taken
into account when specifying its rating. Losses also occur in the current transformer wiring and
these must also be taken into account if there are long lengths of cable between the current
transformer and the reactive power control relay.
Power losses in copper conductors from the current transformer with a secondary current of 5 A
are displayed in Table 2.
Table 2- Power losses in copper conductors.
Note! The current transformer must be installed in one of the three phases so that the entire
current to the consumers requiring PFC and the capacitor current flow through it(as shown in
Figures 14 and 15). Terminal P1(K) is connected to the supply side, to the consumer side, terminal
P2(L) to the consumer side(?).
Caution! When the primary circuit is broken, voltage surges occur which could destroy the
current transformer. The terminals S1(k) and S2(l) must therefore be short-circuited before the
transformer circuit is broken.
3.2 Overcurrent Protection And Cables
When installation work is carried out, the regulations IEC 60364-6 and IEC 60831 the
conditions of supply of the utility company concerned ‘alakadar etm., ilgilenm.’ must be complied
with ‘uygun olm.’. IEC 60831 states that capacitor units must be suitable for continuous r.m.s.
current of 1.3 times the current that is drawn at the sinusoidal rated voltage and nominal frequency.
If the capacitance tolerance of 1.1xCₙ is also taken into account, the maximum allowable current
can reach values of up to 1.38xIₙ. This overload capability together with the high inrush current to
~61~
the capacitors must be taken into account when designing protective devices and cable crosssections.
3.3 Ingress Protection
The standard EN 60529 specifies the degree of protection for electrical enclosures by means of
two letters and a two-digit number. IP stands for ingress ‘hava girişi’ protection, while the first and
second numbers specify the protection against solid objects and liquids respectively.
Note:
Table 1. Summary of power quality variation categories.
* Note: Energy Storage Technologies refers to a variety of alternative energy storage
technologies that can be used for standby supply as part of power conditioning(e.g. superconducting
magnetic energy storage, capacitors, flywheels, batteries). TECHNICAL DOCUMENT OF
‘interpretation and analysis of power quality measurements’
Not: Harmoniklerin etkileri: Lineer olmayan bir yüke sıfır kaynak empedanslı gerilim
uygulandığında, oluşan akımın dalga şekli gerilimin dalga şeklinden farklı olacaktır. Bu bozulmuş
akım; trafo, iletkenler ve devre kesiciler gibi yalnızca yolunun üzerinde bulunan elemanları etkiler.
Ancak sıfır kaynak empedansı ideal bir durumdur. Gerçekte, bozulmuş akım kaynak empedansı
üzerinde bir gerilim düşümü meydana getirir, bu da kaynak empedansından sonraki bütün yüklere
bozulmuş bir gerilim uygulanmasına neden olur.
Akım ve gerilim harmoniklerinin güç sistemi içindeki etkilerini dört ana grup altında toplamak
mümkündür:
• Paralel ve seri rezonans dolayısıyla harmonik seviyelerinin yükselmesi,
~62~
• Elektrik üretim, iletim ve tüketiminde verimin azalması,
• Harmonikler elektrik tesislerinde yalıtımı zayıflattığı için tesis elemanlarının ömürlerinin
azalması,
• Tesislerde arızalar meydana gelmesi.
Bu grupların alt maddeleri başlıca şu gibi problemlerdir:
• Ek kayıpların oluşması ve gerilim düşümünün artması,
• Generatör ve şebeke geriliminin dalga şeklinin bozulması,
• Kondansatörlerin aşırı akıma maruz kalarak zarar görmeleri,
• Asenkron ve senkron makinelarda aşırı ısınma ve gürültülü çalışma,
• Ölçme, koruma ve kontrol sistemlerinin hatalı olarak çalışmaları,
• Rezonans olayları sebebiyle güç sistem elemanlarının aşırı akım veya aşırı gerilime maruz
kalmaları.
Not: Güç sistemlerinde harmoniklerin en önemli etkileri; a- Generatör ve şebeke gerilimin dalga
şeklinin bozulması, b- Harmonik seviyelerindeki yükselme olasılığı ile sistemde ortaya çıkabilecek
paralel ve seri rezonanslar, c- Elektrik enerjisinin üretim, iletim ve dağıtım gibi tüm kademelerinde
ek kayıpların ortaya çıkması ve dolayısıyla sistem verimliliğinin azalması, ç- Elektriksel
ekipmanların yalıtımsal özelliklerinde yaşlanmaya sebebiyet vermeleri ve kullanım ömürlerinin
kısalması ve delinme *, d- Sistem bileşen ya da ekipmanlarının arızaya uğraması, e- Gerilim
düşümünün artması, f- Toprak kısa devre akımlarının daha büyük değerlere yükselmesi, g- Temel
frekans için tasarlanmış kompanzasyon tesislerindeki kondansatörlerin harmonik frekanslarında
düşük kapasitif reaktans göstermeleri sebebiyle aşırı yüklenmeleri ve yalıtım zorlanması nedeniyle
hasar görmeleri, ğ- Koruma sistemlerinin hatalı çalışması, h- Kesintisiz güç kaynaklarının veriminin
düşmesi, ı- Aydınlatma elemanlarında, monitörlerde görüntü titreşimi meydana getirmesi, i- Temel
frekansta rezonans olayı olmadığı halde harmonik frekanslarında şebekede rezonans olaylarının
meydana gelmesi, aşırı gerilim-akımların oluşması, j- Sesli ve görüntülü iletişim araçlarının
parazitli ve anormal çalışması, k- Mikroişlemcilerin hatalı çalışması, l- Harmoniklerden
kaynaklanan gürültü nedeniyle kontrol sistemlerinin hatalı işletimi, m- Başta motor olmak üzere
diğer cihazlarda ek gürültülere neden olması, n- Harmoniklerden dolayı dalga şeklindeki
değişikliklerin elektrik sayaçlarının hatalı okumalarına sebebiyet vermeleri olarak özetlenebilir.
Not: Typical non-linear loads: 1- Uninterruptable Power Supply(UPS), 2- Induction furnaces
‘endüksiyon fırını’ and welding machines ‘kaynak makinası’, 3- AC and DC variable speed drives,
4- Battery chargers and other DC supplies, 5- LED and fluorscent lighting circuits, 6- Computers
and other devices containing uncontrolled rectifiers.
- Some typical effects of harmonics are: 1- Overheating of transformers, switchboards, cables,
and motors due to increased current flow. 2- Nuisance tripping of thermal protection devices such
as overloads and circuit breakers, 3- Poor power factor and premature ‘zamanından önce gelişen’
failure of PFC(Power Factor Correction) capacitors, 4- Failure of PLC, DCS(Distributed Control
System), computer, and other sensitive low voltage power supplies. 5- Premature ‘erken, zamansız’
failure of motors and poor motor performance.
~63~
- Harmonics in an electrical system can cause: 1- Degradation ‘bozulma’ of motors, especially
the bearings ‘mil yatağı, rulman’ and insulation= higher costs, 2- Significant reduction of the
lifespan ‘ömür’ of equipment due to excessive heat= higher costs, 3- Although you get billed
‘faturalandırm.’ for the supplied power, large percentage of that power may be unusable= higher
costs, 4- Unusual events such as flickering lights, alarms going off, or MCBs, MCCBs, RCDs and
earth leakage devices tripping for no apparent reason= more downtime ‘aksaklık süresi, çalışmama
süresi’= higher costs TECHNICAL DOCUMENT OF ‘recognizing and solving power quality
issues corrected final’
CAUSES OF VOLTAGE FLUCTUATION IN THE ELECTRIC GRID
Note: In general: Reactive power variations cause voltage variations(flicker).
Note: Voltage fluctuation: Oscillation of voltage value, amplitude modulated by a signal with
low frequency.
Voltage fluctuations are caused when loads draw currents having significant sudden or periodic
variations. The fluctuating current that is drawn from the supply causes additional voltage drops
‘gerilim düşümü’ in the power system leading to fluctuations in the supply voltage. Loads that
exhibit ‘gösterm., ortaya koym.’ continuous rapid variations are thus the most likely ‘muhtemel’
cause of voltage fluctuations.
Examples of loads that may produce voltage fluctuations in the supply include 1-Arc furnaces
‘ark fırını’, 2-Arc welders ‘kaynak makinası’, 3-Installations with frequent motor starts(air
conditioner units, fans), frequent start/stop of electric motors(for instance elevators), 4- Motor
drives with cyclic ‘periyodik’ operation(mine hoists ‘ocak vinci, maden asansörü’, rolling mills
‘hadde makinası’), 5-Equipment with excessive motor speed changes(wood chippers ‘ağaç
öğütücü’, car shredders ‘parçalama makinası’)
Often rapid fluctuations in load currents are attributed to ‘to say or think that something is the
result of a particular thing(bir olayı bir başkasına bağlam.)’ motor starting operations where the
motor current is usually between 3-5 times the rated current for a short period of time. If a number
of motors are starting at similar times, or the same motor repeatedly starts and stops, the frequency
of the voltage changes may produce flickering ‘ışık titremesi-sönüp yanma; yanıp sönen’ lighting
installations that is perceivable ‘hissedilebilir’ by the human eye. *
Note: Consequences of voltage fluctuations: 1-) The most met ‘karşılaşılan’ consequences are
common to under voltages ‘voltaj düşmesi’. 2-) Flickering of lighting and screens.
ANSI C84.1 ELECTRIC POWER SYSTEMS AND EQUIPMENT - VOLTAGE RANGES
ANSI C84.1 is the American National Standard for Electric Power Systems and Equipment –
Voltage Ratings(60 Hertz). In 1954, the first version of ANSI C84.1 was basically a combination of
the Edison Electric Institute Standard that represents utilities, and the National Electrical
Manufacturers Association ‘dernek’(NEMA). Currently, the latest version is ANSI C84.1-2011.
The standard establishes the nominal voltage ratings and operating tolerances for 60-Hz electric
power systems above 100 volts up to a maximum system voltage of 1200 kV(steady-state voltage
~64~
levels only). However, in this post, the focus will be on ANSI C84.1 Voltage Ranges. Refer to this
article for standard nominal system voltages and voltage classes: ANSI C84.1 - Voltage Ratings.
ANSI C84.1 specifies the steady-state voltage tolerances for an electrical power system. The
standard divides voltages into two ranges. Range A is the optimal voltage range. Range B is
acceptable, but not optimal ‘en uygun’.
ANSI C84.1 Voltage Ranges.
Notes:
a. The shaded ‘gölgeli’ portions of the ranges do not apply to circuits supplying lighting load.
b. The shaded portion of the range does not apply to 120 V - 600 V’s ystems.
Please take note that transient voltages(i.e. sags and surges) go beyond these limits and are
covered by other voltage standards – ITIC and CBEMA Curves.
From the figure above, the following can be deduced ‘sonuç çıkarm.’:
For 120 V - 600 V Systems
ANSI C84.1 Service Voltage Limits
Ø Range A minimum voltage is 95% of nominal voltage
Ø Range A maximum voltage is 105% of nominal voltage
Ø Range B minimum voltage is 91.7% of nominal voltage
Ø Range B maximum voltage is 105.8% of nominal voltage
ANSI C84.1 Utilization ‘kullanım, kullanma’ Voltage Limits
Ø Range A minimum voltage is 90% of nominal voltage - refer to Note (a) for limitation
Ø Range A maximum voltage is 104.2% of nominal voltage - refer to Note (b) for limitation
Ø Range B minimum voltage is 86.7% of nominal voltage - refer to Note (a) for limitation
Ø Range B maximum voltage is 105.8% of nominal voltage
~65~
For Systems Greater Than 600 V
ANSI C84.1 Service Voltage Limits
Ø Range A minimum voltage is 97.5% of nominal voltage
Ø Range A maximum voltage is 105% of nominal voltage
Ø Range B minimum voltage is 95% of nominal voltage
Ø Range B maximum voltage is 105.8% of nominal voltage
ANSI C84.1 Utilization Voltage Limits
Ø Range A minimum voltage is 90% of nominal voltage
Ø Range A maximum voltage is 105% of nominal voltage
Ø Range B minimum voltage is 86.7% of nominal voltage
Ø Range B maximum voltage is 105.8% of nominal voltage
In addition, the difference between minimum service and minimum utilization voltages is
intended to allow for voltage drop in the customer’s wiring. Moreover, this difference is greater for
service at more than 600 volts to allow for additional voltage drop in transformations between service
voltage and utilization equipment. The National Electrical Code(NEC) allows up to a 5% drop – up to
3% drop in the main feeder and an additional <3% in individual branch circuits.
Therefore, for common nominal system voltages, the recommended range as per ANSI C84.1 for
120 V - 600 V systems will be as indicated below.
ANSI C84.1-2006 Service Voltage Range.
ANSI C84.1-2006 Utilization Voltage Range.
The occurrence of service voltages outside the Range A limits should be infrequent. Range A must
be the basis for the utilization equipment’s design and rating in order to give satisfactory performance.
Range B necessarily results from ‘kaynaklanm.’ the practical design and operating conditions on supply
and/or user systems, which are part of practical operations. However, such conditions should be limited
in extent ‘kapsam’, duration and frequency. Corrective ‘düzeltici’ measures shall be undertaken within a
reasonable time to bring back voltages within Range A limits, in cases of Range B values occurrence.
~66~
Furthermore, it should be recognized that because of conditions beyond the control of the supplier
and/or user, there will be infrequent and limited periods when steady-state voltages exceed Range B
limits. Utilization equipment may not operate satisfactorily under these conditions, and protective
devices may operate to protect the utilization equipment.
Note: All test should be carried out as required in BS 7671, part 7, and an Electrical Installation
Certificate given by the contractor ‘üstenici, müteahhit’ to the person ordering the work.
Many installations now incorporate ‘katm., dahil etm., içerm.’ rcds and fault current operated
protective devices. These also must be tested using appropriate test equipment, full details of which can
be found in BS 7671 or for more elaborate ‘ayrıntılı’ apparatus ‘aygıt, cihaz’ in BS 7430 and Guidance
‘kılavuz; yol gösterme’ Notes which are published separately and amplify the requirements in the
British Standard.
The nominal voltages at present are: 1-) 230 V + 10 % and -6 %, 2-) 400 V + 10 % and -6 %.
TECHNICAL DOCUMENT OF ‘https://electrical-engineering-portal.com/erection-procedures-ofearthing-arrangements-tnc-tn-s-tnc-s-and-tt’ IT IS NOT ADDED TO THE OTHER TECHNICAL
DOCUMENT.
POWER QUALITY BASICS: VOLTAGE FLUCTUATIONS AND FLICKER ‘ışık titremesi’
Voltage fluctuations are described by IEEE as systematic variations of the voltage waveform
envelope ‘bir eğri/yüzey ailesinin her bir öğesine teğet eğri/yüzey; kiplenik dalganın en dışındaki
şekil’, or a series of random voltage changes, the magnitude of which falls between the voltage
limits set by ANSI C84.1. Generally, the variations range from 0.1% to 7% of nominal voltage with
frequencies less than 25 Hz. Subsequently ‘daha sonra, sonuç olarak’, the most important effect of
this power quality problem is the variation in the light output of various lighting sources, commonly
termed as flicker. * This is the impression of instability ‘kararsızlık; dengesizlik’ of the visual
sensation ‘his, algılama’ brought about by a light stimulus ‘uyartı’, whose luminance ‘ışıltı;
ışıklılık’ fluctuates ‘dalgalanm., inip çıkm.’ with time.
Voltage fluctuation and light flicker are technically two distinct terms, but have been
erroneously ‘hatalı bir biçimde’ referred to ‘ifade etm., bahsetm.’ the same meaning. Aggravating
‘ciddileştirme; şiddetlendirme’ the confusion ‘belirsizlik, karışıklık’ is the use of the expression
“voltage flicker”, which does not actually exist, even though it is often heard. In fact, IEEE has
cautioned ‘uyarm.’ on the incorrect usage of these terms.
~67~
Nevertheless, voltage fluctuation and flicker are closely related to each other. This is because
flicker is derived ‘kaynaklanma’ from the impact of voltage fluctuation on lighting intensity
‘yoğunluk’ due to large loads that have rapidly changing active and reactive power demand. * In
fact, voltage variations as low as 0.5% could result in perceptible ‘algılanabilir, görülebilir’ light
flicker if the frequencies are in the range of 6 to 8 Hz.
In other words, voltage fluctuation is the response of the power system to fast changing loads.
On the other hand, light flicker is the response of the lighting system to such load variations as
observed by the human eye.
Moreover ‘ayrıca, bundan başka’, international standards have been developed for characterizing
‘tanımlama’ the voltage fluctuations based on the potential effects on lighting and the human
perception of the lighting variations.
Sources and Causes
Equipment or devices that exhibit continuous, rapid load current variations(mainly in the
reactive component) can cause voltage fluctuations and light flicker. Normally, these loads have a
high rate of change of power with respect to the short-circuit capacity at the point of common
coupling. Examples of these loads include: 1-) Electric arc furnaces ‘ark fırını, ark ocağı’, 2-) Static
frequency converters, 3-) Cycloconverters ‘doğrudan frekans çevirici’, 4-) Rolling mill drives
‘hadde makinası’, 5-) Main winders ‘a person or device that winds ‘sarm.’, as an engine for hoisting
‘yukarı çekm.’ the cages ‘kafes, asansör’ in a mine shaft ‘maden kuyusu’ or a device for winding
the yarn ‘iplik’ in textile manufacture’, 6-) Large motors(starting).
Note: A cycloconveter is one such converter which converts AC power in one frequency into
AC power of an adjustable frequency.
~68~
Note: A converter is an electrical or electromechanical device purpose-built to convert specific
electrical characteristics(voltage, current, frequency) at the input to different values at the output.
Examples of converter usage:
1-) Conversion of AC voltage into DC voltage(or vice versa),
2-) Increasing or decreasing input voltage,
3-) Changing the frequency, for example from 50 Hz(Europe) to 60 Hz(USA),
4-) Driving and controlling the speed of synchronous motors,
5-) Stabilizing mains voltage(clean net),
6-) Feeding equipment that is sensitive to power fluctuations(laboratories, lightning, etc.).
Classification of converter types: We can distinguish four categories of converters, based on
source input voltage and output voltage.
1-) AC to DC converter, or ‘rectifier’,
2-) DC to AC converter, or ‘inverter’,
3-) AC to AC frequency converter, or ‘transformer’,
4-) DC to DC voltage, or ‘current converter’.
Note: In underground mining ‘madencilik’ a hoist or winder is used to raise and lower
conveyances ‘taşıma aracı’ within the mine shaft ‘maden kuyusu’.
Similarly, small power loads such as welders ‘kaynak makinası’, power regulators ‘güç
regülatörü’, boilers ‘kazan; buhar kazanı’, cranes ‘vinç’ and elevators, to name a few, may cause
voltage fluctuation and flicker depending on the electrical system where they are connected.
Other causes include, but not limited to the following ‘aşağıdaki’:
1-) Capacitors switching, transformer on-load tap ‘ara bağlantı’ changers(OLTC), step voltage
regulators and other devices that alter the inductive component of the source impedance.
2-) Variations in generation capacity, particularly intermittent ‘kesik kesik, aralıklı’ types(e.g.
wind turbines).
3-) Low frequency voltage interharmonics.
Furthermore, loose connections may also result to voltage fluctuations and flicker. Lightly
loaded loose connections may cause flickers for longer periods as compared to heavily loaded ones
that quickly burn out.
Note: On-Load Tap-Changing Transformer: The transformer which is not disconnected from the
main supply when the tap setting is to be changed such type of transformer in known as on-load tap
changing transformer. The tap setting arrangement is mainly used for changing the turn ratio of the
transformer to regulate the system voltage while the transformer is delivering the load. The main
~69~
feature of an on-load tap changer is that during its operation the main circuit of the switch should
not be opened. Thus, no part of the switch should get the short circuit.
It is a normal fact that increase in load leads to decrease in the supply voltage. Hence the voltage
supplied by the transformer to the load must be maintained within the prescribed limits. This can be
done by changing the transformer turns ratio. *
The taps are leads or connections provided at various points on the winding. The turns ratio
differ from one tap to another and hence different voltages can be obtained at each tap.
Effects
Flicker is considered the most significant effect of voltage fluctuation because it can affect the
production environment by causing personel fatigue ‘yorgunluk’ and lower work concentration
levels. In addition, voltage fluctuations may subject electrical and electronic equipment to
detrimental ‘hasara neden olan’ effects that may disrupt ‘bozm.’ production processes with
considerable ‘hatırı sayılır derecede, önemli’ financial costs.
Other effects of voltage fluctuation include the following: 1-) Nuisance tripping due to
misoperation ‘hatalı çalışma’ of relays and contactors. 2-) Unwanted triggering of UPS units to
switch to battery mode. 3-) Problems with some sensitive electronic equipment, which require a
constant voltage(i.e. medical laboratories).
Synopsis:







Magnitude: 0.1% to 7%(typical).
Spectral Content ‘içerik’: Less than 25 Hz.
Duration: Intermittent.
Source: Loads that exhibit continuous, rapid variations in load current magnitude.
Symptoms: Light flicker and malfunction of electrical equipment and devices.
Occurrence: Low to medium.
Mitigation Devices: Series Capacitors, Static Var Compensators, STATCOMs.
Measurements
Presently, the basic parameters that determine voltage fluctuations are the short-term flicker
severity ‘derece’(PST) and long-term flicker severity(PLT) index. These factors refer to voltage
fluctuation effects on lighting and their influence on humans.
Flicker measurements are primarily ‘esas olarak’ performed to evaluate the supply quality by
comparing the existing flicker level at the measurement point to the published standard limits. The
second is to gauge ‘ölçm.’ the emission ‘dışarı verme, emisyon’ levels of equipment before it is
introduced to the market - a type test for certification purposes.
The IEC flickermeter is the standard for measuring light flicker. Recently, IEEE has adopted
‘kabul etm.’ the flickermeter method after making necessary modifications for the IEC standard to
become applicable to the 120 V electrical systems in the US. Today, many monitoring equipment
manufacturers have already implemented the flickermeter design specified in IEC 61000-4-15 and
IEEE 1453-2004.
~70~
ABOUT THE VOLTAGE SAGS 'A momentary drop in voltage from the power source.' DUE TO
THE SHORT CIRCUITED FAULT
Introduction: The classical disruptions ‘boz(ul)ma’ present in the distribution network and inside
the industrial plants, the influx ‘kitlesel akın’ of digital computers and other types of electronic
controls used by industries to achieve maximum productivity, the increase of the power based on
renewable energy and the reduced redundancy ‘fazlalık’ in lines and substations, has a negative
impact over the medium and low voltage distribution network power quality, as well as in the
industrial customer installations.
To improve power quality in both voltage levels, at least for those customers that work with
processes ‘süreç’ susceptible to ‘-e açık, -e hassas’ voltage sags and short interruptions, the market
offers at present a wide range of products, based on the traditional technology improvement or in
the use of techniques of conversion with power semiconductors. However, in the future,
economically more attractive solutions will be required ‘gereksinm.’ to face up to ‘karşı koym.’ a
competitive and unregulated electric market. Information Technologies will play an essential role
on this new scene.
TECHNICAL DOCUMENT OF ‘technical methods for the prevention and correction of voltage
sags and short interruptions inside the industrial plants and in the distribution networks’
Sources of Sags and Short Interruptions: Power systems have non-zero impedances, so every
increase in current causes a corresponding reduction in voltage. Usually, these reductions are small
enough that the voltage remains within normal tolerances. But when there is a large increase in
current, or when the system impedance is high, the voltage can drop significantly. * So
conceptually 'in a way that relates to ideas or principles', there are two sources of voltage sags: 1)
Large increases in current. 2) Increases in system impedance.
As a practical matter ‘pratik anlamda’, most voltage sags are caused by increases in current.
It is possible to think of the power system as a tree, with the customer sensitive load connected
to one of the twigs 'ağaç dalı'. Any voltage sag on the trunk 'gövde' of the tree, or on a branch
leading out 'dışarı çıkarm.; lead to sth: to have sth as a result' to the customer twig, will cause a
voltage sag at its load. But a short-circuit out 'uzakta' on a distant branch can cause the trunk voltage
to diminish 'azalm.', so even faults in a distant part of the tree can cause a sag at customer load.
The cause of most voltage sags is a short-circuit fault occurring either within the industrial
facility 'tesis' under consideration' üzerinde düşünülen' or on the utility system. The magnitude of
the voltage sag is mainly determined by the impedance between the faulted bus and the load, and by
the method of connection of the transformer windings. The voltage sag lasts only as long as it takes
the protective device to clear the over current condition(typically up to 10 cycles), therefore the
duration of the sag is determined by the fault-clearing time of that protection system adopted
'kullanm.'. Moreover, if automatic reclosure 'the act of closing(something that was opened) again' is
used by the utility, the voltage sag condition can ocur repeatedly in the case of a permanent fault.
Finally, depending on its magnitude and duration, the sag can cause an equipment trip, thus
becoming a power quality problem.
The most common causes of facility ‘tesis’-sourced voltage sags are: 1) Starting a large load,
such as a motor or resistive heater. 2) Loose or defective wiring, such as insufficiently tightened
~71~
box screws ‘vida’ on power conductors. 3) Faults or short circuits elsewhere ‘başka yerde’ in the
facility(trees, animals, adverse weather such as wind or lightning).
Voltage sags can also originate on the utility's electric power system. The most common types of
utility-sourced voltage sags are: 1) Faults on distant ‘uzak; belirsiz’ circuits, which cause a
corresponding ‘karşılık gelm.’ reduction in voltage on your circuit. 2) Voltage regulator failures(far
less common).
Note: Voltage Sags: A decrease of the normal voltage level between 10 and 90% of the
nominal rms voltage at the power frequency, for durations of 0,5 cycle to 1 minute.
Causes: • Faults on the transmission or distribution network. • Faults in consumer’s installation.
• Connection of heavy loads and start-up of large motors.
Consequences: • Malfunction of microprocessor-based control systems(PCs, PLCs, ASDs, etc)
that may lead to a process ‘süreç’ stoppage. • Tripping of contactors and electromechanical relays. •
Disconnection ‘(devrenin) açılması’ and loss of efficiency in electric rotating machines.
TECHNICAL DOCUMENT OF ‘power quality problems and new solutions’
CAUSES, CONCERNS AND REMEDIATION ‘düzeltme, iyileştirme’ OF STRAY
VOLTAGES ON DISTRIBUTION SYSTEMS
Definition of stray voltage: Stray voltage is the occurrence of electrical potential between two
objects that ideally should not have any voltage difference between them. Small voltages are often
measured between two grounded objects in distant ‘uzakta, mesafeli’ locations, due to normal
current flow in the power system. Large voltages can appear on the enclosures of electrical
equipment due to a fault in the electrical power system, such as a failure of insulation.
Nuisance ‘sıkı verenşey/kimse, baş belası’ shocking — the unpleasant sensation ‘duygu, his’ that
a person or animal can experience when they inadvertently ‘dikkatsizlik sonucu, kasıtlı olmayarak’
get between an electrically energized point and ground — can be something of a mystery. Stories
are told of cows that won't give milk, dogs that avoid metallic grates ‘ızgara’ and manhole covers,
and folks ‘halk’getting an unusual “wake-up call” when they step into their hot tub ‘banyo kuveti’or
~72~
backyard ‘avlu’ pool. However, despite the esoteric ‘olağandışı, anlaşılması zor’ nature of nuisance
shocking, the science necessary for understanding it — and mitigating ‘hafifle(t)m., azal(t)m.’ it —
has advanced ‘ilerle(t)m.’ significantly in recent years. Also, the various mechanisms that can lead
to nuisance shocking are now better recognized. This article provides insights ‘anlayış, kavrama’ on
the utility distribution system aspects ‘bakış açısı’ of nuisance shocking, first defining the sources
of these voltages and then discussion of both traditional and new techniques for mitigating the
problem once it has been identified ‘tespit etm.’.
Understanding Stray Voltage
To make sense of this sometimes-vague ‘belirsiz, anlaşılmaz’ electrical phenomenon,
investigators use the following four terms for describing the sources of nuisance shocking: remote
earth, neutral-to-earth voltage, metallic-object-to-earth voltage and stray voltage.
Each of these terms is defined in the following paragraphs, along with some insight ‘anlama,
kavrayış’ into their most common causes. With an understanding of the terminology and what
causes each condition, useful mitigation ‘azaltma’ techniques can be discussed.
Remote earth is defined as an earthing or grounding point that is at the same voltage potential as
other points on the earth in the surrounding ‘çevrelem., kuşatm.’ area. Electrical current flowing
through grounding or neutral conductors, or even through earth itself, will cause voltage variation
from point to point. The remote earth point is hypothetically ‘varsayımlı olarak’ “beyond” or
outside of the influence of these current paths. Thus, the remote earth point is at zero potential with
respect to the voltage source and provides a consistent ‘sürekli, kalıcı’ and repeatable reference
point. *
Neutral-to-earth voltage(NEV) is a measure of the voltage potential between a neutral-to-ground
bonding point and a remote earth point. In essence ‘aslında’, any time current is flowing through a
neutral conductor, there will be a voltage potential with respect to the earth. This voltage potential
can be metallically ‘metalik olarak’ transmitted over to a remote earth point through code-required
grounding and bonding of waterpipes, neutrals and other metallic objects. * It is important to note
that NEV is a normal occurrence caused by the intentional grounding of the power system.
Metallic-object-to-earth voltage(MOEV) is caused by an accidental or unintentional energization
‘enerjileme’ of a metallic object. The most common scenario for MOEV occurs when an energized
electrical conductor comes in direct contact with a metallic object, such as a street lamp ‘sokak
lambası’, service box, manhole cover ‘menhol kapağı’ or virtually any type of metallic object,
thereby energizing the object as well. MOEV potentials to remote earth can range anywhere from
just a few volts to 120 V or more, depending on the source. * MOEV can also ocur when a pipeline
‘boru hattı’ or other insulated metallic object is close enough to an electric field from a power line
to receive an induced voltage from that electric field. *
Stray voltage from intentional ‘tasarlanmış; isteyerek yapılan’ actions. The U.S. Department of
Agriculture Publication 696 defines stray voltage as “A small voltage(less than 10 V) that can
develop between two possible contact points.” Contact points are generally considered to be points
close enough between the voltage source and a remote earth path that would allow a current to flow
through any human, animal or other object that contacts both points simultaneously. Another
important note about Publication 696 is that the document summary states: “While stray voltage
cannot totally be eliminated, it can certainly be reduced to an acceptable level.” While this
~73~
definition focuses primarily ‘aslında, öncelikle’ on NEV sources, which result from the intentional
grounding of the power system neutral conductor, many cases have been identified ‘belirlem,
belirtm.’ where improper wiring and load faults on the customer side of the meter ‘ölçme aygıtı,
sayaç’ contribute ‘katkı yapm., katkıda bulunm.’ to the measured voltages.
Stray voltage from unintentional actions. The New York Public Utility Commission uses the
term “stray voltage” to describe the unintentional or accidental energization of manhole covers,
street lamps and other urban street-level metallic objects. This definition focuses on MOEV sources
such as contact with the power system phase conductor, or in some cases as the result of induced
voltages from electric fields. *
While the previous two definitions have created some confusion ‘kafa karışıklığı’, the common
element is that stray voltage could be considered an undesirable voltage potential across any two
points that can be simultaneously contacted by an animal or a human. In summary, to develop a
stray voltage we can consider the following sources: 1) currents flowing on primary and secondary
neutral conductors; 2) faulted-phase conductors; and 3) induced voltages from currents flowing
through power lines. *
Remediation
There is a distinct difference between the causes of an elevated NEV concern and the causes of
an energized metallic object concern. For energized metallic objects, there are obviously no
mitigation techniques, as the objective is to identify and isolate the problem and remove or repair
the source of the energization. Research is presently underway ‘başlanmış, yolunda, yapım
aşamasında’ in this area to develop consistent ‘uygun, kalıcı, tutarlı’ and repeatable measurement
protocols to determine where energized objects are present so monitoring and protection devices
can detect the problem using new diagnostic ‘hata bulma, teshis’ instruments such as pen lights and
electric field detectors.
For higher-than-acceptable NEV, the mitigation solutions are well understood but can be
challenging ‘zorlu’ to ascertain ‘doğrusunu bulm., saptam.’. Each method has its proven success
stories as well as potential shortcomings ‘noksanlık’. Traditional mitigation techniques include:
load balancing, resizing neutral conductors, isolation, improved grounding techniques and
equipotential planes ‘düzey; seviye’. *
Load balancing. On three-phase, grounded-wye ‘yıldız noktası topraklanmış’ distribution
systems with equally balanced 60-Hz phase currents, the net neutral current should be zero. That is,
the neutral current from the three phases effectively cancels out ‘etkisini yok etm.’. Unfortunately,
in the real world, perfect balancing can be upset by many factors such as phase shift, load unbalance
and harmonic currents. * These phenomena can cause current to flow in the neutral conductor and
into the ground rod ‘çubuk’ at each of the neutral-to-ground bonding points, which creates a
proportional ‘orantılı’ NEV. Balancing the phase currents can reduce the 60-Hz component of NEV
across the entire distribution system. * Load balancing at a customer's facility can also reduce NEV,
but only at their location.
Resizing neutral conductors. Currents returning on grounded-wye power systems cause a voltage
drop across the impedance of the neutral conductor. * Because the neutral conductor is grounded,
the impedance of the earth return path in parallel with the impedance of the neutral return path
dictates ‘belirlem.’ the percentage of earth current and the corresponding ‘ilişkin, karşılığı olan’
~74~
NEV at that neutral-grounding point. A very simplified way to look at this is to examine a circuit
with a current source(neutral return current) and two current paths(neutral path and earth path). All
else being equal, current will follow all return paths in proportion to ‘ile orantılı olarak’ the
conducting path impedances. Therefore, reducing the impedance of the neutral effectively reduces
the amount of current flowing through the earth path and lowers corresponding NEV at that neutralto-ground bonding point. *
Isolation. A simple and effective means of keeping stray voltage from getting to animal and
human contact points would be to not jumper the primary and secondary neutral conductors at the
service transformer. * If there is no metallic connection, there can be no voltage and no opportunity
for current flow from the primary neutral. The key considerations in removing the primary to
secondary neutral jumper would be the adverse effect on protection of the load-side of the
transformer in the event of a lightning strike, system fault or wiring error(?). Therefore, isolation is
best accomplished through the use of a separate isolation transformer or use of neutral isolation
products that allow voltages greater than 10 V to be equalized ‘eşitlem., dengelem.’ via low-voltage
clamping devices. *
Improved grounding techniques. In terms of NEV and corresponding stray voltages, it is
generally accepted that reducing the impedance of all current return paths — neutral or to earth —
can reduce voltage levels. * From the stand point of ‘yönünden, … açısından bakıldığında’ reducing
the voltage at remote earth, any impedance reduction will provide a corresponding reduction in
NEV because of a reduced voltage drop, given the same currents.
Equipotential planes. Similar to the ground-reference structures ‘yapı’ used for computer rooms
and the ground mats ‘hasır’ that minimize step potentials at utility substations, the equipotential
plane is a useful means of minimizing nuisance shocking at animal contact points. An equipotential
plane typically consists of a conductive wire mesh ‘ağ, şebeke, ağ gözü’ installed under the area
where nuisance shocking has been reported, and attaching ‘bağlam.’ most(if not all) conductive
materials in the area directly to the mesh. * The technique does not reduce NEV levels, but rather
‘daha ziyade, daha doğrusu, daha çok’ moves the problem away from areas where animals are
likely ‘muhtemel’ to insert themselves into the conducting path. *
Innovative ‘yenilikçi, yaratıcı’ Mitigation Techniques
While the traditional mitigation techniques discussed above have been successfully and
consistently ‘sürekli, düzenli olarak’ applied in specific applications, two experimental techniques
are note worthy ‘önemli, mühim, takdire değer’. These include distribution level harmonic filters
and insulated five-wire distribution systems. *
Passive harmonic filters A recent area of research into NEV concern relates to triple ‘üçün katı’
harmonic currents flowing on distribution system neutral conductors. These odd ‘tek(sayı)’
multiples ‘birçok’ of the fundamental 60-Hz current add instead of canceling out ‘etkisini yok etm.’
on the neutral conductor, thereby creating harmonic NEV levels. * The causes of these harmonic
currents include harmonic generating equipment owned by the end user and circuit resonances
created by distributed capacitor banks. * Harmonics due to customer loads is expected to increase
over time as more equipment such as variable frequency drivewashers ‘yıkama makinası, yıkama
ünitesi’ and air conditioning equipment proliferate ‘çoğalm.’ and as more televisions, PCs and other
home entertainment equipment use increases.
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While filters for harmonic load mitigation is not necessarily a new concept, applying passive
harmonic filters to mitigate NEV impacts on the entire utility distribution circuit is new. In under an
ongoing ‘sürmekte olan’ research project, EPRI is working with some U.S. electric utilities to
determine how well filters tuned to the third harmonic reduce NEV levels on circuits where the
neutral-to-earth voltages have been found to be nearly all harmonic in makeup ‘tertip; yapılış’ (?).
The approach used is to convert ‘dönüş(tür)m.’existing distribution capacitor banks to filter banks
by employing a combination of capacitors and one or more inductors. * Modeling results
demonstrate up to a fivefold ‘beş katı, beş misli’ improvement with installation of harmonic filters
in conjunction with ‘ile birlikte, bağlantılı olarak’ grounding modifications ‘değiş(tir)me’.
Harmonic filters appear to be a promising ‘umut verici’ way to reduce NEV impacts on the entire
utility distribution circuit instead of at the traditional single point of interest.
Five-Wire Distribution System
The so-called “five-wire design” is a concept that has been demonstrated to evaluate the
potential to reduce stray voltages and magnetic fields and also make high impedance faults more
easily detectable. * The first four wires of this system are the familiar three-phase conductors plus a
neutral. The fifth wire is a new isolated neutral that carries all of the unbalanced return current,
relieving ‘rahatlatm.’ the original neutral of this burden ‘yük, sorumluluk’. * The multigrounded
ground wire continues to perform the safety functions associated with a multigrounded system. The
five-wire system was tested by EPRI at New York State Electric and Gas(NYSEG), which
converted a section of a circuit in Cooperstown, New York, U.S., to a five-wire configuration.
Benefits included reductions in stray voltages and magnetic fields along with promising ‘gösterm.’
results that high-impedance faults could be detected. Drawbacks ‘dezavantaj, eksiklik’ included
lack of ability to convert underground ‘yer altı, metro’ systems to the five-wire topology, concerns
that an open neutral would cause over voltages for customer and utility system equipment, and the
inability to control stray voltage unless the entire circuit is converted over to the five-wire design. *
Ongoing ‘sürmekte olan’ Stray Voltage Research
Although utilities, the government and research organizations have accomplished much to
minimize undesirable voltages with respect to ‘-e göre, -e ilişkin’ remote earth, additional research
and development will promote ‘desteklem., ilerletm.’ a better understanding of the effects of stray
voltages and the methods to minimize these phenomena. To help further this research and to supply
credible ‘güvenilir’ and unbiased ‘tarafsız’ information on the subject, EPRI has identified a
number of different concerns and topics of interest to include:
 Animal contact areas' health and productivity ‘iş verimi, verimlilik’ concerns
 Residential ‘yerleşim yeri’ contact concerns for swimming pools, hottubs ‘sıcak su havuzu’
and metallic objects
 Power-circuit resonance and harmonic conditions creating magnified ‘büyütm.;
şiddetlendirm.’ stray-voltage potentials
 Voltages induced onto insulated metallic pipelines
 Metallic pipe corrosion
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Questions regarding impacts of power-line-carrier ‘yüksek gerilim iletkeni, enerji hattı
taşıyıcısı’ communication technologies
 Proper specification ‘şartname’ of measurement equipment, measurement protocols and
measurement durations
 Harmonic neutral-current interference with telecommunication circuits and railroad-crossing
‘demiryolu geçidi’ signals
 Modeling and simulation challenges for complete distribution circuits
 Contributions of transmission lines to elevated ‘yüksek, yükseltilmiş’ NEV levels at human
and animal contact areas
 Understanding of comparative ‘karşılaştırmalı’ costs and benefit of various mitigation
techniques
 The energization of metallic objects in urban ‘şehre ait’ areas
 Impacts of nonlinear voltage waveforms and voltage magnitudes on humans and animals
 Better understanding of the voltage levels that warrant ‘garanti etm.’ investigation and
remediation.
Of these concerns, the majority can be distilled ‘özetlem.’ down into four areas of research
related to:
 Measurement devices and measurement protocols
 Modeling and simulation guidelines ‘yönerge, kural’
 Testing and demonstration of mitigation technologies
 Regulatory ‘mevzuata ilişkin’ information and support.
Work at EPRI is presently ongoing in each of these areas to supplement and support the needs of
utilities and end users. The largest challenges to date are not in understanding the issues but in
prioritizing ‘öncelik verme’ the concerns and funding ‘kaynak yaratma’ the research. Stray-voltage
issues are analogous ‘benzer’ to power-quality-related concerns ‘sorun; kaygı’ in that when
problems are identified, limited resources are applied to investigate and resolve the concerns. The
IEEE has started a working group under the power engineering society ‘topluluk’ that will be
focused on instrumentation ‘araçların/aletlerin geliştirilmesi ve bilimsel, teknik ve askerî alanlarda
etkili bir şekilde kullanılması ile uğraşan mühendislik dalı’ and measurement protocols to
standardize efforts in these areas.

AUTO RECLOSING SCHEME OF TRANSMISSION SYSTEM
The extra high voltage transmission lines transmit huge amount of electric power. Hence, it is
always desirable that the continuation of power flow through the lines should not be interrupted for
a long time. There may be a temporary or permanent fault in the lines. Temporary faults get
automatically cleared, and these do not require any attempt for fault rectification 'düzeltme'. It is
normal practice by the operators that after each initial faulty tripping of the line, they close the line.
If the fault is transient 'kısa süreli', the line holds ‘devam etm.’ after the second attempt of
closing the circuit breaker, but if the fault persists 'kalm., sürm., devamlı olm.', the protection
system again trips the line and then it is declared 'açıklam.' as permanent fault.
But as the extra high voltage transmission lines carry huge power, if any delay occurs due to
manual operation for reclosing the circuit, there will be a big loss of system in the view of cost and
stability. By introducing the auto reclosing scheme in the extra high voltage transmission systems,
~77~
we can avoid the unwanted delay due to human operation. We categorize the faults in electrical
transmission system in three ways,
1. Transient Fault
2. Semi-permanent 'yarı sürekli, az sürekli' Fault
3. Permanent Fault
The transient faults are those which automatically removed momentarily. Semi-permanent faults
are also transient in nature but there take few moments to remove. Semi-permanent faults may get
occurred due to the falling of things on the live conductors. Semi-permanent faults get removed
after the cause of faults is burnt away 'yok etm.'. During both of the above mentioned faults, line is
tripped but the line can be restored if the circuit breakers associated with ‘ile ilişkili’ the line are
closed.
Auto-recloser or auto-reclosing scheme exactly does this. In an overhead 'havai' transmission
system, 80% of the faults are transient, and 12% of faults are semi-permanent. In auto-reclosing
scheme if the fault is not cleared at first attempt, there will be double or triple shorts 'kısa devre' of
reclosing until the fault is cleared. It the fault still persists, this scheme permanently opens the
circuit breaker. A prescribed time delay may be imposed 'empose etm., yüklem., zorla benimsetm.'
on the auto-reclosing system to permit the semi-permanent fault to remove from the circuit.
SHUNT REACTORS AND THEIR APPLICATIONS
A shunt reactor is an absorber of reactive power, thus increasing the energy efficiency of the
system. It is the most compact device commonly used for reactive power compensation ‘karşılama;
dengeleme’ in long high-voltage transmission lines and in cable systems. The shunt reactor can be
directly connected to the power line or to a tertiary ‘üçüncü, üçüncü sırada-safhada olan’ winding
‘sargı, bobin’ of a three-winding transformer.
Shunt reactors can be an oil-immersed ‘yağa batırılmış’ type with a conservator‘koruyucu’ or a dry type.
The shunt reactor could be permanently connected or switched via a circuit breaker. To improve
the adjustment of the consumed reactive power the reactor can also have a variable rating. If the
load variation is slow, which it normally is(seasonal, daily or hourly), a variable shunt reactor(VSR)
could be an economical solution for some customer applications.
Shunt reactors are used to compensate for large line charging capacitance of long high voltage
power transmission lines and cables. Their major applications are:
1-) Preventing overvoltages that ocur when the line is lightly loaded(Ferranti Effect). *
2-)Providing voltage control.
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3-) Compensating for line charging reactive power demand of the open-circuit line.
4-) Suppressing ‘zorla durdurm.’ the secondary arc current for successful single pole reclosing
‘yeniden kapatm.’.
Shunt reactors increase the energy efficiency of power transmission systems by improving
power quality and reducing transmission costs.
Why shunt reactors? Shunt reactors are the most compact and cost-efficient way to compensate
for reactive power generation in long high-voltage power transmission lines and in cable systems.
They can be permanently used in service ‘kullanımda, faaliyette’ to stabilize ‘dengelem.’ power
transmission, or switched in ‘devreye girm.’ under light-load conditions for voltage control only.
Increasing energy efficiency in overhead lines. Over long transmission lines, reactive power is
generated as an effect of the capacitance between the lines and earth. * The reactive power cannot
be used for any application and should be balanced to reduce energy losses. Shunt reactors absorb
the reactive power, thus increasing the energy efficiency of the system.
Improving ‘ilerle(t)m., geliş(tir)m.’ voltage stability at low load. At low loads, the voltage
increases along the transmission line. A shunt reactor reduces the voltage increase, keeps the
voltage within the desired limits, and contributes to the voltage stability of the system.
Time-varying load conditions. Transmission systems are subject to daily or seasonal load
variations. Variable shunt reactors allow customers to continuously adjust the compensation, as
loads vary over time. They makes witching in and out of fixed-rating reactors unnecessary, which
eliminates harmful voltage steps.The variable reactor can always be adopted ‘kabul etm.; seçm.;
benimsem.’ to the need, both in today’s operation and in the future grid. In addition, variable shunt
reactors can interact with ‘etkileşimde bulunm.’ other systems such as SVC and HVDC links in
order to optimize the system operation. Variable shunt reactors are therefore economical means
‘vasıta, yol, yöntem’ to improve voltage stability and power quality under time-varying load
conditions.
Cables and renewable energy sources are becoming increasingly common in energy systems.
However, in both cases, reactive power or unpredictable active power generation are negative side
effects. Shunt reactors are playing an increasingly important role to compensate for these variations.
Long transmission lines. Shunt reactors are the most compact and cost-efficient 'masrafsız'
means of compensating for reactive power generation in long transmission lines. Placed
permanently in service to stabilize power transmission, or switched in under light-load conditions
for voltage control only, shunt reactors combine high efficiency and low life cycle costs to cut
transmission costs. Shunt reactors increase energy efficiency and power quality in both new and
existing transmission lines.
Cable systems. The increased use of cables is driven by environmental concerns such as the
development of offshore 'kıyıdan deniz yönünde açıkta bulunan' wind parks and the difficulty in
obtaining the right of way for new overhead lines. Energy trading 'ticaret' and the need for efficient
use of generation and reserves 'kaynak, rezerv' between countries drive the demand for
interconnections ‘ara bağlantı’, sometimes using AC sea cables. However, cables generate more
reactive power than over headlines, which makes shunt reactors even more important for
transmitting active power in the grid. *
Renewable energy sources. Wind power and solar energy are a growing part of the energy mix in
many countries. Compared to conventional large power generation, renewable energy sources
generate unpredictable and fluctuating active power.
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Variable shunt reactors provide an attractive solution to compensate for these variations.
Auxiliary power in remote areas. By adding a secondary winding, shunt reactors can be used to
supply several MVA of power in remotely located substations. These specially designed shunt
reactors can also be used to supply power to remote villages 'köy, küçük belediye' located close to
the substation 'trafo merkezi', without the need for a high voltage stepdown transformer ‘indirici
trafo’.
Flexible spare in larger networks. A variable shunt reactor(VSR) can be used as a flexible
‘bükülebilir; kolayca değiş(tiril)ebilir, uyumlu’ spare 'yedek parça', positioned 'yerleştirm.' on
different locations along larger transmission networks.
Typical example of a shunt reactor is given in figure above.
Not: Reaktör: İndüktör.
Not: Faz farkı neden oluşur? Resistif saf direnç elektrik devrelerinde gerilim ve akım aynı
fazdadır ve reaktif güç oluşmaz. Elektrik devresi tam verimli güç kullanımı ile çalışır. Faz farkı
oluşmasına neden olan sistemler kapasitif devreye sahip olan sistemler ve endüktif devrelere sahip
olan sistemlerdir.
Kapasitif devrelerde akım fazı gerilim fazından ileride hareket eder. Endüktif devrelerde gerilim
fazı akım fazından ileride hareket eder. Kapasitif ve endüktif devrelerde oluşan bu faz farkı enerji
kullanımında verimsizlik oluşturur.
ENERGY EFFICIENCY IN BUILDING
IEEE 519—1992 addresses even ‘çift’ harmonics by limiting them to 25% of the limits for
the odd orders ‘düzen’ within the same range. Even harmonics result in an asymmetrical current
wave which may contain a dc component that will saturate magnetic cores ‘çekirdek, nüve’.

~80~

The permissible limits for the various parameters are neutral current: 8—10% of the RMS
current and neutral voltage: 2V
 As per IEEE 519 standards, the recommended limits of harmonics are:
Current harmonics: 8% THD, Voltage harmonics: 5% THD
Unbalance: Current unbalance: 5%, Voltage unbalance: 4%

Power factor should be maintained ‘sürdürm., korum. devam ettirm.’ close to unity ‘bir’ via
capacitor banks so that current losses in cables and panels are reduced and there is no penalty ’para
cezası’ from the electricity board.
CREST FACTOR(Harmonic distortion indicators)
In a periodically-varying function, such as that of AC, the ratio of the peak amplitude to the
RMS amplitude. Also known as amplitude factor or peak factor. For a sinusoidal signal, the crest
factor is therefore equal to √2. For a non-sinusoidal signal, the crest factor can be either greater
than or less than√2.
The crest fact or for the current drawn by non-linear loads is commonly much higher than √2. It
is generally between 1.5 and 2 and can even reach 5 in critical cases.
A high crest factor signals high current peaks which, when detected by protection devices, can
cause nuisance tripping.
Examples: Figure M7 represents the current absorbed by a compact fluorescent lamp.
Ir.m.s. = 0.16A, IM= 0.6A, THDi= 145%, Crest factor = 3.75
Fig. M7: Typical current waveform of a compact fluorescent lamp.
Figure M8 represents the voltage supplying non-linear loads through a high impedance line, with
a typical "flat top" distorted waveform. Flat top: Tepesi düz.
Vr.m.s.= 500V, VM= 670V, THDu= 6.2%, Crestfactor = 1.34
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Fig. M8: Typical voltage waveform in case of high impedance line supplying non-linear loads.
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