Iraq Kurd Substation
Management Program
Performance Substation
Management 3-Substation
Equipment Specification
(Equipment Specification, Associated System
Design and Tests)
April , 2015
Sang Jin Chung
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Contents
Ⅰ. Specifications for Substation Equipments
Ⅱ. Associated System in Substation
Ⅲ. Tests– Type test, FAT, Site test, etc.
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Ⅰ. Specifications for Substation Equipments
Functions of Substation Equipment
Equipment
Function
1. Bus-Bar
Incoming & outgoing ckts. Connected to bus-bar
2. Circuit Breaker
Automatic switching during normal or abnormal
conditions
3. Isolators
Disconnection under no-load condition for safety,
isolation and maintenance.
4. Earthing switch To discharge the voltage on dead lines to earth
5. Current
Transformer
To step-down currents for measurement, control &
protection
6. Voltage
Transformer
To step-down voltages for measurement, control &
protection
7. Lightning
Arrester
To discharge lightning over voltages and switching
over voltages to earth
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Ⅰ. Specifications for Substation Equipments (2)
Functions of Substation Equipment (cont’d)
8. Shunt reactor
To control over voltages by providing reactive
power compensation
9. Neutral-Grounding
resistor
To limit earth fault current
10. Coupling capacitor
To provide connection between high voltage
line & PLCC equipment
11. Line –Trap
To prevent high frequency signals from
entering other zones.
12. Shunt capacitors
To provide compensations to reactive loads of
lagging power factors
13. Power Transformer
To step-up or step-down the voltage and
transfer power from one a.c. voltage another
a.c. voltage at the same frequency.
14. Series Capacitor
Compensation of long lines.
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Substation Equipment - Circuit Breaker
Circuit Breakers (400kV, 132kV and 66kV)
Ⅰ. Specifications for
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Main Parameters
• Rated Voltage (kV)
• Rate Continuous Current (A)
• Rated short circuit Breaking Current (kA, rms)
• Rated short circuit Making Current (kA, peak)
= 2.5ⅹ Rated Breaking current, rms (Asymmetrical)
• TRV : Transient Recovery Voltage (kV)
- The recovery voltage is the voltage which appears across the
terminals of a pole of a circuit breaker(The voltage difference
between the supply voltage and the load voltage). This voltage
may be considered in two successive time intervals: one during
which a transient voltage exists, followed by a second one during
which a power frequency voltage alone exists.
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Main Parameters (2)
• First–pole–to-clear factor (kpp)
- kpp is a function of the grounding arrangements of the
system. It is the ratio of the power frequency voltage across
the interrupting pole before current interruption in the other
poles, to the power frequency voltage occurring across the
pole or poles after interruption in all three poles.
- For the three-phase short-circuit condition of the neutral
ungrounded system, 1.5 p.u. is required in A phase.
Figure ; Ungrounded system after interruption of the first phase
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TRV
Figure 1. - Recovery voltage in
case of a capacitive load
Figure 2 - Voltages on terminals of
the first pole that clears threephase capacitive currents in a
system with isolated neutral
8 / 72
TRV (2)
Figure 3. Evolution of voltages with
restrike occurring a half cycle after
current interruption, in case of single-
Figure 4. TRV in inductive circuit, 90
degree lagging current
phase capacitive current switching
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POW - Capacitor Switching
• Point On Wave Switching (POW)
- Controlled closing of shunt capacitor banks (POW) is used
to minimize the power system transients by operating each CB
pole at the most favorable time instant.
- For wye-connected grounded-neutral, shunt capacitor banks
are energized when the voltage is equal to zero on each phase.
- All phases are closed within 120 electrical degrees.
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POW - Capacitor Switching (2)
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POW ( Example – Alstom RPH3 )
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Circuit Breaker – Test
Routine Test
Type Test
-
1. Mechanical test
1. Operational test
2. Thermal test
2. Measurement of resistance of the
main circuits
3. Dielectric test
3. One minute p.f. voltage withstand test (dry )
4. Short circuit test
Making capacity test
Breaking capacity test
Duty cycle tests
Short time current tests
※ Detailed Testing for Type test and
Routine test will be explained later in
in Ⅲ. Tests– Type test, FAT, Site test.
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Substation Equipment - Isolator
400kV Isolator
Ⅰ. Specifications for
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Substation Equipment – Isolator (2)
Mechanical Interlock with Earthing switch
Front View
DS Control Box
Top View
Ⅰ. Specifications for
※Two rotating axises can not operate at the same time and DS can be
operated only at a certain position(ES is open).
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Substation Equipment - Current Transformer
400kV Current transformer
Ⅰ. Specifications for
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Substation Equipment - Current Transformer (2)
Equvalent Circuit
CT Excitation curve(Knee Voltage)
Ⅰ. Specifications for
※ The ‘knee-point’ of the excitation curve is defined as ‘that point at which a further
increase of 10% of secondary emf would require an increment of exciting current of 50%’.
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Substation Equipment - Current Transformer (3)
LOCATION of Current Transformer
Case 1. When CT can be accommodated within the CB, both sides
of the circuit breaker should give the desired overlapping of protective zones
Case 2. Due to substation space limitation, in case only on one side of the CB
required, it is generally located on the circuit side of the CB.
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Substation Equipment - CVT
400kV CVT
Ⅰ. Specifications for
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Equivalent Circuit – CVT
Equvalent Circuit (Incl. EMU)
Ⅰ. Specifications for
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Type of VT
Ⅰ. Specifications for
※ Lower cost at voltages 110kV and above, but do not usually
have the very high accuracy required for some special metering
functions.
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Substation Equipment – Surge Arrestor
400kV Surge Arrestor
Selection of Surge Arrestor
Ⅰ. Specifications for
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Substation Equipment – GIS
420kV Gas Insulated Switchgear
Ⅰ. Specifications for
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Substation Equipment – Surge Arrestor
400kV Surge Arrestor
Selection of Surge Arrestor
Ⅰ. Specifications for
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Substation Equipment – Shunt Reactor
400kV Reactor and NGR
Ⅰ. Specifications for
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Substation Equipment – Series Capacitor
500kV Series Capacitor for 1,000 km line
Ⅰ. Specifications for
-2326 / 72
Substation Equipment – Power Transformer
400kV Auto Transformer
Ⅰ. Specifications for
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Power Transformer - Main Parameters
• Rated Voltage, kV (Primary/Secondary), Frequency, Hz
• Rate Power (ONAN/ONAF), MVA
• Winding Connection; Primary-Secondary, D-Y
• Type of Cooling, OA/FA/FAOA
• Temp rise (top oil, winding)
• OLTC, Tap voltage range(%), Number of Taps
• % Impedance
• Insulation level (lightning, power frequency)
• No-load loss(kW), Load-loss(kW), guaranteed values.
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Power Transformer – No Load Current
The no load current If is needed to supply the no load losses and to magnetize
the transformer core.
Ic
IF
E1
Qc
E1
Im
f
If
IF
※ 1) Magnetizing current which is merely utilized for
magnetizing the core, Im,
2) And other component of the source current, Ic, is
consumed for compensating the core losses in
transformer
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IcI
m
Power Transformer – Load Current
Loaded Transformer
Ⅰ. Specifications for
• As I2 is flowing through the
secondary, a self mmf in
secondary winding will be
produced. Here it is N2I2, where,
N2 is the number of turns of the
secondary winding of Tr.
※ mmf is magneto motive force.
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Power Transformer - Equivalent Circuit
Ⅰ. Specifications for
V1: Primary voltage (supply)
I1 : Primary current.
V2: Secondary voltage (load)
I2: : Secondary current
The turn ration, voltage ration, is E1/E2 = N1/N2 .
At the primary winding, On Load Tap Changer (OLTC or ULTC) is installed
where the current is small and its operating range is ±10%.
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Power Transformer - Efficiency

The efficiency of the transformer is the ratio of output (secondary) power to
the input (primary) power. Formally the efficiency is η:
P
  2
P
1

Where,

P1 : The input power (Primary) = V1I1 cosf1

P2 : The output power (Secondary) = V2I2 cosf2
Ⅰ. Specifications for
P1  P2  PL

PL is the power loss in the transformer = Pcopper + Piron
 
V2' I 2' cos f2
V2' I 2' cos f2  I 2'2 Req  Piron
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Power Transformer – Voltage Regulation

The voltage regulation is dependant on the transformer impedance. Also the
load current, I is important. When it is capacitive the voltage regulation
becomes positive, so the transformer reactance increase the output voltage.
Ⅰ. Specifications for
VR  V1  V2'  I 2' Req cosf  I 2' X eq sin f
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Power Transformer - Efficiency

The efficiency of the transformer is the ratio of output (secondary) power to
the input (primary) power. Formally the efficiency is η:
  P2
P
1

Where,

P1 : The input power (Primary) = V1I1 cosf1

P2 : The output power (Secondary) = V2I2 cosf2
Ⅰ. Specifications for
P1  P2  PL

PL is the power loss in the transformer = Pcopper + Piron
 
V2' I 2' cos f2
V2' I 2' cos f2  I 2'2 Req  Piron
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Power Transformer - % Impedance
• The percentage impedance of a transformer is the volt drop on
full load due to the winding resistance and leakage reactance
expressed as a percentage of the rated voltage.
• It influences the voltage regulation, system stability, short
circuit current magnitude, etc.
• Standard %Impedance (ANSI C57.12.10; 230kV and below)
Ⅰ. Specifications for
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Substation Equipment – Post Insulator
400kV Bus Post Insulator
Ⅰ. Specifications for
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Substation Equipment – Wave Trap
Wave Trap
Ⅰ. Specifications for
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PLC & Wave Trap
PLCC component - Coupling Capacitor
• Wave Traps form part of a PLC(Power Line Carrier) communication
scheme. Their function is to present a high impedance at the carrier
frequency band while introducing negligible impedance at the power
frequency itself.
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Substation Equipment – Lightning Mast
Ⅰ. Specifications for
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Ⅱ. Associated System - Functions
System
Function
1. Substation Earthing
system
-- Earthmat
-- Earthing spikes
-- Earthing risers
To provide an earthmat for connecting
neural points, equipment body, support
structures to earth. For safety of
personnel and for enabling earth fault
protection. To provide the path for
discharging the earth currents from
neutrals, faults, Surge Arresters,
overheads shielding wires etc. with safe
step-potential and touch potential.
2. Overhead earth wire
shielding or Lightning masts.
To protect the outdoor substation
equipment from lightning strokes.
3. Illumination system
(lighting)
-- for switchyard lighting
-- buildings
-- roads etc.
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Ⅱ. Associated System – Functions (Cont’d)
4. Protection system
-- protection relay panels
-- control cables
-- circuit breakers
-- CTs, VTs etc.
To provide alarm or automatic
tripping of faulty part from healthy
part and also to minimize damage to
faulty equipment and associated
system.
5. Control cable
For Protective circuits, control
circuits, metering circuits,
communication circuits
6. Power cable
To provide supply path to various
auxiliary equipment and machines.
7. PLCC system power line
carries communication system
-- line trap
-- coupling capacitor
-- PLCC panels
For communication, telemetry, telecontrol, power line carrier protection
etc.
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Ⅱ. Associated System – Functions (Cont’d)
8. Fire Fighting system
-- Sensors, detection system
-- water spray system
-- fire prot. panels, alarm system
-- water tank and spray system
To sense the occurrence of fire by
sensors and to initiate water spray,
to disconnect power supply to
affected region to pin-point
location of fire by indication in
control room.
9. Auxiliary standby power system
-- diesel generator sets
-- switchgear
-- distribution system
For supplying starting power,
standby power for auxiliaries
10. Telephone, telex, microwave,
OPF
For internal and external
communication
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Ⅱ. Associated System – Minimum Clearance
400kV
220kV
1. Phase to Earth
3500 mm
2100 mm
2. Phase to phase
4200 mm
(Rod-conductor
configuration)
4000 mm
(Conductor-conductor
configuration)
2100 mm
3. Sectional
Clearance
6400 mm
4300 mm
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Ⅱ. Asso’n System – Min. Clearance Live Line for Man
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Clearance for Apparatus Maintenance
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Clearance Diagram of Equipment
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Ⅱ. Associated System (Cont’d)
Busbar Design
• Continuous current rating
- Ampacity calculation as per IEEE:738
• Short time current rating (IEC-865)
• Stresses in Tubular Busbar
• Natural frequency of Tubular Busbar
• Deflection of Tube
• Cantilever strength of Post Insulator
• Aeolian Vibrations
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Ⅱ. Associated System (Cont’d)
Gantry Structure

Sag / Tension calculation : as per IS: 802 1995
Sr.
Temp
Wind Pressure
1.
Min.
No wind
2.
Min.
36%
3.
Every Day
No wind
T <= 22% of UTS
4.
Every Day
100%
T <= 70% of UTS
5.
Max. (ACSR
No wind
750C/ AAAC 850C)
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Limits
Clearances
Ⅱ. Associated System (Cont’d)
• Short Circuit Forces calculation
- As per IEC : 865
- Short circuit forces during short circuit
- Short circuit forces after short circuit
- Short circuit forces due to “Pinch” effect for Bundled
conductor
- Spacer span calculation
• Factor of safety of 2.0 under normal condition and 1.5
under short circuit condition
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Ⅱ. Associated System (Cont’d)
Lighting Design

- Adequate lighting is necessary for safety of working
personnel and O&M activities

- Recommended value of Illumination level
–
Control & Relay panel area
- 350 Lux (at floor level)
–
Test laboratory
- 300 Lux
–
Battery room
- 100 Lux
–
Other indoor area
- 150 Lux
–
Switchyard
- 50 Lux (main equipment)
- 20 Lux (balance Area / road
@ ground level)
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Ⅱ. Associated System - Spacer span/Short Circuit forces
GRAPH OF SPACER SPAN Vs CONDUCTOR TENSION FOR
400 KV TWIN MOOSE ACSR CONDUCTOR
CONDUCTOR TENSION PER PHASE IN KG.
12000.00
10000.00
8000.00
6000.00
4000.00
2000.00
0.00
0
2
4
6
8
SPACER SPAN IN MTRS.
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10
12
14
Ⅲ. Test – Type Test, FAT and Site test
Power Transformer
• Measurements of ;- Dissipation Factor & Capacitance
- No-load Loss and Current
- Noise Level
- Load Loss & Impedance
- Efficiency, Regulation,
• Temperature Rise Test – Type test
• Lightning Impulse Test, Full/Chopped Wave – Type test
• Switching Impulse Test (Over 230 kV) – Type test
• Applied Voltage Test and LTAC
• Induced Voltage Test with PD Measurement
• Leak Test with Tank Pressure (24hrs)
• Short Circuit Test – Type test
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Ⅲ. Type Test, FAT, Site Tests
Circuit Breakers- Type Test
-Type tests are the test of one CB or a first few CBs of each
type made to the same specifications (designs).
-Type tests can be classified in following groups
1) Mechanical test
2) Thermal test
3) Dielectric test
4) Short circuit test
a. Making capacity test
b. Breaking capacity test
c. Duty cycle tests
d. Short time current tests
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Ⅲ. Type Tests– Circuit Breakers (Cont’d)
1) Mechanical test (Endurance test):
- The breaker should be opened and closed satisfactory.
- In this test the CB is opened and closed several times (500).
- Some operations (50) are by energizing the relay, remaining are
by closing the trip circuit by other means.
- Mechanical test on a.c CB are conducted without current
and voltage in the main circuit.
- No adjustment or replacement of parts is permitted during
the mechanical test, however lubrication is permitted as per
manufacturer instructions.
- After the test there should be no distortion or wear of parts.
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Ⅲ. Type Tests– Circuit Breakers (Cont’d)
2) Thermal tests:
- AC current of rated value is passed through a closed CB,
continuously, until steady temp is attained.
- Readings of temperature of various conducting, insulating and
structural parts are taken at an interval of 1 or ½ hour.
- When the steady temp is reached, the maxim temp rise of
each part should be less than the permissible limit.
• The temp. rise should not exceed 40º C for In ‹ 800 A,
50º
C for In ≥ 800 A.
- An additional requirement is the measurement of contact
resistances between the moving and fixed contacts, with DC
current of 100 A.
• For Alstom 420kV SF6 circuit breaker, it is about 70 µΩ
(Limit 83 µΩ)
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Ⅲ. Type Tests – Circuit Breakers (Cont’d)
3) Dielectric test:
•
1.
a.
b.
2.
These are conducted to confirm the rated insulation level of the
circuit breaker. These can be classified as ; Power frequency tests.
- Between poles and earth with circuit breaker open,
a. Across terminals with circuit breaker open
b. Between poles with circuit breaker closed,
- The voltage gradually increased and maintained at test value
for 1 minute.
Impulse tests.
- In this test impulse voltage of specified shape and magnitude
is applied to the breaker.
- For outdoor circuit dry and wet tests are conducted.
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Ⅲ. Type Tests– Circuit Breakers (Cont’d)
4) Short circuit testing :
- There are two types of short circuit testing stations to prove the MVA
ratings of the circuit breaker, a)The field type testing station and b) L
aboratory type testing station.
a. The field type testing station
-The power is supplied directly by the power system.
• - It is most convincing method, but it has following drawbacks:
 i) That flexibility of the system available is limited.
 ii) It is difficult to set the system for the specified RRRV for HV CB.
 iii) It is not possible to repeat the test again and again without
disturbing networks, hence not suitable for research/development.
iv) The power available in the field testing station vary according to
load connected on the network and layout of the network.
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Ⅲ. Type Tests– Circuit Breakers (Cont’d)
•
•
•
•
•
•
b. Laboratory type testing station
- It has special generators to supply power for the testing.
- In this it is possible to vary the test condition as required.
- Such station is suitable for design engineer and supply engineer,
and the designer can study the behavior of arc rupture and make
necessary improvements.
- The test can be performed again and again in order to show the
reproducibility of the results.
- The supply engineer can get satisfaction whether his breaker
satisfies the requirements enunciated by specifications.
- The magnitude of the test voltage and the short circuit can be
selected by adjusting generators excitation and connection of the
transformers.
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Ⅲ. Tests– Circuit Breakers (Cont’d)
b. Laboratory type testing station (Cont’d)
- Further variation of current can be effected by means of tapped res
istors and reactors. This also serves control on power factor.
- The circuit is closed by specially designed make switch, designed
for closing on very heavy currents, but never break currents.
- Synchronized closing is controlled by means of a small pilot gener
ator coupled to the generator shaft and can be very accurately set t
o occur at any instant within the voltage wave.
- With this the phase opposition at the commencement of short circu
it can be selected.
- And short circuit current either fully symmetrical or with any degre
e of symmetry can be produced.
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Ⅲ. Type Tests– Circuit Breakers (Cont’d)
b. Laboratory type testing station (Cont’d)
- Master CB is provided as a backup protection, in case of failure of
CB under test to open the circuit.
- By adding capacitor, any desired high frequency can be obtained.
- The breaker under test is enclosed in a test cell made of reinforced
concrete having a provision of observation while test is in progress.
- The recording equipment is located in a control room, and the contr
ol operations are carried out from the control room.
- Direct testing involves subjecting a complete breaker or breaker pol
e to full power or stress during the test.
- The necessary preparation of C.B testing include connecting the equ
ipment, adjusting the magnitude of reactors, connecting transforme
rs to get desired test voltage etc.
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Ⅲ. Tests– Circuit Breakers (Cont’d)
b. Laboratory type testing station (Cont’d)
- The contacts on sequence switch are adjusted to get desired timings.
- The oscillographs are adjusted and calibrated.
- While testing breaking capacity; Master circuit-breaker and C.B und
er test are closed first, Short circuit is applied by closing the makin
g switch.
- The breaker under test is opened at desired moment
- Making capacity test is necessary type test, all C.Bs are tested for th
eir ability to make on to a Short-circuit.
- The master C.B and the make switch are closed first, the breaker un
der test is closed on a three phase short-circuit
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Ⅲ. Tests– Circuit Breakers (Cont’d)
Indirect testing
- The short-circuit power available in testing stations (which is of
the order of 4000 MVA in lab type testing station) is no longer
sufficient to test a complete breaker ( which is of rated breaking
capacity of the order of 10,000 MVA at 245 KV)
- Even single pole of a EHV CB cannot be tested by direct means
, as all EHV CB are with several arc interrupter units per pole,
each unit can be separately tested. This is called unit testing.
- From tests on one unit, the capacity of the complete pole and
breaker is determined.
- Synthetic testing is another popular method which permits
testing of breaker of capacity 5, times that of the plant.
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Ⅲ. Tests– Circuit Breakers (Cont’d)
- The important Indirect Methods include the following:
◦ Unit testing: which means testing one or more units separately.
◦ Synthetic testing: In which the current source providing short
circuit current and voltage source supplying re-striking and
recovery voltage are different.
◦ Substitution test: These are conducted for oil CB, the
characteristics of current versus time are obtained for
different voltages, the performance beyond the tested value is
determined by approximation
◦ Compensation tests: which are conducted on oil CB in critical
range of low current by suitable compensation such as
increased frequency, increase re-striking voltages etc.
◦ Capacitance tests: the capacitor which is charged by a voltage
source is discharged through the breaker, an oscillatory
circuit provides re-striking voltage.
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Ⅲ. Type Tests– Circuit Breakers (Cont’d)
Synthetic testing
64 / 72
Ⅲ. Tests– Circuit Breakers (Cont’d)
Synthetic testing
The synthetic test employs two sources namely,
1)
2)
Current source (of relatively low voltage)
Voltage source (of relatively low current)
- The current source provides short-circuit current, the voltage source
provides restriking voltage plus recovery voltage.
- Other L,r,C etc are used to get desired test conditions, the switch S1
is closed to supply short-circuit current IG.
- At near final current zero switch S2 ( which is usually a spark gap)
is closed and V3 to applied to the breaker at an appropriate
moment, the voltage will have transient because of L and C of
the circuit
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Ⅲ. Tests– Circuit Breakers (Cont’d)
Advantages of this method;
-The breaker can be tested for desired TRV and R.R.R.V
-The short-circuit generator has to supply currents at a relatively
less voltage ( as compared to direct testing)
-Both test current and test voltage can be independently varied,
so test become flexible
-This is a simple method and can be applied to unit testing
-With this method a breaker of capacity of five time that of the
capacity of the test plan can be tested.
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Ⅲ. Tests– Circuit Breakers (Cont’d)
- In parallel current injection method, the voltage circuit (2) is
effectively connected in parallel with current circuit (1) and the
test breaker before the main current IG in test breaker current is
properly simulated.
67 / 72
Ⅲ. FAT (Factory Acceptance Test)
Circuit Breakers
FAT - Routine test, Witness Test
- These are performed for purpose of proving the correctness of
assembly and material used.
- These are performed on each individual circuit breaker.
- Main routine test items include; 1) Operational test, 2) Measure
ment of resistance of the main circuits, 3) One minute power
frequency voltage dry withstand tests.
- The customer can witness the testing process, and called as the
witness test.
68 / 72
Ⅲ. Test – Site test
Site Test–GIS (KEPCO, 170kV)
Test Item
Preparation
Check Point
Criteria
□ Discussion with Operators/Field engineers; Work scope, Inspection procedure,
Time required, Equipment outage, Neces
sity to disconnect the trip circuit.
○
□ Check the equipment drawings/Cable list
○
○
□ Operation voltage for DC/AC ; Closing
90-130V,
voltage, 75~125% ;Trip voltage, 60~125%
Vn=110V)
□ Measuring instrument and special tools.
□ Earthings for the compressor & hydraulic
units.
Insulation Resistance □ DC circuit
of CB control circuit □ AC circuit (over 150V)
Visual Check s
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○
○
-
Remarks
Ⅲ. Site Test – Commissioning Test (GIS)
Test for CB Unit
□ Insulation resistance (Phase-to ground, P
hase-to-phase)
≧ 1000MΩ
□ Closing Time
≦ 150 msec
□ Tripping Time (Coil 1, Coil 2)
≦ 33 msec
□ On/Off time (phase discrepancy)
□ Phase open relay operation (timer, trip
operation)
□ Check interlock for closing circuit
≦ 4 msec
□ Check interlock for trip circuit
yes
○
○
○ (for Loc□ Check Equipment status and Annunciatio
al / Remote
n with on/off operations.
positions)
CB, DS Trip/Alarm □ Check the contact status (Incl. Spare)
○
Signal Test
○ (with
□ Confirm back to normal position after
Relays
alarm test (Air, Gas, Oil)
energized)
70 / 72
Ⅲ. Site Test – Commissioning Test (GIS)
Interlock Test
BCT Insulation
Resistance
□ Interlock between CB, DS, and ES
□ Between Bus ES and Bay #1, #2 Bus DS
□ Between 1ry-2ndry windings, 1ry-Earth,
2ndry – Earth.
□ Between phases of 2ndry windings
□ Polarity test - Subtractive ?
BCT Test
□ CT ratio test- Ratio Correction Factor
□ Saturation characteristics (at max. ratio)saturate over +110% of rated current.
CT Connection
□ Check correct ratio and connection
(short CT neutral at protection side)
□ CT terminal shall be shortened at the
max. tap ratio
Bus/Line PT
Insulation
Resistance
□ Between 1ry-2ndry windings, 1ry-Earth
□ 2ndry windings -Earth
71 / 72
○
○
1ry windings :
≧ 1000MΩ,
2ndry winding
s;≧ 2MΩ
yes
At each taps;
RCF ≦ ± 10%
yes
○ (refer relay
tap setting tab
le)
○ (use short
bar and cable)
≧ 1000MΩ
≧ 2MΩ
Ⅲ. Site Test – Commissioning Test (GIS)
□ Polarity test - Subtractive ?
Bus/Line PT Test
PT Ground
Connection
PT Cable
□ Ratio test-Ratio Correction Factor
yes
RCF ≦
± 10%
□ Local control box
○
□ PT Cable Shield
○
□ Bus/Line PT 2ndary Neutral
○
□ Corrosion protection of PT cable
(Grease Injection)
○
□ Check whether correct ratio is used.
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