Fifteenth National Power Systems Conference (NPSC), IIT Bombay, December 2008
Voltage Dips and Short Interruption
Immunity Test Generator
As per IEC 61000 – 4 – 11
Sneha Bhavsar¹, Prof. Varsha A Shah 2, Mr. Vinod Gupta 3
1, 2
: Department of Electrical Engg., SVNIT, Surat, India.
3
Electrical Research and Development Association, ERDA Road, Makarpura GIDC, Vadodara-390010,
India
E-mail: s_bhavsar132@yahoo.co.in
Abstract-- This paper presents Voltage Dips and Short
Interruption Immunity Test Generator, to check the
immunity of equipment against the voltage dips and short
interruption, which occurs widely in low voltage mains
and interface with electrical and electronics equipment
connected to the mains. The output voltage waveforms of
the immunity test generator are in full compliance with
the standard IEC 61000 – 4 – 11. IEC 61000 – 4 – 11 is a
common reference used to evaluate immunity of
equipment while subjected to voltage dips or short
interruptions. The 3 phase generator is designed for
immunity testing of equipment operating at low voltage
(not exceeding 240 V) and power frequency (50 Hz).
Current rating of the generator is 32 amps. Generator is
having user interface facility – HMI (human machine
interface) using which user can generate the voltage dips
or short interruption of any level and duration defined in
IEC 61000 – 4 – 11. Experiment towards energy meter
has been done to testify the equipment’s feasibility. The
resulting waveform can show that generator can work
properly.
The reason is that the modern electricity utilizing
equipment either in its own design or due to the
incorporated control feature has become more sensitive
to the voltage dips. There is a need of increase
awareness of phenomenon among the supplier and user
of electricity and manufacturer of equipment using
electricity.
System inconvenience can be reduced by proper
cooperation of the supplier and user. Voltage
mitigation is the one of the means for the solution of
the voltage dips problem. Another solution is to
increase the voltage dips immunity of the equipment.
Using standards and a voltage dips and short
interruption immunity test generator, it is fairly easy to
modify a piece of industrial or commercial equipment
to increase its immunity to voltage dips. Also proper
mitigation can be carried out. The modifications are
almost always simple and inexpensive. Consequently
generator for testing the voltage dips and short
interruption immunity of equipment is presented in this
paper which is in full compliance with IEC – 61000 – 4
– 11.
So far prototypical generator specified in the EMC
standards involves waveform oscillator with power
amplifier (WOPA), motorized variac with multi
tapping transformer and throw over switches. From
three strategies we have implemented the second one.
Index Terms: Voltage dips, Short Interruption, Voltage
dips and short interruption immunity testing
I.
INTRODUCTION:
A voltage dips is a short-term reduction in or complete
loss of, RMS voltage. It is specified in terms of
duration and retained voltage, usually expressed as the
percentage of nominal RMS voltage remaining at the
lowest point during the dips. Voltage dips and short
interruptions can be expected at any place at any time
and at any level involving virtually zero voltage and
duration up to and above 1 second. The frequency of
their occurrence and the probability of their occurrence
is at any level is highly variable both from place to
place and one year to another.
So voltage dips is being an in strict feature of public
electricity supply. In recent decades they have become
increasingly troublesome disturbance giving rise to
inconveniency and even considerable economic loss.
II.
A.
VOLTAGE DIPS AND SHORT
INTERRUPTION
Voltage Dips:
The definition of a voltage dips is not unambiguous
and often set only by two parameters depth/magnitude and duration. Different sources
however present different alternatives how these
parameters are interpreted. In this paper, the voltage
dips magnitude is ranged from 80% to 0% of nominal
voltage and with duration from half a cycle to 250
cycles.
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Fifteenth National Power Systems Conference (NPSC), IIT Bombay, December 2008
IEC 61000-2-8 definition [18]:
included the significant source of stored energy,
preventing voltage from reaching to zero during a very
short interruption. Furthermore the most severe voltage
dips implies the zero voltage. Such a voltage dips is
effectively interruption although the connection to the
voltage source remains. Thus there can be difficulty for
measurement instrument to distinguish between voltage
dips and shore interruption.
For these reason in measuring it is necessary to adopt a
boundary voltage greater than zero in order to
distinguish between voltage dips and short interruption.
In the event in which voltage falls below this boundary
voltage is to be considered as short interruption or else
voltage dips.
“According to the IEC 61000 4 11 voltage less than the
20% of the rated voltage is to be considered as the
short interruption.”
A sudden reduction of the voltage at particular point of
electricity supply below a specified dips threshold
followed by its recovery after a brief interval
associated with electromagnetic disturbances.
Vrms
100%
40%
Td
Ts
Tr
Fig. 1. RMS Plot of Voltage Dips Of 40 %
Where,
Td= Delay Time
Tr= Rise Time
Ts = Time of reduced voltage.
It is the two dimensional electromagnetic disturbance.
The level is defined by both voltage amplitude and
time.
Notes:
1 Typically a dips is associated with the occurrence and
termination of a short circuit or other extreme current
increase on the system or installations connected to it.
2 A voltage dips is a two dimensional electromagnetic
disturbance, the level of which is determined by both
voltage and time (duration).”
B.
D.
Need of Voltage Dips and Short Interruption
Immunity Testing:
Equipment on-site is becoming more sensitive to
disturbances that it often self generates. The
disturbances generated by electronic equipment, and its
sensitivity to disturbances, is a factor that should be
included in equipment specifications, and entered into
commercial discussions.
A survey conducted by European Copper Institute in
2001 asked facility and building managers at 1400 sites
in 8 countries about the problems they experience. It
showed that any of the problems listed in figure below
is experienced by 25% of sites. The real incidence rate
may be higher, for lack of awareness of the problem, or
being unable to diagnose it as a PQ problem.
Short Interruption [18]:
A sudden reduction of the voltage on all phases at a
particular point of electricity supply below specified
interruption threshold followed by its recovery after a
brief interval.
Vrms
100%
0%
Td
Ts
Tr
Fig. 2. RMS Plot of Short Interruption.
C.
Distinguishing Between Voltage Dips and
Short Interruption [18]:
A short interruption implies complete disconnection
form all the sources of supply and there for zero
voltage. In practice the disconnected source can be
Fig. 3. Incidence rate for typical power quality problems
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Fifteenth National Power Systems Conference (NPSC), IIT Bombay, December 2008
Above survey presents the need of proper action to be
taken care for the problem of supply voltage dips or
short interruption. One can go for either proper
mitigation technique or to use equipment already
having the enough immunity level. For implying
mitigating method you should know the level till which
equipment can withstand the voltage dip or short
interruption without any malfunction. But again that is
costlier solution of the proper. New trend is to make
the system or the equipment of the higher immunity.
After manufacturing the equipment needs to be
checked out for the designed immunity level. For
above stated requirement that is either for designing
equipment with higher immunity or for applying
mitigation we need some reference which can check
the immunity of the equipment and that reference is
Voltage dips and short interruption immunity test
generator.
III.
variac is used to set the system voltage at the rated
voltage specified by the user. Position of variac is
changed using the increment and decrement relay
which are driven by the signal generated by PIC. Multi
tapping transformer is connected to the load via
bidirectional
switches
connected
in
series.
SK60GM123 bidirectional IGBT is used as a switch.
PIC generates the gate driving signals for the static
switches. Amplitude of the gate driving signal is
increased using M56962L driver IC. PIC and HMI are
interacting with each other via RS 232 cable. PIC will
control the system according to the condition specified
by the user through the HMI. How the all modules are
connected to each other that is shown in the figure
given below.
VOLTAGE DIPS AND SHORT INTERRUPTION
IMMUNITY TEST GENERATOR:
IEC 61000 – 4 – 11 describes three distinct
methodologies of voltage dips and short interruption
immunity test generator. First is Waveform Oscillator
with Power Amplifier, second is Throw over Switch
and third is Motorized Variac With Multi Tapping
Transformer. First method can be proved costly for
higher current rating. One can opt for second or third
method but in this paper we have opted for third that is
Motorized Variac with Multi Tapping Transformer
because of isolation provision. Block diagram of
selected methodology is shown below.
100%
Vrated
Fig. 5. Block diagram of the generator
RESULTS:
In order to validate the generator the wavefroms has
been carried out which are shown below.
80%
70%
40%
Fig. 4. Methodology of the generator
IV.
HARDWARE IMPLEMENTATION:
Test generator is divided in two modules, one is power
circuit module and another one is control card module.
Motorized variac, transformer, switching devices,
driver card are part of the power module. Control
module consists of the PIC controller which is mainly
responsible for generation of voltage dips. It also
consists of HMI (Human Machine Interface) facility
for user to enter the test specifications. Motorized
Fig. 6. Waveform of gate pulse for class 2 of IEC 6100 4 11
standard
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Fifteenth National Power Systems Conference (NPSC), IIT Bombay, December 2008
Fig. 10: Waveform of Class 3 voltage dip:
0% for 1.5 cycles, 40% for 10 cycles
70% for 25 cycles, 80% for 250 cycles.
Fig. 7. Waveform of gate pulse for class 3 of IEC 6100 – 4 - 11
standard
V.
CONCLUSION:
This paper presents the voltage dips and short
interruption immunity test generator which is in full
compliance with the IEC 61000 – 4 – 11. The term
'Power Quality' refers to the degree with which an
electric power supply deviates from its nominal,
sinusoidal waveform, steady state voltage condition; a
larger deviation denoting poorer power quality. It must
first be recognized that unlike other power quality
problems, when there is a voltage dip, there is a
momentary and at times substantial loss of power. This
is also true, and even more so, for voltage short
interruptions. It is clear that voltage dips cause
widespread and serious operational and economic
problems to a very wide range of industrial,
commercial and service operations. Over the last few
years, it has become widely recognized that power
quality is compatibility issue between the supply
system and the load. In other words, it is the tolerance
or sensitivity of electrical loads compared to the quality
that the supply system has to offer. Solution to voltage
dips and short interruption is either to use proper
mitigation method or to increase immunity of system.
To implement any of the above solution we first need
to check the voltage dips and short interruption
immunity of the equipment.
Fig. 8. Waveform of short interruption for 1 sec performed for 3
times
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Fig. 9: Waveform of Class 2 voltage dip:
0% for 1.5 cycles, 70% for 25 cycles.
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Fifteenth National Power Systems Conference (NPSC), IIT Bombay, December 2008
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immunity test.
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BIO-DATA OF AUTHOR(S):
Sneha D Bhavsar is pursuing M Tech in Electrical (Industrial
Electronics) from SVNIT, Surat & obtained B.E. in Electrical from
VNSGU in May-June 2004. She has presented paper in national
conference on current trends in technology.
Shri Vinod Gupta obtained Master of Engineering in Electrical
engineering from M.S. University Vadodara in December 2003 &
B.E. in Power Electronics from L.E. college, Morvi in 1993. He has
more than 13 years of experience in R&D of Power Electronics &
Instrumentation.
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