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TRANSIENT ANALYSIS WITH CURRENT
TRANSFORMER
By:
M. RIYAS AHAMED
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PRESENTATION
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OBJECTIVE:
The objective of this present work is to investigate the
performance and transient behavior
of conventional electromagnetic current during power system
switching faults. This work
has been carried out using MATLAB/Simulink simulation tools.
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INTRODUCTION:
Current Transformer:
Current transformers (CT) are important elements of relay
protection because they
are the main source of information for the measuring organs of
the devices of relay
protection, and the accuracy of the transformation of primary
currents by high voltage and
intervening CT determines the reliability of the operation of
the entire protection.
Types of current transformers:
Electro Magnetic Current Transformer (EMCT)
Hall Effect Current Transformer (HFCT)
Magneto Optic Current Transformer (MOCT)
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INTRODUCTION:- (cont.)
Transient:
The electrical transients are well known and unavoidable
disturbing events that causes severe
problems to the electric power systems. The origin of transients
are switching transients,
lightning, and other faults.
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SCOPE OF WORK:
Different types of switching faults are considered for
conventional electromagnetic current
transformers (EMCT). The switching faults include symmetrical
& unsymmetrical switching, effect
of current transformer secondary opening, and the effect of load
switching. The system is modeled
to be a 120KV constant voltage source supplying a distributed
load of 100MVA through a
transmission line of 300km length.
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SIMULATION:
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TESTING:
Effect of Symmetrical & Unsymmetrical switching.
Effect of CT secondary open.
Effect of Load switching.
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TESTING: (Effect of Symmetrical & Unsymmetrical
switching)
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The current i has two components:
The first component is the AC sinusoidal component having
amplitude
2+22 and
lagging the voltage phasor by an angle .
The second component is DC or transient component which decays
exponentially with a
time constant L/R.
If switching takes place in an instant when = 0, the DC
component will be zero and the current
wave will be symmetrical.
If the switch is closed when - = /2, the DC component will be
maximum and the first peak
of the resultant current i will approach twice the peak of the
final steady state current. It results the
unsymmetrical waveform.
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TESTING: (Effect of Symmetrical & Unsymmetrical
switching)
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TESTING: (Effect of Symmetrical & Unsymmetrical
switching)
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Effect of symmetrical switching Effect of unsymmetrical
switching
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TESTING: (Effect of CT secondary open)
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Effect of CT secondary open
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TESTING: (Effect of CT secondary open)
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Effect of CT secondary open
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TESTING: (Effect of load switching)
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switching a load will cause switching surges, while switching a
heavy load it causes the
transients
Output at
Steady state condition
Transient fault condition
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TESTING: (Effect of load switching)
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TESTING: (Effect of load switching)
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Steady state output of the system
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TESTING: (Effect of load switching)
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Transient fault condition
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CONCLUSION
The simulation results have shown that electromagnetic current
transformers (EMCT) can suffer
heavily from transient saturation during switching of heavy load
and unsymmetrical switching.
Based on this work it is safe to declare that EMCT can be used
for normal monitoring and
measurement applications in utility. It is not good for the
reliable protection and control
application in high power application.
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THANK YOU
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