Answer / iamdon

Voltage instability is due to following reasons:
1)Gradual increse in load.
2)Loss of generating unit or heavily loaded line
3)Poor cordination amoung control action to avert the
situation etc.
In all the cases the system is insufficient to cater the
reactive power requirement of the load.It leads to the
reduction in voltage at load end.

OLTC transformer increases the voltage level at load side
so Q requirement of load increases.The system is already
running short of Q, so it is not possible to supply this
incresed Q by system.This leads to more voltage dip at
load.In this way, instead of stabilizing the voltage, OLTC
transformer aggerevate the voltage instability.

Author:arbelectbit@yahoo.com

Answer / sushil kumar sharma

oltc worked in step not in pid mode only avr worked in pid mode

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