Voltage Stability Enhancement Of Power Systems

Abstract

The phenomena of voltage collapse on a transmission system arc often the cause of generalized incidents .They arc caused by a low voltage initial profile. excessive demand, operation near the maximum power to be transmitted, generating facilities too far from demand and insufficiency of reactive power compensation facilities .At first a gradual voltage drop in one or several consumer regions leads to increase reactive losses in the system and pushes transformer taps towards maximum value . Some generators or compensators can reach their limits of reactive power . Then voltage drops rapidly and it may go so far as to cut off generating units and lines one after the other thus causing a complete voltage collapse or blackout of the system .

Planning , operation and control of power systems are significant areas governed by stability considerations . Two distinct areas of power system stability are recently classified : power system synchronous or ( inertial or angle ) stability and power system node voltage stability or (load stability ).

The heart of voltage stability problem is the mechanism of the voltage dip that occurs when the power system experiences a heavy load or an excessive reactive power demand , suddenly or gradually , which in turn leads to voltage collapse or voltage oscillations or voltage flicker or both .