Improving transient stability by containing accelerating energy

An adaptive method of improving transient instability has evolved from a better understanding of the post-disturbance physical phenomena leading to transient instability. The analysis of the phenomena has shown that a small magnitude of primary accelerating energy produced by generators near the fault is greatly multiplied as it flows through the network, past successive load substations. Further, progressing with the outflow of accelerating energy, there is simultaneously a wave of raised frequency as well as a wave of lowered voltages. The voltage wave reduces each substation´s load magnitude just as the accelerating energy passes and so causes its amplification. This has shown that a pattern of voltage and frequency changes at each substation can not only identify but also actuate measures for the control of transient stability. A study has demonstrated that local control of the switching of shunt capacitors and reactors at each substation can avert transient instability. Not only is this a low cost approach, but it provides an adaptive arrangement that can respond to disturbances anywhere on the transmission grid to prevent its disruption by transient instability. Compared to the use of braking resistors, a fail-safe arrangement is offered which is also effective in damping oscillations after noncritical disturbances.