Analysis Of Generator Over-Voltage And The Impact Of Insulation Aging Due To Over-Voltage

High capacity generator is the key apparatus in power system. Because of its high input-output ratio characteristic, it can cause large loss and impact the stability of power grid if it is halted unplanned. So, its operation reliability plays an important role for power system.The stator winding of high voltage Rotating electrical machine is suffered high field intensity caused by long-standing power frequency voltage, furthermore, it is invaded by transient over-voltage such as lightening or switching over-voltage produced by operating circuit breaker transferred from electrical network too. As a result, it causes the insulation accident. As the voltage level of power grid rising, transient over-voltage does more harm to high capacity generator, because the dielectric level of generator is lower than other apparatus in power system. Rotating electrical machine often be subjected to invasion of over-voltage in power system. The insulation which has potential flaw may be broken while severe transient over-voltage invaded. Moreover, it can change the distribution of the electric field of stator slot, And then, induce the partial discharge of stator insulation, weaken the insulation level step by step, after all, cause the insulation accident. So, it is significant to monitor and analyze the over-voltage of generator and study the aspect of insulation influenced by over-voltage.This dissertation presents a study of influence of generator insulation affected by over-voltage. Firstly, analyzes the principle of over-voltage invade generator and the typical over-voltage waves monitored in plant. Secondly, analyze the amplitude of over-voltage by using mathematical statistics method and present an attitude of the relationship of insulation co-ordination with statistic of over-voltage. Lastly, introduce the attribute parameter which abstracted from the over-voltage into the algorithm of end life of generator insulation, further more, apply the new method to evaluate the end life of 2# generator of NanYa river power station.