Shunt reactor bank switching transients and analysis.

摘要

Shunt reactor banks are used for voltage regulation to limit the rise brought about by Ferranti Effect. However, the transients associated with the switching operations of the shunt reactors can induce severe overvoltages that are detrimental to the switching circuit breaker and the reactor itself. The cascading equipment failures brought about by current chopping, reignition and associated transient recovery voltages (TRV) result in a huge loss of capital and man power investment. The protective influence of conventional surge arresters to limit the stress produced by the high rate of rise of recovery voltages (RRRV) is found to be insufficient. A detailed analysis of the overvoltages provoked by the de-energization transients of a shunt reactor bank are presented. The techniques to successfully combat and mitigate them are examined. Various approaches to modeling of shunt reactors and the circuit breaker behavior are discussed and demonstrated. An effort is also made to illustrate the possible failure mechanism brought about by the propagation of reignition surges through the reactor windings. Through simulations it is found that reignition surges may in some cases exceed the BIL ratings of the shunt reactors and insulation stress levels allowed by the standards. The designed protection package consists of a standard 2 x 22.8-kV 50-kVAr 0.25-F surge capacitor and a 29-kV MCOV surge arrester installed at the reactor phase terminals. Simulations showed this was effective in curbing the high RRRV and probability of reignitions. Also, the surge distribution investigation conducted helps in identifying the sections of the windings which would be more prone to insulation breakdown.