发变组失灵保护的探讨及改进

Analysis and improvement of breaker failure protection for generator-transformer unit

对于发变组失灵保护,目前还存在模糊认识和错误认识,影响到保护的可靠性。通过对“转子两点接地”等保护量动作结果的分析,说明有些保护量没有能力启动失灵,需借助“程跳逆功率”保护启动失灵,但“程跳逆功率”保护的逻辑回路宜修改;通过对“失磁”等保护量动作结果及其保护目的分析,说明有些保护不需启动失灵。在电流判别方面,从失磁和逆功率2种情况分析,可得出其整定计算原则;在电压判别方面,规程规定的复合电压闭锁会造成失灵拒动,有2种方案可供改进。改进后的失灵保护逻辑加上明确的电流判别整定计算原则,将使发变组失灵保护更加完善可靠。

There is existing confused and wrong understanding about breaker failure protection for generator-transformer unit, which impacts the reliability of the protection. Upon analysis of the action results of such protections as ＂rotor 2-point earthing＂ etc, it is shown that some protections are unable to actuate breaker failure protection, and have to make use of the ＂inverse power caused by sequential trip＂ element; however, the logic circuit thereof should be revised. Through analysis of the action results and the protection purpose of protections such as ＂loss of excitation＂ etc, it is indicated that some protections do not have to actuate breaker failure protection. As to current block, the principle of setting computation for it can be derived by analyzing loss of excitation and reverse power. As to voltage block, the composite voltage blocking stipulated in relevant code may make breaker failure protection fail to operate. There are two schemes for improvements. The improved breaker failure protection logic together with specific setting computation principle of current block will further improve the reliability of breaker failure protection for generator-transformer unit.