大型水轮发电机组保护若干技术问题探讨

针对水轮发电机组保护的若干实际应用问题进行了探讨,包括厂用变压器(以下简称厂变)高压侧电流是否差入主变压器(以下简称主变)差动保护、失磁保护阻抗圆选择、转子接地保护的实现方式、注入式定子接地保护启动失灵问题、发电机复压过流保护跳母联断路器问题、接地变短路阻抗对基波零序电压定子接地保护的影响等。针对上述问题给出了具体的建议:厂变高压侧电流不计入主变差动电流计算的前提是厂变低压侧母线上发生短路故障时,该电流产生的差流不会导致主变差动保护误动;水轮发电机失磁保护宜选择静稳阻抗圆;转子接地保护宜就地安装;注入式定子接地保护动作后,动作接点不会快速返回,启动断路器失灵时可靠性有所降低;发电机复压过流保护不宜动作于跳母联断路器;应校核接地变短路阻抗对基波零序电压定子接地保护的影响。

Several Technology Issues of Large Hydro-generator Unit Protection

A number of practical application problems are presented for the protection of hydro-power generator unit,including whether the high-voltage side current is calculated in the main transformer differential protection,impedance circle selection of excitation-loss protection,implementation mode of rotor earth fault protection,start failure of voltage injection type stator earth fault protection,over-current protection to jump the bus connection switch with generator complex pressure,the impact of short-circuit impedance of grounding transformer on the fundamental zero-sequence voltage stator ground fault protection,etc.Concrete suggestions for the above mentioned problems are given such as: high-voltage side current of station transformer is not calculated in the main transformer differential protection under the situation that when short-circuit fault occurs on the low voltage bus and the difference between the current flow does not result in main transformer protection malfunction;excitation-loss protection of hydro-power generator should be selected static impedance circle;rotor earth fault protection should be installed locally;after the action of voltage injection type stator earth fault protection,the act contact point will not return fast enough so the reliability of start breaker failure gets lower,and over-current protection should not act on the bus connection switch under generator complex pressure;impact of grounding transformer short-circuit impedance on the fundamental zero-sequence voltage earth fault protection should be checked.