对发电厂低压厂用变压器速断保护范围的探讨

Probe into Quick-acting Protection Limit for Low-voltage Station-service Transformer of Power Plant

相电流速断保护作为发电厂低压厂用变压器的主保护,其保护范围整定时原则为按躲过厂用低压母线三相短路电流和空载励磁涌流计算,即保护范围为:当变压器高压侧发生两相金属性短路时可靠动作;当变压器低压侧发生三相金属性短路时不动作。本文通过对一起400 V开关烧坏案例进行分析,讨论延伸相过流速断保护范围的可行性,从而提出对高压侧过电流保护将采用为不完全星形的两电流元件改为三电流元件的原理。

As the main protection for low-voltage station-service transformer, the phase current quick-acting protection＇ s adjustment followed with the rule of lower than the three-phase short-circuit current and no-load exciting current of station-service low-voltage busbar, as well as reliably acted just at metal two-phase short-circuit of the trans- former high-voltage side and no acted just at metal three-phase short-circuit of the transformer low-voltage side. Through analyzing a case of 400V switch be damaged, the article discussed the feasibility of extending the limit of phase current quick-acting protection, thus put forward the proposal of transforming incomplete star two current component into three current for phase current protection of transformer high-voltage side.