发电厂厂用电经中阻接地系统零序保护优化

Optimization of Zero-Sequence Protection for Neutral Resistance Grounding System in Power Plant

国内发电厂厂用电系统多采用高压厂用变低压侧经中电阻接地方式。当馈线发生接地保护时由定时限接地保护做动作于跳闸故障馈线,但当馈线发生高阻接地时,因保护装置测得接地电流较小,保护可能发生拒动情况,导致厂用电系统长期带病运行,如果不及时消除可能扩大故障范围。提出在原有定时限保护的基础上,增加反时限保护用于发信,可以快速对故障馈线进行处理,定、反时限相结合的零序过流保护可以保证高阻接地时按一般反时限曲线定位故障馈线并发出告警,接地电阻较小时按定时限快速跳闸。结合实际中高压厂用变低压侧零序一、二时限出口整定方式与厂用电快切装置功能相矛盾,提出解决方案,以保证厂用电系统安全运行。

Domestic power plant auxiliary power systems mostly use high-voltage auxiliary transformer low-voltage side grounding through medium resistance.When the feeder is grounded,it is moved by a fixed time-limit grounding protection to the hop fault feeder.But when the feeder is grounded with high resistance,the grounding current measured by the protection device will be small,which may resist the protection action.As a result,the factory power system sickly runs for a long term.If it’s not eliminated in time,the fault range may be expanded.It is proposed that on the basis of the original fixed time-limit protection,anti-time protection can be added for sending letters,which can quickly process fault feeders.The zero-sequence over current protection combined with fixed and anti-time limits can ensure that the fault feeder is positioned and alarmed according to the general anti-time limit curve when grounding is high.When the grounding resistance is small,it can quickly jump according to the fixed time limit.The zero-sequence one and second time-time export tuning methods of high-voltage plants contradict the functions of the factory power fast cutting device.This paper puts forward solutions to the problems above mentioned in order to ensure the safe operation of the factory power system.