摘要
在星形/三角形连接组的变压器差动保护设计上,原有做法一般是对星形(Y)侧电流转角,进行二次电流的幅值和相位校正,之后与三角形(△)侧绕组的线电流构成差动保护,即线电流差动判据。有观点认为,线电流差动消去了零序电流,造成接地故障时的灵敏度降低。因此,需要引入零序差动保护等补偿措施。通过理论分析发现,原有的设计并没有消去零序电流,其对差动电流的作用从相电流差动判据的显式助增转化为线电流差动的隐式助增,并以相电流差动为参照,考核线电流差动判据的性能。在一致安全性的前提下,确定了线电流差动和相电流差动进行比较的前提。进一步通过灵敏性分析发现,相电流差动对灵敏性的提高不是体现在对差动电流的修正上,而是体现在对制动电流的改善上。
For the differential protection of power transformers with Y/Δ connection, the currents on the Y-winding are usually revised on magnitudes and phase angles. The purpose is to set up the differential protection in line with the line currents of Δ-winding, which is named as line current differential protection in this paper. Some manufacturers claim that the zero sequence current is removed in the line current differential criterion and the sensitivity of the protection in the event of the earth fault is lowered. Therefore, the zero-sequence current differential criterion is introduced. According to the theoretical analysis in this paper, it is disclosed that the design of the line current differential does not remove the zero sequence current, which assists the phase current differential current via apparent action whereas assists the line current differential current via latent action. The phase current differential criterion is introduced as the reference to checkout the performance of the line current differential criterion. On the basis of consistent security, the premise of the comparison between the phase current differential and the line current differential is determined. Furthermore, it is proved by sensitivity analysis that the improvement to the sensitivity arising from the phase current differential comes from the revision of the bias current rather than the differential current.
出处
《电力系统自动化》
EI
CSCD
北大核心
2005年第3期21-25,共5页
Automation of Electric Power Systems
基金
国家自然科学基金资助项目(50177011)。
