陕西电网“8.14”故障330 kV主变压器差动保护动作分析

330 kV Main Transformer Differential Relay Operation Analysis of 8.14 Fault in Shaanxi Power Grid

介绍了陕西电网某330 kV变电站"8.14"故障简况。对故障报告重新分析整理,采用主变差动保护装置动作时记录的故障数据,研究实际故障过程、保护动作行为及原因,找出主变区内、外故障的特征,得出主变区外低压侧故障诱发主变内部故障的判断,并经主变大修后证实主变内部存在轻微损伤,澄清了原保护动作分析报告中存在的疑点,分析了保护不正确动作的原因。指出应重视并防范此类故障发生,研究改进差动保护原理,尽量缩短保护动作时间;国产主变抗低压侧短路能力严重不足,不满足IEC和国标抗短路水平要求。建议变压器制造厂家优化主变的结构和制造工艺,提高主变的制造质量。

This paper introduces the 8.14 fault occurred in certain 330kV substation in Shaanxi power grid. By reviewing the fault investigation report, the actual fault data, relay operation behavior and causes are studied. The characteristics from external fault to coexistence of external and internal fault are put forward by using the fault data retrieved from transformer current differential relays. The judgment that transformer internal minor fault is induced by transformer tertiary winding external fault is made, and is verified by the transformer overhaul that followed. Therefore the doubts are clarified in the fault report and the relay operation mal-operation causes are analyzed. Finally it is concluded that the indigenously manufactured power transformer is unable to meet IEC and GB standard when high fault current occurred in tertiary winding. It is suggested to optimize transformer structure and manufacturing technique by the manufactures for raising the transformer quality level and shortening the protection duration as possible.