基于4PT中性点二次电压的PT短路故障在线监测

Online Monitoring of PT Short Circuit Faults Using 4PT Neutral Point Secondary Potential

4PT接线方式广泛应用于10 kV、35 kV等不接地系统,实现电压实时监测。PT在长期工作中,可能会因为某种原因引发匝间、层间等绕组短路故障。为此提出了一种基于4PT中性点二次电压的PT短路故障在线监测方法。首先对典型4PT接线方式下,二次三相电压、零序电压值进行理论分析;其次对PT短路故障现象及发生短路故障后PT电气特征变化情况进行了详细分析;然后分析了PT短路故障对4PT接线方式下电压、电流的影响,并提出了PT短路故障的在线监测方法;最后通过试验、仿真对提出的PT短路故障在线检测方法进行验证,证实了理论分析的正确性、方法的可行性。所提出的在线监测方法能够在PT不退出运行、不拆卸的情况下对PT的健康状态进行实时准确监视,有效避免因无法及时发现PT短路故障而导致的严重后果。

The 4PT wiring method is widely used in ungrounded systems such as 10 kV and 35 kV to achieve real-time voltage monitoring.In long-term operation,PT may encounter inter-turn,inter-layer,and other types of winding short circuit faults due to certain reasons.This paper proposes an online monitoring method for PT short circuit faults based on 4PT neutral point secondary potential.First theoretical analysis is conducted on the secondary three-phase potential and zero sequence potential values under a typical 4PT connection mode.Second the phenomenon of PT short circuit fault and the change of PT electrical characteristics after the occurrence of short circuit fault are analyzed in detail.Then the influence of PT short circuit fault on potential and current under 4PT connection mode is analyzed,and an online monitoring method for PT short circuit fault is proposed.Finally experiments and simulations are carried out for verification,confirming the correctness of theoretical analysis and the feasibility of the proposed method.This online monitoring method can accurately and real-time monitor the health of PT without exiting the operation or disassembling the PT,thereby effectively avoiding serious consequences caused failure to promptly discover PT short circuit faults.