双回线路跨线故障及保护动作行为分析

Analysis of Overhead Line Fault and Protection of Double-circuit Transmission Lines

以山西220kV系统某线路的一次实际跨线故障录波数据为基础,分析了同杆双回线路保护安装处的电流电压特征,研究了该线路上4套不同厂家、不同型号常规微机型线路保护的动作行为,提出了同杆并架双回线保护选型应注意的问题。结果表明,异名相跨线故障期间,各端保护可以检测到零序电流,但无零序电压；变化量方向元件可以正确判断方向；采用零序电流(?)_0和负序电流(?)_(2A)构成的稳态量选相元件能正确选相；零序方向元件的动作行为不确定；相间测量阻抗增大、接地测量阻抗减小均不能正确反映故障位置。

Based on the actual overhead line fault recorded data of a transmission line in the 220 kV electric power system of Shanxi Province, the current and voltage characteristics at the site of the protection equipment for double-circuit transmission lines on the same pole are analyzed. The action-behaviors of four conventional microcomputer-based line protections with different types and from different manufactures are studied. The problems related to the protection selection of double-circuit transmission lines are highlighted. The results show that： （1） the zero-sequence current but not the voltage can be detected by the protections located at both sides of transmission lines during overhead line fault between different phases; （2） the differential directional elements can be identified accurately; （3） the steady-state phase selection elements formed by the zero- sequence current I0 and negative-sequence current I2A can be used to select phase exactly; （4） the action-behaviors of the zero- sequence directional element is uncertain; （5） both the increase of the measured impedance between phases and the decrease of the measured grounding impedance can not reflect the fault location correctly.