Northwest China Branch of State Grid Corporation of China, Xi'an 710048, China
The line protection mal-operation caused by current secondary circuit defects has taken place many times in China. By analyzing two typical cases of the line differential protection and zero-sequence protection mal-operations caused by the open circuit and short circuit of current secondary circuit of other devices which are connected to the line protection current circuit, it is pointed out that the practice of connecting other devices with the line protection current circuit in series increases the complexity of the whole current circuit. The reliability of line protection operation is reduced, and there is a risk of simultaneous mal-operations of multiple sets of protections connected to the same current circuit. In order to simplify the secondary current circuit wiring and reduce external interference, it is proposed that line protection should use a dedicated current circuit, which is separated from other devices, and two circuit breaker currents are separately introduced to the line protection. At the same time, combined with the development requirements of power grid, it is proposed to add one set of 5P current windings to the existing windings and optimize the distribution and use of each current winding. The proposed method has been applied in the construction and operation of 750 kV power grid in Northwest China.
WEI Lin, ZHANG Jiankang, SU Xiaohua,et al.Analysis and Countermeasures for Line Protection Mal-operation Caused by Current Secondary Circuit Defects[J].Automation of Electric Power Systems,2019,43(19):194-199.DOI:10.7500/AEPS20190321011Copy