Distance protection is a very important backup protection used in high-voltage power transmission line. Malfunctions of distance protection caused by overload during large-scale blackouts in the world expand the accident scope. For overload of transmission line, the load impedance decreases with the increasing of load and when it goes into action zone of distance protection, the distance protection will be mal-operated. Thus, it is important to identify line overload and fault to avoid mal-operation of distance protection.
Normally, load limit line is used to identify transmission line fault and normal overload in impedance plane. However, there are also some disadvantages. Firstly, the load limit line is difficult to avoid mal-operation of distance protection in overload condition. Secondly, it reduces the action zone of distance protection and weakens the distance protection performance of faults with high resistances. Characteristics of transmission line overload and fault are analysed in voltage plane and criterion
based on Ucosφ is proposed to identify overload and fault.
Wang Xingguo, Zhou Zexin, Liu Huanzhang, Du Dingxiang, In Proc. Cigre Canada 2019, Montreal, QC, September 2019
KEYWORDS: Distance protection, transmission line faults, overload, voltage plane, Ucosφ