The influence of temperature on the differential current protection of EHV shunt capacitor bridges

The shunt capacitor is a very important part of the EHV (Extra High Voltage) transmission system in China. Shunt capacitors can compensate reactive power and improve the power quality. It plays an important role in the regulations of voltages and power factors. At the same time, high repairing rates are always found in the outlet terminal shunt capacitors in each EHV station. Therefore, the protection scheme for EHV shunt capacitor is widely used: a single capacitor fuse protection acts as the primary protection, and the double bridge differential current protection acts as the backup protection. However, most of the existing research is based on the analysis of different fault conditions. The discussions on external factors, such as temperature, are limited. This paper studies the influences from temperature variations on the double bridge differential current protection of shunt capacitors. The influences are demonstrated by theoretical calculations as well as simulations.