Performance Analysis of a Communication-Supported Earth Fault Protection System of Medium Voltage Loop and Meshed Networks

A communication-supported system for the earth fault protection in medium voltage loop and meshed networks with unearthed neutral, is proposed and assessed. The system is based on directional relays installed at both ends of each line, which communicate with each other. The directional relays implement an innovative transient fault detection technique that determines the directionality of the fault by calculating the angle between the earth mode voltage and the current at the dominant transient frequency. The performance of the protection system in response to cross-country faults, is assessed by using a specifically developed software tool that interfaces EMTP-RV with Matlab. The influence of the communication network limitations, i.e. latency and complete loss of communication, on the protection system performance and the effect of the sampling frequency on the operation zones are also analyzed.