A robust THD based communication-less protection method for electrical grids with DGs

Abstract

In this paper, a protection method with two cascaded algorithms is proposed to face fault events in Electrical Distribution Systems (EDSs). The first algorithm uses the Total Harmonic Distortion (THD), the estimates of the amplitude voltages, and the zero-sequence component of the grid voltages for defining an adaptive algorithm that provides a secure detection and identification process for the faults in the grid network. The second algorithm uses the behavior of the positive and negative-sequence components of the grid voltages during the fault events to locate and isolate the faults. Its main merit is that it doesn’t need to employ communication lines for transmitting trip signals between the protective devices (PDs) of the system. A Second Order Generalized Integrator (SOGI) is used for obtaining the estimated variables and sequence components, which allows fast detection with a low computational burden. The harmonic content existing prior to the fault is taken into consideration for not affecting the detection of the fault. The performance of the protection method’s is evaluated experimentally and by using simulations in MATLAB/Simulink and employing the IEEE 9-bus standard ring system. The proposed method shows the capability for detecting, identifying, and isolating different fault types with different DG penetrations and fault resistances in different locations of the proposed network and even when the grid configuration is changed. The method is robust to the possible harmonic distortion of the network.