Distance protection with penetration of Distributed Generation infeed in transmission lines

Abstract

The grids changed from passive to active grids with Distributed Generation units (DG) allowing the power flow in either direction. The main objectives of DG units are providing a continuous power supply to the load, providing power where the main grid cannot supply electric power, increasing energy efficiency, improving voltage profile, reducing line losses, reducing the emission of pollutants, improving the system voltage stability, and improving system reliability. However, DG connections give significant influence on the protection coordination. When DGs are connected to the same network, the protection devices will be able to detect and sense the flow of fault currents in different directions. Without DG, the only source of short circuit current was the grid, and protection systems were designed accordingly. The operation of protective devices would be affected by the changes in the fault current level in the power system. The integration of DG into protective equipment could cause reverse power flow, false tripping, loss of protective devices grading, and blinding of protection. In this research, a new distance relay model built using MATLAB Simulink is proposed to compensate the effect of DG integration with the distribution grid. A simple communication-based scheme for accurately calculating the distance to fault in the presence of infeed is proposed. The proposed model is tested by different faults location, different fault arc resistance, and different penetration levels of DG. The proposed protection communication has high accuracy to trip the faults, the fault is cleared by the distance relay in case of distance relay cannot sense the fault, the overcurrent will trip the circuit and the system maintain in operation state, the proposed distance relay is not affected by the infeed in case of the fault present in zone two.