Improved Protection Scheme for High Voltage Transmission Lines Connecting Large-Scale Solar PV Plants

The fault current characteristics of power electronics interfaced large-scale solar photovoltaic (PV) plants satisfying fault ride through requirement are quite different compared to the traditionally used synchronous generator-based power system. Consequently, the conventional distance relaying scheme face underreaching problem large-scale solar PV plant connected transmission lines. In this paper, a modified distance relaying technique is proposed to overcome the underreaching problem faced by conventional distance relay while used for protection solar PV plant connected transmission lines. In this approach, the net apparent power supplied from the PV side and grid side during ground faults in the interconnected transmission line is calculated using the line end synchronized voltage and current measurements. From the calculated values of the apparent power, the fault path resistance and hence the incremental impedance due to the fault path resistance is calculated and subtracted from the impedance seen by the PV side distance relay to obtain the correct line impedance between the PV side relay and fault point. This helps in estimating the correct fault location from the PV side distance relay. The efficacy of the method is validated data simulated on a 2-bus system through MATLAB/Simulink.