Simulation Studies on the Grounding of Clustered Single Phase Transformers in Rural Electrification

Rural electrification serves as the catalyst for reduction in urban-rural inequalities. Under the ongoing Self Help Electrification Project in Ghana, clustered single-phase transformers are advantageously replacing single unit three-phase transformers in rural settings. In this research, the integrity of the clustered transformers to grounded faults are investigated. Single and three phase ground faults are studied by way of computer simulations of power system using MATLAB/Simulink software. Simulation results showed that the normal operating condition gave 11 kV at the input and 410 V/20 A at the output of both transformers. For the condition of three-phase short-circuit faults, the clustered transformers experienced high voltages and currents 100 000 times the rated values of 433 V/250 V and 20 A, respectively. Also, distorted waveforms experienced by the clustered transformers were worse than those of the unit three-phase transformer. Under the condition of single-phase to ground fault of the distribution system, output current and voltage readings of affected phases reduced from 20 A to phase-to-phase value of 11 A and 240 V to 180 V, respectively. The three-phase ground faults must be avoided so as to benefit from any advantage associated with use of clustered transformers in distribution systems.