General fault admittance method solution of a balanced line to line to line to ground fault

• The general fault admittance method was used to solve a metallic fault.
• Simulating the four-impedance three phase balanced metallic fault was a challenge.
• Short circuits replaced with low impedances gave the best simulation convergence.
• Results validate solutions from classical approach for a positive sequence network.
• The method eliminates need for sequence component networks layout.

In the classical approach, balanced line to line to line to ground faults are analysed using knowledge of symmetrical component sequence networks connections. At the fault point negative and zero sequence currents are zero, therefore their networks are not used in finding the sequence currents. The positive sequence voltages at various bus bars and the positive sequence line flows in the networks are calculated from the positive sequence current at the fault point. The phase voltages and voltages are found by transforming the sequence values respectively. The solution proceeds from the knowledge of the sequence networks connections for a particular fault. In contrast, the general fault admittance method solution does not require prior knowledge of the sequence networks connections. Therefore more versatile than the classical methods. The paper presents a procedure for simulating the balanced three phase to ground short circuit, which is a prerequisite for using the general fault admittance method for a balanced line to line to line to ground fault. Based on the general fault admittance method a computer simulation model is developed to analyse a power system with a delta earthed star connected transformer. The results obtained are as accurate as those obtained using the classical approach.