This led to what AEMO calls in its report a "single phase to ground fault".
On 14 March 2005 the 275kV transmission backbone of Northern – the same as the one that was hit last week – suffered the same single phase to ground fault, in that case due to dirty insulators.
Numerous internal fault types such as single phase to ground fault, phase to phase fault, double phase to ground fault, and three phase fault at different locations, inception time and pre-fault loading were applied using the prescribed laboratory system.
Fig. 3 Single phase to ground fault on a double circuit line with current reversal.
The waveforms during three phase to ground fault is shown in Fig. 6.
The simulation output voltage and current waveforms are shown in Figs. 2, 3, 4, 5, 6 and 7. Fig. 2 Phase-A to ground fault Fig. 3 Residual error curve during phase-A to ground fault Fig. 4 Phase-AB to ground fault Fig. 5 Residual error curve during phase-AB to ground fault Fig. 6 Three phase to ground fault Fig. 7 Residual error curve during three phase to ground fault.
Fig. 9 Stator currents for an internal single phase to ground fault at 50% of phase A winding Fig. 10 Recorded stator currents for an internal single phase to ground fault at 50% of phase A winding.
Fig. 6 Response of SVM1 and SVM2 to a three phase to ground fault at 75% of stator windings.
A three phase to ground fault is simulated at 75% of stator windings away from the neutral point.
According to the MMC-HVDC system state Eq. (7), common types of fault, e.g. phase A to ground fault, phase-AB to ground fault, three phase to ground fault are simulated based on the 61-level MMC-HVDC system using Matlab/Simulink and RT-LAB.
For example, simulation and laboratory results for internal single phase to ground faults at 50% of phase A winding are shown in Figs. 9 and 10 respectively.
