Auas SVC, performance verification by RTDS and field tests

The new 400 kV interconnection between Namibia and South Africa was successfully commissioned in the last quarter of 2000. The 890 km single circuit 400 kV AC transmission line interconnects the two systems, ESKOM and NamPower, at the Aries substation near Kenhardt in South Africa and the Auas substation near Windhoek in Namibia. With the new interconnection, the NamPower system is strengthened, but the new 400 kV line is also very long with a large charging capacitance which aggravates the inherent problems in the NamPower system; namely voltage stability and near 50 Hz resonance. The charging capacitance shifts the existing parallel resonance very close to 50 Hz and makes the network more voltage sensitive during system transients such as 400 kV line energisation or recovery after clearing of line faults. The authors describe how the SVC performance of this system has been verified by RTDS and field tests.