Oscillation phenomena in isolated high voltage networks caused by lightning strokes

Isolated networks are common practice for operating high voltage networks up to a small earth fault current defined by standards. The reason for choosing this type of network are the saving of the arc suppressing coils by coexistence of a self-healing grid in case of an earth fault. During the starting up of a 110-kV-isolated network long-time measurement were installed. During these measurements several unexpected voltage oscillation phenomena were detected. Investigations show that lightning strokes in the area around the high voltage line are the sources of the voltage oscillation. Comparisons between the measurement of the voltages and currents of the high voltage line and the detection protocol of the Austrian Lightning and Detection System (ALDIS) proofed this hypothesis. This paper describes the phenomena based on measurement, the correlation with lightning strokes and will confirm the measurement with simulation examples.