Experimental studies of breakdown characteristics of a 12-kV arcing horn under a lightning impulse superimposed on AC voltage

This paper presents the studies of breakdown characteristics of a 12-kVarcing horn under a lighting impulse superimposed on an AC power frequency voltage at various angles. The lightning impulse is superimposed on the AC power frequency voltage at a phase angle varied from 0° to 360. The 12-kV arcing horn under test has dimension and configuration according to DIN 42531 standard. The critical breakdown voltages (U_b50%) with and without superposition of an impulse voltage on the AC voltage are investigated and made comparison. It is found that the statistical breakdown voltages are depended on the phase angle of the AC voltage superposed by the lightning impulse voltage. From the test results, the AC voltage affects the insulation level and it should be taken into account in an insulation design and insulation coordination.