Factors influencing the switching impulse testing in laboratory conditions

The main aim of this paper is to discuss important aspects with respect to the switching impulse voltage testing of insulator sets under laboratory conditions. Those factors include mainly rain parameters, clearances to the ground, laboratory walls and larger grounded objects (like a rain tower). The testing of glass cap&pin "V" single suspension insulator sets with a setup simulating a tower window (center phase) and a setup acc. to lEe 60383-2 (outside phase) were done in different positions and under dry and wet conditions to see differences in their switching impulse dielectric strength. Repeatability of the testing under dry and wet conditions is discussed also. Finally comparison of measured switching impulse flashover voltage values of given setups with values calculated from a gap factor concept is discussed.