Damped oscillatory wave test:
This phenomenon is representative of switching actions in HV/MV open air stations, and is particularly related to the switching of HV busbars. The oscillation frequency ranges from about 100 kHz to a few megahertz , depending on the length of the circuit and on the propagation time. The minimum repetition frequency, in respect to each phase, is twice the power frequency (100/s per phase for 50 Hz and 120/s per phase for 60 Hz). The repetition rate 40/s and 400/s represents a compromise of a three phase system.

Impulse withstand test 1.2/50 µs:
The classic insulation withstand test is carried out with a 1.2/50 µs waveform. This waveform must remain within tolerances, when applied to the device under test. As long as the devices under test are resistive, capacitive or inductive the 1.2/50µs wave shape can be kept within the tolerances. With protection circuits involved, it would no longer be possible to keep the waveform within tolerances. As a consequence, in IEC 255-5 a generator and a test procedure are specified for insulation withstand tests based on a defined source energy and impedance. The waveform is verified without the device under test. During tests the waveform must not be monitored.