Test of the insulation performance of the EUT.
IEC 62052-11, part 7.3 Insulation
Energy meters have typically protection class II. The rated impulse voltage is 4 kV for meters < 150 V ph-earth or 6 kV for meters with ph-earth voltage between 150 V and 300 V.
For each test the impulse voltage is conducted ten times with one polarity and ten times with reversed polarity. The minimum time between the impulses shall be 3 s. Impulse waveform is 1.2/50 μs.