| Impulse withstand voltage Required – KV | Minimum Clearance Required in air – mm |
|---|---|
| Uimp = 0.33 KV | 0.01 mm |
| Uimp = 0.4 KV | 0.02 mm |
| Uimp = 0.5 KV | 0.04 mm |
| Uimp = 0.6 KV | 0.06 mm |
| Uimp = 0.8 KV | 0.1 mm |
| Uimp = 1.2 KV | 0.25 mm |
| Uimp = 1.5 KV | 0.5 mm |
| Uimp = 2 KV | 1 mm |
| Uimp = 2.5 KV | 1.5 mm |
| Uimp = 3 KV | 2 mm |
| Uimp = 4 KV | 3 mm |
| Uimp = 5 KV | 4 mm |
| Uimp = 6 KV | 5.5 mm |
| Uimp = 8 KV | 8 mm |
| Uimp = 10 KV | 11 mm |
| Uimp = 12 KV | 14 mm |
IEC 60947 – Low voltage switchgear and controlgear
IEC 60947 the Standard for Low Voltage Switchgear and Controlgear – ACB, MCCB, SDF, MCB, Contactor, Relay, Transfer Switch, Arc Quenching Devices.