Insulation coordination for Switchgear and Assembly as per IEC 60664

Rated Impulse Voltage (Uimp) for Overvoltage category -- I, II, III, IV at various nominal Voltage (Ue) is suggested in IEC 60664.

Rated Impulse Voltage (Uimp) for Overvoltage category — I, II, III, IV at various nominal Voltage (Ue)

Nominal Voltage
Ue
Line to Neutral		Uimp for
Overvoltage
category — I		Uimp for
Overvoltage
category — II		Uimp for
Overvoltage
category — III		Uimp for
Overvoltage
category — IV
Vph – 50330 V500 V800 V1500 V
Vph – 100500 V800 V1500 V2500 V
Vph – 150800 V1500 V2500 V4000 V
Vph – 3001500 V2500 V4000 V6000 V
Vph – 6002500 V4000 V6000 V8000 V
Vph – 10004000 V6000 V8000 V12000 V
Insulation coordination

Min Impulse Withstand Voltage for Rated Operatonal Voltage of 230VAC

Impulse
withstand
category		Required
Impulse
withstand voltage		Equipment
in category
Cat – I
(low impulse
voltage)		1.5 KVSensitive electronic equipment –
Eg: TV, Laptop, Electronic Equipments
Cat – II
(normal impulse
voltage)		2.5 KVDomestic appliances –
Eg : Washing Machine, Fridge,
Cat – III
(high impulse
voltage)		4 KVMain Distribution Boards
Cat – IV
(very high impulse
voltage)		6 KVNear the Energy Meter
Min Impulse Withstand Voltage for Rated Operatonal Voltage of 230VAC
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