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 – 50	330 V	500 V	800 V	1500 V
Vph – 100	500 V	800 V	1500 V	2500 V
Vph – 150	800 V	1500 V	2500 V	4000 V
Vph – 300	1500 V	2500 V	4000 V	6000 V
Vph – 600	2500 V	4000 V	6000 V	8000 V
Vph – 1000	4000 V	6000 V	8000 V	12000 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 KV	Sensitive electronic equipment – Eg: TV, Laptop, Electronic Equipments
Cat – II (normal impulse voltage)	2.5 KV	Domestic appliances – Eg : Washing Machine, Fridge,
Cat – III (high impulse voltage)	4 KV	Main Distribution Boards
Cat – IV (very high impulse voltage)	6 KV	Near the Energy Meter

Min Impulse Withstand Voltage for Rated Operatonal Voltage of 230VAC

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