As per BS 7671 the minimum resistance required during insulation test for 500 V DC voltage is

Electrical Engineering MCQs on Power Transmission

As per BS 7671 the minimum resistance required during insulation test for 500 V DC voltage is

1. 0.25 MΩ 
2. 0.5 MΩ 
3. 1 MΩ 
4. 2 MΩ 
5. 100 MΩ

Correct answer: 3. 1 MΩ

Insulation resistance

The insulation resistance is defined as the resistance in ohms of wires, cables and electrical equipment. It is the resistance between electrically insulated parts, such as charged metal parts and uncharged metal parts. The insulation resistance is important in order to guard against electric shocks and avoid equipment damage from accidental discharges.

According to BS 7671, insulation resistance should be approximately one megohm for1000 volts. The table below indicates test voltage and the minimum required resistance in accordance with BS 7671.

Nominal Circuit Voltage	Test Voltage	Minimum Resistance
Between 0 V and 50 V a.c.	250 V d.c.	0.5 Mohm
Between 50 v and 500 V a.c.	500 V d.c.	1Mohm
Between 500 V and 1000 V a.c.	1000  V d.c.	1 Mohm