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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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As per BIS the measured insulation resistance of any wiring installation should not be less than:
100 ohm
1000 ohm
100 Kohm
1000 Kohm
1000 Kohm
According to the Bureau of Indian Standards (BIS) and the Indian Electricity (IE) Rules, the insulation resistance of a low and medium voltage wiring installation should be at least 1 MΩ (1000 kΩ) when measured between phases and earth. This ensures that leakage currents are minimized, thereby preventing electric shocks and potential fire hazards due to insulation failure.
According to the Bureau of Indian Standards (BIS) and the Indian Electricity (IE) Rules, the insulation resistance of a low and medium voltage wiring installation should be at least 1 MΩ (1000 kΩ) when measured between phases and earth. This ensures that leakage currents are minimized, thereby preventing electric shocks and potential fire hazards due to insulation failure.
Rins=IleakageVtest — Ohm's Law application for insulation resistance measurement
Rlimit≥1000 kΩ — BIS minimum threshold for wiring installations
The insulation resistance test is performed using an instrument called a 'Megger'. The principle involves applying a high DC voltage (typically 500V DC) across the conductors and the earth connection. The Megger measures the ratio of the applied voltage to the resulting leakage current (R=V/I), which indicates the integrity of the dielectric insulation material surrounding the wiring.
Measured between phase conductors and earth.
Ensures safety against electric shock and prevents leakage currents.
Usually tested at 500V DC for standard 230V domestic installations.
Low insulation resistance often indicates moisture, damaged insulation, or short circuits.
Prevents catastrophic short circuit failures.
Reduces energy wastage through leakage paths.
Cannot detect insulation faults occurring at voltages higher than the test voltage.
Requires complete isolation of sensitive electronic devices during testing.
Domestic wiring certification.
Industrial motor maintenance.
Cable health monitoring in distribution systems.
The 1 MΩ rule is a standard safety benchmark intended to provide a sufficient factor of safety against dielectric breakdown.
Option C (100 kΩ) is generally considered inadequate for new installations under modern safety codes.
D is correct — The minimum insulation resistance permitted by BIS for low and medium voltage installations is 1000 kΩ (1 MΩ).
Remember that for higher voltage systems, the insulation resistance requirement increases significantly; always check if the question specifies 'Low Voltage' (up to 250V/650V) versus HV systems.