Insulation Resistance of Ground to Earth

Unregistered said:

Sir,

I would like to know what is the acceptable Insulation resistance of Neutral to Earth in a 3 Phase 380 VAC 4 wire ... where we get a 220 VAC supply from neutral to ground... 220 VAC is supplying computer, Lighting, water cooler and some CCTV loads

Are there any website that have this information?

Thank You very much

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Testing wiring and cable installations
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When testing wires or cables, they should be disconnected from panels and machinery to keep them isolated. The wires and cables should be tested against each other and against ground (see Figure 4 on page​

4). The Insulated Power Cable Engineers Association (IPCEA)provides the following formula that suggests minimum insulation resistance values.​

R = K x Log10 (D/d)​

R​

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- MΩs per 1000 feet (305 meters) of cable. Based on dc test potential of 500 volts, applied for one minute at 15.6ｰC (60ｰF)temperature)​

K - Insulation material constant.(For example: Impregnated Paper-2640, Varnished Cambric-2460, Thermoplastic Polyethlene-50000, Composite Polyethylene-30000)​

D - Outside diameter of conductor insulation for single conductor wire and cable D = d + 2c + 2b diameter of single conductor cable​

d - Diameter of conductor​

c - Thickness of conductor insulation​

b - Thickness of jacket insulation​

For example, one thousand feet of number 6 A.W.G. Heat Resistant Natural Rubber insulation type stranded conductor with 0.125 insulation thickness will have K = 10,560 and Log10 (D/d) = 0.373 inches. According to the formula (R = K x Log10 (D/d), R = 10,560 x 0.373 = 3,939 MΩ per 1000 feet) the expected minimum insulation resistance for single conductor per thousand feet at temperature of 60ｰF will be 3,939 MΩ​

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