Insulation Resistance of the Complete Installation to Earth

Insulation Resistance of the Complete Installation to Earth Points : insulation resistance of the complete installation to earth The aim of this test is to know whether the wires used in the system are quite sound to avoid current leakage. The voltage used for insulation resistance tests mast be a D.C. voltage not less than twice that to which the circuit will normally by subject, but not necessarily exceeding 500V. A 500V testing set, the “Megger”, may conveniently be used. Before making an insulation resistance tense of the complete installation, all fuse links are provided, al lamps are put in position all switches are made on. The live wire and the natural wire are shorted as shown and shown and connected to the line terminal of the megger and earth terminal of megger is connected to earth continuity conductor or directly to the earth electrode as is Fig.

The measured resistance for satisfactory wiring must not be less than.
50 megohms/number or oulet + swichtes

It is desirable that for complete installation, the value of resistance measured should not be more than I mega ohm. The value of 50 can, however, be further-reduced to 121/2 for installalions using P.V.C. Insulated cables. The control rheostats, heating and power appliances, and electric signs, if desired, may be disconnected from the above test. In this case, the insulation resistance between the case or the frame-work and all live parts of each appliance shall not be less than that specified in the appropriate Standard, or where there is no such standard, it should not be less than /2 megohm.