Technical Information Power And Control Cables Power Appendixes Guide to the Wiring Regulations Inspection, Testing and Certifcation ; Insulation testing صفحه Inspection, Testing and Certifcation ; Insulation testing
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Inspection, Testing and Certifcation ; Insulation testing Insulation testing is fundamental and will be used as cables are being installed. On completion of the circuit and before energization, the circuit insulation is again checked. The tests show faults or shorts as well as low insulation caused by moisture and similar. Electrical equipment and appliances such as controlgear and lamps should be disconnected prior to testing. Many such devices if left in-circuit would show as an insulation failure; also, sensitive electronic equipment such as dimmer switches and electronic ballasts could be damaged in the test. Insulation resistance is measured between: * Live conductors, including the neutral; * Live conductors and the protective conductor connected to the earthing arrangement. |
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ESSENTIALS (of Insulation Testing) : Tests : with CPC connected to each system Test :between all live conductors to neutral and to earth Readings : should be approximately tens of MOhm |
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| Insulation testing of a motor circuit | Insulation testing a group of circuits |
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It should be noted that Regulation states that insulation testing is to be made between the live and protective conductors with the protective conductors connected to the earthing arrangement. This is an additional requirement compared with previous editions of the Standard where, for example, cable could be tested to its cpc and then terminated. This procedure may catch you out as you may not be accustomed to carrying it out. The minimum values of insulation resistance of 1 MOhm is an increase from the 0.5 MOhm of the IEE 16th Edition. For most new circuits values would be way in excess of this, usually approaching the maximum scalon the meter. Perhaps an underused technique is that of carrying out insulation testing on groups of circuits together as shown in above Figure, and it is recommended that this is limited to 50 outlets per test. |
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