Cable Insulation Resistance Test Procedure

The insulation resistance of cable is measured using a megohmmeter.

Cable insulation resistance test procedure. Basically you re applying a voltage specifically a highly regulated stabilized dc voltage across a dielectric measuring the amount of current flowing through that dielectric and then calculating using ohm s law a resistance measurement. Either turn off the breaker or if you re testing the wiring in a piece of equipment unplug it. The insulation resistance test consists in measuring the insulation resistance of a device under test while phase and neutral are short circuited together. Perform insulation resistance test on each conductor with respect to ground and adjacent conductors.

Inspect exposed sections of cables and conductors for physical damage. Applied potential shall be 500 volts dc for 300 volt rated cable and 1000 volts dc for 600 volt rated cable. Test duration shall be one minute. The test measures the insu lation resistance between the phases and or between phase and ground.

This is a simple nondestructive method of determining the condition of the cable insulation to check for contamination due to moisture dirt or carbonization. The megger insulation tester is a small portable instrument that gives you a direct reading of insulation resistance in ohms or megohms. When performing insulation tests on conductors and cable apply the following procedure. With a little record keeping and common sense however you can get a good picture of the insulation condition from values that are only relative.

Insulation resistance testing is a non destructive test procedure. Insulation resistance decreases in temperature or moisture. The insulation resistance test is the second test required by the electrical safety testing standards. Sample insulation resistance megohmeter test connections for cable and transformer using guard terminal.

What is insulation resistance testing. A cable insulation test is basically a continuity test so the power to the circuit must be off. Test period must be for 1 minute using a voltage according to manufacturer s published data. 7 3 2 2 2 2009.

This test is used to detect conductor insulation damage that may have been caused during installation. General testing information for single conductor non shielded cable on a reel insulation resistance testing cannot be. Let s clarify our use of the term current. It is commonly used in the industry for acceptance testing prior to energizing the cable and for maintenance testing programs.

Replace or repair sections that exhibit damage. Developed early in the 20th century the insulation resistance ir test is the oldest and most widely used test for assessing the quality of insulation. Locate the connection point of the wire or cable you want to test so you have access to the exposed conductors. Inspect cables and conductors for proper grounding cable support and termination.