Cable Megger Test Insulation Resistance Values Table

Based upon equipment rating.

Cable megger test insulation resistance values table.

The first thing to check is the cable testing environment and cable preparation. Reverse side of card at right is used to record the test data. The megger insulation tester is essentially a high range resistance meter ohmmeter with a built in direct current generator. It s also known as an insulation tester.

Figure 3 typical scale on the megger insulation tester. If during periodical testing insulation resistance of cable is found between 5 and 1 mω km at buried temperature the subject cable should be programmed for replacement. A rated line to line voltage for three phase ac machines line to ground voltage for single phase machines and rated direct voltage for dc machines or field windings. At a pressure of 1000 v applied between each live conductor and earth for a period of one minute the insulation resistance of hv installations shall be at least 1 mega ohm or as specified by the bureau of indian standards.

B kv is the rated machine terminal to terminal voltage. If during periodical testing insulation resistance of cable is found between 5 and 1 mω km at buried temperature the subject cable should be programmed for replacement. If the cable does not pass if a cable does not pass the test the cable still may be good but additional cable evaluation should be per formed. As per ie rules 1956.

Electric heat tracing systems are widely used inprocessindustriesand have applications in many other areas as well. Values based on ieee std 43 2013. If insulation resistance of the cable is found between 1000 and 100 kω km at buried temperature the subject cable should be replaced urgently within a year. Insulation resistance testing of heat trace cable.

Curve a shows test values as measured. Figure 4 typical record of insulation resistance of a mill motor. 2621 van buren avenue. Insulation resistance testing of heat trace cable.

To test a cable with a megger you connect one probe to the outside of the cable and with the power turned off you touch the probe to the conducting wire at the point of connection. The megger insulation tester is a small portable instrument that gives you a direct reading of insulation resistance in ohms or megohms. A megger is an ohmmeter that measures resistance in the megohm scale. For good insulation the resistance usually reads in the megohm range.

Curve b shows same values corrected to 20 c see page 22 giving a definite downward trend toward an unsafe condition. One meg ohm rule for ir value for equipment. If insulation resistance of the cable is found between 1000 and 100 kω km at buried temperature the subject cable should be replaced urgently within a year. Ansi neta mts 2015 table 100 11 insulation resistance test values rotating machinery for one minute at 40 c.