Cable Megger Test Insulation Resistance Values Table

Figure 4 typical record of insulation resistance of a mill motor.

Cable megger test insulation resistance values table.

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. 1k v 1 mω minimum 1kv 1 mω 1kv. One meg ohm rule for ir value for equipment. A megger is an ohmmeter that measures resistance in the megohm scale.

It s also known as an insulation tester. Insulation resistance testing of heat trace cable. Based upon equipment rating. 2621 van buren avenue.

The first thing to check is the cable testing environment and cable preparation. The megger insulation tester is essentially a high range resistance meter ohmmeter with a built in direct current generator. In general these systems are used to maintain a preferred temperature. Ansi neta mts 2015 table 100 11 insulation resistance test values rotating machinery for one minute at 40 c.

Comparing this result with the correct row of table 2 shows that our cable passes the insulation resistance test. 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. 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. Electric heat tracing systems are widely used inprocessindustriesand have applications in many other areas as well.

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 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. 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.

The megger insulation tester is a small portable instrument that gives you a direct reading of insulation resistance in ohms or megohms. B kv is the rated machine terminal to terminal voltage. Curve a shows test values as measured. Curve b shows same values corrected to 20 c see page 22 giving a definite downward trend toward an unsafe condition.

Figure 3 typical scale on the megger insulation tester. For good insulation the resistance usually reads in the megohm range. Values based on ieee std 43 2013. Insulation resistance testing of heat trace cable.