Cable Megger Test Insulation Resistance Values Table

Comparing this result with the correct row of table 2 shows that our cable passes the insulation resistance test.

Cable megger test insulation resistance values table.

Electric heat tracing systems are widely used inprocessindustriesand have applications in many other areas as well. Curve a shows test values as measured. 1k v 1 mω minimum 1kv 1 mω 1kv. It s also known as an 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. 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. Ansi neta mts 2015 table 100 11 insulation resistance test values rotating machinery for one minute at 40 c. Values based on ieee std 43 2013.

Curve b shows same values corrected to 20 c see page 22 giving a definite downward trend toward an unsafe condition. As per ie rules 1956. One meg ohm rule for ir value for equipment. 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.

B kv is the rated machine terminal to terminal voltage. 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. For good insulation the resistance usually reads in the megohm range. A megger is an ohmmeter that measures resistance in the megohm scale.

Figure 3 typical scale on the megger insulation tester. 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 essentially a high range resistance meter ohmmeter with a built in direct current generator. 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.

2621 van buren avenue. Insulation resistance testing of heat trace cable. The first thing to check is the cable testing environment and cable preparation. Insulation resistance testing of heat trace cable.

The megger insulation tester is a small portable instrument that gives you a direct reading of insulation resistance in ohms or megohms. Reverse side of card at right is used to record the test data. Figure 4 typical record of insulation resistance of a mill motor. In general these systems are used to maintain a preferred temperature.