Acceptable Cable Insulation Resistance Test Values

The results obtained from ir test are not intended to be useful in finding localized defects in the insulation as in a true hipot test but rather give information on the quality of the bulk material used as the insulation.

Acceptable cable insulation resistance test values. For cables rated 600 v the minimum acceptable insulation resistance values for cable lengths from 100 to 1000 feet would be as shown in the following table from ieee 525. Even when not required by the end customer many wire and cable manufacturers use the insulation resistance test to track their insulation manufacturing processes and. The level of humidity influences the insulation accord ing to the degree of contamination of the insulating surfaces. 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.

Since 80 of electrical maintenance and testing. Insulation for cables rated 600 v the minimum acceptable insulation resistance values for cable lengths from 100 to 1000 feet would be as shown in the following table. Insulation resistance tests are made to determine insulation resistance from individual windings to ground or between individual windings. 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.

B kv is the rated machine terminal to terminal voltage. Curve b shows same values corrected to 20 c see page 22 giving a definite downward. 3 shows a typical scale which reads increasing resistance values from left up to infinity or a resistance too high to be measured. Minimum acceptable insulation resistance for 600 v cable from 100 to 1000 feet.

Temperature halves the insulation resistance while a 10 c reduction doubles the insulation resistance value. Hands down without a doubt one of the most universally searched topics on ec m s website from a historical perspective is insulation resistance testing as a result some of our most popular evergreen articles like understanding insulation resistance testing continue to top the charts when it comes to most popular content. 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. Figure 4 typical record of insulation resistance of a mill motor.

A megger sends voltage through a cable and measures any current leakage in megohms 1 000 ohms. 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. Care must always be taken not to measure the insulation resistance if the temperature is lower than.

Ansi neta mts 2015 table 100 11 insulation resistance test values rotating machinery for one minute at 40 c.