Acceptable Cable Insulation Resistance Test Values

Is the length of the cable in meters if the cable length is in feet replace the number 304 8 with 1000.

Acceptable cable insulation resistance test values.

Insulation resistance acceptance test values for motor windings 1 minute 40 c 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. Second the range of a megohmmeter is in megohms as its name implies instead of ohms as in a multimeter. For example a motor rated at 2 400 volts should have a minimum insulation resistance of 2 4 megohms.

You perform this insulation resistance test on the cable and record the data on a copy of the attached form. The resistance values will increase over time due to capacitive and insulation charging. 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. 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.

Also noted is the practice of recording the insulation resistance values when. The insulation resistance test is an electrical test which uses a certain type and level of voltage 500v d c. A corrected measurement at 20 degrc would be 200 megohms 100 megohms times two. For low voltage installations i e.

The measured resistance indicates the condition of the insulation between two conductive parts. For a good cable you will see results similar to those on the following page. You have a single conductor 500 kcmil 15kv cable. The insulation resistance is deemed satisfactory if the circuits as tested result in values not values for a 400 230 volt system are acceptable down to 0 dc field test for medium voltage cables dc field test for medium voltage cables.

Historically many field electricians use the somewhat arbitrary standard of 1 megohm per kv. The ieee43 2000recommendationon recommended practice for testing insulation resistance of rotating machinery defines the minimum value of the polarization index pi for ac and dc rotating machinery in temperature classes b f and h as 2 0. 230v to measure insulation resistance in ohm s. Also acceptable values of insulation resistance depend upon the equipment you re testing.