1- Power cable test:

Cable is a group of insulated conductor. Different types cable are used for current carrying in electricity system like as HT cable for HT system, LT cable for LT system and other general utilization cable. Low volt or small cable can be tested multimeter but power cable or high voltage cable will be tested through Megger which is available in 500V DC, 1KV DC, 2KV DC, 5KV DC. All types of megger testing procedure is same. For LT cable testing, 500V or 100V DC megger is used and for HT voltage the 2K or 5K megger is used.

2-Testing diagram :

3-Safety guideline of testing:

Power cable is tested with high voltage so safety precaution must be taken. These points are below mentioned.

• Disconnect the power supply.
• Use lock out and tag out.
• Discharge the cable through earth.
• Disconnect the both ends of cable.
• After testing discharge the cable through earth.
• Remove the LOTO after complete the task.

4-Testing kit:

• Lock out and tag out safety kit
• Megger testing instrument
• 5 mtrs wire for discharging.
• Tools for cable disconnecting.

5-Testing Procedure::

Megger meter black and red probe is connected according below mentioned testing points.

• R phase with armoured earth strip
• Y phase with armoured earth strip
• B phase with armoured earth strip
• R phase with Y phase
• Y phase with B phase
• R phase with B phase
• R phase with neutral
• Y phase with neutral
• B phase with neutral
• Neutral with Earth

1- Testing Procedure with analog megger:

For LT cable the megger is selected 500V or 1000V DC. It is moved at 150 rpm through handle. Connect the meter probe on testing points as above mentioned.

• Connect the prove into testing points as above.
• Move the megger at 150 rpm.
• Check the resistance value on the display.
• If the test value is zero then cable is short.
• If the test value is infinity then cable is ok or not short.
• If the test value is below 2M ohm then the cable insulation is weak.

2- Testing procedure with digital megger.

For LT cable the megger is selected 500V or 1000V DC. It is operated with test button. Connect the meter probe on testing points as above mentioned.

• Connect the prove on testing points according above list.
• Press the test button.
• Check the test value on display.
• If the value is zero then cable is short.
• If the value is infinity then cable is normal.

6-Testing observation:

After testing all ten points the testing value should be compare each other and we can find out what is the insulation part of cable is faulty. If the resistance value is low then the cable is leakage . If the resistance value is zero then the cable is short or not usable. If the resistance value is above 2M ohm then the cable is ok or usable.

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