# Megger test / Sheath resistance test procedure for cables

**URL:** <https://forumautomation.com/t/megger-test-sheath-resistance-test-procedure-for-cables/2549>\
**Category:** Electrical\
**Tags:** instrumentation\
**Created:** [November 1, 2017, 9:34am UTC](https://forumautomation.com/t/megger-test-sheath-resistance-test-procedure-for-cables/2549 "2017-11-01T09:34:37Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![sivaranjith](https://forumautomation.com/letter_avatar_proxy/v4/letter/s/ba9def/32.png) [@sivaranjith](https://forumautomation.com/u/sivaranjith)\
**Post date:** [November 1, 2017, 9:34am UTC](https://forumautomation.com/t/megger-test-sheath-resistance-test-procedure-for-cables/2549/1 "2017-11-01T09:34:38Z")

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A Megger test or sheath resistance test is used to diagnose cable faults, either short circuit problem, water penetration, moisture or current leakage. A Megohmmeter is used to measure the resistance of the crossed-link to an applied DC voltage.

A Megohmmeter applies current for 1 minute through the cable before being measured and recorded. The voltage applied varies depending on cables.

> **Megger tester**

 ![](https://cdn.forumautomation.com/original/1X/efecc8eddd17cd00df41ce85cffb455d57c4b1ff.png)

- Megger tester consists of an inbuilt generator. Rotating the pedal in the generator produce current in the circuit.

- Megger normally work on 500v, 1000v tester for higher voltage testing.

- There are three connection line terminals in the tester, Gaurd terminal, Line terminal and Earth terminal.

- Resistance is measured between Line and Earth terminals. Gaurd terminal is used for special situations.

- The high DC voltage passes a small current through and over the surface of the insulation being tested. Which is indicated in the ohm meter’s indicator scale.

**Procedure:**

- Before going to test the cable disconnect the cable with all the devices.Ensure both ends of the cable are separated from each other.

- Make sure that there is no Eddy current the device by earthing it.

- Now connect the Megger terminals to the cable which has to be measured, as shown in the diagram

- Hand crank the Megger to generate a high voltage, which causes a small current through and over the surface of the cable.

- If the current reading shows infinity in the ohm meter then the cable as good insulation.