Recently, many parts of the Midwest have been impacted by flooding. Wet or flooded electrical equipment and cables can cause potential functionality, reliability and safety hazards. To avoid these hazards, test your electrical equipment to find out when the insulation is free of moisture. This is commonly referred to as an insulation resistance test or Megger test using a megohmmeter or cable locator /fault finder.
Water damaged electrical equipment should first be cleaned with a suitable solvent if it came into contact with oil or grease. The equipment then needs to dry out or be tested using a Megger tester or insulation resistance tester to determine if the insulation is free of moisture. Insulation resistance tests can be done accurately if you have records of previous tests on the equipment to compare the readings. These tests should also be performed at the same temperature because the resistance of insulation decreases as temperature increases.
What Type of Insulation Resistance Tester Should I Use?
There are many varieties of Megger testers but there are certain ones recommended for the use of testing wet equipment. Since flooded or water-induced electrical equipment can lead to voltage breakdown, Megger recommends that a 100 or 250 VDC low voltage Megger tester be used. A kilohms (kW) measurement takes place at a few volts and is the ideal initial measurement for equipment impacted by flooding. kW measurement can be used as a benchmark in the drying out process because it measures below the Megohm. It is recommended that equipment be tested and dried until reaching the range of a Megohm – this reading tells you when higher voltage tests are safe to perform.
The information from this article comes from PMC’s trusted supplier, Megger. PMC has worked with Megger for many years and provided application assistance both over the phone and on-site. Our experts are trained on performing insulation resistance tests and can offer the assistance you need to safety perform the right test for your equipment.
Megohmmeters and Cable Locators / Fault Finders for Rent
PMC has megohmmeters from Megger, Fluke, Flir and more available for rent or for purchase along with ISO/IEC 17025 accredited calibration services for your current equipment or newly purchased equipment. To test the reliability and functionality of your cables, PMC offers cable locators/fault finders from Dynatel, Greenlee and JDSU.