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Ecmweb 16059 Thinkstockphotos 177026594 Preparationchecklistwebversion 0
Ecmweb 16059 Thinkstockphotos 177026594 Preparationchecklistwebversion 0
Ecmweb 16059 Thinkstockphotos 177026594 Preparationchecklistwebversion 0
Ecmweb 16059 Thinkstockphotos 177026594 Preparationchecklistwebversion 0
Ecmweb 16059 Thinkstockphotos 177026594 Preparationchecklistwebversion 0

Tip of the Week: Preparing for Insulation Resistance Tests

Sept. 5, 2017
Make sure you follow these steps for safe and accurate testing.

Before actually conducting insulation resistance tests, you need to prepare for them. Here are some steps you don’t want to skip:

 Understand the associated system. What will taking those cables out of service do? How much equipment must be taken out of service, and how far beyond the scope of electrical does that go? For example, there may be mechanical isolation requirements, cooldown and heat-up requirements, and process material issues. And, of course, production deadlines.

 Understand the test set-up. The real value of insulation resistance testing comes from trending the results over time. For the trending to be valid, the test must be performed the same way every time. As an example, if load equipment is connected then it must be the same equipment as the last X times. The test equipment needs to be set up the same way and used the same way every time, also.

• Take the equipment out of service. This doesn’t mean just the breaker supplying the cables under test. You need to ensure that you disconnect the entire machine or apparatus from all other circuits; that includes applying lockout/tagout to the protective ground connections and the neutral.

• Discharge any capacitance. Wherever you have power factor correction, such as in power factor corrected variable speed drives, you have an energy source. Note that your insulation resistance testing also creates a hazard in this regard. So after testing is completed, you need to discharge the capacitance of the cables under test. The general rule of thumb for determining the discharge time is to multiply the time under test by four.

About the Author

Mark Lamendola

Mark is an expert in maintenance management, having racked up an impressive track record during his time working in the field. He also has extensive knowledge of, and practical expertise with, the National Electrical Code (NEC). Through his consulting business, he provides articles and training materials on electrical topics, specializing in making difficult subjects easy to understand and focusing on the practical aspects of electrical work.

Prior to starting his own business, Mark served as the Technical Editor on EC&M for six years, worked three years in nuclear maintenance, six years as a contract project engineer/project manager, three years as a systems engineer, and three years in plant maintenance management.

Mark earned an AAS degree from Rock Valley College, a BSEET from Columbia Pacific University, and an MBA from Lake Erie College. He’s also completed several related certifications over the years and even was formerly licensed as a Master Electrician. He is a Senior Member of the IEEE and past Chairman of the Kansas City Chapters of both the IEEE and the IEEE Computer Society. Mark also served as the program director for, a board member of, and webmaster of, the Midwest Chapter of the 7x24 Exchange. He has also held memberships with the following organizations: NETA, NFPA, International Association of Webmasters, and Institute of Certified Professional Managers.

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