Insulation Resistance Testing: How To Prevent Catastrophe In Your Emergency Power System

Insulation Resistance Testing: How To Prevent Catastrophe In Your Emergency Power System

Insulation resistance testing is one of the most misunderstood elements in commercial generator maintenance. Why? Blame it on that old saying, “out of sight, out of mind.”

If the winding on the insulation is worn or expired, switching on your emergency power system could have catastrophic effects. But the problem is, a simple visual inspection will not reveal if the insulation needs replacement. There must be an insulation resistance test performed by a qualified technician to determine whether replacement is necessary.

What’s important to remember is that not every generator service company routinely performs an insulation resistance test. This is because the only way to determine whether an insulation resistance test is even necessary is to perform a voltage test first on each of the three legs of your commercial generator. This means that if you’re not covered by a quality generator service contract, this potentially hazardous condition may go completely undetected.

What is an insulation resistance test?

An insulation resistance test (also called “meggering,” based on the megohmmeter used to perform the test) is performed to check the winding on insulation. It detects shorts and other issues with bad insulation. The test takes about an hour, depending on the size of the generator.

An insulation resistance test measures the total resistance between any two points separated by electrical insulation. The test determines how effective the dielectric is in resisting the flow of electrical current.

How is an insulation resistance test performed?

There are three commonly used methods for testing insulation resistance: a spot reading test, a time resistance test, and the step voltage test. These three tests are used in commercial generators as well as other electrical equipment.

Insulation resistance measurement is done using an IR tester (the Megohmmeter, mentioned above). This portable tool with a built-in generator is used to produce a high DC voltage. The voltage usually measures at least 500 volts, which causes a current to flow around the surface of the insulation.

When should I get an insulation resistance test for my generator?

Though we think it’s best to have an insulation resistance test every quarter, you’re probably safe having the test performed semi-annually.

But here’s the part where most generator service companies fall short.

It takes a qualified technician to determine whether you need an insulation resistance test, because this problem cannot be seen visually. Typically, the only time a test is performed is after a 3-phase generator shows a bad voltage reading on any of its three legs. And at that point, it can be too late.

Electro-Motion includes insulation resistance testing as a regular part of its service agreements. We don’t wait to see if there’s a problem with voltage flow before performing the test. Our certified technicians are trained to detect a problem with the insulation in your generator before it becomes a problem for your business.

Call us today at 650-321-6169 or click here to schedule a free consultation. Let us show you how Electro-Motion can work within your budget to keep your backup power system running efficiently and reliably.