Zakaria El Intissar

Zakaria El Intissar is an automation and industrial computing engineer with 12+ years of experience in power system automation, electrical protection, and SCADA systems. He founded InsulationTesting.com to share practical, field-tested guides on insulation resistance testing, equipment, and industry standards. His writing is used by electricians and maintenance engineers worldwide. Based in Morocco.

Author Archives: Zakaria El Intissar

SFRA Testing: A Practical Guide to Sweep Frequency Response Analysis

A transformer winding that has shifted 2 mm inside the tank will pass every conventional electrical test. The turns ratio is unchanged. The winding resistance is unchanged. The insulation resistance is unchanged. The DGA is clean if the movement hasn’t caused arcing yet. Energize the transformer, run it for years, and the shift slowly progresses — until one… Read More: SFRA Testing: A Practical Guide to Sweep Frequency Response Analysis »

Transformer Winding Resistance Test: Method and Limits

Inject DC, measure the voltage drop, divide. That’s the whole test on paper. In practice the reading climbs for ten minutes before it settles on a large unit. The value you write down is meaningless unless you also wrote down the winding temperature. The number your meter shows is not the resistance of the winding you think you… Read More: Transformer Winding Resistance Test: Method and Limits »

Transformer Turns Ratio (TTR) Testing: A Practical Guide to Doing It Right

The turns ratio test looks like the simplest measurement in transformer work. Apply a small voltage to one winding, measure what comes out the other, divide, compare to nameplate. A handheld instrument does it in seconds and prints a pass/fail. That simplicity is exactly why it gets done badly. People read the ratio number, see it’s within tolerance,… Read More: Transformer Turns Ratio (TTR) Testing: A Practical Guide to Doing… »

Witnessing a Transformer Factory Acceptance Test: A Guide From the Test Chair

A factory acceptance test is the last good chance to catch a problem before a transformer becomes the utility’s problem. Once it leaves the factory, a defect that could have been a warranty conversation in the test bay becomes a field failure, an outage, and a multi-month replacement. The witness in the chair is the line between those… Read More: Witnessing a Transformer Factory Acceptance Test: A Guide From the… »

Lightning Impulse Testing for Power Transformers: Why It Works and What It Catches

A lightning strike on a transmission line lasts microseconds. A power transformer is designed to run for forty years. The lightning impulse test is the bridge between those two facts — it proves, in the factory, that the transformer can survive the microsecond event so it can deliver the four decades of service. The test applies a standardized… Read More: Lightning Impulse Testing for Power Transformers: Why It Works and… »

The IVPD Test Explained: Why Power Transformers Are Tested for Partial Discharge

Every power transformer above 72.5 kV gets an IVPD test before it ships. The test takes more than an hour, costs the manufacturer significant test bay time, and is the final dielectric test in the sequence. Why? Because partial discharge is what kills transformer insulation slowly, and most other tests can’t see it. A lightning impulse test stresses… Read More: The IVPD Test Explained: Why Power Transformers Are Tested for… »

IEEE 43-2013 Explained: A Clause-by-Clause Guide to Motor Insulation Testing Standards

If you’ve been doing motor insulation testing for any length of time, you’ve heard the standard cited a hundred times. “IEEE 43 says the PI minimum is 2.0.” “IEEE 43 requires correction to 40°C.” Most techs and engineers work from the rules without ever opening the document. That works fine until it doesn’t. Until an auditor asks where… Read More: IEEE 43-2013 Explained: A Clause-by-Clause Guide to Motor Insulation Testing… »

How Motor Insulation Ages: The Five Stresses That Decide How Long It Lasts

Every motor failure has a story. Most start the same way — insulation that gave out before the winding did. Heat, vibration, moisture, voltage spikes, chemicals. One or all of them. The question isn’t if insulation degrades. It’s how fast — and what’s driving it. This article covers the five aging stresses, what each one actually does to… Read More: How Motor Insulation Ages: The Five Stresses That Decide How… »

DC Hipot Testing of Motor Stator Windings (IEEE 95)

The DC hipot test is the most consequential offline test you can run on a stator winding. It applies a high DC voltage — well above operating levels — to the groundwall insulation and holds it there. If the insulation fails during the test, you know before the machine goes back into service. If it passes, you have… Read More: DC Hipot Testing of Motor Stator Windings (IEEE 95) »

Stator Winding Failure Mechanisms: What’s Actually Killing Your Motor

Most stator failures are not sudden. They are the end point of a process that has been running for months or years — visible if you know what to look for, detectable by testing before the insulation finally fails in service. Understanding the failure mechanism behind a bad test result is the difference between cleaning a winding and… Read More: Stator Winding Failure Mechanisms: What’s Actually Killing Your Motor »