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 »
Most people who run a Polarization Index test can tell you the formula: 10-minute IR divided by 1-minute IR. Fewer can tell you why that ratio is meaningful, where it stops being meaningful, or what a result of 1.1 on a modern epoxy-mica winding actually implies — compared to the same reading on an asphaltic machine from 1965.… Read More »
Insulation resistance testing is one of the most practical condition assessment tools in electrical maintenance. Apply DC voltage to a winding, measure the leakage current, divide one by the other — you get a number in megohms that tells you whether the insulation is clean and dry, wet and contaminated, or failing. IEEE 43-2013 is the standard that… Read More »
Choose the wrong insulation tester and you’ll either waste money on capabilities you don’t need or get stuck with equipment that can’t handle the job. Both happen often. A residential electrician buying a $3,000 5-kV tester to verify branch circuits, or an industrial maintenance team trying to test 13.8 kV motor windings with a 1 kV handheld —… Read More »
If you’ve spent any time shopping for an insulation tester, you already know the market is flooded with options. But when it comes to professional-grade instruments trusted in the field, three names keep coming up: Fluke, Megger, and Hioki. Each brand has built a serious reputation — and each takes a meaningfully different approach to what an insulation… Read More »
A megohmmeter sitting on a shelf for two years still reads numbers when you pull the trigger. The display lights up. The needle deflects (or the digital readout shows MΩ). The test seems to work. But the readings could be off by 30% and you’d never know — until an audit catches it, a critical test produces wrong… Read More »
A 132 kV underground cable runs eight kilometers between two substations. After installation, before energization, a single test must verify that the cable, terminations, and joints will hold off operating voltage reliably for the next 30+ years. Insulation resistance testing won’t detect the small voids in joint accessories. Hi-pot testing might catch gross defects but won’t see the… Read More »
A hipot tester applies a voltage well above the equipment’s rated operating voltage and watches what happens. If the insulation holds, the equipment passes. If the insulation breaks down, the equipment fails. This sounds simple, but the practical implementation is full of decisions that affect what you can detect, what you can damage, and what your test results… Read More »
A power transformer survives a nearby short-circuit fault. It rides through the event, the protection clears the fault, and the transformer goes back to service. Oil tests come back normal. Insulation resistance is healthy. DGA shows no concerning gas evolution. Everything looks fine. But inside the tank, the windings have shifted. Not enough to fail immediately. Not enough… Read More »
You’ve decided your equipment needs partial discharge testing. The next question is operational: do you take the equipment out of service for offline measurement, or install sensors and monitor while it operates? The answer drives equipment selection, budget, outage planning, and the diagnostic value you’ll get. This article compares offline and online PD testing in detail — how… Read More »