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 »
A modern container-scale BESS holds enough energy to power a small town for several hours — and enough energy density to start a sustained fire if anything goes wrong inside the cell stacks. Between the cells and a thermal runaway event sits one critical safety layer: the insulation system. Cell-to-cell, cell-to-rack, rack-to-container, container-to-earth — every interface must hold… Read More »
A solar PV array is a power source that you cannot turn off. As long as light hits the panels, voltage is present at the DC connectors. This single fact changes everything about how insulation testing works on solar systems compared to conventional grid equipment. The DC side of a typical utility-scale array operates at 1000–1500 V DC.… Read More »
An electric vehicle battery operates at 400V or 800V DC — voltages that can kill a technician who makes a mistake. Unlike the utility grid, where one side of the system is grounded, EV batteries float. Neither the positive nor the negative terminal is connected to the vehicle chassis. This is called an IT (isolé terre) system, and… Read More »
You have two different windows into a transformer’s health. One is the DGA report — a lab analysis of gases dissolved in the insulating oil. The other is a PD test — a direct measurement of partial discharge activity in the windings. Both diagnose insulation problems. Neither alone tells the full story. When they agree, you have high… Read More »
You’re looking at a PRPD plot from a transformer test. There are clusters of dots forming distinct shapes against the 50 Hz voltage waveform. One cluster sits at the voltage peaks. Another spreads across the whole cycle. A third forms a thin band with a distinctive “rabbit ear” shape. Each cluster tells a different story. One is corona… Read More »
A motor passes its insulation resistance test with a 500 MΩ reading and a PI of 3.2. Six weeks later it fails catastrophically in service. How? The IR test was measuring the bulk resistance of the insulation system, but somewhere inside the winding there was a tiny void in the epoxy-mica tape. That void had been producing partial… Read More »
The reading is 2 MΩ. The motor is supposed to be above 100 MΩ. You’re standing at the terminal box with a megger in one hand and a maintenance log in the other, trying to figure out what to do next. This guide walks through the actual troubleshooting sequence for low insulation resistance readings. Not theoretical — the… Read More »