Run an IEC 60112 test and the specimen can go bad in two completely different ways. One leaves a conductive path. The other leaves a hole. The headline number — the CTI or PTI — only tracks the first. The second gets measured separately, if at all, and it is the one people forget to ask for. Same… Read More: Tracking vs Erosion: Two Failure Modes in IEC 60112 »
The impulse voltage withstand test fires a short, steep surge across the insulation to see whether it survives the kind of spike that arrives from a lightning strike or a switching event. The waveform is 1.2/50 µs — roughly 1.2 µs to reach peak, 50 µs to fall to half. Here’s the part most write-ups skip. This is… Read More: Impulse Voltage Withstand Test: Clearances and Solid Insulation »
A withstand test tells you the insulation did not break down for one minute. It tells you nothing about what happens over ten years. Solid insulation with a void inside will pass a hipot shot and still erode from the inside out, one small discharge at a time, until it doesn’t. That’s the gap a partial discharge test… Read More: Partial Discharge Test for Solid Insulation in Low-Voltage Equipment »
Insulation testing in a wind turbine is not the same job as insulation testing in a plant motor room. The machine sits 80 to 150 meters up, inside a steel box that breathes damp air all night. It spends half its life stopped and cold. It is bolted to a power converter that a 500 V megohmmeter will… Read More: Wind Turbine Insulation Testing: Procedures, IEEE 43 Requirements, and Best… »
There is no single insulation resistance formula. There are five, and people mix them up constantly — using the measurement equation when they need the correction equation, or applying an acceptance formula built for 1950s asphalt to a modern epoxy winding. This page lays them out one at a time: what each equation is for, what the symbols… Read More: Insulation Resistance Formula: Every Equation You Need »
For a century, insulation testing meant sending a technician out with a megohmmeter every so often to take a reading. That model is being replaced, piece by piece, with continuous online monitoring — sensors left permanently on the asset, watching insulation condition in real time and raising an alarm when it drifts. The shift is furthest along where… Read More: Online Insulation Monitoring: The Shift From Periodic Tests »
Short answer: The routine AC withstand test applies 3.5 times the cable’s rated voltage (U₀) on medium-voltage cable, 2.5 times on high-voltage cable, and as little as 2 times on extra-high-voltage cable. The multiplier falls as the cable’s voltage class rises because the absolute test voltage would otherwise become impossible to generate and would damage the very insulation… Read More: AC Withstand Testing of Cables: Why the Multiplier Drops »
Most oil tests tell you something has already gone wrong. Interfacial tension tells you it’s about to. It’s the smoke detector of oil analysis — a small, sensitive force measurement that drops at the first whiff of oxidation, long before acid climbs or sludge ever appears. The idea is simple. Pour clean oil onto water and the two… Read More: Interfacial Tension (IFT): The Early Warning for Oil Oxidation »
A transformer dies when its paper dies. The oil can be cleaned, dried, even replaced — the paper can’t. So the real question in condition assessment isn’t “how’s the oil?” It’s “how much life is left in the cellulose?” And that question has a frustrating catch: you can’t measure it directly. The number that answers it is the… Read More: Furans & DP: Reading Transformer Paper Aging from the Oil »
Of all the tests you can run on transformer oil, this is the one that gets run first. It’s fast, it’s cheap, and a single number in kilovolts tells you whether the oil is doing its main job: holding off voltage without arcing. The breakdown voltage test — BDV — measures the highest voltage the oil can take… Read More: Oil Breakdown Voltage: The BDV Test Explained (IEC 60156) »