You test a motor at 20°C and read 200 MΩ. Looks good. You test the same motor three months later at 45°C and read 40 MΩ. Has the insulation degraded? Or is it just the temperature? Without correction, you can’t tell. A 200 MΩ reading at 20°C and a 40 MΩ reading at 45°C can represent exactly the… Read More: Temperature Correction for Insulation Resistance Tests: The Complete Guide »
Cable insulation fails silently. Unlike a motor that vibrates or a transformer that overheats, a cable with degrading insulation gives you no warning until it faults. And when it does fault, it takes out the circuit — sometimes causing arc flash, fire, or hours of downtime while you trace the problem. Regular insulation testing on cables catches degradation… Read More: Cable Insulation Testing: How to Test, What Values to Expect,… »
Three numbers come off an insulation test: the spot reading, the ratio, and the trend. Most people look at the first one and stop. The spot reading is the weakest of the three. It swings with temperature and surface moisture and tells you almost nothing about the winding underneath. The ratio — DAR or PI — filters most… Read More: How to Read Megger Test Results: Good, Bad, and Marginal »
Transformer insulation is the single most critical component determining the life and reliability of a power transformer. Over 60% of transformer failures are linked to insulation breakdown. Once it fails, you’re looking at months of downtime and repair costs that can reach hundreds of thousands of dollars. The good news: insulation problems don’t happen overnight. They develop over… Read More: Transformer Insulation Testing: Complete Guide to Methods, Standards, and Field… »
Megger testing and hi-pot testing both involve applying high voltage to insulation. Both measure how current behaves through that insulation. And both help you find problems before they cause failures. But they’re not the same test. They serve different purposes, use different voltage levels, and are used at different stages of an equipment’s life. Mixing them up —… Read More: Megger vs Hi-Pot: What’s the Difference? »
A megger test on a motor takes about five minutes. Reading the result correctly takes a bit more than that. The number on the display means nothing on its own. A 50 MΩ reading is fine on a 6.6 kV machine and a warning sign on a 400 V one. Temperature moves it. Humidity moves it. A dirty… Read More: How to Megger a Motor: Steps, Voltages, and Good Readings »