For many of us it’s the rainy season and with that comes elevated concerns about the insulation integrity of our electric motors and generators. It never ceases to amaze us how water finds a way into places that it’s not supposed to be in. As a gentle reminder, the IEEE-43 standard tells us that low voltage random wound motors should have an insulation resistance-to-ground (RTG) reading of >5MΩ for continued operation. For a DC or medium voltage form wound motor the insulation RTG should be >100MΩ for continued operations. If your motor was manufactured before 1970 the guidelines suggest 1MΩ per 1000V + 1MΩ. As an example, a low voltage (460v) motor manufactured in 1965 should have a minimum RTG value of 1.46MΩ.

For the latest in IEEE Standards visit their website at https://standards.ieee.org. To see a case study on water and insulation systems visit the PdMA YouTube channel at https://www.youtube.com/watch?v=9SG3lNm8u8w.