Determination of the Minimum Acceptable Value of Insulation Resistance for Formwound Motor Winding EQ Test

Usually, the large motors important to safety for NPPs located outside containment in PWRs. Though they work important part to safety function, they don't have to be environmentally qualified because they are located in mild conditions. But the large motors in PHWRs, important to safety, must be environmentally qualified according to IEEE Std 323 due to their location, inside containment. Type test are recommended qualifying method for electric equipment, it is determined to carry out the type test to qualify large motors in PHWRs. To carry out the type test for large motor or motor winding according to IEEE Std 323, IEEE Std 334-2006 and IEEE Std 43-2000 are referred during the whole type test procedure and function test. One of the function test step is insulation resistance(IR) testing. The minimum acceptable value of IR is mentioned in IEEE Std 43-2000 as 100MΩ at 40 .deg. C with the approximating coefficient equation regarding to the temperature. The temperature varies 48.8 .deg. C to 148.3 .deg. C during EQ DBE testing, there is no mention about the acceptable IR value during DBE testing. In this paper, by the comparison the data using the approximation coefficient equation with the data measured in the experiment, tried to find out the acceptable IR value during motor winding DBE testing