Effect of Measurement Instrumentation on the Insulation Resistance Profile

In this paper we will review the effects of test equipment on the measurement of the Insulation Resistance Profile (IRP) as found in Annex D of IEEE 43-2013. There are several areas in which test equipment may affect the IRP such as High Voltage (HV) and Low Voltage (LV) power supply noise, HV and LV filtering, and Data Acquisition (DAQ). To evaluate the effects of the test equipment on the IRP, we used simulation models created from actual field tests whose results were previously published. We modified the models to include power supply noise such as found in common switch mode power supplies and basic filtering circuitry used in test equipment. Using these simulation models, we evaluated various aspects of how the power supply noise and filtering circuits of test equipment may affect the Insulation Resistance Profile. We will then present summary results of these simulations.