by Reza Tajali, P.E.

Power monitoring devices are sometimes used on ungrounded and impedance grounded systems to record and alarm on line to ground voltages. This recorded line to ground voltage data can be manipulated using a host of data analysis tools to evaluate insulation stress on power system components . However, ungrounded and impedance grounded systems have specific issues that impact proper application of metering equipment. Voltage transformers are especially prone to misapplication. This paper is intended to provide a road map for proper application of power monitoring in these circuits.