Simultaneous measurement of partial discharge and radio-interference voltage

A new instrument has been developed which allows simultaneous measurement of partial discharge (PD) and radio-interference voltage (RIV) in insulation of high-voltage power apparatus. A distinctive feature of this instrument is that it fulfills the low input impedance (150-Ω) requirement of the RIV measuring standard (NEMA 107) at 1 MHz and, at the same time, presents a high input impedance in the frequency bandwidth used for PD measurement; this high input impedance is required for acceptable measurement sensitivity of PD on power transformers. The instrument has shown stable measuring characteristics during the 16 months that it has been in service at the IREQ HV Laboratory where it is used to test power transformers, reactors, disconnecting switches, capacitors, current and voltage transformers, and other apparatus. The HV Laboratory personnel confirm that the device is practical and easy to handle during tests and saves a considerable amount of time.