IEEE - The Institute of Electrical and Electronics Engineers@ Inc.
Scope
This guide describes the test procedure for electrical measurement of partial discharges (PD) in bushings and instrument transformers using wide-band measuring instruments for the evaluation of the apparent charge level of PD occurring under AC and DC test voltages. Purpose To recognize partial discharge (PD) events in bushings and instrument transformers when subjected to high voltage tests@ it is a common practice to measure the apparent charge of the current pulses originating in insulation defects. Depending on the bandwidth used for electrical PD signal processing it is distinguished between narrow-band and wide-band methods. Without giving preference to one or the other procedure this document refers to the wide-band PD signal processing described in IEC 60270. The general diction of this guide when referring to the PD measuring systems reflects the common use within AC systems. Nevertheless@ PD measurements are also mandatory during testing of DC system components under DC high voltage and are therefore also considered in this guide. Since possible partial discharging is no longer synchronized to any mains AC power frequency the time related pattern of those PDs are completely different. The internal high impedance resistive DC current distribution of an insulator under test becomes the main factor for the size and time-behavior of possible PDs. Single PD impulses may size up to some thousands of pC and repeat after recovery intervals longer than minutes.