Application of electrical field sensors in GIS for measuring high voltage signals over the frequency range 10 Hz to 100 MHz

The measurement accuracy of conventional electrical field sensors (mainly used as partial discharge sensors for the UHF-method) in gas insulated switchgear (GIS) was investigated over a frequency range of 10 Hz to 100 MHz. The scale factor of the measuring systems was determined at power frequency voltage only and used for all measurements. This is of special importance for the application to GIS in service, where only power frequency voltage is available. Frequency and step response measurements were performed, yielding an overall accuracy within 5% over the frequency range of interest. Measurements with standard waveforms according to IEC 60-1 were performed. The accuracies for the measurement of power frequency voltage, lightning impulse peak and switching impulse peak were determined to be 1.2%, 3% and 5% respectively, confirming the results of the frequency and step response measurements. Time parameters of the waveforms could be determined with an accuracy within 10%.