Parameter Design and Transfer Characteristic Optimization of Floating-Ground Capacitive Voltage Divider for Wideband High Voltage Measurement

Voltage measuring equipment in power grids often requires capacitive voltage dividers to realize conversion of high voltage electrical quantities to low voltage signal quantities. The new floating-ground capacitive voltage divider (FG-CVD) can eliminate original lumped capacitors and its supporting insulation structures by adopting precisely designed parasitic capacitance as a high voltage arm capacitor, which can greatly save cost and volume. However, the utilization of parasitic capacitance not only makes FG-CVD sensitive to external conductor interference, but also causes transient waveform distortion, especially when the connecting lead between the FG-CVD and high-voltage conductor is lengthy. On the basis of transfer characteristic analysis, this paper proposes a complete parameter design method for FG-CVD to improve stability of its transfer ratio under interference of the external conductor. Moreover, by establishing a wideband equivalent model with lead inductance, the transient waveform distortion problem of FG-CVD is well explained, and a resistance compensation scheme is also proposed to reduce ratio error. Finally, a 500:1 FG-CVD prototype with a measurement bandwidth of 2MHz is developed. Experimental results show the prototype has high accuracy in both power frequency and lightning pulse voltage measurement, and ratio error decreases from 20.33% to less than 1.3%.