A current clamp based high voltage monitoring system

The feasibility of accurate monitoring a high voltage is investigated, which based on measuring a current through a capacitor, which is already installed in the grid. A current clamp based measuring system with high-resolution digitizer was developed. In order to adapt the system for different capacitors, the current clamp sensor is designed for a.c. currents in the rant of 150 μA to 12 A, while the acieved accuracy of the sensor is better than 0.1%. An implemented high quality analogue a.c. integrator processes the measuring signal to get a proportional scaled high voltage waveform at the sensors output. This feature is helpful for calculating the narmonics distortion in the HV grid. If a high-quality and well-known HV capacitor is available, accurate measurements within 0.5% for rms valuse and phase angles are possible in the HV grid under on-site conditions. Such accuracies are ususally more than adequate for monitoring purposes.