A Practical Ground Potential Rise Prediction Technique for Power Stations

The determination of fault-produced Ground Potential Rise (GPR) at a power station has historically posed a number of practical and technical problems. This paper presents a GPR prediction technique which overcomes these problems without requiring a staged fault test. The technique consists of: 1) the diligent application of the fall-of-potential method for measuring the impedance to remote earth of a power station ground grid with all normal external connections to the grid maintained, using an ac test signal of approximately 60 Hz. 2) the use of electronic instruments with improved sensitivity and signal-to-noise ratio, 3) multiplication of the measured grid impedance by the appropriate total single phase fault current.