Measurements of power system voltages using remote electric field monitoring

The implementation of a multiple point electric field measurement system for monitoring voltage changes on three-phase power systems is described. To prove the viability of the technique an array of electric field sensors has been installed at ground level below a scale model of such a three-phase busbar system. The electric field at each sensor position is shown to be the same as that below a full-size system provided that the dimensions and voltages are scaled in the same proportions. Using the outputs of the array of sensors the voltages on the individual conductors have been determined, in real time, over extended periods, The deduced voltages agreed with direct measurements obtained using conventional resistive divider networks; in particular, events occurring on a single conductor were reliably detected. As the sensor array is not directly connected to the high voltage system measurements of voltage are made without the use of cumbersome and expensive insulating structures. Hence the technique can be used where cost or physical location difficulties preclude the use of conventional methods.