A Method for Surface Voltage Measurement of an Overhead Insulated Conductor

Surface voltage measurement of an insulated overhead conductor assumes importance for understanding corona, radio interference voltage and for design purposes. Surface voltage measurement of a bare overhead conductor is quite simple as a voltage divider can be directly connected. However, there are challenges in the measurement of surface voltage on an insulating surface of an insulated covered conductor using voltage dividers. In case of ac measurements, the capacitance parameter dominates in deciding the potential distribution. In this paper, it is demonstrated that the measuring system itself will alter the voltage division between the capacitance of the cylindrical insulated conductor and that of surrounding air acting as a capacitive divider. The voltage distribution is shown to be drastically influenced by the measuring system capacitance. In view of these issues, a novel experimental method is proposed for the measurement of surface voltage of an overhead insulated covered conductor. In general, the method can be applied to any cylindrical insulated conductor and for calibration of sensor based measurements. The proposed empirical method is tested by a validated simulation of the entire system and it is proven analytically. The radial voltage gradients are then estimated from measured surface voltages. The analytical, experimental and simulation results are in close conformity.