Determination of the Phase Sequence and Voltage Level of Overhead Conductors Using Non-contact Sensors

This paper describes how the phase sequence and voltage level (132 kV, 275 kV or 400 kV) of single-circuit overhead conductors can be determined from the measurements which are made by passive, non-contact sensors situated on a moving platform at ground level. The investigation relies on sensing of the electric field along the lateral profile beneath overhead conductors. Firstly, the passive sensor fabricated is described together with an analysis of its performance. Then experimental results obtained in the laboratory have led to the determination technique of voltage level and phase sequence from the spatial variation of the amplitudes and phase angles of electric field. 1 kHz AC supply has been used to energize overhead conductors rather than 50 Hz supply. This greatly improves the signal noise ratio (SNR) of induced voltage measured and makes the investigation of electric field in vicinity of conductors with low-level voltage possible in the laboratory. Finally, investigations made in a 400 kV substation in the UK shows that the proposed technique can successfully evaluate the phase sequence and voltage level of high-voltage overhead conductors