Ground-level DC Electric Field Sensor for Overhead HVAC/HVDC Transmission Lines in Hybrid Corridors

Measurement of electric fields is crucial for the evaluation of the electromagnetic environment in electric power transmission system. Due to limited transmission corridor resources, the hybrid transmission lines including high-voltage alternating current and high-voltage direct current (HVAC/HVDC) are more common nowadays. However, commonly used field-mill direct current electric field sensors (DC EFSs) can only be used beneath HVDC lines and the emergence of alternating current (AC) electric fields has adversely affected measurement results recorded by DC EFS. In this work, a DC EFS was designed that is capable of measuring ground-level DC electric fields generated by overhead HVAC/HVDC transmission lines in a hybrid corridor. A field-mill structure was used to modulate the DC and AC hybrid electric field and then a narrow band-pass filter was used to realise suppression of the AC electric field signal. Subsequently, the phase-sensitive detection method was used to realise amplitude demodulation and phase discrimination of the DC electric field. Sensor prototypes based on the foregoing method were experimentally tested in the China national high-voltage base. These DC EFSs could be mass-produced conveniently from current field-mill for hybrid corridors application.