Non-contact measurement of lightning current in transmission line based on differential loop

Measurement of lightning current is essential for lightning protection in grid, because only if accurate amplitude and waveform of the lightning current is obtained can the correct lightning protection measures be taken. However, in high voltage power systems, it is almost impossible to directly measure the lightning currents accurately and safely. We put forward a contactless lightning current sensor for transmission tower based on the differential loop which has been widely used in the pulse power measurement technique, and it could measure the lightning current on overhead transmission lines contactless. Moreover, we introduced the principle of differential loop for measuring lightning current and the design of the detector. In laboratory, the lightning current was simulated by a high impulse current generator. The experimental results showed that the sensor can accurately reproduce the waveform and amplitude of the current generated by the high impulse current generator, based on a specific measuring distance under reasonable design. And this sensor has the advantages of safety, strong anti-interference ability, and good linearity and accuracy. To analyze propagation characteristics of the lightning transient magnetic field, a 3D model of transmission line struck by lightning was established. The results showed that the transient magnetic field around the tower can reproduce the waveform and the amplitude of the current on the wires when the transmission line is stoked. So the lightning measurement method based on the differential loop is feasible.