Research on Electromagnetic Interference of Lightning Current on Secondary Cable in Substation

Abstract

Secondary cable is an important equipment for ubiquitous power Internet of things to transmit information. When the substation grounding grid is struck by lightning, part of the lightning current flows through the shielding layer of secondary cable and produces core-to-sheath potential difference, which seriously threatens the safety of the secondary system. Fourier transform was used to decompose the lightning current in frequency domain, and the core-to-sheath potential difference at the end of the secondary cable was obtained by calculating the shielding layer current and transfer impedance at each frequency component. The effects of soil resistivity, lightning current waveform, distance between lightning stroke point and cable and grounding grid on the core-to-skin potential difference of secondary cable were studied. It is shown that the core-to-sheath potential difference of secondary cable increases with the increase of soil resistivity, the peak value, and the tail time of lightning current. The core-to-sheath potential difference decreases with the increase of the distance, while the core-to-sheath potential difference increases with the increase of conductor spacing of the grounding grid. The core-to-sheath potential difference with copper grounding grid is smaller than that with steel grounding grid.