A Study on Induced Surge voltages on a Control Cable by a Lightning Current Flowing into a Grounding Grid

摘要

In this paper, to study the lightning surge characteristics of a low-voltage control circuit, we set up a test system of a low-voltage control circuit, which is composed of a grounding grid with a size of 30 m×60 m,a GIS (gas insulated switchgear) model with a 66 kV VT (voltage transformer) and CT (current transformer), and digital-type protection-relay equipment. The GIS model is located above the grounding grid, while the protection-relay equipment is installed in a control building situated above another subgrounding grid. The VT or CT is connected with the protection-relay equipment via a control cable. Using the test system, when a lightning current is injected into the grounding grid with a pulse generator, we measure the induced voltage at the signal-input terminal of the protection-relay equipment to analyze the effects of the wavefront time of the injected current, a grounding wire connecting the subgrounding grid to the main grounding grid, the type of the control cable, the grounding position of the sheath of the control cable, and the height of the control cable.