Mitigation of Switching-Induced Transient Electromagnetic Interference on Control Cable Using Ni-Zn Ferrite Rings over Cable Sheath in Gas-Insulated Substations

The transient electromagnetic fields during switching operation in gas-insulated substations (GISs) have rise times on the order of nanoseconds. These fields leak into the external environment through the discontinuities of gas-insulated modules and affect the control cables and induce the transient voltage on cables, which results in malfunctioning of the equipment. The amplitudes of the electric and magnetic fields could be a few tens of kilovolts per meter and a few hundred amperes per meter according to layout of GIS, respectively. In this work, the induced voltage in the central conductor of a control cable and the induced current in its sheath, which is parallel to bus duct in a GIS with rated voltage of 230 kV, are calculated. Influence of the sheath material on the induced voltage and the type of its grounding on the induced current are analyzed. Furthermore, the impact of installing ferrite rings over the control cable sheath in mitigating the induced voltage and current is investigated. (c) 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.