Analysis of the Impact of Improper Termination and Grounding of Substation Cables

A substation has a combination of high-voltage electrical power equipment, referred to as the primary plant and low-voltage electronic devices on the secondary plant, which is interconnected electromagnetically through electromagnetic fields and electrically by cables. Most articles on substation cable termination and grounding focus on how to divert transient magnetic fields propagating in the cable shield to eliminate common-mode currents. However, this work focuses on analyzing the impact of improper termination and grounding of substation plant cables as it has a serious impact on the operation of protection and control devices. MATLAB Simulink is used to model, simulate and analyse the results of primary and secondary systems interconnected with control/low-voltage cables. The model is configured as per International Electrotechnical Commission (IEC) standards and Eskom protective intelligent electronic devices. According to simulation results, the improper termination and grounding of the cable results in an intense transient with high peak amplitudes, but a less intense transient if properly terminated and grounded on a medium voltage (MV) network.