Cable-Capacitance Discharge Time With and Without the Application of Grounding Device

This paper provides inherent cable capacitance, its stored energy, its maximum transient voltage, and time to discharge such a voltage and energy to a safe level with and without the application of a grounding device. Maintenance procedures require that appropriate grounding devices be applied to electrical equipment upon its deenergizing before performing inspection or maintenance for safety reasons. The authors have not come across published literature describing how to determine the discharge time of an inherent cable-capacitance charged voltage. Shore power supply to a berthing ship is called cold ironing; it helps to minimize air pollution. In the cold-ironing power system design, medium-voltage heavy plug and receptacle assemblies are required to make and break shore power connections to the ship power system as the ship arrives and leaves the port after the cold-ironing operation. Therefore, there was a need to know the discharge time of the cable capacitance without the application of the grounding device for safety reasons. A recommendation for a future research project to develop a recording/measuring device for the cable-capacitance voltage discharge time to validate the calculated discharge time presented in this paper is included. For safe and efficient operation of the cold-ironing operation, implementation of a grounding switch key interlocked with an associated main disconnect switch and power plugs (for discharging quickly cable-capacitance voltage and charged energy to ground) shall be included.