High voltage shore connections (HVSC), an IEC/ISO/IEEE 80005-1 compliant solution: The neutral grounding system

Abstract

Air pollution regulations are forcing ports all over the world to implement Alternative Maritime Power (AMP) solutions to improve the air quality of port areas. At this aim, the port operators have to provide safe and reliable electrical connections to the docked ships. The IEC/ISO/IEEE 80005-1 standard identifies the global criteria that allow ships from all over the world to connect to the compliant ports. As underlined from the standard itself, the electrical connections shore to ship may generate risks, also considering that the interface area between the shore and the ship is a special location for electric shocks. These concerns regard not only the safety of the operators for ground fault interferences causing transferred touch potentials, but also the integrity of the ship itself that may be subjected to a galvanic corrosion. This paper analyzes the current grounding solutions and proposes the adoption of a TN-island system compliant with the international standard that allows reducing the risks for ship's corrosion due to DC currents and transferred touch potentials

Grounding Strategies for High Voltage Shore Connection of Large Passenger Vessels

“…Several automated control functions must be performed before the circuit breakers are closed. In a few cases, such as in the port of Oslo, an automatic connection does not require the assistance of port personnel [7].…”

“…Ground fault interferences are originated by the grounding system common to the primary and the secondary side of the onshore transformer substation. When a ground fault happens on the primary side of the transformer substation, the double grounding connection of the PE causes a touch voltage transfer to the ship-side system with a value related to the tripping settings of the protective device on the primary side [7]. The voltages admitted might therefore be higher than the 30 V prospective touch voltage limit prescribed by the international standards for the interface area between the shore and the vessel.…”

“…The PE conductor can be broken by placing an isolation transformer either on the vessel or on shore. This results in the TN-island grounding system, which is compliant with the IEC/ISO/IEEE 80005-1 standard [7]. This grounding system is used for low voltage shore connection (LVSC), and suggested in the standard for HVSC of cruise ships [8].…”

“…The hull and the ground electrode thus form a steel-copper galvanic cell, and the current flow between these two electrodes favours the corrosion of the anode (the hull of the vessel), since steel is the less noble metal. The low resistance conductor between the vessel's hull and the ground network can also lead to transferred touch voltages higher than 30 V in the case of a fault, posing a safety hazard [7].…”

“…hull is broken. A solution compliant with the standard is the TN-island grounding system, in which a neutral conductor is used instead of the PE conductor [7]. This will also contribute towards minimising the corrosion problems.…”