High-Voltage Shore Connection Systems: Grounding Resistance Selection and Short-Circuit Currents Evaluation

Abstract

Cold ironing represents an effective solution to remove air polluting emissions from ports. The high voltage shore connection system is the key enabling facility that allows to provide power from the shore side electrical system to the ship. The design of the shore connection needs a comprehensive assessment of the fault currents in different operating scenarios. International standards require the neutral point of the shore connection transformer be equipped with a neutral grounding resistor. Its value has to be defined to guarantee safety and protection of equipment and personnel in case of single phaseto-ground faults. Moreover, three-phase short circuits need to be considered to size equipment and protection devices. A crucial role is played by the frequency converter control system, required to adapt the mains frequency to the frequency of the ship. In this work, a complete electro-magnetic dynamic model of the high voltage shore connection has been developed, including frequency converter, shore-side transformer, connection MV cables and power system of the ship, to analyze in detail the behavior of the system in case of single phase-to-ground fault and three-phase short circuit, taking into account relevant standards and best practices.

Voltage Drop Estimation during Shore Connection with the Use of Motor Drives Modified as Static Frequency Converters

“…These two standards enabled the implementation of new shore connection systems, which are consistent with global standards [13]. It is important to mention that, according to the Standards of Training, Certification, and Watch-keeping for Seafarers (STCW) Code, in marine applications, the term high voltage refers to systems above 1 kV [14]. It can be stated that naval HV networks and MV networks on land are synonyms [15].…”

Assessing High-Voltage Shore Connection Safety: An In-Depth Study of Grounding Practices in Shore Power Systems

“…The HRG method effectively suppresses the fault current on the line, preventing overvoltage and ensuring the safety of personnel and equipment. The HRG method requires ensuring that the fault current is equal to or slightly higher than the system charging current [24,35,36]. In Section 6.2.3 of IEEE 80005-1, the fault current generated by the impedance should be at least 1.25 Two types of NGRs (R N ) are commonly used: HRG and LRG.…”

“…The HRG method effectively suppresses the fault current on the line, preventing overvoltage and ensuring the safety of personnel and equipment. The HRG method requires ensuring that the fault current is equal to or slightly higher than the system charging current [24,35,36]. In Section 6.2.3 of IEEE 80005-1, the fault current generated by the impedance should be at least 1.25 times the system charging current, with a value exceeding 25 A-5 s. However, the same shore power system paired with different ship types and electrical architectures can result in varying system charging currents [32].…”

“…These IEC 60909-0 [22] and IEC 61363-1 [23] are currently the most commonly used standards for calculating fault currents. Among them is IEC 61363-1, which, although applicable to calculating fault currents for ships, does not explicitly specify its use for shore power systems [24]. During HVSC operation, operators plug in the power cable to the shore-and ship-side sockets to supply power to the ship.…”

“…The setting of the neutral grounding resistor (NGR) can help to reduce fault currents and ensure safety. Previous literature has discussed the selection of appropriate grounding resistance [24,[35][36][37].…”