Dev Paul

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.

Designing Cold Ironing Power Systems: Electrical Safety During Ship Berthing

Cold ironing power system design requires unique components to supply shore power to ships for cold ironing operation. Currently, the development of new standards is in progress, and operating procedures are being written to maximize electrical safety, standardization of the process, and interchangeability from one location to another. This article describes the power system design, including a power system protection scheme, which should enhance the electrical safety by design. The power system grounding, equipment grounding, and touch potential that can impact personnel safety are described. A very basic outline of the operating procedures and training needed for the operators to maximize electrical safety during cold ironing operation are also included in this article. In addition, this article provides the current status of the draft International Electrotechnical Commission (IEC)/International Organization for Standardization (ISO)/IE Standards 80005-1 [5] and 80005-2 [6].

Transient Overvoltage Protection of Shore-to-Ship Power Supply System

It is known that unpredictable threat of transient overvoltage exits in a power system, therefore; transient overvoltage protection analysis; commonly known as insulation coordination should be performed to design cold-ironing power system. This paper provides a review of the transient surge environment, transient overvoltage analysis and application of metal-oxide surge arresters at specific locations within the shore-to-ship power supply system to enhance transient overvoltage protection.

DC Stray Current in Rail Transit Systems and Cathodic Protection [History]

Stray current is current that seeks unintended paths through earth and metallic utilities. This current can be from a dc or an ac source. Stray current from an ac source is expected to only produce 1-5% of the corrosion produced by an equivalent amount of dc source. Cathodic protection (CP) is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell [6]-[8], [11]-[13], [15], [20].

Shore-To-Ship Power Supply System for a Cruise Ship

The power demand for a large cruise ship during berthing is close to 10 MVA. Such a power demand from the shore-to-ship requires multiple parallel feeds at medium voltage to match with the ship’s connection point voltage. The cruise ship authority required installation of a neutral grounding disconnect switch (DS) and insulated ground conductor (IG) at the shore power transformer neutral grounding resistor (NGR) such that during cold ironing the DS will be opened to complete the shore-side, line-to-ground fault current path through the equipment grounding conductor to reach the ship hull first before it returns to the transformer neutral via IG and NGR. Such an installation of the DS appears to violate National Electrical Code (NEC) [1] requirements of a power system grounding. For clarification of this issue, this paper provide example of a ground fault at the shore and a ground fault at the ship using DS and IG in the system. The need to know the ship’s on-board homo-polar grounding-equipment ratings and the ship’s system-charging current in designing shore-power-system grounding is discussed. This paper will provide input for the present IEEE and IEC draft standards on Cold Ironing [2] [12]. Index Terms — cable management system, cathodic protection, ground-fault relay, homo-polar grounding, insulated grounding conductor, neutral-grounding resistor, power plugs, shore power, system-charging current

High-Resistance Grounded Power System

To minimize ground fault during a line-to-ground fault condition, it has been a common practice to use high-resistance grounded (HRG) power systems, both at low voltage and at medium voltage (MV). The criteria for designing HRG systems are very well known to the industry; however, the opinion of industry experts has been divided on limiting the use of HRG systems for MV systems to voltages of less than 4.16 kV and phase-ground fault currents of less than 10 A without clarifying that it applies to systems that require continuous operation upon first detecting line-to-ground fault, as it is now in the Recommended Practice for Grounding of Industrial and Commercial Power Systems. This paper will review the background history of HRG power systems and their application to MV systems for specific industries and will make the case that voltages need not be limited to less than 4.16 kV and the phase-ground fault current to less than 10 A, so long as the faulted power system is isolated within ten cycles and that there are no directly connected motors. This paper will discuss the potential damage and protection requirements of HRG systems for MV applications to ensure that a line-to-ground fault is cleared before it involves other phases to make a multiphase arcing ground fault.

Cold Ironing Power System design and electrical safety

Cold Ironing Power System design requires unique components to supply shore power to ships for “cold ironing” operation. Currently; development of new standards are in progress and operating procedures are being written to maximize electrical safety, standardization of the process and interchangeability from one location to another. This paper describes the power system design including power system protection scheme which should enhance the electrical safety by design. Power system grounding, equipment grounding, and touch potential that can impact personnel safety are described. A very basic outline of the operating procedures and training needed for the operators to maximize electrical safety during cold ironing operation are also included in the paper. In addition, paper provides the current status of the Draft IEC/ISO/IEEE Standards 80005-1 [5] and 80005-2[6].

Transient overvoltage protection of shore-to-ship power supply system

It is known that unpredictable threat of transient overvoltage exits in a power system, therefore; transient overvoltage protection analysis; commonly known as insulation coordination should be performed to design cold-ironing power system. This paper provides a review of the transient surge environment, transient overvoltage analysis and application of metal-oxide surge arresters at specific locations within the shore-to-ship power supply system to enhance transient overvoltage protection.

Phasor and directions of a bolted single-phase-ground fault current in a high-resistance grounded (HRG) power system

This paper reviews the phasor and directions of a single-phase-ground fault current (s) in a high-resistance grounded (HRG) power system. A brief review of the published literature, which is inconsistent, has caused confusion on what should be the correct phasor and fault current directions to be used in dot standard P3003.1. An application concept that during single-phase-ground fault condition, “distributed capacitive current direction reverses in the two un-faulted phases” compared to the direction under normal system operation. This concept has been applied before [2] [6]; however, some application engineers raised the question on this concept. The concept is currently used in the modern ground fault protection relays used for HRG and ungrounded power systems. It has no impact on the operation of the power system during the phase-ground fault condition, but it helps in providing ground-fault current flow from faulted location to ground, a normal industry convention. The paper will provide guidance on how to update the contents of the HRG system contained in the current edition of IEEE STD. 142 to be used for Dot Standard P3003.1 [23].

High-Resistance Grounded Power-System Equivalent Circuit Damage at the Line–Ground Fault Location—Part I

This paper provides the electrical equivalent circuits of high-resistance grounded (HRG) power systems other than the delta-wye-connected utility power supply transformer included in Part I of this paper. This paper also provides the HRG of a medium-voltage generator for connection to an industrial power system and to a utility power system, and this paper discusses a line-ground fault with fault resistance. Three-line diagrams of ungrounded power systems are also included to illustrate the HRG application and its effect on the ground fault current during the line-ground fault. The damage at the fault location is based on the assumption that the fault remains a line-ground fault until it is cleared by appropriate ground fault protection relays. The fault resistance and the fault current that have an effect on the damage at the fault location are included. This paper provides guidance to update the current edition of the IEEE STD. 142, with respect to HRG systems.