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Ground-Fault Circuit Interrupters (GFCIs) – from a Standards Perspective
... A ground fault is a defect that permits current to flow to ground through an unintended path, for example, through the external housing of an appliance (and possibly through the body of any person who touches it). Ground faults are among the leading causes of electrical injuries (El-Sherif et al., 2020). ...
Electric shocks claim about 300 lives and cause thousands of nonfatal injuries in the U.S. each year. Sources of hazardous electric current range from high-voltage power lines to everyday household wiring and plug-in appliances. Figure 1 illustrates a case in which a worker was electrocuted by a ground fault in an electric drill. A ground fault is a defect that permits current to flow to ground through an unintended path: For instance, through the external housing of an appliance (and possibly through the body of any person who touches it). Ground faults are among the leading causes of electrical injuries. In this article, we will apply Ohm’s law to estimate the magnitude of current that may flow through a human body during electric shock. These exercises will help illustrate the range of conditions under which electric current may cause serious injury or death.
This paper proposes a novel non-isolated on-board charger that can reduce common-mode leakage current and balance the voltage of Y-capacitors on a high-voltage battery. The proposed non-isolated on-board charger is configured with an inverter power factor correction circuit and a non-isolated LC series resonant converter. A new pulse width modulation method is applied to inverter PFC, which can balance the voltage of Y-capacitors and prevent the misdiagnosis of high-voltage battery isolation breakdown by the battery management system. Additionally, a non-isolated LC series resonant converter is applied to the DC/DC stage to reduce common-mode leakage current. The effectiveness of the proposed on-board charger is verified by prototype circuit experimental results.
Special-purpose ground-fault circuit-interrupters (SPGFCIs) are incredibly important across many industries, and yet—many people are unaware of this proactive engineering control. SPGFCIs recently premiered in the 2023 edition of the National Electrical Code (NEC). While the NEC now requires SPGFCIs only for specific applications, there are many other places where shock hazards are just as prevalent and dangerous—if not more so—especially where workers are exposed to higher voltages such as in industrial, manufacturing, and construction environments. This paper will review the design principles mandated by the NEC and discuss SPGFCI technology, which react to hazards before they develop into shock events.
Residential fires of electrical origin have been a major concern for a long time. A fire can be initiated by excessive current (due to an overload or a short circuit) or arcing current. Therefore, both the Canadian Electrical Code (CE Code) Part I and the National Electrical Code (NEC) require the installation of overcurrent protection devices (OCPDs) to detect and clear excessive current. Conversely, arcing current is too low for OCPDs to detect. It could take an electric arc minutes, days, weeks, months, or even years to initiate a fire. Therefore, a new solution was required for detecting those slowly developing arcs. Thus, arc-fault circuit-interrupters (AFCIs) were born. AFCIs are capable of detecting an arcing condition (while still developing) and de-energizing the circuit before the arcing circuit ignites.
Ground-fault circuit interrupters (GFCIs), ESPEcially class A GFCIs, have been instrumental in reducing electrocution. A trinational North American standard governs the testing and certification requirements for class A GFCIs in Canada, the United States, and Mexico. However, the standard governing the requirements for special-purpose GFCIs (SPGFCIs), which include GFCI classes C, D, and E, is defined only in the United States. On the other hand, installation requirements for GFCIs in Canada and the United States are defined in Part I of the Canadian Electrical Code (CEC) and National Electrical Code (NEC), respectively. The certification and installation requirements for GFCIs have evolved through time. This article covers their development. The physiological effect of current, the theory of operation, and various types of GFCIs are explained. Finally, GFCI application issues and the effect of frequency on the operation of GFCIs are discussed.
Most refineries, drilling platforms, and chemical plants are equipped with receptacles used for powering equipment. This can present a shock hazard; therefore, NFPA and OSHA require ground-fault circuit interrupter (GFCI) on all receptacles powering equipment used by personnel and are not part of the building permanent wiring. Due to the lack of GFCI at voltages above 240 V, both NFPA and OSHA require employers to implement the assured equipment grounding conductor program for all temporary wiring installations. Recently, UL defined special purpose GFCIs in UL 943C that can be used on systems up to 600 V and allows for a leakage current of 20 mA. UL 943C requires GFCIs to monitor ground wire continuity and interrupt power if ground integrity is lost. This is very valuable for employers because it eliminates the need for assured equipment grounding conductor and guarantees that there is always a return path to ground. This paper describes the danger of electric shock, reviews the UL 943C requirements and addresses the new GFCI Classes C, D, and E. It will also discuss field applications of a Class C GFCI in a crude oil refinery.
HISTORICALLY, CLASS A GROUND-fault circuit interrupters (GFCIs) have been responsible for a substantial reduction in residential electrocutions. Yet they have not had much success in industrial applications because of the limitation on system voltage (maximum 240 V) and the 6-mA maximum allowed leakage current. As a result, industrial personnel protection has been lagging behind its residential counterpart. UL realized this gap and defined new GFCI classes to specifically address personnel protection in industrial applications. UL 943C defines the requirements of special-purpose GFCIs that can be used on systems up to 600 V and allows for a leakage current of 20 mA. This article describes the UL 943C requirements and the newly defined GFCI classes. The difference between equipment ground-fault protective devices (EGFPDs) and GFCIs is also addressed. Finally, the application of a Class C GFCI in a pulp and paper plant is described.
Ground-Fault Protection of Personnel: The Field Applications of a Class C GFCI in a Crude Oil Refinery
- N El-Sherif
- R Mendler
- J Trotte
- A Pathak
Deleterious Effects of Electric Shock
- C F Dalziel