Circuit interrupting device providing ground fault and open neutral protection in temporary power applications

Abstract

A temporary power delivery system includes a power source, a partition beam, and a portable GFCI device. The GFCI device receives current from the power source through a first terminal and delivers current to the partition beam through a second terminal. An electronic processor of the GFCI device compares a combined magnitude of current flowing through first and second phase conductors of the GFCI device to a magnitude of current flowing through a neutral conductor of the GFCI. The electronic processor also compares a first voltage between the first phase conductor and the neutral conductor to a second voltage between the second phase conductor and the neutral conductor. A circuit breaker of the GFCI device opens if a difference between the combined magnitude of the phase conductor current and the magnitude of the neutral conductor current exceeds a first threshold, or a difference between the first voltage and the second voltage exceeds a second threshold.

Description

[0001] Related Applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 936,053, filed November 15, 2019, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] Embodiments relate to circuit interrupting devices used in temporary power distribution applications, such as ground fault circuit interrupters (GFCIs). SUMMARY

[0004] The Occupational Safety and Health Administration (OSHA) requires that temporary wiring devices used in potentially wet environments, such as construction sites or outdoor trade shows, include circuit interrupters for protection of personnel from electrical shock. Specifically, all 15 A, 20 A, and 30 A outlet branch circuits (including extension cords and booth stringers that are not part of the permanent wiring of a building or structure but are used by personnel) should include GFCI protection of personnel.

[0005] A GFCI is a fast-acting device that limits the flow of current to a load in response to detecting a current leak to ground (“ground fault”). For example, a GFCI senses a ground fault by detecting an imbalance of current between a hot line and a neutral line that supplies power to a load. In other words, a GFCI operates by comparing the amount of current flowing to a load along a circuit conductor to the amount of current flowing back from the load. When the amount of current flowing to a load differs from the amount of current flowing back from the load by a predetermined amount (e.g., at least 6 mA), the GFCI interrupts the current.

[0006] OSHA also requires that GFCIs provide open neutral protection for temporary wiring devices. An open neutral condition occurs when there is an open circuit or other fault in the neutral conductor, which can cause a portion of the neutral conductor to remain energized even when the load is no longer operating. Accordingly, a damaged neutral conductor (or a portion thereof) remains energized without a current return path, and thus, an open neutral condition can lead to a ground fault or provide other dangerous conditions. However, because a GFCI device can be powered by a damaged neutral conductor, a GFCI can not operate unless specifically designed to trip when an open neutral condition occurs.

[0007] One aspect of the present disclosure provides a temporary power delivery system, the system comprising: a power source, a compartment stringer having at least one outlet box, and a portable ground fault circuit interrupter (GFCI) device. The portable GFCI device comprises: a first terminal configured to receive current from the power source, a second terminal configured to deliver current to the compartment stringer, a first phase conductor, a second phase conductor, a neutral conductor, and a circuit breaker. The portable GFCI device further comprises an electronic processor configured to: compare a combined magnitude of current flowing through the first phase conductor and the second phase conductor to a magnitude of current flowing through the neutral conductor, and compare a first voltage between the first phase conductor and the neutral conductor to a second voltage between the second phase conductor and the neutral conductor. The electronic processor is further configured to: open the circuit breaker to interrupt current flow from the power source to the compartment stringer if a difference between the combined magnitude of current flowing through the first phase conductor and the second phase conductor and the magnitude of current flowing through the neutral conductor exceeds a first threshold, or if a difference between the first voltage and the second voltage exceeds a second threshold.

[0008] Another aspect of the present disclosure provides a method of operating a temporary power delivery system. The method comprises: receiving, by a first terminal of a portable ground fault circuit interrupter (GFCI) device, current from a power source; delivering, by a second terminal of the portable GFCI device, current to a compartment stringer; and supplying, by an outlet box of the compartment stringer, power to a load. The method further comprises: comparing, by an electronic processor of the portable GFCI device, a combined magnitude of current flowing through first and second phase conductors of the portable GFCI device to a magnitude of current flowing through a neutral conductor of the portable GFCI device, and comparing, by the electronic processor, a first voltage between the first phase conductor and the neutral conductor to a second voltage between the second phase conductor and the neutral conductor. In addition, the method comprises: interrupting, by a circuit breaker of the portable GFCI device, current flow from the power source to the compartment stringer when a difference between the combined magnitude of current flowing through the phase conductors and the magnitude of current flowing through the neutral conductor exceeds a first threshold, and interrupting, by the circuit breaker, current flow from the power source to the compartment stringer when a difference between the first voltage and the second voltage exceeds a second threshold.

[0009] Other aspects of the application will become apparent by consideration of the detailed description and accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 A temporary power delivery system according to some embodiments is shown.

[0011] Figure 2 A perspective view of a GFCI device according to some embodiments is shown. Figure 1 A perspective view of a GFCI device according to some embodiments is shown.

[0012] Figure 3 A method of operating a temporary power delivery system according to some embodiments is shown.Figure 1 FIG. 3 is a flowchart of a method 300 of a temporary power delivery system. DETAILED DESCRIPTION

[0013] Before any embodiments are explained in detail, it is to be understood that the embodiments are not limited in their application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. Embodiments are capable of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings.

[0014] In addition, it should be understood that embodiments can include hardware, software, and electronic components or modules that, for purposes of discussion, can be illustrated and described as if the majority of the components were implemented solely in hardware. However, one of ordinary skill in the art will recognize that the various components can be implemented in one or more computers or other processing devices operating in a distributed computing environment, and that various computer programs can be executed on such computers or processing devices to implement the various processes, methods, and functions described herein. In addition, it should be understood that embodiments can be implemented using a variety of hardware, software, and firmware configurations, and that specific designs and implementation details can depend on the particular application at hand.

[0015] Figure 1 A block diagram of a temporary power delivery system 100 is shown in accordance with some embodiments. The temporary power delivery system 100 includes a power source 105 configured to supply current to a compartment stringer 110 via a portable GFCI device 115. In some embodiments, the power source 105 is a three-phase 120 / 208V AC power source. In other embodiments, the power source 105 can be, but is not limited to, a three-phase 250V AC power source, a three-phase 480V AC power source, a three-phase 600V AC power source, or a three-phase 347 / 600V AC power source, a single-phase 125V AC power source, or a single-phase 250V AC power source. In some embodiments, the power source 105 receives power directly from a power distribution line. In other embodiments, the power source 105 is a generator.

[0016] The booth stringer 110 is configured to supply power to one or more loads, such as electrical equipment on display at a trade show, via one or more outlet boxes 116. Figure 1 A three-phase 30A booth stringer 110 is shown, which includes six outlet boxes 116. Each outlet box 116 includes two power outlet ports 117. Alternatively, the booth stringer 110 can include more or less than six outlet boxes 116 (e.g., two, three, four, etc.). In some embodiments, the booth stringer 110 is rated to carry 20A of current. In other embodiments, the booth stringer 110 is a single-phase booth stringer rated to carry up to 20A or 30A of current. The booth stringer 110 also includes a plug 118 configured to removably connect to the portable GFCI device 115.

[0017] Figure 2 A perspective view of a portable GFCI device 115 according to some embodiments of the application is shown. The portable GFCI device 115 includes a housing 120. The housing 120 includes a first end wall 122, a second end wall 124, and a sidewall 126 extending from the first end wall 122 to the second end wall 124. A front face 128 of the sidewall 126 provides a power indicator light 130 and a fault indicator light 132. The power indicator light 130 is illuminated when the portable GFCI device 115 permits current to flow from the power source 105 to the booth stringer 110. The fault indicator light 132 is illuminated when the portable GFCI device 115 inhibits or interrupts current flow from the power source 105 to the booth stringer 110. Current flow from the power source 105 to the booth stringer 110 can be interrupted, for example, in response to a ground fault. The front face 128 of the portable GFCI device 115 also includes a reset button 134 and a test button 164.

[0018] The portable GFCI device housing 120 supports a first terminal 140 and a second terminal 142, respectively. The first terminal 140 includes a plug 144 Figure 1 ) configured to connect to the power source 105 and receive current therefrom. The second terminal 142 is configured to connect to the booth stringer 110 and deliver power thereto. In some embodiments, the second terminal 142 includes a female connector 146 configured to receive the plug 118 of the booth stringer 110. In other embodiments (not shown), the second terminal 142 includes a pigtail connector configured to be wired directly to a wire within the booth stringer 110. In the above embodiments, the booth stringer 110 and the portable GFCI device 115 are separate components that are operable to be detachably connected to one another. However, in some embodiments, the booth stringer 110 and the portable GFCI device 115 are integrally formed as one component.

[0019] In some embodiments, the portable GFCI device 115 is a three-phase 120 / 208V AC device. In such embodiments, the portable GFCI device 115 can be a four-pole five-wire connection type. The first terminal 140 and the second terminal 142 are electrically connected via five wires (three separate phase wires, one neutral wire, and one ground wire) that are configured to carry three-phase AC current. In some embodiments, the wires can be composed of #10 AWG cable rated to carry 30A of current. In some embodiments, the wires can be of the #12 AWG type rated to carry 20A of current. In some embodiments, the portable GFCI device 115 can be, but is not limited to, one of the following: a three-phase 250V AC device, a three-phase 480V AC device, a three-phase 600V AC device, or a three-phase 347 / 600V AC device. In some embodiments, the portable GFCI device 115 is implemented as a single-phase device rated to be, but is not limited to, one of the following: 125V AC, 250V AC, or 125 / 250V AC.

[0020] In some embodiments, the portable GFCI device 115 is of the National Electrical Manufacturers Association (NEMA) 4X rating. Thus, in such embodiments, the housing 120, the first terminal 140 and the second terminal 142, the plug 144, and the connector 146 of the portable GFCI device 115 are weatherproof and provide protection against damage from, for example, dirt, rain, hail, snow, sleet, splashing water, hose-down water, and external icing. Additionally, the components of the portable GFCI device 115 are corrosion resistant and are rated to operate in a temperature range of -35°C to 66°C.

[0021] The portable GFCI device 115 also includes a protection circuit disposed within the housing 120. The protection circuit includes an electronic processing device, such as an integrated circuit (IC) device, that is configured to detect whether a fault exists within the temporary power delivery system 100. For example, in some embodiments, the IC device can be implemented as a well-known 4141 device, such as the RV4141 device manufactured by Fairchild Semiconductor. In some embodiments, other processing devices are used in place of the RV4141 device. In response to detecting that a fault exists, the electronic processing device will open a circuit breaker included in the protection circuit to interrupt the flow of current from the power source 105 to the compartment girder 110.

[0022] In particular, the protection circuit is configured to detect the occurrence of a ground fault within the temporary power delivery system 100. The electronic processing device of the protection circuit is configured to determine whether the difference between the combined magnitude of the current flowing through the phase conductors of the portable GFCI device 115 and the magnitude of the current flowing through the neutral conductor of the portable GFCI device 115 exceeds a ground fault threshold. The ground fault threshold can be, for example, 6 mA or greater. If the electronic processing device determines that the difference between the combined phase conductor current and the neutral conductor current exceeds the ground fault threshold, the electronic processing device interrupts the flow of current from the power source 105 to the compartment stringers 110 by opening a circuit breaker included in the protection circuit.

[0023] For example, if the portable GFCI device 115 includes two phase conductors and one neutral conductor, the electronic processing device can be configured to determine whether the difference between the combined magnitude of the current flowing through the first and second phase conductors and the magnitude of the current flowing through the neutral conductor exceeds the ground fault threshold by an amount. When the difference between the combined magnitude of the current flowing through the first and second phase conductors and the magnitude of the current flowing through the neutral conductor exceeds the ground fault threshold (e.g., 6 mA), the electronic processing device interrupts the flow of current from the power source 105 to the compartment stringers 110 by opening a circuit breaker.

[0024] In addition, the protection circuit is configured to detect the occurrence of an open neutral condition within the temporary power delivery system 100. The protection circuit can be configured to detect the presence of an open neutral condition using one of a variety of known methods. For example, according to one embodiment, the electronic processing device of the protection circuit is configured to detect a first voltage equal to the voltage between a first phase conductor of the portable GFCI device 115 and a neutral conductor of the portable GFCI device 115. In addition, according to this example embodiment, the electronic processing device is configured to detect a second voltage equal to the voltage between a second phase conductor of the portable GFCI device 115 and the neutral conductor of the portable GFCI device 115. If the difference between the first voltage and the second voltage exceeds an open neutral threshold, the electronic processing device determines that an open neutral condition exists. In response to determining that an open neutral condition exists, the electronic processing device interrupts the flow of current from the power source 105 to the compartment stringers 110 by opening a circuit breaker included in the protection circuit.

[0025] While the above examples of the protection circuit are described with respect to a temporary power delivery system including two phase conductors and one neutral conductor, it should be understood that the protection circuit can also be implemented in a temporary power delivery system including more or less than two phase conductors. For example, the protection circuit can be included in a temporary power delivery system including one, three, or more phase conductors.

[0026] Figure 3is a flowchart illustrating a method 300 of operating a temporary power delivery system 100, in accordance with some embodiments. It should be understood that the order of the steps disclosed in operation 300 can be changed, but still be within the scope of the disclosed embodiments. At block 305, the portable GFCI device receives current from the power source 105 via the first terminal 140. At block 310, the portable GFCI device delivers current to the compartment rail 110 via the second terminal 142. At block 315, the electronic processor of the GFCI device 115 (e.g., IC device) compares the combined magnitude of the current flowing through the first and second phase conductors of the portable GFCI device 115 to the magnitude of the current flowing through the neutral conductor of the portable GFCI device 115. At block 320, the electronic processor of the GFCI device 115 compares the first voltage between the first phase conductor and the neutral conductor to the second voltage between the second phase conductor and the neutral conductor.

[0027] At block 325, the portable GFCI device 115 determines whether the difference between the combined magnitude of the current flowing through the first and second phase conductors and the magnitude of the current flowing through the neutral conductor exceeds a first threshold (e.g., 6 mA). If the difference exceeds the first threshold, the electronic processor opens the circuit breaker of the portable GFCI device to interrupt the current flowing from the power source 105 to the compartment rail 110 (block 330). At block 335, the electronic processor determines whether the difference between the first voltage and the second voltage exceeds a second threshold. If the difference between the first voltage and the second voltage exceeds the second threshold, the electronic processor opens the circuit breaker to interrupt the current flowing from the power source 105 to the compartment rail 110 (block 330).

[0028] Accordingly, the present disclosure provides, among other things, a system and method for protecting against ground fault and open neutral conditions in a temporary power system. Various features and advantages of the present application are set forth in the following claims.

Claims

1. A temporary power delivery system, comprising: a compartment girder comprising at least one outlet box; and a portable ground fault circuit interrupter (GFCI) device comprising: a first terminal configured to receive electrical current; a second terminal configured to deliver electrical current to the compartment girder; a first phase conductor, a second phase conductor, and a neutral conductor; a circuit breaker; and an electronic processor configured to: compare a combined magnitude of electrical current flowing through the first phase conductor and the second phase conductor to a magnitude of electrical current flowing through the neutral conductor; compare a first voltage between the first phase conductor and the neutral conductor to a second voltage between the second phase conductor and the neutral conductor; and open the circuit breaker to interrupt electrical current flowing to the compartment girder when one or more of: a difference between the combined magnitude of electrical current flowing through the first phase conductor and the second phase conductor and the magnitude of electrical current flowing through the neutral conductor exceeds a first threshold value; and a difference between the first voltage and the second voltage exceeds a second threshold value.

2. The temporary power delivery system of claim 1, wherein, the second terminal is configured to deliver 30 A of three-phase alternating current to the compartment girder.

3. The temporary power delivery system of claim 1, wherein, the second terminal of the portable GFCI device comprises a plug.

4. The temporary power delivery system of claim 1, wherein, the second terminal of the portable GFCI device comprises a fiber optic connector.

5. The temporary power delivery system of claim 1, wherein, the first terminal of the portable GFCI device comprises a plug.

6. The temporary power delivery system of claim 1, wherein, the electronic processor is further configured to illuminate a power indicator light and a fault indicator light of the portable GFCI device depending on an operating condition of the portable GFCI device.

7. The temporary power delivery system of claim 1, wherein, the portable GFCI device is NEMA 4X rated.

8. The temporary power delivery system of claim 1, wherein, the portable GFCI device and the compartment girder are integrally formed as a single component of the temporary power delivery system.

9. The temporary power delivery system of claim 1, wherein, the electronic processor is further configured to determine that a ground fault exists within the temporary power delivery system if the difference between the combined magnitude of electrical current flowing through the first phase conductor and the second phase conductor and the magnitude of electrical current flowing through the neutral conductor exceeds the first threshold value.

10. The temporary power delivery system of claim 1, wherein, the electronic processor is further configured to determine that an open neutral condition exists within the temporary power delivery system if the difference between the first voltage and the second voltage exceeds the second threshold value.

11. A method of operating a temporary power delivery system, comprising: receiving electrical current from a power source by a first terminal of a portable ground fault circuit interrupter (GFCI) device; delivering electrical current to a compartment girder by a second terminal of the portable GFCI device; supplying power to a load by an outlet box of the compartment girder; comparing, by an electronic processor of the portable GFCI device, a combined magnitude of electrical current flowing through a first phase conductor and a second phase conductor of the portable GFCI device to a magnitude of electrical current flowing through a neutral conductor of the portable GFCI device; comparing, by the electronic processor, a first voltage between the first phase conductor and the neutral conductor to a second voltage between the second phase conductor and the neutral conductor; and opening a circuit breaker of the portable GFCI device to interrupt electrical current flowing to the compartment girder when one or more of: interrupting, by a circuit breaker of the portable GFCI device, current flowing from the power source to the cubicle girder when a difference between the first voltage and the second voltage exceeds a second threshold value. and interrupting, by a circuit breaker of the portable GFCI device, current flowing from the power source to the cubicle girder when a difference between the first voltage and the second voltage exceeds a second threshold value.

12. The method of claim 11, further comprising: delivering, by the second terminal, 30 A of three-phase alternating current to the cubicle girder.

13. The method of claim 11, wherein, The second terminal of the portable GFCI device comprises a plug.

14. The method of claim 11, wherein, The second terminal of the portable GFCI device comprises a fiber optic connector.

15. The method of claim 11, wherein, The first terminal of the portable GFCI device comprises a plug.

16. The method of claim 11, further comprising: illuminating, by the electronic processor, a power indicator light and a fault indicator light of the portable GFCI device depending on an operating condition of the portable GFCI device.

17. The method of claim 11, wherein, The portable GFCI device is NEMA 4X rated.

18. The method of claim 11, wherein, The portable GFCI device and the cubicle girder are integrally formed as a single component of the temporary power delivery system.

19. The method of claim 11, further comprising: determining, by the electronic processor, that a ground fault exists within the temporary power delivery system if a difference between a combined magnitude of current flowing through the first phase conductor and the second phase conductor and a magnitude of current flowing through the neutral conductor exceeds the first threshold value.

20. The method of claim 11, further comprising: determining, by the electronic processor, that an open neutral condition exists within the temporary power delivery system if the difference between the first voltage and the second voltage exceeds the second threshold value.

Images