TO DETERMINE OPERATION WITHIN NORMAL LIMITS AFTER A TRIP

[0001] This application claims the benefit of U.S. Provisional Application No. 63/278,544, filed November 12, 2021, the entire contents of which are incorporated herein.

TECHNICAL FIELD

[0002] The present disclosure generally relates to restoring power in an electrical system after a GFCI device in said electrical system is tripped. More specifically, the present disclosure relates to determining an appropriate time to attempt reclosure so to avoid closing onto a fault. More specifically still, the present disclosure relates to a non-contact means of measuring an imbalance in a three-phase electrical system and determining when to attempt reclosure based on said measured imbalance.

BACKGROUND

[0003] Certain electrical systems (e.g., high voltage) are required to have adequate grounding - particularly if there is a risk of equipment damage or persons being exposed to portions of a circuit and unintentionally forming a part of the circuit and/or a path to ground. Oftentimes, grounded electrical systems include devices to actively monitor the integrity of grounding, as well as devices intended to interrupt power to at least a portion of one or more circuits during an event or condition. While it the aforementioned are effective in preventing or minimizing impact from said event or condition (what will be generically referred to as a “fault”), these means do not adequately address what happens after a fault and subsequent interruption of power by a GFCI device (what will be generically referred to as a “trip”).

[0004] Consider, for example, a high voltage electrical system enabled with both a ground monitoring system (GMS) and one or more ground-fault circuit-interrupter (GFCI) devices, with one or more electrical circuits of the system geographically dispersed or otherwise generally inaccessible or inconvenient to access after installation, such as in Figures 1 A and B. Here, electrical power is delivered from a utility company or other energy provider at a transformer 10 to a service enclosure 30 via power wiring 20. Grounding of enclosure 30 is provided via a grounding electrode 28 which is connected to a conductive landing point 21 of enclosure 30 via conductor 29; this is likewise provided for enclosures 40 and 50 via grounding electrode 28/conductor 26,29/conductive landing point 22 and grounding electrode 24/conductor 25/conductive landing point 20, respectively. Grounding of components in each enclosure (e.g., control module 42) is achieved by mounting said components to a conductive surface in operative connection with the aforementioned (e.g., mounting part 42 to a conductive plate in operative connection with part 22). At least a portion of ground integrity of the aforementioned is monitored at GMS system 23.

[0005] Power is distributed from service enclosure 30 to multiple loads 300 - here, each load 300 comprises an array of LED lighting fixtures together with associated LED drivers 400 elevated on poles 60 - on multiple circuits located a long distance (e.g., several dozens of feet or more) from one another and/or enclosure 30. Most typically, three-phase power wiring 71, 72 is isolated, buried underground, or generally inaccessible by persons after its installation at the target area - here, a baseball field 100 and surrounding area.

[0006] With respect to the flow and interruption of power, manual elective interruption could occur at transformer 10 (which would terminate power to all electrical systems at the site), main breaker 31 (which would terminate power to all circuits of the electrical system at field 100), circuit breaker 32 (which would terminate power to a particular circuit of the electrical system at field 100), or disconnect switch 51 (which would terminate power to a single array of lighting fixtures 300). In each of the aforementioned instances, access and contact from persons is required - for example, a person must physically travel to field 100, unlock an enclosure, locate and access a breaker, and manually operate a switch or actuator to interrupt power.

[0007] Remote elective interruption of power could occur by actuation of contacts of contactor modules 43 as effectuated by a signal from a control module 42 in communication with a remotely located control center 1000 via wireless communications (e.g., two-way antenna radio assembly 41). Automatic or otherwise non-elective termination of power could occur by activation of GFCI devices 44. In both the remote elective and non-elective instances just described, there is no contact required of persons to interrupt power, and in the case of remote elective interruption of power, power can also be restored remotely (which is beneficial insomuch that on/off schedules for events at field 100 can be implemented remotely).

[0008] However, in the event of a trip, power cannot typically be restored remotely; again, a person must travel to field 100, unlock an enclosure, locate and access GFCI device 44, and manually operate a reset button. However, there is no guarantee manually operating the reset will restore power and enable correct operation of the impacted circuit. For instance, if a fault is still present, the GFCI device will simply trip again (what will be generically referred to as “closing onto a fault”).

SUMMARY

[0009] Consider again the outdoor sports lighting system represented in simplified form in Figures 1 A and B. If a fault occurred, GFCI means in the electrical system of Figures 1A and B would trip, and power would be removed from at least a portion of the electrical system. The result of the GFCI trip would be that some number of LED lighting fixtures 300 would lose power (or at least some individual LEDs which make up an LED lighting fixture, depending on the circuit arrangement). Troubleshooting efforts to determine which GFCI device tripped might be aided by visually assessing which lighting fixtures appeared to be “out”, but this requires travel to the site, ability to access field 100, and assumes there is not a sporting event or other activity which otherwise impedes troubleshooting efforts. Further, many GFCI devices are behind locked enclosures, making access difficult. Still further, there may be a large number of GFCI devices which are geographically dispersed and difficult to locate. And even in the event the tripped GFCI device is located, determining the cause of the trip is another issue; troubleshooting efforts may be impeded because conductors are buried underground and therefore handheld devices are impractical or inoperative. So there is no guarantee in such a situation that putting forth the time and effort to locate a tripped GFCI device and attempt reclosure will result in correct operation of the electrical system instead of simply closing onto a fault - which is not only a waste of efforts, but can have consequences depending on governing rules.

[0010] Therefore, there is a benefit to having some degree of certainty that attempting reclosure in a GFCI-enabled electrical system will, in fact, restore correct operation of the electrical system - before investing the time and labor in traveling to the site, locating the impacted circuit, unlocking an enclosure, and manually resetting the GFCI device. There are traditional means of generally assessing whether a fault or potential for a fault is still present after a trip - for example, a handheld meter (e.g., any model of leakage current clamp meter such as those available from Fluke Corporation, Everett, WA, USA) can be used to determine if leakage current is present which could lead to another trip - but traditional means still have limitations insomuch that they are still labor-intensive and/or require actual contact of portions of the electrical system (thereby potentially posing a hazard to persons operating said means). [0011] The techniques described herein may determine with some degree of certainty that attempting to close a GFCI device after a trip (what will be generically referred to as “reclosure”) will result in correct operation of the electrical system - before investing the time and labor to reestablish power after an automatic or otherwise non-elective termination of power. Such certainly cannot typically be provided by existing GMS devices (as they monitor integrity of grounding only) and cannot typically be provided by existing GFCI devices once tripped (as they cannot measure current or voltage in the open state).

[0012] In general, the techniques described herein include a method for automatic (or elective, if desired), non-contact measurement of one or more inputs (e.g., current) in an electrical system which can be used to determine operation within normal limits after a trip, and apparatus for such. Further objects, features, advantages, or aspects of the present disclosure may include one or more of the following: means for measuring an induced current due to a phase imbalance in a three-phase electrical system; means for measuring said induced current upstream of any GFCI device (or comparable means) in the electrical system; and means for comparing said measurement to a threshold such that one can ensure with some degree of certainty that reclosure will effectuate the desired response (e.g., correct operation of the electrical system).

[0013] In one example, the disclosure is directed to a non-contact measurement system comprising a current transformer, a dummy load, and a conductor.

[0014] In another example, the disclosure is directed to a method of determining a phase imbalance in an electrical system having a GFCI device following a trip of the GFCI device, the method comprising installing a non-contact measurement system in the electrical system upstream of the GFCI device, the non-contact measurement system comprising a current transformer, a dummy load, and a conductor. The method further includes tying the conductor to each phase of a power line of the electrical system and running the conductor through the current transformer. The method also includes measuring an induced current in the current transformer. The method further includes correlating the measured current to a phase imbalance in the electrical system.

[0015] The details of one or more examples of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF DRAWINGS

[0016] The following drawings are illustrative of particular examples of the present disclosure and therefore do not limit the scope of the invention. The drawings are not necessarily to scale, though examples can include the scale illustrated, and are intended for use in conjunction with the explanations in the following detailed description wherein like reference characters denote like elements. Examples of the present disclosure will hereinafter be described in conjunction with the appended drawings.

[0017] Figures 1A and B illustrate atypical GFCI-enabled electrical system which is large, inaccessible, and/or inconvenient for purposes of troubleshooting tripped GFCI devices, attempting manual reclosure, or may otherwise benefit from aspects according to the present disclosure. Figure 1A illustrates an overview of the entire outdoor sports lighting system, and Figure IB illustrates a partial block diagram of at least some of the components of the outdoor sports lighting system of Figure 1A; note that for clarity, only one load and one complete circuit (at Pole A) is illustrated in Figure IB.

[0018] Figure 2 illustrates Figure IB as modified according to aspects of the present disclosure.

[0019] Figure 3 illustrates a detailed view of component 23/80 of Figure 2 according to a first example and showing diagrammatically phase imbalance (see annotations A - D).

[0020] Figure 4 illustrates an alternative to the configuration of Figure 3 according to a second example and showing diagrammatically phase imbalance (see annotations A - D). [0021] Figure 5 illustrates one possible method of creating and implementing the non-contact measurement system of Figures 2 - 4 according to aspects of the present disclosure.

DETAILED DESCRIPTION

[0022] The following detailed description is exemplary in nature and is not intended to limit the scope, applicability, or configuration of the techniques or systems described herein in any way. Rather, the following description provides some practical illustrations for implementing examples of the techniques or systems described herein. Those skilled in the art will recognize that many of the noted examples have a variety of suitable alternatives.

[0023] Regarding terminology, reference is given herein - in the singular, plural, or both singular and plural - to terms such as “part”, “means”, “device”, “element”, and “component”; it should be noted that these terms are used for purposes of convenience, these terms may be used interchangeably, and that none of the aforementioned terms purports any limitations unless explicitly stated herein. Further, terms such as “fault” and “trip” have been used herein to describe one or more situations which might benefit from aspects according to the present disclosure; it should be noted that there are other situations that may benefit from aspects according to the present disclosure and that use of the aforementioned terms does not place any limitations (e.g., regarding action or level of safety) on when the techniques of this disclosure may be practiced or who may practice the techniques of this disclosure.

[0024] Figure 2 illustrates Figure IB as modified according to aspects of the present disclosure. As previously stated, three-phase power 71 generally flows from breaker 32 in service enclosure 30 to contactor module A (reference no. 43), which is in operative connection with GFCI means 44; note that for clarity, as in Figure IB, Figure 2 only illustrates a complete circuit for the load at Pole A, though in practice complete circuits would exist for all loads at Poles A - D. When a fault occurs contacts of contactor module 43 open in response to sensing of the fault by GFCI means 44; e.g., a trip occurs. A change in active or passive monitoring of contact position would provide indication of the trip to remote control center 1000 (e.g., via control module 42 and two-way radio assembly 41). Once contacts are open and the GFCI device has tripped, an electrical system such as that illustrated in Figures 1 A - 2 is left without monitoring of line conditions or phase conditions. Upstream of contactor module 43 is GMS means 23, but this type of device typically only monitors the integrity of grounding. This could be an additional risk if integrity is lost, but is not a substitute for monitoring line or phase conditions. As such, a person has no degree of certainty that traveling to site 100, locating the relevant enclosure 40, and resetting the relevant GFCI device 44 will result in correct operation of the electrical system by reestablishing power to the impacted load 300. If the fault is still present, reclosure will be ineffective (e.g., efforts will amount to closing onto a fault).

[0025] One solution is to implement sensing means upstream of GFCI 44; see again Figure 2. Here, a non-contact measurement system 80 comprises a number of components which collectively determine (i) whether or not there is an imbalance between phases, and (ii) the amount of imbalance - and in a manner that requires no manual operation or contact by persons. This imbalance (if any) induces a current in a measurement device (e.g., current transformer (CT)) which can be communicated back to remote control center 1000 for evaluation for elective action (e.g., dispatching persons to the site to manually restore power). Alternatively, modules 23 and/or 42 could be programmed in a factory setting prior to shipment to automatically attempt reclosure upon some predetermined condition (e.g., upon non-contact measurement system 80 measuring an imbalance less than 10% of anticipated during normal operating conditions a signal could be communicated to module 42, which in turn could generate a command signal to GFCI devices 44 to close). Specific apparatuses and methods for achieving either (or both) elective or automatic responses to non-contact measurement of electrical system conditions after a trip are described below.

[0026] Figure 3 illustrates a first example of non-contact measurement system 80; here, shown in combination with a portion of GMS means 23 - see current transformer (CT) 27 - since systems 23 and 80 share grounding electrode 28, though this is by way of example and not by way of limitation. Here a capacitive dummy load 83 (e.g., 0.22 pF, 330 VAC film capacitor available from Digi-Key Electronics, Thief River Falls, MN, USA) exists on each phase of three-phase power line 73 which, as can be seen from Figure 2, are pulled at a point upstream of contactor modules 43 in the circuit so measurements can be taken after a trip (e.g., to determine if operation is within normal limits and reclosure can be attempted without closing onto a fault).

[0027] The three phases are connected to a single conductor 85 following the series elements 83 (i.e., downstream of the elements), the current of which is measured via CT 82 before being tied to grounding electrode 28. Functionally, this means if there is an imbalance in A to D versus B to D versus C to D - for example, A to D carries 120 V, B to D carries 120 V, and C to D carries 90 V - the result will be a measurable induced current in CT 82. Alternatively, if there is no imbalance - for example, A to D carries 120 V, B to D carries 120 V, and C to D carries 120 V - the result will be no induced current in CT 82.

[0028] If desired, non-contact measurement system 80 may further include a plastic enclosure 81 to provide insulation of the aforementioned within enclosure 40.

[0029] An alternative example according to aspects of the present disclosure is illustrated in Figure 4 and envisions replacing capacitive components 83 with resistive components 84 (e.g., any model of flame proof/safety resistors such as ROX5SSJ100K available from TE Connectivity Ltd., Muhlenstrasse 26, 8200 Schaffhausen, Switzerland). It is well known that capacitors are more sensitive to high frequencies as compared to resistors insomuch that there is more noise; the result being that, in some electrical systems, a system 80 of Figure 3 might include a filtering element or additional step to method 200 (later discussed) to average out noise over time whereas a system 80 of Figure 4 may not include such a filtering element. Contrarily, resistors dissipate power in the form of heat - and so a system 80 of Embodiment Figure 4 may run much hotter than a system 80 of Figure 3, and therefore may include a modification of associated method 200 (see Figure 5) or addition of a fan to enclosure 40, for example. [0030] Figure 5 is a flow chart illustrating an example mode of operation. The techniques of Figure 5 may include creating and implementing the non-contact measurement system of Figures 2 - 4 in an electrical system such as that illustrated in Figures 1A and B. For purposes of illustration only, the techniques of Figure 5 are described within the context of Figures 1 - 4, although systems having configurations different than that of Figures 1 - 4 may perform the techniques of Figure 5.

[0031] As can be seen, method 200 includes a first step of choosing an imbalance (step 201); in essence, determining what phase imbalance might be encountered and determining a correct CT accordingly. For example, a previously given scenario stated that (i) a balanced system may be one in which A to D carries 120 V, B to D carries 120 V, and C to D carries 120 V, and (ii) an imbalanced system may be one in which A to D carries 120 V, B to D carries 120 V, and C to D carries 90 V. One would take this knowledge of the electrical system into consideration according to step 201. Of course, one could simply select CT 82 with no knowledge of the electrical system, but as CTs come in a range of accuracies, classes, physical sizes, and heat generation, there is a benefit tailoring selection of a CT according to step 201 of method 200 (e.g., reducing generated heat in an enclosure). In practice, for the electrical system illustrated in Figures 1A - 2, an imbalance of 10% is reasonable.

[0032] Taking into account the imbalance from step 201 one may design an adequate dummy load (see again Figures 3 and 4) and wire said dummy load such that a single conductor is run through CT 82 (step 202). Non-contact measurement system 80 is then installed in the electrical system (see again Figure 2) according to step 203; as illustrated non-contact measurement system 80 is integrated with GMS system 23 as they share a common ground 28, though this is by way of example and not by way of limitation. In practice, steps 202 and 203 comprise pulling power from a terminal upstream of GFCI devices 44, through the series elements 83/84, tying together the three phases at a point in enclosure 81 (which is mounted in enclosure 40), running conductor 85 through aforementioned CT 82 (which can likely be installed on the same board containing CT 27), and establishing a ground (e.g., by landing conductor 85 at landing point 22). More specifically, according to the present embodiments, steps 202 and 203 comprise pulling three-phase power to a PCB (on which is installed the series elements), running the back side of the series elements to traces, and terminating traces at a landing point to which said conductor 85 is connected (see again Figures 3 and 4), though, again, this is by way of example and not by way of limitation, and is but one way to practice method 200 according to aspects of the present disclosure. [0033] According to step 204, a measurement indicative of phase imbalance occurs; as previously stated, an imbalance between phases (e.g., A to D versus B to D and C to D) induces a current in CT 82 - which is a measurable quantity and can be correlated to the percent imbalance. If the measurement exceeds the threshold determined according to step 201 (here, 10% imbalance), some form of a response is triggered according to step 205. A response can be automatic and non-elective; a measurement above the threshold could send a feedback signal from system 80 to GFCI 44 to prevent reclosure, for example. Alternatively, said feedback signal from system 80 could simply illuminate a warning light at enclosure 40; in this sense the response is still automatic, but does not prevent elective reclosure (either remotely or on site). The benefit to illuminate a warning light may be limited if GFCI devices or other parts of the electrical system are geographically dispersed or otherwise generally inaccessible or inconvenient to access after installation. As such, in some instances, a measurement according to step 204 by system 80 may instead send a feedback signal when the measurement is below said threshold (e.g., the opposite of sending a signal if a measurement exceeds the threshold of step 201) or within some acceptable range. This feedback signal could be sent from system 80 to remote control center 1000 (e.g., via parts 42, 41) which provides an “all clear” signal to dispatch persons to a site to attempt reclosure according to step 205. All of the aforementioned are possible, and envisioned, according to step 205.

[0034] The techniques and systems of this disclosure may take many forms and embodiments. The foregoing examples are but a few of those. To give some sense of some options and alternatives, a few examples are given below.

[0035] With respect to method 200, it is important to note that there may be more, fewer, or different steps than are illustrated and not depart from aspects of the present disclosure. For example, measurement step 204 may not be automatic (as is illustrated) - but rather, elective. This could be achieved by elective powering of three-phase line 73 via, e.g., a gate-type system. As another example, measurements 204 may not be continuous (whether automatic or elective) - for example, induced current in CT 82 could be gathered and averaged over some time, and only the average sent via signal for response according to step 205.

[0036] With regards to further options and alternatives, it is important to note non-contact measurement system 80 may be installed in electrical systems other than an outdoor sports lighting system (as is illustrated), may not include optional enclosure 81, may not share a ground 28 with GMS system 23, or may differ in implementation in a number of other ways, and still provide at least some of the benefits described herein. [0037] Finally, while discussion has been given herein to three-phase, high voltage systems which (i) have adequate grounding, (ii) monitoring of ground integrity, (iii) and some form of GFCI means to interrupt power to at least a portion of a circuit of said electrical system in the event of a fault, it is important to note the techniques of this disclosure are not limited to such. For example, an electrical system without ground monitoring may still benefit from non-contact methods of determining with operation is within normal limits - regardless of whether reclosure after a fault is attempted. A variety of electrical systems may benefit from aspects of the present disclosure.

[0038] It is to be recognized that depending on the example, certain acts or events of any of the techniques described herein can be performed in a different sequence, may be added, merged, or left out altogether (e.g., not all described acts or events are necessary for the practice of the techniques). Moreover, in certain examples, acts or events may be performed concurrently.

[0039] In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer- readable medium and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another, e.g., according to a communication protocol. In this manner, computer-readable media generally may correspond to (1) tangible computer-readable storage media which is non-transitory or (2) a communication medium such as a signal or carrier wave. Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code and/or data structures for implementation of the techniques described in this disclosure. A computer program product may include a computer-readable medium.

[0040] By way of example, and not limitation, such computer-readable storage media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage, or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. It should be understood, however, that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transitory media, but are instead directed to non-transitory, tangible storage media. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0041] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor,” as used herein may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein. In addition, in some aspects, the functionality described herein may be provided within dedicated hardware and/or software modules configured for encoding and decoding, or incorporated in a combined codec. Also, the techniques could be fully implemented in one or more circuits or logic elements.

[0042] The techniques of this disclosure may be implemented in a wide variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC) or a set of ICs (e.g., a chip set). Various components, modules, or units are described in this disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but do not necessarily require realization by different hardware units. Rather, as described above, various units may be combined in a codec hardware unit or provided by a collection of interoperative hardware units, including one or more processors as described above, in conjunction with suitable software and/or firmware.

[0043] Various examples of the disclosure have been described. Any combination of the described systems, operations, or functions is contemplated. These and other examples are within the scope of the following claims.