Patent Publication Number: US-8537516-B1

Title: Apparatus, method, and system for monitoring of equipment and earth ground systems

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119 to provisional U.S. application Ser. No. 61/201,065, filed Dec. 5, 2008, hereby incorporated by reference in its entirety. 
    
    
     I. BACKGROUND OF INVENTION 
     The present invention generally relates to monitoring the integrity of grounding components in an electrical system. More specifically, the present invention relates to various apparatuses and methods by which a signal may be imposed on an electrical system by a first inductive element and received by a second inductive element such that grounding system impedance may be determined and integrity of grounding components assessed. 
     It is well known that methods of equipment grounding are necessary to protect the equipment in an electrical system from adverse electrical effects that may result in equipment failure, such as electrical surges. Methods of equipment grounding are well known in the art and are required in most applications by the United States National Electric Code (NEC), National Fire Prevention Association (NFPA), and local codes. It is also well known that methods of earth grounding are necessary to provide an electrical system with a low impedance path to ground such that electrical energy from adverse electrical effects, such as lightning, may be dissipated and risk of personal injury from electrical shock hazards may be minimized. Methods of earth grounding are well known in the art and are generally subject to the same governing codes as equipment grounding. 
     Said governing codes generally require impedance measurements of the equipment and earth grounding systems, which may be completed during installation using commercially available methods. One such method utilizes portable clamp-on meters which, while functional, require onsite personnel and may be time-consuming and unreliable due to operator error and inconsistent methods of measuring. Further, clamp-on meters and other methods of measuring impedance in grounding systems are generally single channel devices that may be prohibitively expensive to utilize in an electrical system with a plurality of grounding systems or components therein. 
     Also challenging is that commercially available methods of measuring impedance in grounding systems produce an instantaneous measurement and do not allow for practical recurrent testing. Impedance measurements of equipment and earth grounding systems completed at the time of installation may verify adherence to governing codes, however, impedance of the grounding systems may increase over the life of the electrical system (e.g. due to corrosion or theft). In the current state of the art, to accurately measure the impedance of an equipment and earth grounding system after installation is complete, trained personnel must repeatedly return to the site with specialized equipment, which may be time-consuming and cost-prohibitive. 
     However, repeated impedance measurements by trained personnel returning to an application site do not ensure the overall electrical system is compliant with governing codes during periods of time between visits. The current state of the art may benefit from methods of actively monitoring the integrity of the equipment and earth grounding components of an electrical system such that changes in system impedance may be tracked, a user of the electrical system notified when system impedance increases to undesirable levels, and optionally, methods of disabling components of an electrical system in response to impedance increases. Thus, there is room for improvement in the art. 
     II. SUMMARY OF THE INVENTION 
     Over time, the effectiveness of grounding components in an electrical system may be diminished for a variety of reasons. Currently available methods of measuring system impedance, while generally adequate when an electrical system is first installed, may become cost-prohibitive and ineffective over the life of the electrical system and, thus, inadequate to determine grounding component effectiveness long-term. Envisioned are apparatus, methods, and systems whereby grounding components of an electrical system may be monitored and tested over the life of an electrical system such that effectiveness of grounding components may be verified and, optionally, provisions made to address inadequate effectiveness (e.g. disabling power to components of the electrical system, notifying the user of the electrical system, etc.). One typical application may be a large area outdoor sports lighting system and the grounding system components therein, but any electrical system with grounding components or conductive elements to be actively monitored may likewise benefit. 
     It is therefore a principle object, feature, advantage, or aspect of the present invention to improve over and/or solve problems and deficiencies in the state of the art. Further objects, features, advantages, or aspects of the present invention may include one or more of the following:
         a. identifying, isolating, and grouping grounding components of an electrical system,   b. imposing a signal or plurality of signals on each isolated group of grounding components,   c. receiving an imposed signal or plurality of signals and determining impedance for each isolated group of grounding components,   d. monitoring, tracking, and testing the impedance of grounding components in an electrical system,   e. determining an impedance threshold and issuing some form of alarm if said threshold is approached and/or exceeded, and   f. communication between ground monitoring components and:
           a. a control device or system (located remote from or integral to the electrical system),   b. a power regulating component of the electrical system, and/or   c. other components of the electrical system.   
               

     These and other objects, features, advantages, or aspects of the present invention will become more apparent with reference to the accompanying specification. 
     A method according to one aspect of the present invention comprises creating a ground loop circuit whereby an imposed signal or plurality of signals may travel and a response or responses may be measured. A ground loop circuit, as described throughout the specification, may comprise any number and/or combination of electrical system components (e.g. electrode connective device(s) (e.g. bolts, lugs, terminal blocks, etc.), earth ground wire(s), equipment ground wire(s), ground monitoring system module(s), etc.) operatively connected to each other (whether directly or indirectly) such that a complete electrical circuit (as defined for an application) exists. For example, the ground loop circuit could be completely hardwired, or it could include a leg or section that is a current path either between two conductors such as spaced apart conductors in the earth or through a conductive medium such as a metal enclosure box or metal tubular conduit. 
     An apparatus according to one aspect of the present invention comprises circuitry and power supply elements controlling a plurality of inductive elements installed on each ground loop circuit so that a signal or a plurality or signals may be imposed by a first inductive element and a response measured by a second inductive element. 
     An apparatus according to another aspect of the present invention comprises a user interface controlling onsite test functionality of the inductive elements, as well as display functionalities and alarm notification, for each ground loop circuit. 
     A system according to one aspect of the present invention comprises integration of equipment and earth grounding in a sports lighting system, and monitoring and testing the impedances in the grounding components therein. 
    
    
     
       III. BRIEF DESCRIPTION OF THE DRAWINGS 
       From time-to-time in this description reference will be taken to the drawings which are identified by figure number and are summarized below. 
         FIG. 1A  illustrates a typical system sports lighting system according to at least one aspect of the present invention. 
         FIG. 1B  illustrates a partial block diagram of the electrical components of the system illustrated in  FIG. 1A . 
         FIG. 1C  illustrates a typical ground loop circuit for the system illustrated in  FIG. 1A . 
         FIGS. 2A-2C  illustrate a sports lighting system with ground loop circuit according to an exemplary embodiment. 
         FIG. 3A  illustrates diagrammatically the functionality of a first toroid according to exemplary embodiments. 
         FIG. 3B  illustrates diagrammatically the functionality of a second toroid according to exemplary embodiments. 
         FIGS. 4A-4D  illustrate one possible housing for the ground monitoring system (GMS) module and its components therein according to the exemplary embodiments. 
         FIGS. 5A and 5B  illustrate a sports lighting system with ground loop circuit according to an alternative exemplary embodiment. 
     
    
    
     IV. DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     A. Overview 
     To further understanding of the present invention, specific exemplary embodiments according to the present invention will be described in detail. Frequent mention will be made in this description to the drawings. Reference numbers will be used to indicate certain parts in the drawings. The same reference numbers will be used to indicate the same parts throughout the drawings. 
     As has been stated, methods of equipment and earth grounding are required by most national and local governing codes for many electrical systems, particularly those which pose electrical shock hazards if not properly grounded. An electrical system according to at least some aspects of the present invention is illustrated in  FIG. 1A-C  and may generally be characterized by the following.
         With respect to  FIG. 1A , four banks of light fixtures  61  are powered via electrical cables  32  from a service distribution cabinet  44  and control/contactor cabinet  45 .
           Distribution cabinet  44  and contactor cabinet  45  are connected via electrical cable  32  and equipment ground wire  24 .   Distribution cabinet  44  is connected to equipment ground wire  29  and equipment ground electrode  28 .   
           Each fixture bank  61  is housed at a pole  60 .
           Each pole further comprises a pole cabinet  46 , earth ground wire  27 , and earth ground electrode  26 .   Equipment ground wire  25  connects each pole with control/contactor cabinet  45 .   
               

     Remote control functionality of the electrical system may be enabled by a control center  90 . An example of remote operation may be found in U.S. Pat. No. 6,681,110, incorporated by reference herein, and commercially available under the trade name CONTROL-LINK® from Musco Sports Lighting, LLC, Oskaloosa, Iowa, USA. As may be appreciated by one skilled in the art, the currently commercially available CONTROL-LINK® product may differ from that described in U.S. Pat. No. 6,681,110 as a mode of communication between an onsite component and a central server discussed in said patent (e.g. analog cellular signal) may comprise alternate modes of communication (e.g. satellite, Global System for Mobile communications (GSM), Code Division Multiple Access (CDMA), etc.). 
     A partial block diagram of the electrical components in  FIG. 1A  may be found in  FIG. 1B . With respect to  FIG. 1B , the flow of electrical power to a pole may generally be characterized by the following.
         1. Electrical power flows from service distribution cabinet  44  to breaker A  31 .   2. Power flows from breaker A  31  to control/contactor cabinet  45  via electrical cables  32  housed in conduit  23 .   3. Power in electrical cables  32  reaches contactor module A  41  and leaves control/contactor cabinet  45 .
           a. Moderator module  42 , which directs power to the contactor modules and collects system data, may be operated remotely by control center  90  and via antenna  43 .   
           4. Power in electrical cables  32  reach pole cabinet  46  at Pole A where power passes through disconnect switch  52 , the current is regulated at ballast  51 , and fixture bank  61  is powered.       

     It is of note that for the sake of brevity,  FIG. 1B  shows a complete circuit for Pole A only; however, one skilled in the art would know similar circuitry exists for Poles B-D illustrated in  FIG. 1A . Further, as can be seen in  FIG. 1B  only one ballast  51  and capacitor is diagrammatically illustrated for a bank  61  of six lamps; this is intended merely to illustrate typical components of a lighting system and should not be considered representative of the number of ballasts  51  and capacitors required to operate a fixture bank  61 . One skilled in the art would know that a fixture bank  61  of six lamps would likely utilize six ballasts and six capacitors, though other configurations are possible. Still further, it is of note that, as illustrated, conduit  23  is comprised of conductive material (e.g. steel) and conduit  22  is comprised of non-conductive material (e.g. PVC). The aforementioned qualifying statements regarding complete circuits, ballasts and capacitors, and conduit materials may be likewise applied to  FIGS. 2B and 5A . 
       FIG. 1C  illustrates a ground loop circuit produced for Pole A according to the electrical circuit illustrated in  FIG. 1B . With respect to  FIG. 1C , the flow of an imposed signal may generally be characterized by the following.
         1. An imposed signal leaves a monitoring module  200  at control/contactor cabinet  45  along equipment ground wire  25  which terminates at pole cabinet ground bar  35 .   2. The imposed signal continues along earth ground wire  27  to pole ground lug  62 , and continues to earth ground electrode  26 .   3. The imposed signal at earth ground electrode  26  travels through earth  100  to equipment ground electrode  28 .   4. The imposed signal at equipment ground electrode  28  travels along equipment ground wire  29  to service cabinet ground bar  33 .   5. The imposed signal continues along equipment ground wire  24  to contactor cabinet ground bar  34 .   6. The imposed signal continues along equipment ground wire  25  to monitoring module  200  where results are monitored, measured, and compared against a baseline to calculate system impedance.       

     It is of note that  FIG. 1C  illustrates one possible ground loop circuit for Pole A only. However, one skilled in the art would know that similar ground loop circuits exist for Poles B-D illustrated in  FIG. 1A . 
     While proper grounding methods produce the benefits of equipment and personal protection from electrical shock hazards, additional benefits may be achieved by active monitoring of the ground loop circuit illustrated in  FIG. 1C . Active monitoring of the ground loop circuit, whether remotely (e.g. via control center  90 ) or onsite (e.g. via a user interface in monitoring module  200 ), may allow a user to ensure installation of the grounding system was performed correctly. For example, if earth ground electrode  26  was installed for all the poles illustrated in  FIG. 1A  except for Pole A, active monitoring of each pole&#39;s ground loop circuit (as illustrated in  FIG. 1C ) may show an impedance an order of magnitude or more higher for the Pole A ground loop circuit, clearly indicating to the contractor or remote control center  90  that Pole A is insufficiently grounded. It is of note that active monitoring of the signal(s) imposed on a ground loop circuit—whether remotely or onsite—is completed via inductive coupling, thus isolating the circuitry used to calculate impedance from the grounding components; this is a benefit over direct impedance measurements made on grounding components, which may present electrical shock hazards to personnel completing the measurements. 
     As a further benefit, active monitoring may allow a user to track increases in system impedance over the life of the electrical system which may not be readily observed otherwise (e.g. increases in grounding system impedance due to degradation of buried conductor insulation). Still further, once monitored impedance for a ground loop circuit has approached a threshold (as defined by governing codes, a user, or otherwise), monitoring module  200  may display an alarm onsite, as well as relay the alarm status to control center  90  which may, in turn, contact a user and/or disable components of the electrical system until the situation is remedied. 
     B. Exemplary Method and Apparatus Embodiment 1 
     A more specific exemplary embodiment, utilizing aspects of the generalized example described above, will now be described. An electrical system such as that illustrated in  FIGS. 2A-2C  is enabled with a ground monitoring system (GMS) module as illustrated in  FIGS. 4A-4D . The GMS module comprises a series of toroids the functionality of which are illustrated in  FIGS. 3A and 3B . 
     In this embodiment each pole  60  has two conductors ( 25  and  56 ) which run from a pole cabinet  46  to a contactor cabinet  45 . A first ground loop circuit comprises loop grounding bar  36 , conductor  56 , ground lug  62 , section of earth ground wire  27 , pole cabinet ground bar  35 , equipment ground wire  25 , contactor cabinet ground bar  34 , and GMS module  80 . A second ground loop circuit comprises GMS module  80 , equipment ground wire  24 , contactor cabinet ground bar  34 , service cabinet ground bar  33 , service cabinet  44 , conduit  23 , and contactor cabinet  45 ; note service cabinet  44 , conduit  23 , and contactor cabinet  45  are electrically conductive to facilitate a complete electrical connection in the ground loop circuit. 
     As can be seen from  FIG. 4C , each conductor entering GMS module  80  (e.g. conductor sections  24  and  25  from ground bar  34  to GMS module  80  illustrated in  FIG. 2C ) passes through a first toroid  20  and second toroid  21  before landing at lug  71 . First toroid  20  imposes a signal on the conductor (and thus, the ground loop circuit) and second toroid  21  receives said signal.  FIG. 3A  diagrammatically illustrates the functionality of first toroid  20 , which may generally be characterized by the following.
         1. A 120 to 24 VAC voltage transformer  8  powers a DC power supply  7  which, in turn, powers a crystal oscillator circuit (OSC)  3 .   2. OSC circuit  3  produces a first voltage signal at 1.66 kHz with a square waveform.
           a. OSC  3  further acts as a 20 MHz clock input for the multiplexer output circuit. The use of OSCs as clock signals for integrated circuits is well known in the art.   
           3. The 1.66 kHz square wave from OSC  3  is converted to a sine wave by a sine wave generator  9 .   4. An analog transmitter  10  directs the voltage signal to any one of a plurality of channels (shown to be five in  FIGS. 3A and 3B , though this is by way of example and not by way of limitation) as determined by a processor module  1 .
           a. An inherent benefit of analog transmitter  10 /processor module  1  is such that a single ground loop circuit may be isolated, its impedance measured, and results displayed. Further, the energy required to run the multiplexer output circuit is minimized since only one toroid  20  is energized at a given time. However, other transmitter  10 /processor  1  setups may be utilized without realizing the aforementioned benefits and still provide the necessary functionality for the exemplary embodiment.   
           5. The constant voltage signal is amplified by a power amplification circuit  15 , maintaining a frequency of 1.66 kHz, and used to energize first toroid  20 .   6. The constant voltage signal, at a frequency of 1.66 kHz, is imposed on a ground wire (see reference nos. 24 and 25) running through toroid  20 .   7. A second voltage signal according to the above process is produced at 0.83 kHz and imposed on the ground wire (see reference nos. 24 and 25) running through toroid  20 .       

     With respect to processor module  1 , functionality further comprises calculation of ground loop circuit impedance, comparison of ground loop circuit impedance to threshold levels, display of ground loop circuit impedance values, and communication with a control system (whether remotely operated or otherwise). Processor module  1  may comprise any commercially available microcontroller (e.g. model UPSD 3233B-40U6 available from STMicroelectronics, Geneva, Switzerland) or analogous device. 
     Generally, the signal traveling through the ground loop circuit may be imposed at any frequency (given circuitry to impose and receive the signal at said frequency). However, if it is desirable for the ground monitoring system as envisioned to be integrated with other systems which may regulate power to the electrical system to allow for corrective action of an alarm condition (e.g. ground-fault circuit interrupters (GFCIs)), it may be beneficial for the frequency of the imposed signal to reflect that of the incoming power to the electrical system. For example, Underwriters Laboratories Inc. (UL) Guideline KCYC defines the acceptable voltages to ground for different classes of circuits. The electrical system illustrated in  FIGS. 2A-C  is generally defined as a Class C circuit as the incoming power is typically 480V—three phase at 60 Hz with each conductor measuring 277V to ground (assuming installation in the United States); UL-KCYC defines Class C as a circuit with reliable equipment grounding (per NEC code) with each conductor measuring no more than 300V to ground. Thus, if one were to integrate the ground monitoring system as envisioned with a Class C GFCI device, for the electrical system illustrated in  FIGS. 2A-C , one would need to ensure reliable equipment grounding to satisfy the UL-KCYC requirement. As has been stated, the integrity (and thus, reliability) of the equipment grounding may be verified by the ground monitoring system described herein. Thus, for the system illustrated in  FIGS. 2A-C  operating at 480V—three phase at 60 Hz, it is beneficial to impose a signal at 60 Hz. It is of note, however, that the aforementioned method of determining the frequency of an imposed signal is equally applicable to other electrical systems (e.g. 240V—three phase at 50 Hz, which is common in Europe) and envisioned. 
     However, the difficulty in imposing and measuring a signal on a ground loop circuit for the electrical system illustrated in  FIGS. 2A-C  at 60 Hz is the amount of noise present at that frequency. One solution, then, is to measure impedance at two frequencies, calculate the resistive (R) and inductive (L) components of the impedance, and calculate impedance at 60 Hz (Z 60 ). In the present embodiment signals are imposed and measured at 1.66 kHz and 0.83 kHz as these frequencies are not harmonics of 60 Hz. The calculation of impedance at 60 Hz is described by the following:
 
 Z   1 =√{square root over ( R   2 +(2 πf   1   L ) 2 )}
 
 Z   1   2   =R   2 +(2 πf   1   L ) 2  
 
 Z   2 =√{square root over ( R   2 +(2 πf   2   L ) 2 )}
 
 Z   2   2   =R   2 +(2 πf   2   L ) 2  
 
wherein Z 1  is the impedance of the ground loop circuit at a first measurement frequency, R is the resistance of the ground loop circuit, f 1  is the first measurement frequency (e.g. 1.66 kHz), L is the inductance of the ground loop circuit, Z 2  is the impedance of the ground loop circuit at a second measurement frequency, and f 2  is the second measurement frequency (e.g. 0.83 kHz).
 
     The aforementioned formulas for the impedance of the ground loop circuit at two measurement frequencies may be solved simultaneously to provide the following formulas for the inductance, L, and the resistance, R, of the ground loop circuit. 
     
       
         
           
             
               
                 
                   
                     
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     The calculated formulas for the inductance L, and resistance, R, may then be substituted for said variables in the original equation and solved for the impedance of the ground loop circuit (Z 60 ) at a frequency of 60 Hz (f 60 ). 
     
       
         
           
             
                 
             
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     The imposed voltage signals induce current in a second toroid  21  of each ground loop circuit being monitored, the functionality of which is diagrammatically illustrated in  FIG. 3B  and may generally be characterized by the following.
         1. The induced current produces a small voltage in second toroid  21 .   2. A receiver circuit  16  amplifies and buffers the signal front toroid  21 .   3. An analog receiver  11 , as directed by processor module  1 , routes the signal to a notch filter  4  which filters out noise from the voltage signal to isolate the frequency of interest (e.g. 1.66 kHz for the first frequency and 0.83 kHz for the second frequency), with a pass bandwidth of ±100 Hz.   4. The signal is converted from AC to DC by a RMS to DC converter  5 .   5. The DC signal is then converted by a 12-bit analog to digital converter  6  from an analog waveform to a binary code, which is processed and stored by processor module  1 .
           Ground loop circuit impedance is measured at the time of installation, thus providing a baseline value. When second toroid  21  is energized and produces a signal to the multiplexer input circuit, any changes in ground loop circuit impedance are reflected in the value of said signal. Thus, knowing the imposed constant voltage (at both 1.66 kHz and 0.83 kHz), the measured second toroid signal (at both 1.66 kHz and 0.83 kHz), and the ground loop circuit baseline impedance, processor module  1  is able to calculate changes in impedance of the ground loop circuit at 60 Hz by calculations well known in the art and previously described.   
               

     Activation of the multiplexer input and output circuits may be enabled by a remote operation functionality (e.g. CONTROL-LINK®) at regularly scheduled intervals, or when deemed necessary by a control center  90  or by a user. Alternatively, or in addition, activation of the multiplexer input and output circuits may be enabled onsite by a user interface on GMS module  80 . One possible user interface and housing for GMS module  80  is illustrated in  FIGS. 4A-4D  and may generally be characterized by the following.
         A housing  70  which may display user interface functionality comprising:
           A pair of pushbuttons  76  which toggle through the channels in processor module  1 ,
               Note that there may be any number of channels available but at least enough such that each ground loop circuit has a dedicated channel. For example,  FIG. 4C  illustrates five conductors entering five pairs of toroids. Thus, for this example there would be at least five channels available.   
               A display  77  to illustrate which channel is active,   A display  73  to illustrate the impedance value for the active channel,   A pair of LEDs  72  (e.g. one green and one red) to visually indicate alarm status (e.g. green to indicate sufficient ground loop circuit impedance and red to indicate an alarm notification),   A pushbutton  75  which, when pressed, displays an instantaneous maximum impedance value (as indicated by channel display  77  and value display  73  for the channels in processor module  1  for a finite period of time (e.g. two seconds), and then displays an instantaneous minimum impedance value (as indicated by channel display  77  and value display  73  for the channels in processor module  1 ) for a finite period of time (e.g. two seconds),   A pushbutton  74  which, when pressed, may erase impedance values stored in processor module  1  and reset max/min values,   A pushbutton  79  which, when pressed, will initiate operation of the multiplexer input and output circuits, as was described for  FIGS. 3A and 3B , and display the results on channel display  77  and value display  73  for each channel in processor module  1  for a finite period of time (e.g. two seconds for each channel); and,   An optional pushbutton  78  which, when pressed, may display alternative data on value display  73 .   
           A series of landing lugs  71  for each channel (shown by way of example and not by way of limitation to be five lugs for five incoming conductors, each of which has a dedicated channel).   A first toroid  20  and a second toroid  21 , the functionality of which was described for  FIGS. 3A and 3B , for each channel.       

     It is of note that the alternative data available via the optional pushbutton  78  may vary depending on the application. For example, in many applications it may be beneficial for an electrical system such as that illustrated in  FIGS. 2A-C  to comprise methods of disabling power to components of the electrical system (e.g. via GFCI) if component impedance increases to an unacceptable threshold, in addition to monitoring and reporting such conditions. If such were the case, optional pushbutton  78  may allow data relevant to GFCI functionality (e.g. leakage current) to be displayed. As a further example, display of information relevant to the application layout may be enabled by optional pushbutton  78  (e.g. ground wire size, earth ground electrode material, etc.). 
     The present exemplary embodiment detects the presence and functionality of the grounding components of the electrical system illustrated in  FIGS. 2A-C  including equipment ground electrode  28 , equipment ground wire  29 , equipment ground wire  24 , and connections associated with the service cabinet  44  and contactor cabinet  45  via the second ground loop circuit as previously described; as well as the equipment ground wire  25 , conductor  56 , section of earth ground wire  27  spanning lug  62  to ground bar  35 , and connections associated with each pole  60  via the first ground loop circuit as previously described. 
     A primary benefit of the exemplary embodiment as described is such that a reliable ground is ensured for the electrical system illustrated in  FIGS. 2A-C  (thus adhering to UL Class C requirements). Additionally, if it is desirable for the electrical system illustrated in  FIGS. 2A-C  to further comprise systems which may regulate power to the electrical system to allow for corrective action of an alarm condition (e.g. GFCIs), active monitoring of the grounding components allows the voltage to ground to be limited to a specified value (thus adhering to UL KCYC requirements). 
     C. Exemplary Method and Apparatus Embodiment 2 
     An alternative embodiment of the invention envisions an electrical system such as that illustrated in  FIGS. 1A ,  5 A, and  5 B enabled with a GMS module as illustrated in  FIGS. 4A-4D . The GMS module comprises a series of toroids the functionality of which is described in Exemplary Method and Apparatus Embodiment 1. 
     Similar to Exemplary Method and Apparatus Embodiment 1, in this embodiment the electrical system has two ground loop circuits. The first ground loop circuit comprises GMS module  80 , equipment ground wire  25 , contactor cabinet ground bar  34 , pole cabinet ground bar  35 , earth ground wire  27 , pole ground lug  62 , earth ground electrode  26 , earth  100 , equipment ground electrode  28 , equipment ground wire  29 , cabinet ground bar  33 , and equipment ground wire  24 . Note that the flow of an imposed signal from electrode  26  to electrode  28  via earth  100  is diagrammatically illustrated by a dashed line in  FIG. 5B . The first ground loop circuit detects the presence and functionality of grounding components of the electrical system illustrated in  FIGS. 1A ,  5 A, and  5 B including equipment ground wire  25 , earth ground wire  27 , earth ground electrode  26 , connections associated with each pole  60 , equipment ground electrode  28 , and equipment ground wire  29 . The second ground loop circuit in this embodiment is the same as the second ground loop circuit in Exemplary Method and Apparatus Embodiment 1. 
     A primary benefit of the exemplary embodiment as described is such that one can determine if poles are properly grounded without extensive testing or digging up electrodes. Whereas the benefits in Exemplary Method and Apparatus Embodiment 1 are of a personal protection nature, the benefits in the present embodiment are of an equipment longevity nature. 
     D. Options and Alternatives 
     The invention 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. 
     Generally, the exemplary embodiments described herein illustrate a complete electrical circuit for a single bank of light fixtures (see  FIG. 1B ). It is of note, however, that this is by way of example and not by way of limitation. For example, those skilled in the art would know that moderator module  42  may regulate all of the contactor modules within control/contactor cabinet  45 , and/or a pole cabinet  46  and the components therein may power a plurality of fixtures  61 . As a further example, a single control center  90  may enable remote operation of a plurality of GMS modules  80 , thus facilitating active monitoring of grounding systems at multiple equipment locations from a single point. 
     Further, the methods of monitoring and testing grounding components described herein may be applied to electrical systems other than those illustrated in the exemplary embodiments (e.g. street lighting, food display cases, HVAC units) without departing from at least some aspects of the invention. For example, an electrical system similar to those illustrated and referenced herein, but not adhering to UL class requirements (e.g. Class C, KCYC), may still glean benefits (e.g. personal protection from electrical shock hazards) from aspects of the invention. 
     Generally, the exemplary embodiments described herein illustrate remote operation of GMS module  80  enabled by control center  90 , a specific example of which is commercially available from Musco Sports Lighting, LLC under the trade name CONTROL-LINK®. However, it is of note that the remote operation functionality may comprise any methods of communicating between GMS module  80  and a central server and is not limited to CONTROL-LINK®. 
     Further, location of GMS module  80  is not limited to those illustrated in the exemplary embodiments. For example, if the application is a food display case there may not be a contactor cabinet  45  in which to house GMS module  80 —some other enclosure may be available. Aspects according to the invention (e.g. imposing and receiving a signal to determine impedance, determining trends in system impedance over time, etc.) are equally applicable to systems which comprise components other than those described herein (e.g. light fixtures  61 ), house GMS module  80  in alternative locations, and/or comprise ground loop circuits other than those described herein.