Abstract:
A ground fault protection device includes an electrically-conductive main body defining a reservoir having a plurality of drainage ports, and having downwardly-extending, ground-penetrating electrodes configured for minimal ground penetration. The device has handles for manual lifting and transportation, plus grounding terminals for connection of grounding cables. The device may be installed at a desired field location by applying downward force to the device to press the electrodes into the earth, thereby establishing an electrical connection between the grounding terminals and the ground via the main body and the electrodes. Grounding cables may then be connected between the grounding terminals and structures or equipment requiring grounding. Optionally, the reservoir may be filled with water, which will drip through the drainage ports and moisten the soil surrounding the electrodes, thereby decreasing the soil&#39;s electrical resistance and consequently improving electrical conductivity between the electrodes and the soil.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/377,643, having a filing date of Oct. 9, 2010, and said earlier application is incorporated herein by reference in its entirety for continuity of disclosure. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure relates in general to electrical ground fault protection (GFP) systems, chiefly but not solely for use in temporary applications. In particular, the disclosure relates to GFP systems and apparatus for use in conjunction with construction, well-drilling, remote dwellings, and other applications where portable electrical generation facilities are employed, and more particularly in applications where it is necessary or desirable to provide ground fault protection for equipment and structures with minimal ground disturbance or ground penetration, and where removal and recovery of GFP devices may be necessary or desirable. 
     BACKGROUND 
     Known ground fault protection (GFP) technologies commonly rely on electrically-conductive elements (i.e., electrodes) driven, augered, or buried a significant depth into the ground in order to effectively conduct electrical current into the ground. Such conductive elements, commonly known as earth rods or ground rods, are driven or augered at least 8 feet into the ground to ensure that desired functional effectiveness is achieved. Alternative known GFP technologies use conductive elements in the form of ground mats that conduct electrical current to the ground by contacting the ground over a substantial interface area, with minimal if any ground penetration. 
     An ideal grounding connection maintains zero voltage regardless of how much electrical current flows into or out of the ground. The electrical resistance of the electrode-to-earth connection determines the quality or effectiveness of the grounding connection. The quality of a grounding connection may be improved in a number of ways, for example: by increasing the electrode surface area in contact with the earth; increasing the depth to which the ground rod is driven or augered (in cases where the electrode is a driven or augered ground rod); using multiple connected electrodes; increasing the moisture content of the soil; improving the conductive mineral content of the soil; and/or increasing the ground surface area covered by the grounding system. 
     The installation of driven or augered earth rods typically entails the use of specialized rod-driving or augering equipment, and even with the use of such equipment earth rod installation can be difficult due to soil conditions (for example, rock formations close to surface). Even when soil conditions are readily conducive to earth rod installation, the presence of buried utilities (e.g., gas lines, electrical power lines, water lines) can give rise to the risk of personal injury and expensive utility repair costs should such buried utilities be contacted or penetrated by earth rods during the rod installation process. These latter risks can be mitigated or avoided by the use of ground mats not having ground-penetrating elements, but such devices may have less than desired or optimal functional effectiveness. 
     For the foregoing reasons, there is a need for improved electrical ground fault protection devices that provide effective grounding with minimal penetration of conductive elements into the ground. 
     BRIEF SUMMARY 
     The present disclosure teaches a ground fault protection (GFP) device for providing electrical grounding with minimal ground penetration. The GFP device is particularly suitable for temporary grounding in places such as remote well sites where the location of underground services is unknown, and/or where it is necessary or desirable to remove any grounding devices after work at the site (such as well servicing) is completed. 
     In a first embodiment, the GFP device includes a main body made of an electrically-conductive material (such as carbon steel) and defining a reservoir that can be filled with water. Drainage ports are provided in the main body to allow water to drain from the reservoir at a rate controlled by the size of the drainage ports or by other means. A number of downwardly-extending ground-piercing members (i.e., electrodes) are connected to the main body by electrically-conductive means (e.g., welding or bolting). The number, configuration, and length of the ground-piercing members may be sized to suit specific electrical requirements and site conditions (such as maximum permissible ground penetration). Suitable handles are provided to facilitate manual lifting and transport of the GFP device, plus grounding terminal means for effecting a grounding connection to the GFP device. In a preferred embodiment, the handles are adapted to serve as the grounding terminal means, instead of providing grounding terminal means as a separate and discrete component. 
     After the GFP device has been situated at a desired installation location, downward force is applied to the GFP device as appropriate to press the force the ground-piercing electrodes into the ground, thus establishing an electrically-conductive connection with the ground. This may be done in any suitable fashion, but in one embodiment the GFP device is provided with two or more impact abutments that can be struck with a sledge hammer or other means to drive the electrodes into the ground. 
     To ground a structure or equipment component, a suitable conductive cable is extended between the structure or component and the GFP device&#39;s grounding terminal means and electrically connected to both, by any suitable means (such as conventional alligator clips). In situations where conductivity between the electrodes and the ground is less than optimal, due to the particular nature and characteristics (including moisture content) of the soil in which the electrodes have been or are to be installed, water may be added to the GFP device&#39;s reservoir such that it will drip into the soil below the GFP device, thereby moistening the soil around the electrodes and improving conductivity therebetween. The addition of water also softens the soil and thereby facilitates installation of the GFP device by reducing physical resistance to penetration of the electrodes. Water may be added periodically to the reservoir as desired or appropriate to maintain or extend the beneficial effects of adding water to the soil in the vicinity of the GFP device. 
     When the GFP device is no longer needed (such as in temporary installations), it is a simple matter for workers to lift the device out of the ground (using pry bars or other implements if necessary), and then manually transport the device (using the integral handles) away from the site as appropriate. 
     In one alternative embodiment, the main body of the GFP device comprises a solid member (e.g., a solid plate) with top and bottom surfaces and not including a water reservoir. In a further alternative embodiment, the main body comprises a hollow member that is sealed but does not serve as a water reservoir; in this embodiment, the hollow or tubular configuration of the main body is selected for other design purposes (such as to provide desired levels of structural strength and rigidity while minimizing weight). 
     In variant embodiments of GFP devices in accordance with the present disclosure, the ground-penetrating electrodes may be provided in the form of spikes, castellations, flat sheets, or other shapes, or combinations thereof. 
     Optionally, GFP devices in accordance with the present disclosure may be provided with bridging bars extending between the ground-piercing electrodes near or slightly below the bottom of the main body. These bridging bars act as stops to prevent excessive ground penetration by the electrodes. As well, they keep the main body at a desired height above the ground surface, which may be beneficial to optimize soil wetting from water dripping out of the reservoir (for GFP devices having a reservoir as in the first embodiment described above). Preferably, the bridging bars will be made of an electrically-conductive material (e.g., steel), such that when the GFP device is installed so as to bring the bridging bars into contact with the ground surface, the bridging bars will provide additional conductivity and thus enhance the effectiveness of grounding connections made using the device. Preferably, the bridging bars will extend across or between the electrodes on all four sides of the GFP device. Alternatively, bridging bars may be provided only between selected pairs or groups of electrodes, while still providing functional benefits as described above. 
     GFP devices in accordance with the present disclosure may be operated for protection of personnel and equipment on sites where independent electrical generation is employed, at sites where power is provided from a main electrical grid, and/or for fault protection against lightning strikes. By way of non-limiting example, industries and sites where embodiments of the GFP device may be advantageously used include construction; mining; drilling and servicing of oil and gas wells; and temporary shelters. 
     Accordingly, in a first aspect the present disclosure teaches a ground fault protection (GFP) device comprising: a hollow main body defining a reservoir, with an inlet port for introducing water into the reservoir and at least one drainage port for water to drain from the reservoir; a plurality of laterally-spaced ground-penetrating electrodes extending downward from the main body; handle means for manual transportation of the device; and grounding terminal means in electrically-conductive communication with the electrodes; with the main body being adapted to receive impact forces and transfer said impact forces to the electrodes such that the electrodes penetrate the ground. 
     In a second aspect the disclosure teaches a GFP device comprising: a main body; a plurality of laterally-spaced ground-penetrating electrodes mounted to and extending downward from the main body; handle means for manual transportation of the device; and grounding terminal means in electrically-conductive communication with the electrodes; with the main body being adapted to receive impact forces and transfer said impact forces to the electrodes such that the electrodes penetrate the ground. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will now be described with reference to the accompanying figures, in which numerical references denote like parts, and in which: 
         FIG. 1  is a front perspective view of one embodiment of a ground fault protection (GFP) device in accordance with the present disclosure. 
         FIG. 2  is an isometric view of the GFP device in  FIG. 1 . 
         FIG. 3  is a bottom perspective view of the GFP device in  FIG. 1 . 
         FIG. 4  is a cross-section through the GFP device in  FIG. 1 , shown in use, with grounding cables connected to the device. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1-4  illustrate a first embodiment of a ground fault protection (GFP) device  10  in accordance with the present disclosure. In the illustrated embodiment, GFP device  10  comprises a hollow main body  20  made from an electrically-conductive material. Main body  20  has a top plate  21 , a top surface  21 A, a bottom plate  23 , a bottom surface  23 A, and defines an internal reservoir  40 . A suitable reservoir inlet port  24  (shown by way of non-limiting example as comprising a pipe stub and an associated opening  24 A in top plate  21 ) is provided to allow reservoir  40  to be filled with water. Bottom plate  23  has a plurality of drainage ports  25 , which may be provided in any suitable or desired pattern. 
     A plurality of downwardly-extending, ground-penetrating electrodes  30  are connected to main body  20  by electrically-conductive means (such as welding or bolting). In the illustrated embodiment, main body  20  is of rectangular configuration, and electrodes  30  are arranged in a rectangular pattern generally corresponding to the perimeter of reservoir  40 . However, this is by way of example only; main body  20  could be of various other configurations and electrodes  30  could be arranged in other patterns without material effect on the functionality of GFP device  10 . Electrodes  30  are shown as being substantially perpendicular to main body  20 , but this is not essential. In alternative embodiments, electrodes  30  could be oriented at a non-perpendicular angle relative to main body  20 . 
     To facilitate installation of GFP device  10  in a desired field location, main body  20  is preferably provided with one or more impact abutments  22  that can be impacted either manually (such as by a sledge hammer) or mechanically (such as by the bucket of a backhoe or a front-end loader) to force electrodes  30  into the ground G. In the illustrated embodiment, impact abutments  22  are provided in the form of pipe stubs projecting upward from top plate  21  of main body  20 . However, this is by way of example only, and impact abutments  22  could be provided in other configurations and in different locations without departing from the scope of the present disclosure. Moreover, alternative embodiments of GFP device  10  could be designed with sufficient structural strength to permit installation by directly impacting main body  20  to force electrodes  30  into the ground G, thus making it unnecessary to provide discrete impact abutments for this purpose. 
     Optionally, GFP device  10  may include bridging members  32  connected between one or more adjacent pairs of electrodes  30  in upper regions thereof, for purposes explained elsewhere herein. Where provided, one or more of bridging members  32  will preferably (but not necessarily) be made from an electrically-conductive material to establish electrical conductivity between bridging members  32  and electrodes  30 . 
     GFP device  10  preferably has two or more handles  26  mounted to main body  20  by means of suitable brackets  27  as shown in the Figures, to facilitate lifting and carrying of device  10 . The locations and configuration of handles  26  in the illustrated embodiment are by way of example only; handles  26  could be of alternative configurations, and/or could mounted to device  10  in locations other than specifically as illustrated, without departing from the scope of the present disclosure. 
     Main body  20  is provided with grounding terminal means to facilitate connection of grounding cables from structures or equipment requiring either temporary or permanent electrical grounding. The grounding terminal means can be provided in any form functionally effective to establish electrical communication with electrodes  30 . By way of example, handles  26  in the illustrated embodiment also serve as grounding terminal means, such that a grounding cable  52  can be connected to a selected handle  26  by means of alligator clips  50  as shown in  FIG. 4 , thereby establishing an electrical connection between grounding cable  52  and electrodes  30  via handles  26 , brackets  27 , and main body  20 . Although not shown, suitable insulation materials may be provided on portions of handles  26  to protect against electrical shock in cases where handles  26  also serve as the grounding terminal means. 
     Ground-piercing electrodes  30  are illustrated as comprising pointed square bars with threaded ends for connection to nuts welded to the bottom of main body  20 . However, this is by way of example only, and GFP devices in accordance with the present disclosure are not limited or restricted to electrodes of any particular configuration or means of connection to main body  20 . There is also no restriction or limitation with respect to the length of electrodes  30  or their depth of penetration into the ground. 
     However, the suitability of a given embodiment of GFP device  10  for specific intended uses may be enhanced by limiting the length of electrodes  30  so as to minimize ground penetration and thus avoiding the need for special measures or approvals that might otherwise be required under government regulations. For example, the Pipeline Act in Alberta, Canada, requires special measures or approvals in connection with any ground disturbance to a depth of 30 centimeters (11¾ inches) or more. With this particular regulatory provision in mind, one particular embodiment of GFP device  10  has electrodes  30  sized and configured for maximum ground penetration of 11½ inches, as measured perpendicular to the ground surface. Other embodiments of GFP device  10  may have shorter electrodes as necessary or desired to suit specific site conditions and/or regulatory requirements, with the number of electrodes being selected as appropriate to provide desired levels of electrical conductivity. By way of non-limiting example, satisfactory grounding effectiveness has been achieved using electrodes  30  sized and configured to limit ground penetration to 7 inches. 
     When provided, bridging bars  32  help to structurally stabilize electrodes  30  and to prevent deformation of electrodes  30  when they are being driven into the ground G during installation of GFP device  10 . In addition, bridging bars  32  can be effective as stops to prevent excessive ground penetration by electrodes  30 , while also keeping main body  20  above the ground surface. As well, bridging bars  32 , when made from an electrically-conductive material, can enhance the overall grounding effectiveness of GFP device  10  by virtue of the incremental conductive ground contact provided by bridging bars  32 . In embodiments not having bridging bars, GFP device  10  may be installed such that main body  20  is in direct contact with the ground, thereby providing supplemental electrical conductivity with the ground, over and above that provided by electrodes  30 . 
     Using a GFP device  10  in accordance with the illustrated embodiment, the effectiveness of a grounding connection can be enhanced by filling the reservoir  40  with water, such that the water will drip onto the ground through drainage ports  25  in bottom plate  23  of main body  20 , as graphically represented by water drops  42  in  FIG. 4 . This is because the electrical conductivity of soil generally can be increased by the addition of moisture, due to a resultant decrease in the soil&#39;s electrical resistance. Table 1 below, which is derived from the inventor&#39;s experimental test results, illustrates the increased grounding effectiveness of GFP devices in accordance with the present disclosure (as evidenced by reduced electrical resistance), as compared to known GFP devices: 
     
       
         
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                 Measured 
                 Measured 
               
               
                   
                   
                 Resistance - 
                 Resistance - 
               
               
                   
                 GFP Device 
                 Dry Ground 
                 Wet Ground 
               
               
                   
                   
               
             
             
               
                   
                 Standard 8-foot ground rod 
                 90 ohms 
                 30 ohms 
               
               
                   
                 Plate-type ground mat 
                 98 ohms 
                 56 ohms 
               
               
                   
                 GFP device per FIG. 1 
                 30 ohms 
                 15 ohms 
               
               
                   
                 (with 8-inch ground penetration) 
               
               
                   
                   
               
             
          
         
       
     
     In general, the lower the resistance value, the more effective the ground fault protection device will be. Accordingly, and as may be understood from Table 1, GFP devices in accordance with the present disclosure provide improved ground fault protection over existing devices, with the additional benefit of leaving minimal evidence of the devices&#39; prior presence after removal from site. 
     In the illustrated embodiment of GFP device  10 , the rate at which water  42  flows out of reservoir  40  will be determined in part by the number and size of drainage ports  25 . Persons skilled in the art will readily appreciate that GFP device  10  can be modified to provide flow restriction means to regulate or meter water flow through one or more of drainage ports  25 , and alternative embodiments having such flow restriction means are intended to come within the scope of the present disclosure. Flow restriction means for this purpose could comprise screens, slide gates, removable plugs, or any other suitable means within the knowledge of persons skilled in the art. 
     Although GFP device  10  may have a reservoir  40  and drainage ports  25  as in the illustrated embodiment, this is not essential. In alternative embodiments, main body  20  could be provided in the form of a solid member such as a plate or a structural frame of any suitable configuration, without incorporating or having an associated a reservoir. Main body  20  could also comprise a hollow member but without means for filling the hollow interior with water, such that the hollow interior does not function as a reservoir. Moreover, in GFP devices that do have a water reservoir, it is not essential that the soil-wetting utility provided by such embodiments be implemented in all uses or applications, as the need or desirability of implementing that utility will vary according to site conditions (including but not limited to soil type and existing soil moisture content). 
     In preferred embodiments, GFP device  10  has a total weight such that it can be manually lifted and transported by two workers without great difficulty. This of course will be a function of the strength of the particular workers lifting and carrying the device. However, without stipulating or suggesting specific weight limits, GFP device  10  in a particularly preferred embodiment has a total weight of approximately 25 to 35 pounds. 
     In a variant embodiment of GFP device  10 , electrodes  30  are electrically isolated from main body  20 , such that direct contact with main body  20  does not present an electrical shock hazard. For example, the required electrical connection between the grounding terminal means and electrodes  30  could be provided by an insulated cable extending directly between the grounding terminal means and the electrodes, or between the grounding terminal means and conductive elements (such as bridging bars) connected to the electrodes, thus by-passing main body  20 . In such variant embodiments, main body  20  does not need to be made from an electrically-conductive material, but electrodes  30  will still be structurally connected to main body  20  by suitable means such that electrodes  30  will penetrate the earth surface in response to impact forces applied to main body  20  or associated impact abutments  22 . 
     In one alternative embodiment, main body  20  could be made from an electrically-conductive material but with the electrical connection between the grounding terminal means and electrodes  30  by-passing main body  20  as described above. In this embodiment, the required structural connection between electrodes  30  and main body  20  will preferably incorporate electrical isolation means to prevent electrical current flowing to main body  20  while at the same time providing a sufficient structural connection between electrodes  30  and main body  20 . Persons skilled in the art will appreciate that this result can be accomplished in a variety of ways using known means (for example, by bolting electrodes  30  to main body  20  using non-conductive bolts in conjunction with insulating washers). 
     It will be readily appreciated by those skilled in the art that various alternative embodiments of the disclosed GFP device may be devised without departing from the scope of the present teachings, including modifications that may use equivalent structures or materials subsequently conceived or developed. It is to be especially understood that GFP devices in accordance with the disclosure are not intended to be limited to any described or illustrated embodiment, and that the substitution of a variant of a claimed element or feature, without any substantial resultant change in the working of the device, will not constitute a departure from the scope of the disclosure. It is also to be appreciated that the different teachings of the embodiments described and discussed herein may be employed separately or in any suitable combination to produce desired results. 
     In this patent document, any form of the word “comprise” is to be understood in its non-limiting sense to mean that any item following such word is included, but items not expressly mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one such element is present, unless the context clearly requires that there be one and only one such element. Any use of any form of the words “connect”, “engage”, “couple”, “attach”, or any other term describing an interaction between elements is not intended to limit that interaction to direct interaction between the subject elements, and may also include indirect interaction between the elements such as through secondary or intermediary structure. 
     In this document, the terms “ground” and “earth” are both used with express or implicit reference to the physical earth or soil. In addition, the term “ground” is used in both noun and verb forms with reference to electrical grounding and electrical ground connections. The intended meaning of any form of the word “ground” in a given instance will be readily apparent to persons skilled in the art having due regard to the context in which it is used.