Abstract:
The detrimental effects of environmental hazards on units having withdrawable stabs or contacts may be overcome by using fixed feed units in compartments in a manner akin to withdrawable units. In particular, multiple fixed feed units may be provided in a single section or column by implementing vertical bus bars providing multiple connection points particular to fixed feed units. As a result, fixed feed units may be mounted to the vertical bus bars, as opposed to horizontal main bus bars or requiring complex wiring, thereby allowing multiple fixed feed units to be efficiently provided to maximize space. An electrically insulating bus support, which may be supplemented with bracing, may provide improved short-circuit protection. Electrically insulating covers over fixed feed unit connections may also provide electrical isolation in the system in accordance with industry standards. Moreover, in one aspect, fixed feed units and withdrawable units may be intermixed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 62/248,942, entitled “Fixed Vertical Distribution Bus Bar,” filed on Oct. 30, 2015, which is herein incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to motor control centers, and more particularly, to electrical power distribution in such systems. 
       BACKGROUND 
       [0003]    Electrical systems with packaged electrical and electronic components are known and are in use. For example, Motor Control Centers (MCC&#39;s) are used for power and data distribution in large and industrial operations. In MCC&#39;s, a variety of components, such as switchgear, semiconductor power electronic circuits, programmable logic controllers, motor controllers, and so forth, are housed in large electrical enclosures that may be subdivided into sections or columns, which may be further subdivided into compartments. The MCC includes associated bus bars, interconnections and supporting structures for distribution of electrical power to the various compartments. 
         [0004]    Typically, the MCC is connected to a main power line that may feed three-phase AC power to horizontal bus bars of the MCC. The horizontal bus bars, in turn, may feed the three-phase power to vertical bus bars disposed in each of the sections or columns of the MCC. The vertical bus bars, in turn, may feed the three-phase power to various units (which typically include electrical components) that are installed in compartments of a section. The units, in turn, may provide power terminals (conductors), such as copper bus bars, for feeding the three-phase power to a system environment, such as motors, as may be required for various applications. 
         [0005]    Units are typically plug-in or “withdrawable” in that they often use a set of stabs or contacts to connect to or disconnect from the MCC for mechanical and electrical engagement/disengagement. Such withdrawable units may be readily supplied by vertical distribution bus bars, and are convenient in that they may be more easily moved around or replaced than non-withdrawable units which are often screwed or wired to horizontal main bus bars of the MCC (also referred to as “fixed feed” or “frame mounted” units). 
         [0006]    However, in some industries, such as mining, conductive or abrasive dust in the environment may make withdrawable units undesirable due to fretting corrosion and/or debris. Such hazards may cause contact intermittency and/or increased contact resistance for withdrawable stab contacts, which could thereby lead to a system failure. 
       SUMMARY OF THE INVENTION 
       [0007]    The present inventors have recognized that the detrimental effects of environmental hazards on units having withdrawable stabs or contacts may be overcome by using fixed feed units in compartments in a manner akin to withdrawable units. In particular, multiple fixed feed units may be provided in a single section or column by implementing vertical bus bars providing multiple connection points particular to fixed feed units. As a result, fixed feed units may be mounted to the vertical bus bars, as opposed to horizontal main bus bars or requiring complex wiring, thereby allowing multiple fixed feed units to be efficiently provided to maximize space. An electrically insulating bus support, which may be supplemented with bracing, may provide improved short-circuit protection. Electrically insulating covers over fixed feed unit connections may also provide electrical isolation in the system in accordance with industry standards. Moreover, in one aspect, fixed feed units and withdrawable units may be intermixed. 
         [0008]    Aspects of the invention may allow for a fixed module solution to maximize space inside a section or column of an electrical system, such as an MCC, by allowing multiple control modules to be placed in one column. Accordingly, fixed modules may be supplied by conductors fed by vertical distribution bus bars, rather than the horizontal main bus bars, in order to maximize space and/or reduce costs. Also, continuously supporting the vertical distribution bus bars may further ensure withstanding short circuit hazards and may provide improved internal arcing fault mitigation and performance, given a continuous separation of conductors from one another. 
         [0009]    Accordingly, in one aspect, the invention may provide a mechanism for connecting fixed motor control center modules by specially forming continuously supported round copper bus bars. Wires may be connected to vertical distribution bus bars using straight or bent crimp lugs and fasteners such as square shank carriage T-bolts. Connection points, and vertical bus bars, may be covered with continuous (electrically insulating) plastic covers, which may provide separation between the vertical bus and the functional unit space in accordance with International Electrotechnical Commission (IEC) 60529 IP2X (International Protection Rating for fingers or similar objects), IP4X and/or similar standards. Accordingly, a compact fixed module design may be provided. 
         [0010]    One or more advantages of the invention may include: providing a substantially curved or round vertical bus bar, such as a solid or hollow seamless copper tubing provided based on electrical current ratings of the system; continuously supporting the bus bar, such as by a molded bus support which may be, for example, plastic or a glass filled thermoset, and which may support and isolate the vertical bus bars from a horizontal main bus bar compartment; transitioning the bus bar from a round cross-section to a flat cross-section in multiple locations (such as twelve), thereby providing a flat point of contact to land feed conductors for functional units in the MCC; flat contact points containing square through holes to accept square neck carriage bolts or T-bolts in order to solidly bolt crimp lugs directly to the bus bar, thereby providing a solid, reliable electrical connection with minimal maintenance required; providing a continuous bus support molding covered by a polycarbonate (electrically insulating) cover providing openings at each contact point location, along with accessory one or more covers proving IP2X and/or IP4X separation between a vertical distribution bus bar compartment and a functional unit compartment; and/or providing fully encapsulated vertical distribution bus bars to form are ignition protected zones per IEC TR 61641, thereby providing improved internal arcing fault prevention (due to spacing and configuration of the bus bars) and/or personnel protection. 
         [0011]    Specifically then, one aspect of the present invention provides a bus system including: multiple vertical bus conductors, each vertical bus conductor having multiple substantially flat areas between substantially curved areas, the substantially flat areas each having an aperture configured to receive a fastener, and an electrically insulating bus support having multiple vertical channels configured to receive the vertical bus conductors. 
         [0012]    Another aspect may provide an electrical system including: multiple compartments, each compartment being configured to receive a unit having an electrical component; multiple vertical bus conductors, each vertical bus conductor having a multiple substantially flat areas between substantially curved areas, the substantially flat areas each having an aperture providing a fastener exposed in a compartment; multiple horizontal bus conductors; and an electrically insulating bus support having multiple vertical channels configured to receive the vertical bus conductors. The electrically insulating bus support electrically isolates the vertical bus conductors from the horizontal bus conductors. Each horizontal bus conductor is attached to a different vertical bus conductor. 
         [0013]    These and other features and advantages of the invention will become apparent to those skilled in the art from the following detailed description and the accompanying drawings. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Preferred exemplary embodiments of the invention are illustrated in the accompanying drawings in which like reference numerals represent like parts throughout, and in which: 
           [0015]      FIG. 1  is an isometric view of an exemplar electrical system in which electrical units of various types may be housed in accordance with an embodiment of the invention; 
           [0016]      FIG. 2  is an interior view of the electrical system of  FIG. 1 ; 
           [0017]      FIG. 3  is an interior view of a section of the electrical system of  FIG. 1 ; 
           [0018]      FIG. 4  is an exemplary exploded view of a 3-pole bus system with an electrically insulating bus support which may be used in the electrical system of  FIGS. 1-3 ; 
           [0019]      FIG. 5  is an exemplary exploded view of a 4-pole bus system with an electrically insulating bus support which may be used in the electrical system of  FIGS. 1-3 ; 
           [0020]      FIG. 6  is a plan view of an exemplar vertical bus conductor in accordance with an embodiment of the invention; 
           [0021]      FIG. 7A  is a detailed plan view of a substantially flat area of the vertical bus conductor of  FIG. 6 , and  FIG. 7B  is an isometric view of the substantially flat area of  FIG. 7A , in accordance with an embodiment of the invention; 
           [0022]      FIG. 8A  is a detailed plan view of substantially flat areas in one plane and an additional, larger substantially flat area (which may connect to a horizontal bus conductor) in another plane of the vertical bus conductor of  FIG. 6 , and  FIG. 8B  is an isometric view of the substantially flat areas in one plane and the additional substantially flat area in another plane of  FIG. 8A , in accordance with an embodiment of the invention; 
           [0023]      FIG. 9  is a detailed exploded view of a vertical bus conductor receiving a fastener in accordance with an embodiment of the invention; 
           [0024]      FIG. 10  is an isometric view of an exemplar vertical bus conductor having substantially flat areas and substantially curved areas according to a first arrangement in accordance with an embodiment of the invention; 
           [0025]      FIG. 11  is an isometric view of an exemplar vertical bus conductor having substantially flat areas and substantially curved areas according to a second arrangement in accordance with an embodiment of the invention; 
           [0026]      FIG. 12  is a side view of a substantially flat area receiving a straight crimp lug and being covered by an electrically insulating cover in accordance with an embodiment of the invention; 
           [0027]      FIG. 13  is a side view of a substantially flat area receiving multiple bent crimp lugs and being covered by an electrically insulating cover in accordance with an embodiment of the invention; 
           [0028]      FIG. 14  is an isometric view of a substantially flat area of a vertical bus conductor exposed through an opening of a bus cover in accordance with an embodiment of the invention; 
           [0029]      FIG. 15  is an isometric view of an exemplar fastener in accordance with an embodiment of the invention; 
           [0030]      FIG. 16  is an isometric view of substantially flat areas connected to straight crimp tugs for providing electrical connections to fixed feed electrical units in a compartment of an electrical system in accordance with an embodiment of the invention; 
           [0031]      FIG. 17  is an isometric view of an electrically insulating cover mounted to a bus cover with wires egressing from the electrically insulating cover in accordance with an embodiment of the invention; 
           [0032]      FIG. 18  is an isometric view of a first electrically insulating cover which may be used for a 3-pole or a 4-pole bus system in accordance with an embodiment of the invention; 
           [0033]      FIG. 19  is an isometric view of the electrically insulating cover of  FIG. 18  mounted to an electrically insulating bus support in accordance with an embodiment of the invention; 
           [0034]      FIG. 20  is an isometric view of a second electrically insulating cover which may be used in a 3-pole or a 4-pole bus system in accordance with an embodiment of the invention; and 
           [0035]      FIG. 21  is an isometric view of a plate mounted over a bus cover when corresponding electrical connections are not needed in accordance with an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0036]    Referring now to  FIGS. 1 and 2 , an exemplar electrical system  10  is provided in which electrical units  12  of various types may be housed. The electrical system  10  may be, for example, a Motor Control Center (“MCC”) or other industrial, commercial, marine, or other electrical system. In general, the electrical system  10  may provide one or more sections  14 , each forming a shell around a device mounting volume (compartment) for supporting the units  12 . The shell may be made of any suitable material, such as heavy gage sheet metal, reinforced plastics, and so forth. The electrical system  10  may typically receive three-phase power from an external power supply, such as a power supply grid, and/or data signals, via appropriate conduits (not shown), and distribute the received power and/or data signals to one or more of the sections  14  in various manners. The sections  14  may be electrically isolated from one another, or alternatively, may be electrically joined with other sections  14 , such as via common horizontal power buses  16 . 
         [0037]    The units  12  may each include a door for covering an assembly of components  18  that are supported within each unit  12  via known methods, such as screwed (“fixed feed” or “frame mounted”) or plug-in (“withdrawable”) engagement, thereby providing mechanical and electrical connection to the electrical system  10 . Exemplary components  18  of the units  12  may include relays, motor starters, and Programmable Logic Controllers (“PLC&#39;s”), among others. Doors for the units  12  may include, for example, a lever (such as a rotary lever to turn ON and OFF a Circuit Breaker inside the unit and enabling opening of the door when the Circuit Breaker is OFF), a lock for preventing the door from opening, and/or light for indicating a safe condition for opening the door. A latch rail (not shown) may be provided in each section  14  to interface with latches on the individual doors of the units  12 . 
         [0038]    The sections  14  may also include wire-ways  20  and  22  in which line and load wiring, cabling and so forth may be installed to service the components  18 . The sections  14  may optionally include preconfigured isolation areas between sections  14  for variations in which greater electrical isolation between sections  14  is desired, such as in compliance with IEC 61439-2 Forms 3, 3a, 4 or 4b. 
         [0039]    Referring also to  FIG. 3 , along a rear wall of each of the sections  14  may be disposed a vertical bus system  24  configured to facilitate distribution of power throughout a corresponding section  14 , such as in a plug-in manner. The bus system  24  may be generally formed as a backplane having slots  26  for receiving conventional stab-type electrical connections on rear surfaces of device supports received within a section  14 . Such slot and stab arrangements are generally known in the art. As illustrated, the slots  26  may be divided into pairs to receive a corresponding two-pronged stab for each phase of electrical power. Rows of such slots  26  may be provided to allow device supports to be mounted at various levels within a section  14 . 
         [0040]    Referring now to  FIG. 4 , an exemplary exploded view of a 3-pole bus system  28  which may be used in the electrical system  10  of  FIGS. 1-3  is provided. The bus system  28  may include multiple power busses disposed within a section  14 . In the illustrated embodiment, the bus system  28  includes first, second and third vertical bus conductors  30  disposed proximal to one another, which may correspond to differing phases of a three-phase power system (power conductors). Further, the bus system  28  includes first, second and third horizontal bus conductors  40  disposed proximal to one another, which may also correspond to the differing phases of the three-phase power system (power conductors), but in a different direction. 
         [0041]    In certain embodiments, the horizontal bus conductors  40  could be coupled to cabling that supplies three-phase power from an external power supply, such as a power supply grid, and the first, second and third horizontal bus conductors  40  could be coupled to the first, second and third vertical bus conductors  30 , respectively. Also, in certain embodiments, the horizontal bus conductors  40  of one section could be coupled (or “spliced”) with the horizontal bus conductors  40  of another (flanking) section. In alternative embodiments, more horizontal and/or vertical bus conductors could be provided, such as the 4-pole bus system  68  of  FIG. 5 , for example providing a neutral conductor, a protective earth, ground or additional power phase. In other arrangements, even more horizontal and/or vertical bus conductors could be provided, or fewer could be provided, as may be appropriate for the environment. 
         [0042]    The bus system  28  may include one or more bus covers  46  and a rear bus support  50  that will be described in greater detail below. In the illustrated embodiment, the bus covers  46  may comprise a molded sheet of synthetic material disposed over the vertical and horizontal bus conductors and may serve to prevent contact with underlying power busses except through the openings  29  (and corresponding slots  26 ) where provided. The vertical bus conductors  30  are typically made of a bar stock or tubing stock with a flat area that permits them to be mechanically and electrically coupled to corresponding horizontal bus conductors  40  in the bus system  28  as will be described below with respect to  FIGS. 7-11 . 
         [0043]    Connection of component supports (such as mounted on plates or drawers, not shown) may be made by fixed feed units which receive fasteners from the vertical bus conductors  30 . In alternative aspects, connections may also be made in certain spots by two pronged stabs (withdrawable units) that are received through the slots  26  where provided and engage the individual bus bars behind the bus covers  46  (see  FIGS. 10 and 11 ). 
         [0044]    The bus system  28  further includes an electrically insulating bus support  50  configured to support the vertical and horizontal bus conductors  30  and  40 , respectively. The bus support  50  may be a preconfigured isolated bus support for supporting the power busses of the bus system  28 . As illustrated, the bus support  50  may be a molding with vertical channels  52  to receive the vertical bus conductors  30  of  FIG. 2 . Each of the vertical channels  52  may include pockets  54  (which form rear protrusions on a rear side of the bus support  50 ). In the illustrated embodiment, the bus support  50  mechanically supports the various horizontal and vertical bus conductors. Within the bus system  28 , and generally between the bus support  50  and the bus covers  46 , each vertical bus conductor  30  may generally include a connection area that is engaged by either fasteners (for fixed feed units) or stabs (for withdrawable units) of component supports and a bus anchoring area. The bus support  50  may be electrically insulating to electrically isolate the vertical bus conductors  30  from the horizontal bus conductors  40 . 
         [0045]    Accordingly, the horizontal bus conductors  40  may be generally supported on a rear surface of the bus support  50 , while the vertical bus conductors  40  may be supported on a front surface thereof. In the illustrated embodiment, the bus support  50  includes a series of apertures  58  or holes for receiving mounting bolts or screws. These apertures  58  will generally be aligned with corresponding apertures in a rear of the electrical system  10  to support the bus system  24  when mounted therein. The vertical bus conductors  30  may be received within corresponding recesses of the vertical channels  52 . The recesses may generally be semicircular grooves in which the vertical bus conductors  30  may lie. 
         [0046]    Opposing the aforementioned rear protrusions on the rear side of the bus support  50 , which may be somewhat deeper than the recesses, are the pockets  54  which may house fasteners for connecting directly to fixed feed units. Alternatively, the pockets  54  may receive and accommodate stabs (not shown) of component supports, when provided, that may protrude through the slots  26  in the bus cover  46 . 
         [0047]    In the illustrated embodiment, the bus support  50  may be formed as a single piece of molded plastic material. The material is preferably one that will not degrade or melt with elevated temperatures that may occur during normal operation. In certain embodiments, the bus support  50  may comprise glass filled polyester, a thermoset plastic. 
         [0048]    The bus support  50  may also include add-on bus support braces  60  disposed transverse with respect to the vertical channels  52 . The bus support braces  60  may be configured to limit movement of the vertical bus conductors  30  during a high current event (such as a short-circuit). In addition, or alternatively, the bus support  50  could include add-on bus support braces (not shown) disposed on the rear side of the bus support  50  which may be configured to contact a rear side of the vertical channels  52 , also to limit movement of the vertical bus conductors  30  during a high current event. 
         [0049]    Referring now to  FIG. 6 , a plan view of an exemplar vertical bus conductor  30  configuration is provided in accordance with an embodiment of the invention. The vertical bus conductor  30  may have multiple substantially flat areas  70  between substantially curved areas  72 , which may generally be circular, vertical bus round segments. As may best be seen in the detailed view of  FIG. 7A , the substantially flat areas  70  may each have an aperture  74  or opening configured to receive a fastener. The substantially flat areas  70 , and the apertures  74 , may align with the pockets  54  of the vertical channels  52  of the bus support  50  (such as for the bus system  28  or the bus system  68 ) for accommodating connections to fixed feed units (see  FIGS. 12 and 13 ). The vertical bus conductors  30  could be, for example, copper bus bars having multiple substantially flat areas  70 , such as twelve substantially flat areas  70  illustrated in  FIG. 6 , for accommodating an equivalent number of fixed feed units in a section. The vertical bus conductors  30  may be formed by a substantially curved or round vertical bus bar, which may be solid or hollow copper tubing seamlessly provided, based on electrical current ratings of a system, and which is selectively flattened in predetermined areas to accommodate fixed feeds for units in a section. 
         [0050]    In one aspect, the apertures  74  may be rectangular in shape. Such shape may advantageously allow a correspondingly shaped fastener to be securely positioned for subsequent fastening to a fixed feed unit. An exemplar corresponding fastener may be a square shank carriage T-bolt or similar screw (see  FIG. 15 ). It will be appreciated that other shapes may be provided to achieve a similarly function within the scope of the invention. 
         [0051]    Referring briefly to  FIG. 9 , for attaching to a fixed feed unit, a fastener  86  may pass through an aperture  74  (perhaps securing the fastener  86  to the shape of the aperture  74 ) of a substantially flat area  70  and, in turn, an opening  29  of a bus cover  46 . On an opposing side of the substantially flat area  70 , a nut  90 , spring washer  92 , washer  94 , and/or the like may be used to retain the fastener  86 . 
         [0052]    As may best be seen in the isometric view of  FIG. 7B , the substantially curved areas  72  may be provided in a first plane  80 , and the substantially flat areas  70  may be provided in a second plane  82  parallel to the first plane  80 . Accordingly, the substantially flat areas  70  may provide an accommodation space  84 , between a substantially flat area  70  and a pocket  54 , for a fastener  86  (see  FIGS. 12 and 13 ). The accommodation space  84  may provide a volume allowing room for a variety of fasteners, in the case of fixed feed units, and/or stabs or contacts, in the case of withdrawable units. 
         [0053]    As may best be seen in the detailed view of  FIG. 8A , vertical bus conductor  30  may also include an additional, larger substantially flat area, or horizontal bus conductor attachment area  76 , for attachment to a horizontal bus conductor  40 . The horizontal bus conductor attachment area  76  may be provided between substantially curved areas  72  and substantially flat areas  70 . The horizontal bus conductor attachment area  76  may also include two (or more, depending on an electrical current rating) apertures  78  or openings configured to receive fasteners for attaching to a horizontal bus conductor  40 . Accordingly, each horizontal bus conductor  40  may be attached to a different vertical bus conductor  30  (see  FIGS. 4 and 5 ). The horizontal bus conductor attachment area  76  may also be flattened in a predetermined area for connection, similar to the substantially flat areas  70  for attachment to fixed feed units. 
         [0054]    As the horizontal bus conductors  40  may typically be provided on a rear surface of the bus support  50 , the horizontal bus conductor attachment area  76  may be provided in a third plane  88 , different from the first and second planes  80  and  82 , respectively. As may best be seen in the isometric view of  FIG. 8B , the horizontal bus conductor attachment area  76  may be provided in the third plane  88  parallel to the first and second planes  80  and  82 , respectively. Moreover, the first plane  80  (curved area) may be between the second and plane  82  (flat area for feed units) and the third plane  88  (flat area for horizontal bus conductor), respectively. 
         [0055]    Referring now to  FIGS. 10 and 11 , isometric views of exemplar alternative first and second vertical bus conductors  100  and  110 , respectively, are provided in accordance with embodiments of the invention. The first and second vertical bus conductors  100  and  110 , respectively, could each be provided, for example, in a section or column which might accommodate twelve electrical units (labeled “A” through “L” as illustrated), which may be fixed feed or withdrawable units, received in s compartment. 
         [0056]    In the first vertical bus conductor  100 , adjacent electrical units at an upper end, A and B, may be fixed feed units connecting directly to substantially flat areas  70  with apertures  74  via fasteners  86 . However, subsequent electrical units C, D and E may be withdrawable units connecting to substantially curved areas  72  via stabs or contacts. A next electrical unit F may be a fixed feed unit, followed by a horizontal bus conductor attachment area  76 , and then another electrical unit G which may also be a fixed feed unit. Subsequent electrical units H, I and J may be withdrawable units, again connecting to substantially curved areas  72  via stabs or contacts, and ending electrical units K and L may be fixed feed units, again connecting directly to substantially flat areas  70  with apertures  74  between via fasteners  86 . Each of the electrical units A-L, whether fixed feed units or withdrawable units, may align with pockets  54 , which pockets may be evenly spaced or symmetrically distributed along the bus support  50 . 
         [0057]    In another aspect, the second vertical bus conductor  110  could provide, for example, for all fixed feed units in an upper half, and all withdrawable units in a lower half. It will be appreciated that significant flexibility may be realized with varying vertical bus conductor configurations, including with horizontal bus conductor attachment areas  76  at differing locations, all of which are deemed within the scope of the invention. 
         [0058]    Referring now to  FIGS. 12 and 13 , side views of substantially flat areas  70  receiving crimp lugs in connection areas  118  for making electrical connections to fixed feed units, and including electrically insulating covers for providing electrical isolation, are provided in accordance with embodiments of the invention. In  FIG. 12 , a substantially flat area  70  of the vertical bus conductor  30  may be exposed through openings  29  of the bus cover  46  (see  FIG. 14 ). The fastener  86  may pass through the vertical bus conductor  30 , at the aperture  74 , through the opening  29 , and through a straight crimp lug  120  provided on an opposing side of the vertical bus conductor  30 . A nut  90  may be provided over the straight crimp lug  120  to secure the straight crimp lug to the vertical bus conductor  30  to form the connection area  118 . A wire  122 , which may be crimped to the straight crimp lug  120 , may lead to a fixed feed unit or other hardware in the system as desired. 
         [0059]    An electrically insulating cover  124  may be provided over the straight crimp lug  120 , the nut  90 , and an end  126  of the fastener  86 . The electrically insulating cover  124  could be formed from plastic or another electrically insulating material. Accordingly, the electrically insulating cover  124  may cover a rear side of the connection area  118  to provide separation between the vertical bus compartment and the functional unit space (electrical isolation), such as in accordance with IEC 60529 IP2X, IP4X and/or similar standards. The electrically insulating cover  124  may include an upper aperture  128 , or upper opening, allowing an egress path for the wire  122 , (following a natural curve of the wire  122 ) from the connection area  118  to the system. The upper aperture  128  may ensure that the connection area  118  is substantially covered and electrically isolated while still making an electrical connection via an insulating wire. 
         [0060]    In the alternative aspect of  FIG. 13 , the fastener  86  passes through the vertical bus conductor  30 , at the aperture  74 , then through first and second bent crimp lugs  130  and  132 , respectively, provided on an opposing side of the vertical bus conductor  30 . A nut  90  may be provided over the first and second bent crimp lugs  130  and  132 , respectively, to secure the bent crimp lugs to the vertical bus conductor  30  to form the connection area  118 . First and second wires  134  and  136 , respectively, crimped to the first and second bent crimp lugs  130  and  132 , respectively, may lead to a fixed feed unit or other hardware in the system as desired. 
         [0061]    The electrically insulating cover  124  may also be provided over the first and second bent crimp lugs  130  and  132 , respectively, the nut  90 , and end  126  of the fastener  86  to provide the electrical isolation. However, the upper aperture  128  may be plugged or closed via an electrically insulating cap, and first and second mid apertures  140  and  142 , respectively, may be provided instead for allowing egress paths for the first and second wires  134  and  136 , respectively from the connection area  118  to the system. The first and second mid apertures  140  and  142 , respectively, may ensure that the connection area  118  is substantially covered and electrically isolated while still making electrical connections via insulating wires (the first and second mid apertures  140  and  142 , respectively, could also be plugged or closed via an electrically insulating cap when not in use, such as in the embodiment of  FIG. 12 ). 
         [0062]    Referring now to  FIG. 16 , an isometric view of three connection areas  118  (such as for a 3-pole configuration), including substantially flat areas  70  connected to straight crimp lugs  120  for providing electrical connections to a fixed feed electrical unit, is provided in accordance with an embodiment of the invention. Referring also to  FIG. 17 , the electrically insulating cover  124  may be mounted to the bus cover  46  to cover the connection areas  118 . The wires  122  may egress from the electrically insulating cover  124  to provide connections in the system (such as via fixed feed unit retaining lugs  150 ), in accordance with an embodiment of the invention. Accordingly, the electrically insulating cover  124  may be positioned over a substantially flat area of each of the vertical bus conductors 
         [0063]    Referring now to  FIG. 18 , an isometric view of a first electrically insulating cover  160 , and associated components, which may be used in a 3-pole or a 4-pole bus system is provided in accordance with an embodiment of the invention. A mounting bracket  162  and a mounting flange  164  of the first electrically insulating cover  160  may be used to mount the first electrically insulating cover  160  to the bus system (such as, to the bus support  50  and/or support structure  170 ) (see  FIG. 19 ). In one arrangement, such as when used in a 3-pole configuration, an electrical separation plate  166  may also be mounted beneath the electrically insulating cover  160  to electrically isolate egress openings  168  that are not being used. In another arrangement, such as when used in a 4-pole configuration, the separation plate  166  may be removed, and one or more of the egress openings  168  may be used. Grommets  172  may also be provided at egress openings where necessary (such as the first or second mid apertures  140  and  142 , respectively) to provide improved electrical isolation and/or strain relief for wires. 
         [0064]    Referring now to  FIG. 20 , an isometric view of a second electrically insulating cover  180 , and associated components, which could be used in a 4-pole bus system, for example, is provided in accordance with an embodiment of the invention. The second electrically insulating cover  180  has a lower profile than the first electrically insulating cover  160 , with only single mid apertures  143  (for bent crimp lugs) and smaller upper apertures  129  (for straight crimp lugs). Also, instead of grommets  172 , electrically insulating caps  182  as illustrated, which could be plastic caps, for example, may be provided to plug or close the apertures for wire egresses when not in use. 
         [0065]    Referring now to  FIG. 21 , an isometric view of a cover  190  or wall mounted over the electrically insulating bus cover  46  when corresponding electrical connections are not used is provided in accordance with an embodiment of the invention. The cover  190  may cover openings  29  in the bus cover  46  to provide electrical separation between the vertical bus compartment and the functional unit space in accordance with IEC 60529 IP2X, IP4X and/or similar standards. 
         [0066]    Certain terminology is used herein for purposes of reference only, and thus is not intended to be limiting. For example, terms such as “upper,” “lower,” “above,” and “below” refer to directions in the drawings to which reference is made. Terms such as “front,” “back,” “rear,” “bottom,” “side,” “left” and “right” describe the orientation of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. Similarly, the terms “first,” “second” and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context. 
         [0067]    When introducing elements or features of the present disclosure and the exemplary embodiments, the articles “a,” “an,” “the” and “said” are intended to mean that there are one or more of such elements or features. The terms “comprising,” “including” and “having” are intended to be inclusive and mean that there may be additional elements or features other than those specifically noted. It is further to be understood that the method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
         [0068]    Various features of the invention are set forth in the following claims. It should be understood that the invention is not limited in its application to the details of construction and arrangements of the components set forth herein. The invention is capable of other embodiments and of being practiced or carried out in various ways. Variations and modifications of the foregoing are within the scope of the present invention. It also being understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention: The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention. All of the publications described herein including patents and non-patent publications are hereby incorporated herein by reference in their entireties. 
         [0069]    The present invention may be part of a “safety system” used to protect human life and limb in a field, construction or other environment. Nevertheless, the term “safety,” “safely” or “safe” as used herein is not a representation that the present invention will make the environment safe or that other systems will produce unsafe operation. Safety in such systems depends on a wide variety of factors outside of the scope of the present invention including: design of the safety system, installation and maintenance of the components of the safety system, and the cooperation and training of individuals using the safety system. Although the present invention is intended to be highly reliable, all physical systems are susceptible to failure and provision must be made for such failure.