WORK PLATFORM FOR AN ELECTRICAL GRID SUBSTATION

Abstract

A work platform for attaching to a breaker stand in an electrical grid substation is disclosed, comprising a platform constructed of metal I-beam frame and tubular members and supported on adjustable legs. A foot plate is attached to the bottom of each leg. A short stairway is attached to the platform to provide access to the work platform. The work platform and the stairway are separately connected electrically to the subsurface ground grid system of the electrical grid substation. The platform, while adapted to be connected to a substation breaker stand, may be readily detached for re-placement within the substation or transport.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention concerns platforms for use by technicians and service personnel in construction and maintenance operations of infrastructure facilities and more particularly to work platforms for facilitating service operations within electrical grid substations that are integral to the systems and networks for the distribution of electrical power to utility company customers.

2. Background of the Invention

The infrastructure of electrical power distribution systems includes a network of high voltage power lines and a series of electrical grid substations (“substations”) for housing terminals, transformers, switches, circuit breakers, power line connections, etc. within a secure area that limits entry to all but authorized service personnel. The presence of very high voltages requires robust components and supporting structures for handling the switching, control, and distribution of electricity to utility customers. These components are typically supported on heavy-duty towers and support frames to maintain adequate separation between the various components.

An essential feature of the substations is a robust system of electrical ground that is buried in the Earth's subsurface just below the floor of the substation. This earth ground system comprises a subsurface grid of heavy-duty, exothermically welded conductors for connecting ground wiring from the substation components above ground to the ground system grid. All of the non-current carrying portions of the substation components are connected to the earth ground to ensure that such surfaces are held at electrical ground potential to protect personnel servicing the substation equipment from electrical shock if they happen to come in contact with these surfaces within the substation.

To facilitate maintenance on the substation equipment, work platforms constructed of metal—usually steel—are provided to elevate the workers to a convenient height relative to the equipment being inspected or serviced. The work platforms are connected to the substation's earth ground system to provide a reliable connection to electrical ground, thereby maintaining a safe work environment for maintenance personnel. In the prior art, the work platforms are permanently installed next to each substation grid component that may need periodic maintenance or emergency attention in the event of fault circumstances. However, since not every substation grid equipment needs service at the same time, permanent work platforms represent a very substantial cost to the maintenance operations of the substations.

Accordingly, there is a need for non-permanent work platforms that can be readily moved to various locations within the substation and adapted to minor terrain variations yet are configured for stability and ease of connecting to the substation supporting framework and the earth ground system of the substation.

SUMMARY OF THE INVENTION

A work platform for an electrical grid substation is disclosed constructed of metal I-beam frame and tubular members and supported on legs adjustable for length. In one embodiment each adjustable leg is configured as a telescoping assembly of an outer member and an inner member, each member having a series of adjustment holes disposed along spaced cross-sections thereof. Each telescoping assembly includes a pin inserted through an aligned pair of adjustment holes in the outer and inner members to fix the adjustable length. Each inner leg member includes a foot plate attached perpendicularly to the lower end thereof.

In an alternate embodiment each adjustable leg includes a hollow upper leg member having a threaded nut attached within its lower end for receiving a threaded lower leg member therein. The threaded lower leg member is rotated within the nut attached within the hollow leg member to adjust its length. Each lower leg member includes a foot plate attached perpendicularly to the lower end thereof.

In other aspects, the work platforms disclosed herein may include features wherein:

• • the platform includes a floor constructed of metal rectangular bar grating; an access stairway is connected to one side of the platform; a hand rail is disposed along portions of the perimeter of the deck and the sides of the stairway; the platform is configured for connecting to a breaker stand frame through first and second cross members; and the first and second cross members are secured between the breaker stand frame and the platform by bolts through a mounting plate at each end of the first and second cross members.

In other aspects, the work platforms disclosed herein may include features wherein: a first ground wire connected between the platform frame and a subsurface ground grid; and a second ground wire connected between the stairway and the subsurface ground grid; wherein the first and second ground wires are formed of 500 MCM copper wire exothermically welded to the subsurface ground grid; the first and second ground wires are respectively connected to the platform frame and the stairway frame using a corrosion-resistant terminal for use with 500 MCM copper wire; and the corrosion-resistant terminal is a bronze terminal lug for receiving a 500 MCM copper wire.

In other aspects, each upper leg member may include an adjustment mechanism operatively coupled to the lower leg member for adjusting the overall length of the legs and the height of the platform.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a perspective view of an embodiment of a work platform according to the present invention;

FIG. 2 illustrates a detail perspective view of the attachment of the embodiment of FIG. 1 to a breaker stand frame in an electrical grid substation;

FIG. 3 illustrates one embodiment of an adjustable platform leg;

FIG. 4 illustrates a second embodiment of an adjustable platform leg;

FIG. 5 provides a schematic perspective view in partial cutaway to depict other alternate embodiments of the adjustable legs; and

FIG. 6 illustrates one embodiment of a ground connection from the work platform of the embodiment of FIG. 1 to a substation ground grid system.

DETAILED DESCRIPTION OF THE INVENTION

Introduction

An electrical grid substation (“substation”) is an enclosed area bounded by a security fence. The substation includes electrical distribution grid terminal equipment such as high voltage power lines, transformers, terminating devices, switches, circuit breakers, etc. The floor of the substation may typically be a layer of aggregate crushed rock spread upon the earth's surface. Circuit breaker equipment may be enclosed in metal cabinets supported on breaker stands to facilitate access for servicing by maintenance personnel. In a typical substation a breaker stand is mounted on a concrete base that supports the cabinets containing the circuit breaker apparatus on metal frames.

In an advance in the state of the art, the present invention provides a work platform for use in an electrical grid substation. The work platform may be temporarily attached to a breaker stand for servicing by connecting removable frame members between the work platform and the breaker stand frame. The work platform preferably includes a short stairway to enable access to the deck or floor of the work platform. The work platform and the stairway are supported on the substation floor by adjustable leg members so that the work platform may be leveled and aligned with the breaker stand to which it is attached. Moreover, the adjustable legs are supported on flat metal foot plates (or “sand foot”) that rest on top of the aggregate surface of the substation terrain. This structure permits the work platform to be readily moved from one location to another.

For safety, each breaker stand and a work platform attached thereto are connected to a subsurface earth ground system installed throughout the substation area. The ground connection may be provided through flexible stranded copper wire of 500 MCM (500,000 circular mils), a unit of cross-section area. A 500 MCM wire has a diameter of approximately 0.4 inch. The grounding wire is detachably terminated at the upper end to the metal frames of the breaker stand and work platform by a cast bronze terminal called a TLS lug for connecting the ground wiring to equipment frames. The grounding wire is terminated to the substation grid conductors below the Earth's surface by an exothermic weld that provides a molecular bond between the grounding wire and the subsurface ground grid. An example of the ground connection wiring to be described is shown in FIGS. 1 and 5.

The Work Platform (FIGS. 1 and 2)

FIG. 1 illustrates a perspective view of a preferred embodiment of the claimed invention, which depicts a work platform 10 attached to a breaker stand 54 along one side of the work platform 10. A stairway 12 is attached to one end of the work platform 10. The work platform 10 includes a safety handrail 44 around a portion of its perimeter except at the side next to the breaker stand 54 and the end near the stairway 12. The handrail 44 is also preferred on both sides of the stairway 12 itself. The handrail 44 may be constructed as extensions of the platform framework and forms the highest structural portion of the work platform. The handrail 44 may be approximately six feet above the terrain of the substation. This height allows for ease of movement within the substation thereby avoiding interference with other structures extending above the substation terrain.

The breaker stand 54 as shown in FIG. 1 supports enclosures 50, 52 containing circuit breaker hardware and associated components (Not shown because they are not part of the invention disclosed herein). The breaker stand 54 is supported on representative near-side frame members 56 and 58 and far side frame members 64 and 66.

The work platform 10 may be rectangular in shape, configured as a framework that supports a deck or floor 16 approximately 24 to 36 inches above the terrain of the substation. The floor 16 and the treads 18 of the stairway 12 may be constructed of metal, rectangular bar grating. The open grating prevents puddles from forming during rain and provides a non-skid floor for standing or walking. Access to the work platform 10 may be provided by the stairway 12, typically having four or five steps as needed, also formed of the rectangular bar grating material.

In the preferred embodiment, the work platform 10 and the stairway 12 are supported by adjustable, two-piece legs 20 to enable leveling the work platform 10 so that its floor remains in horizontal alignment with the breaker stand 54. The lower end of each adjustable leg includes a flat metal foot plate 24 to support the adjustable legs 20 on the aggregate floor 100 of the substation terrain without sinking into the aggregate material 102. The work platform 10 may be attached to the breaker stand 54 through metal cross members 60, 62. The cross members include end plates 70, 72 welded to each end thereof so that the cross members 60, 62 can be bolted between the work platform 10 and the breaker stand frame 56, 58 using bolts (not shown). This detachability permits the work platform 10 to be moved to another location in the substation. This configuration reduces the number of work platforms that must be retained in the substation, thereby providing a significant cost savings.

The Adjustable Legs (FIGS. 3, 4 and 5)

In one embodiment shown in FIG. 3, the adjustable legs 20 may be formed of an outer and an inner portion, where the inner portion nests telescopically within the inside of the outer portion. In the embodiment of FIG. 3, the telescopic configuration includes a slight clearance between the outer 20 and inner 22 portions to allow a sliding fit. This construction will minimize lateral movement of the inner 22 and outer 20 leg portions to provide stable legs. Both the inner 22 and outer 20 portions of the leg include a series of holes 26 evenly spaced along opposite sides of the tubular legs and aligned to permit inserting a pin or bolt 28 through each pair of aligned holes 26. This adjustability permits setting the length of each leg to compensate for variations in the elevation of the substation terrain 100 at the position of the leg. The inner portion 22 of each leg is preferably welded to a flat metal foot plate 24, which provides a stable footing for each leg upon the aggregate floor 100 of the substation. The work platform 10 may typically require four adjustable legs, one at each corner, and a fifth and sixth adjustable leg at each end of the lowest step of the stairway.

In an alternate embodiment shown in FIG. 4, the outer portion 120 of each leg is fitted with a threaded nut endpiece 126 that may be welded within the lower end of the outer portion 120. The threaded endpiece 126 receives a threaded inner leg 22 to enable adjustment of the length of each leg. The inner leg 22 is preferably welded to a flat metal foot plate 124, which provides a stable footing for each leg upon the aggregate floor 100 of the substation.

FIG. 5 provides a schematic perspective view in partial cutaway to depict an alternate embodiment 150 of the adjustable legs having several structural variations. In general, an upper leg member 140 is shown with a lower leg member 142 partially inserted within the upper leg member 140. Enclosed and fixed within the upper leg member 140 is a mechanism 144 that is operative to adjust the amount of insertion of the lower leg member 142 within the upper leg member 140 through a linkage or coupling 146. In one embodiment, an operative extension 148 protrudes from the mechanism 144 through an opening 152 in the side wall of the upper leg member 140. The operative extension 148 may include an attachment port 154 to attach an operative device such as a lever or fluid line (hydraulic oil or air) for activating the mechanism to lengthen or shorten the length of the combined upper leg member 140 and lower leg member 142.

The mechanism 144 may be selected from the group consisting of a mechanical jack disposed within the upper leg member 140 and operatively linked to the lower leg member 142, a hydraulic cylinder disposed within the upper leg member 140 and operatively linked to the lower leg member 142, or a compressed air cylinder disposed within the upper leg member 140 and operatively linked to the lower leg member 142.

The mechanical jack may be a lever operated linkage between the upper and lower leg members 140, 142 that is similar to the hand operated jack that may be supplied with a new car, for example. The jack may be operated with a lever (not shown) connected to the operative extension 148 adapted to receive the lever.

The hydraulic cylinder may be similar in structure and operation to a simple cylindrical floor jack such as used in servicing small vehicles. The hydraulic cylinder may be operated by a pump (not shown) connected through an oil line to the operative extension 148 that injects or extracts hydraulic oil into or from the hydraulic cylinder to extend or retract the lower leg member 140 within the upper leg member 142.

The compressed air cylinder may be formed as a small tank to contain compressed air to extend or retract its length for adjusting the length of the combined upper and lower leg members 140, 142. A compressor may be connected through an air line to the operative extension 148 to lengthen or shorten the combined length of the upper and lower leg members 140, 142

The Grounding Connections (FIG. 6)

A copper ground cable 32, 38 as depicted in FIG. 6 is required to electrically connect the frames of the platform 10 and the stairway 12 to the substation electrical ground system (not shown) installed below the surface of the Earth. The upper ends of the copper ground cables 32, 38 are preferably terminated to the frames of the platform 10 and stairway 12 in “tower leg single” (TLS) lug terminals 34, 40 formed of bronze to ensure corrosion-resistant connections. The upper end of the ground cable 32, 38 is secured within the lug terminals 34, 40 with a set screw 90. The lower ends of the copper ground cables 32, 38 are installed below the surface aggregate 102 of the substation floor 100 and connected by exothermically welding the lower ends of the copper cables 36, 42 to the subsurface ground grid system (not shown). An exothermic welded connection uses chemical heating to provide the heat necessary to bond dissimilar metals (e.g., copper and steel) together molecularly. This process ensures a low-resistance connection that remains solid and corrosion-free for the life of the connection. The process of exothermic welding to bond dissimilar metal conductors is well-known to persons skilled in the art.

With the earth grounding system for the work platform 10 as described, all devices in the substation, including transformers, columns, fencing, breaker stands, work platforms, etc. are connected to a common earth ground system to enable the discharge of excess electricity in the event of electrical faults.

Installation

The mechanical connection of the work platform 10 to the breaker stand 54 is provided by first and second cross members 60, 62 (See FIGS. 1 and 2). The first and second cross members 60, 62 may be formed of ¼ inch thick steel angle iron and include steel mounting plates 70, 72 (See FIG. 2) welded to each end of the cross beam members 60, 62. The mounting plates 70, 72 may preferably be attached and secured to the respective frames of the work platform 10 and breaker stand 54 by bolts and nuts. Thus, the first and second cross beams 60, 62 provide secure electrical and mechanical connections between the frames of the work platform 10 and the breaker stand 54 to provide the permanent electrical ground connection between them.

CONCLUSION

In accord with the foregoing description, a removable work platform for an electrical grid substation is disclosed, comprising a platform constructed of metal members and supported on vertically adjustable legs. The work platform is configured on one side to attach to a substation breaker stand while maintaining the integrity of the electrical ground connections between them. A stairway is connected to one end of the platform, and the platform and the stairway are connected through heavy copper conductors to a subsurface grounding grid of the substation.

The adjustable leg members are described in two embodiments to enable leveling and adjusting the height of the work platform on the uneven terrain of the substation. One adjustable leg embodiment uses telescoping leg members having a series of matching adjustment holes disposed along spaced cross-sections of the leg members. Each leg member includes a pin inserted through an aligned pair of adjustment holes to fix the adjustable length. An alternate adjustable leg embodiment includes upper and lower leg members. The lower leg member is threaded for being rotatably inserted into the lower end of the upper leg member using a threaded end formed within the bottom of the upper leg member. Both adjustable leg embodiments include a flat foot plate attached to the bottom end of each lower leg member to provide stable footing of the work platform. Alternate mechanisms for adjusting the length of the legs are also described.

While the invention has been shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit thereof.

Claims

1. A work platform for an electrical grid substation, comprising: a platform constructed of metal I-beam frame and tubular members and supported on legs adjustable for length;first and second cross members bolted between the platform and a frame of a substation breaker stand; whereineach adjustable leg is configured as a telescoping assembly of an outer member and an inner member, each member having a series of adjustment holes disposed along spaced cross-sections thereof;each inner member includes a foot plate attached perpendicularly to the lower end thereof; andeach telescoping assembly includes a pin inserted through an aligned pair of adjustment holes in the outer and inner members to fix the adjustable length.

2. A work platform for an electrical grid substation, comprising: a platform constructed of metal I-beam and tubular members and supported on legs adjustable for length;first and second cross members bolted between the platform and a frame of a substation breaker stand; whereineach adjustable leg includes a hollow upper leg member having a threaded nut attached within its lower end for receiving a threaded lower leg member therein; andeach threaded lower leg member includes a foot plate attached perpendicularly to the lower end thereof; whereinthe threaded lower leg member is rotated within the threaded nut attached within the hollow leg member to fix the adjustable length.

3. The platform as in claim 1 or 2, further comprising: the platform includes a floor constructed of metal rectangular bar grating.

4. The platform of claim 3, wherein: an access stairway is connected to one side of the platform.

5. The platform of claim 4, further comprising: a first ground wire connected between the platform frame and a subsurface ground grid; anda second ground wire connected between the stairway and the subsurface ground grid; whereinthe first and second ground wires are formed of 500 MCM copper wire exothermically welded to the subsurface ground grid.

6. The platform of claim 5, wherein: the first and second ground wires are respectively connected to the platform frame and the stairway frame using a corrosion-resistant terminal for use with 500 MCM copper wire.

7. The platform of claim 5, wherein: the corrosion-resistant terminal is a bronze terminal lug for receiving a 500 MCM copper wire.

8. The platform of claim 3, further comprising: a handrail disposed along portions of the perimeter of the deck and the sides of the stairway.

9. A work platform for an electrical grid substation, comprising: a platform constructed of metal I-beam frame and tubular members and supported on legs adjustable for length;a floor constructed of metal bar grating;an access stairway connected to one side of the platform;a handrail disposed along portions of the perimeter of the floor and the sides of the stairway;a first ground wire connected between the platform frame and a subsurface ground grid;a second ground wire connected between the stairway and the subsurface ground grid; whereineach adjustable leg includes an upper member and a lower member configured with a smaller cross section and partially disposed within the upper member;a mechanism for securing the amount of disposition of the lower member within the upper member of each adjustable leg; anda foot plate attached to the bottom end of each lower member; whereinthe mechanism for securing is selected from the group consisting of a telescoping lower member disposed within an associated upper member and secured with a pin through holes along a diameter common to both leg members, a threaded lower member secured within a threaded opening in the bottom end of an associated upper member, a mechanical jack disposed within the upper member and operatively linked to the lower member, a hydraulic cylinder disposed within the upper member and operatively linked to the lower member, and a compressed air cylinder disposed within the upper member and operatively linked to the lower member.

10. The work platform of claim 1, wherein: the platform is configured for connecting to a breaker stand frame though first and second cross members; andthe first and second cross members are secured between the breaker stand frame and the platform through a mounting plate at each end of the first and second cross members.

11. The work platform of claim 1, wherein: the first and second ground wires are formed of 500 MCM copper wire exothermically welded to the subsurface ground grid.

12. The work platform of claim 3, wherein: the first and second ground wires are respectively connected to the platform frame and the stairway frame using a corrosion-resistant terminal for use with 500 MCM copper wire.

13. The work platform of claim 4, wherein: the corrosion-resistant terminal is a bronze terminal lug configured for receiving a 500 MCM copper wire.