11 gauge minimum, stretcher leveled sheet steel is used for all enclosures and doors. All-welded construction is standard to prevent deformation of the enclosure during shipping and installation and to ensure breakers will rack in, even if the concrete pad or piers are not completely level. |
Continuous seam welded wall and roof panels ensure that the enclosure will not leak over its 40-year life span (unlike designs using gasketed or caulked construction) and to provide a safe, continuously grounded structure. |
The enclosure can be shipped in one piece, with no re-assembly required at the job site. One-piece shipment eliminates the need for re-assembly of weatherproof seams in the field, since all joints are continuously-welded at the factory. |
Integrally welded structural lifting lugs are provided on top, requiring only steel cables and hooks to lift the structure (spreader bars with frames are not required). |
1/4" steel floor plates are utilized for floors to prevent bowing when breakers are rolled across the floor and to maintain the dimensional integrity of the floor/base. A skid-resistant epoxy finish is applied to the floor prior to shipment.
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Undercoating is applied to all base surfaces, since they are inaccessible after equipment is placed on a concrete pad. Undercoating material is non-hardening and will not crack and flake off over the life of the enclosure.
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An Instruction Manual and drawing rack/pocket are provided along with a storage rack for accessories and spare fuses.
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Dual tube, 48" long fluorescent light fixtures, with zero degree ambient rated ballasts, are provided for illumination of the maintenance and work areas.
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Rear access doors are provided with a heavy duty stainless steel vault handle with padlocking provisions and three-point latching mechanism using heavy duty aluminum square tubular operating rods with nylon rollers to hold top and bottom edges tight against the door gasket.
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Stainless steel hinges are provided for exterior doors to ensure long life without wear or corrosion. Four heavy-duty hinges are welded to the door and door frame for extra strength and are concealed by the door frame when the door is closed.
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An extra return flange is standard on interior and exterior doors. On exterior doors, the extra flange serves to protect the gasket from deterioration that would occur if exposed directly to the elements. The extra rigidity provided by the double flange ensures a continuous seal against the gasket surface around the entire door perimeter.
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A one-inch wide rain gutter is provided on the top and both sides of exterior door openings. This gutter channels water directly to the ground and prevents it from flowing against the door gasket. Contact surface between the door flange and door gasket is a minimum of 1/2" to ensure resistance to all forms of moisture, as well as dust.
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Tamperproof exterior doors, since there is no hardware that can be removed to gain access to equipment or high voltage compartments by unauthorized personnel.
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Filter boxes are mounted externally on the outside of all rear doors. A back-to-back louver design, with intervening filter, prevents entry of wind-driven moisture into the switchgear. Filters can be changed without requiring access to high voltage compartments.
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All interior steel panels and barriers are painted. No unpainted galvanized panels or doors are utilized. GPO-3 Glastic cable supports are provided in the power cable termination compartment to take the weight of the cables off the terminations and to provide additional fault bracing. Extra distance is provided from bottom of switchgear to the cable termination to allow sufficient room for stress cone assembly.
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Easy-to-handle aluminum plates are provided over the conduit openings. These plates are corrosion-resistant, allow easy punching for conduit fittings and prevent heating due to circulating currents.
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Door stops on metering and relay doors limit door swing to prevent damage to instruments and controls on adjacent cubicles. |
A continuos piano hinge is provided to handle the extra weight of relays, meters, and controls. A welded steel bar is utilized to tie down the control wire bundle to the door and to keep device wiring neat.
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An 11 gauge steel, 12" wide wireway is provided across top of all switchgear cubicles with access grommets to protect the cable insulation.
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A relay guard is provided on all breaker compartment doors to prevent damage to door mounted devices when rolling a breaker out from the cubicle. Sub-panels are utilized for all surface-mounted devices to eliminate extra holes and protruding hardware on door fronts.
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Guards are provided over all strip heaters to prevent burns due to accidental contact.
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Bus bar is insulated with fluidized bed applied epoxy that has been tested for use at 38kV. All bus bar is insulated at the 38kV level. This epoxy formulation has been in service for over 25 years without signs of aging or deterioration. Each insulated bar is tested at full system voltage, to detect any hidden voids or pinholes.
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Silver plating is electroplated onto 100% of the connection surface area on both sides of the bus bar after insulation. |
Wet process porcelain main bus feed-thru supports are utilized to prevent the possibility of tracking and corona. A PVC bushing is provided between the porcelain feed-thru supports and insulated bus bar to prevent inception of corona and to cushion the bus bar during shipment.
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Fully rated, 6", 95kV BIL porcelain supports are utilized on the load side bus for strength and resistance to tracking. Grade 5 steel bolts attach the bus to the insulators with fiber washers installed against the bus installation surface to protect it from damage. A PVC cap is installed on the bolt head afterward. Phase markers are placed on each load side bus riser.
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Insulated ring-tongue terminals are utilized for control wiring. Control terminations are made with a ratcheting type crimping tool that will not allow the crimp to be released until it has been properly made.
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All cables for primaries of PT's and station service transformer/fuses are fully rated for the voltage class of the switchgear. Porcelain feed-thru bushings are used to support the cables. The design allows for inspection of the completed connection through a viewing window in the door and a clear lexan barrier mounted on the draw-out drawer.
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Operation of the door automatically engages or disengages the primary and secondary connections. It is possible to easily disengage this mechanism so that the door can be closed without moving the drawout drawer. |
A molded-case circuit breaker is provided on the secondary of station service transformers that is interlocked with the door using a through-the-door operating mechanism that prevents opening of the door before the breaker is opened.
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Bottom breakers roll in off the floor without the need for a breaker lifting device or ramps. This feature is provided through the use of an extra carriage with wheels on the bottom of the breaker frame.
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Drawings have bill-of-material callouts next to each device that match the item number of that device in the detailed bill-of-materials. Each bill-of-material item includes a complete description along with the manufacturer's name and part number. |
Complete ANSI test reports for the switchgear and breaker combination are available for customer review. All tests have been performed at and are certified by independent third-party labs. Complete data and graphs are presented for review.
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