October 17, 2005
Product Spotlight: Special Applications for Vista® Underground Distribution Switchgear (UDS).
Wind-Turbine Style Vista is a slim, single-way three-phase model of Vista designed for use in wind-turbine towers. It can fit through a turbine’s typical 24" wide opening. Wind-Turbine Style Vista provides connection and switching points for medium-voltage cables from the wind-turbine generator output.
Wind-Turbine Vista is operated from the side — allowing the switch to be positioned along the inside wall of the wind-turbine tower — providing more space for personnel access and equipment. Rated 600-amperes at 38 kV, this switchgear is typically specified with resettable fault interrupters, but can also accommodate load-interrupter switches. It can also be applied anywhere where installation space is limited.
Manhole Style Vista UDS is a cylindrical version of the single-way, three-phase Vista UDS designed for installation through the round “manhole” access opening of an underground vault. Manhole Style Vista features a 630-ampere, three-pole load-interrupter switch or vacuum fault interrupter which is sealed in a rugged stainless-steel SF6 insulated tank. Cable entrance and exit is via 600-ampere bushings or optional 200-ampere bushing wells.
At 15 kV, the tank of the Manhole Style Vista is only 29-1/2 inches in diameter; as a result it easily fits through most utility's manhole openings. An optional voltage indicator lifts up to expose a large viewing window, allowing a clear view of the switch, open gap, and gas pressure indicator. The Manhole Style Vista is fully submersible, and offers three mounting choices — floor, stand, or wall.
“Mobile” Heavy-Duty Vista® Designed to MIL Spec E-810
Designed in conjunction with branches of the US Military Mobile Vista UDS is rugged enough to withstand air transport to provisional military bases . . . and can be used for temporary or permanent electrical installations. Vista is small and lightweight, so it’s ideally suited for airlifting.
Mobile Vista passed the MIL Spec E-810 20-hour shaker-table vibration test, verifying that stacked units could withstand 10,000 miles of travel aboard aircraft, and it passed tests verifying that switchgear performance is not affected after the gear has been subjected to low pressure at an altitude of 40,000 feet. Mobile Vista can be stacked two-high to save space aboard airplanes and in storage.
To comply with the stringent E-810 specifications, the Vista UDS enclosure was completely redesigned and outfitted with an integral steel skid. The skid and enclosure frame utilize heavy-duty steel I-beams and channels. Four alignment pins at the top corners of the enclosure facilitate stacking of the units. Stacked units are lifted by eyebolts on the skid frame. Channels at the bottom allow for forklift handling and reinforced tabs at the lower corners of the skid allow the gear to be dragged along the ground. Turnbuckles, attached to eyebolts on front and rear sides of the skid, hold stacked units together during transport. Plates, attached to the floor of the enclosure, protect the switchgear during transport and storage and can be removed for cable entry while the gear is in use.
Even after the numerous design changes listed above, all the unique features of Vista UDS were retained. Mobile Vista has a 600-ampere continuous current rating and 16-kA short-circuit and fault-interrupting capability. Each unit includes two load-interrupter switch ways and four fault-interrupter ways. Optional voltage indicators are also included.
Vista® For Use In Metal-Enclosed Switchgear
When an existing metal-enclosed switchgear lineup needed two new feeders and there was only room for one bay, an enclosure was built that matched the others in the lineup, and a unit of Vista Underground Distribution Switchgear was installed inside.
SF6-insulated Vista gear is much smaller than conventional metal-enclosed gear. A typical 25-kV metal-enclosed gear feeder bay is about 52 inches wide. So the two bays usually required for this application would require 104 inches. But one three-way Vista UDS unit can be housed in a bay about 58 inches wide, reducing the space required by almost half.
The new bay was constructed to match the existing lineup in size and color as closely as possible. Inside is a Vista UDS Model 302 with one incoming way and two fault-interrupter ways. The three-pole, group-operated fault interrupters, rated 29 kV, 600 amperes continuous and 16,000 amperes RMS symmetrical short-circuit, feed the new loads.
The Vista UDS unit is operated from a control panel that’s completely isolated from medium-voltage components. The position of each fault-interrupter disconnect — open, closed, or grounded — is easily seen through large viewing windows in the Vista tank. With the disconnect in full view, the operator can verify the open gap and ground cables without having to remove elbows or T-bodies. And by using the optional push-button voltage indicator furnished, the operator can check voltage without ever moving the cables. A door at the rear of the bay allows access to the elbow connectors.
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