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Vista and Vista Green Underground Distribution Switchgear for UtilitiesImproves reliability, sustainability, and safetywhile reducing maintenance costs

Vista and Vista Green UndergroundDistribution SwitchgearIntroductionAs the grid becomes more complex, utilities are facinga variety of challenges pressuring them to reassess theirmedium-voltage switchgear. In fact, some switchgear evenposes risks that increase operation and maintenance (O&M)expenses while reducing reliability. As utilities reevaluate theswitchgear on their system, they importantly should considerthe scope of the challenges they may face and the breadth ofswitchgear products available that can best meet the needsof today’s grid.Risks and expenses of oil-insulted switchgear. Oilinsulated switchgear is a common utility choice. However,such switchgear comes with environmental and maintenancechallenges. Utilities must routinely monitor oil switchgearto maintain performance, especially during colder months.Additionally, lack of routine maintenance can lead to equipment failure, causing an outage to all customers served bythe affected line. Leaks from oil-insulated switchgear havealso had negative environmental impacts, resulting in costlyclean-up efforts. Some oil-insulated switchgear also requiresmandatory testing, meaning more time, effort, and moneyare wasted to routinely inspect the gear.Regulatory pressures. Utilities are also facing greater pressure to limit the use of sulfur hexafluoride (SF6) gas andreduce the carbon footprint of their switchgear, with anincreased focus on meeting corporate sustainability goalsand adhering to forthcoming federal greenhouse gas regulations. As a result, utilities are reconsidering SF6 gas-insulatedswitchgear because of concerns operations may result ingreenhouse gas emissions. Solid-dielectric switchgear canreplace SF6 gas-insulated switchgear, but solid-dielectrictechnology has limitations, such as lower ratings and lack ofthree-position switching. In addition, solid-dielectric switchgear has a higher carbon footprint because of the type andmass of materials used in their construction and limitedrecyclability versus alternatives such as air- or gas-insulatedswitchgear.2Space constraints. Additionally, utilities that serve sprawlingurban areas may face challenges with the physical footprintof their gear. Compact medium-voltage switchgear that canfit in a tight underground vault is often required to alleviatethe safety concerns public-facing equipment presents. If theswitchgear does not have clearly visible breaks, utility crewscan find it challenging to confirm the switchgear’s operationstatus while working in a vault. Moreover, if the switchgeardoes not have front-facing cable terminations and operators,crews may have difficultly installing and navigating aroundthe switchgear in a vault to effectively deenergize the device.Fortunately, S&C’s Vista and Vista Green UndergroundDistribution Switchgear provide a suite of solutions toaddress the specific challenges each utility faces. S&Cdesigned these solutions to provide reliable protection,regardless of location or environmental conditions, includingin areas that experience flooding. Both switchgear offeringsare also available in multiple above- or below-grade installation styles and an eco-friendly insulation technology optionis available. With their single-handle operation, visible gaps,and flexible cable orientations, Vista or Vista Green switchgear are simple to routinely operate. Vista and Vista Greenswitchgear can tackle whatever challenges a utility mightface.

ApplicationVista and Vista Green UndergroundDistribution SwitchgearVista and Vista Green Underground Distribution Switchgearare designed to simplify operating tasks and enhance safetywhile minimizing the traditional switchgear footprint. Vistaand Vista Green switchgear introduce a new level of safetyand simplicity by eliminating the need for cable-handlingduring routine operation. Just one person is needed tooperate Vista and Vista Green switchgear, and there’s nonecessary exposure to medium voltage.Vista and Vista Green switchgear are available in manual,remote-supervisory, and source-transfer models in ratingsthrough 38 kV and 25 kA symmetrical short-circuit. Allmodels are elbow connected and enclosed in a submersible,welded steel tank. Vista and Vista Green switchgear canaccommodate any combination of up to six bus taps, loadinterrupter switches, or fault interrupters. Each modelfeatures load-interrupter switches and resettable vacuumfault interrupters or arc spinners in series with disconnectswitches. The load-interrupter switches provide three-polelive switching of 600-ampere or 900-ampere three-phasecircuits.Vista Green switchgear features all the benefits of Vistaswitchgear, but instead uses an eco-friendly 3M Novec 4710 Insulating Gas* and CO2 mixture.Vista and Vista Green switchgear are available in six installation styles:Pad-Mounted Style. This style improves aesthetics andreduces real-estate requirements—especially at 34.5 kV,where air-insulated gear is too large to be practical in manyapplications.UnderCover Style. Out of sight, yet easy to operate fromground level, submersible UnderCover Style Vista and VistaGreen switchgear are ideal where aesthetics are importantor where space limitations make it difficult to deploy gearabove ground.Vault-Mounted Style. This style provides a compactswitching-and-protection solution for subsurfaceapplications, electrical rooms, and sidewalk vaults, wherespace is very limited. A single unit accommodates up to sixload-interrupter switches, fault interrupters, or a combinationof each.Single-Way Wind-Turbine Style. This slim, single-way threephase version fits through a 24-inch (610-mm) wide opening.It provides connection and switching points for the mediumvoltage cables from the generator output. Because of its sideoperation, it can be positioned along a wall.Mobile Heavy-Duty Style. This unique version of Vistaand Vista Green switchgear is suitable for temporary orpermanent installations. Developed for the U.S. military, thissmall, lightweight Vista and Vista Green switchgear style isspecially designed to withstand the rigors of extended airtransport at high altitude.Special Applications. Vista and Vista Green switchgear canbe engineered to suit a variety of “special” applications. Forexample, if a utility expands a conventional metal-enclosedswitchgear lineup to accommodate two additional feeders—but there is only room for one more bay—a new bay externally matching the others can be constructed that contains aVista switchgear unit.*3M and Novec are trademarks of 3M Company.3

ConstructionVista and Vista Green UndergroundDistribution SwitchgearABHGCDEFOptional VOLTAGE Indicator with Liquid-CrystalDisplay—Includes a self-test featureGFMicroprocessor-Based Overcurrent Control—Housed in a watertight enclosure (Currenttransformers provide power and signal inputs.)Compact Welded-Steel Tank—Protects switchingand protection components from the environment(Stainless steel construction is standard inUnderCover Style.)GBlade-Viewing Window—Located underthis cover, allows visual confirmation of the bladepositionCPressure Gauge —Located under window,temperature and altitude compensatedHDOperating Mechanisms—For switches and faultinterrupters, padlockable in any positionEFOperation Selector—Prevents operations fromthe Closed position directly to Grounded positionand vice versaAB4Motor Operators—The operators facilitate remotepower operation of load-interrupter switches andfault interrupters. The operators can be decoupledto permit testing of the motor and controls. Factoryinstallation is optionally available.

FeaturesSimple, One-Hand Operation. Access and operate theswitchgear without cable-handling or high-voltage exposurefor a higher level of safety.No External Grounds. Ground medium-voltage cables usinga standard internal ground switch. External grounds are notrequired.Dust-, Corrosion-, and Leak-Proof. The hermetically-sealedtank prevents leaking, rusting, or switchgear contamination.Submersible. Switchgear is built to operate without beingaffected by water hazards, such as storm-surge flooding ortides.High degree of protection against the environment. Thehermetically sealed tank protects elements from exposure tomoisture or wildlife.Large viewing windows and visible open gap. This provides a clear indication of the switch position and a clear viewof the isolating disconnects, allowing operating personnel toeasily confirm the positions of load-interrupter switches andfault interrupters.Improved Worker Safety. No fuse handling is required,minimizing access and exposure to medium-voltagecomponents.Overcurrent Control. Superior coordination, flexibility, andreliability are made possible with a self-powered and userfriendly control. The overcurrent control detects faults andinitiates operation of the resettable fault interrupters. Thisproven device offers special, customizable “coordinating”speed TCC curves that provide complete coordination withupstream relays and downstream fuses. Separate phase- andground-overcurrent curves coordinate with the ground-tripsettings of source-side circuit breakers. Both main and tapcurves are included for complete coordination between faultinterrupters applied on main feeders and those applied onsubloop taps.The overcurrent control is programmed with a personalcomputer, in the shop or in the field. The overcurrent controlrecords up to a total of 64 of the most recent trip events.Aesthetic Improvement. The switchgear comes in a compact, low-profile design. At 15, 25, and even 34.5 kV, padmounted Vista and Vista Green switchgear are 6 to 14 inches(152 to 356 mm) shorter than, and the total real-estaterequirement is less than one-third of, the average gasinsulated gear and less than half the real estate of metal-cladswitchgear. See the figure below.Another innovative installation offering is the UnderCoverStyle, which is ideal for areas with stringent real-estaterestrictions or where aesthetics are important. The Vistaand Vista Green switchgear are installed underground, butall operations are easily performed by one operator aboveground.252 inches (6401 mm)Typical 38-kV Metal-CladOutdoor Switchgear (6 Ways)113 inches (2870 mm)Vista and Vista GreenUnderground DistributionSwitchgear 38 kV(6 Ways)116 inches (2946 mm)39.31 inches (998 mm)Vista and Vista Green Underground Distribution Switchgear versus typical metal-clad outdoorswitchgear size comparison.5