power distribution - Siemens

Medium Voltage EquipmentGM-SG OverviewSiemens GM-SG 5kV, 7.2kV and 15kV metal-clad powerswitchgear assemblies with horizontal drawout type GMSGvacuum circuit breakers take advantage of the latestdevelopments in vacuum interrupter technology. Up to twocircuit breakers can be stacked in a single vertical section,allowing significant space savings.The equipment meets or exceeds the latest standards of ANSI,IEEE, and NEMA.GM-SG switchgear is designed for use in industrial plants,commercial buildings, electric utility systems, cogenerationinstallations, and other electrical systems. It is commonlyused for protection and switching of transformers, motors,generators, capacitors, buses, distribution feeder lines, and, ingeneral, for protection of any medium voltage power circuit.Siemens experience gained in over 80 years of supplying metalcladswitchgear in the U.S. has been captured in the GM-SGdesign. The objective has been to incorporate features designedto provide safety, while simplifying operation, maintenance, andminimizing installation cost.The switchgear structure and the drawout vacuum circuitbreaker are an integrated design, with dielectric, thermal, andinterruption integrity built directly into the basic design, notadded as an afterthought.Siemens 3AH3 Operating MechanismThe GMSG circuit breaker uses the proven Siemens 3AH3stored-energy operating mechanism. This operator is anevolution of the 3A family of operators first introduced in 1976.Over 60,000 3AH3 operating mechanisms have been producedsince 1998.Faster InterruptionStandard interrupting time is 5-cycles with an option availablefor 3-cycle interrupting time.Siemens Vacuum InterruptersThe vacuum interrupters used in the GMSG circuit breaker aremanufactured by Siemens and have been proven in thousandsof installations since 1976. The chrome-copper contact designused in these interrupters assures low chopping levels,eliminating the need for surge protection on most circuits.Front Mounted Operating MechanismThe simple GMSG operating mechanism makes maintenanceand inspection easy. The mechanism is located on the front ofthe circuit breaker, rather than underneath.GeneralMaintenance IntervalsIf applied under ANSl “usual service” conditions, maintenanceof the circuit breaker mechanism is only needed at ten yearintervals.Maintenance of the switchgear cubicle is recommended at fiveyear intervals, and primarily consists of cleaning insulation.Floor RolloutNo lift truck or dolly is needed to insert or remove circuit breakersin the lower cell of switchgear located at floor level. For indoorswitchgear located on a raised “housekeeping” pad or foroutdoor non-walk-in switchgear, a lift truck is required to handlecircuit breakers."Universal" Spare Breaker (up to 50kA)The physical configuration and interlock logic allow the use of asingle circuit breaker to serve as a “universal” spare breaker atan installation site for up to 50kA. The interlock logic checks theprincipal rating characteristics (continuous current, maximumvoltage, and interrupting current), and allows a circuit breaker tobe inserted in any circuit breaker cell, provided that the circuitbreaker equals or exceeds the ratings required by the cell.Single Source ResponsibilitySingle source responsibility is assured since the completeequipment is designed by Siemens and is manufactured andtested in a single facility. The vacuum circuit breakers arechecked in the switchgear cells as part of production testing,and shipped in the switchgear to assure interchangeabilityand reduce the possibility of damage to circuit breakers inshipment.Full ANSI Design BackgroundFull design integrity is assured. ANSl C37.09 and C37.20.2require design tests on circuit breakers and structures together.The 3AH3 operator is produced in our global center ofcompetence for circuit breakers in Berlin, and final assemblyof both the drawout GMSG circuit breaker and the switchgearstructures occurs in a single facility. Siemens controls theentire process, from design concept to production. Recordsare maintained to document compliance with ANSl standards.UL or C-UL Listing AvailableWhere the arrangement of components allows, UL or C-ULListing is available.Quality SystemsFacilities involved with application, engineering, design andproduction are certified to ISO 9001 requirements.13 SWITCHGEARSiemens Power Distribution & Control, SPEEDFAX 2007-2008 Product Catalog 13-3