power distribution - Siemens

Medium Voltage EquipmentGM-SG Vacuum Circuit BreakersType GMSG Vacuum Circuit Breakers5kV, 7.2kV and 15kVSiemens Type GMSG circuit breakers are available in 25kAthrough 63kA* interrupting classes, or 250MVA through1000MVA on the older “constant MVA” rating basis.Continuous current ratings include 1200A, 2000A, and 3000Aself-cooled. 4000A is available using a 3000A circuit breakertogether with forced-air (fan) cooling in the switchgear cubicle.*Consult factory for availability of 63kAMaintenance FeaturesThe GMSG circuit breakers incorporate many featuresdesigned to reduce and simplify maintenance, including:▪ Virtually maintenance-free vacuum interrupter▪ Ten year maintenance interval▪ Floor rollout▪ Front mounted operator▪ Common operator family▪ Simple outer-phase barriers▪ “Universal” spare circuit breaker concept▪ Non-sliding current transfer▪ Rugged secondary disconnectsTen Year Maintenance Interval on GMSG Circuit BreakerWhen applied under mild conditions (ANSI “usual service”conditions), maintenance is only needed at ten year intervalson the circuit breaker. The maintenance interval for theswitchgear cubicles is five years.Low Maintenance RequirementsThe interrupter is a sealed unit, so the only maintenancenecessary is to clean off any contaminants and to check thevacuum integrity. The vacuum interrupters can bedisconnected from the stored energy mechanism quickly,without tools, and vacuum integrity inspected by hand;alternatively, a simple hi-pot test can be used.GeneralFloor RolloutWhen located in the lower cell, the circuit breakers arearranged to rollout directly on the floor in front of theswitchgear if the switchgear is not located on a“housekeeping” pad. No adapter, hoist, or lift truck isnecessary.Mechanism OperationThe mechanism is arranged to pre-store closing energy in theclosing springs. The closing springs are selected so that theyprovide sufficient energy not only to close the circuit breakersafely into maximum "close and latch" currents, but also topre-store the tripping energy necessary to open the circuitbreaker. The closing springs can be manually charged duringmaintenance or in emergency conditions, but are normallycharged electrically automatically after each closing operation.InterlocksThe racking system prevents racking of a closed circuitbreaker, and keeps the circuit breaker trip-free during racking.The racking mechanism can be padlocked to preventunauthorized operation. Padlocks can also be applied to theracking mechanism to maintain the circuit breaker in the tripfreecondition.Stored Energy OperatorThe GMSG circuit breaker utilizes the Siemens 3AH3 storedenergy operator for long life, high reliability, and ease ofmaintenance. Parts used in the manufacture of the circuitbreaker are precision tooled or produced on numericallycontrolled equipment. The circuit breaker design includesfrequent use of inherent alignment techniques.13 SWITCHGEARFront Side (barriers removed) RearFigure 2: GMSG Circuit BreakerSiemens Power Distribution & Control, SPEEDFAX 2007-2008 Product Catalog 13-5