10 CFR 50.71(e) - Maritime Administration - U.S. Department of ...

Updated Final Safety Analysis Report - (STS-004-002)Existing 120 VAC sections of the Main Switchboard No. 2, and the EmergencySwitchboard are fed via new molded case circuit breakers.A simplified one line diagram of the original distribution system is shown in Figure 8-1. Thecurrent system is shown in Figure 8-2.8.5.2.2. Main Switchboard Description (Original)Supply breakers to deactivated, disabled and/or inactive equipment have been verified open.The main switchboard for the control of all normal power sources was located in the maincontrol room. This switchboard was divided into two 450-volt sections; each section was fed byone 1500 kW SSTG and one 750 kW ADG. The two 450-volt sections were permanentlydeenergized by installation of a shore power switchboard in 2010.Additionally, the main switchboard lineup included a 120-volt, three-phase, a-c bus; a 125-volt,d-c bus; and a 120-volt, a-c bus. All normal power requirements were served by these busesthrough group-control centers and power panels located throughout the ship.Main switchboard bus section 1 was fed by SSTG 1 or ADG 1. Bus section 2 was fed by SSTG2 or ADG 2.Main switchboard bus section 1 was fed by the shore connection, and, by way of a circuitbreaker, bus section 2 can be fed by the shore connection. Bus sections 1 and 2 were connectedtogether through a normally closed bus tie circuit breaker located in section 2.Bus section 1 includes a 125-volt, d-c bus which could have been fed from the followingsources that are deactivated, disabled and perform no active function:1. Bus section 1 by a 40 kW motor generator 1.2. Bus section 2 by a 40 kW motor generator 2.3. The 125-volt, d-c vital instrument bus floating battery.A 120-volt, single-phase, 60-cycle, a-c vital bus is also included in the bus section 1 lineup.The 120-volt, a-c final bus was fed by the two 25 kW motor generators which were connectedto the 125-volt, d-c bus. These motor generators are deactivated, disabled and perform noactive function.Bus section 2 includes a 120-volt, three-phase, 60-cycle bus fed from the Shore PowerSwitchboard after modifications in 2010. Originally, bus section 2 was fed from bus section 1or 2 by way of an automatic transfer switch and a bank of three 50 kVA transformers. Bussections 1 and 2 are also connected to the emergency switchboard byway of an automatictransfer system located on the emergency switchboard.All outgoing feeders from the 450-volt buses of the main switchboard were protected byWestinghouse Tri-Pac, molded-case circuit breakers with the exception of the drawout aircircuit breakers for the auxiliary propulsion motor. All outgoing feeders from the buses for125-volt dc, 120-volt, single-phase ac, and 120-volt, three-phase a-c are protected by moldedcasecircuit breakers.Rev. VI 79