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{{#Wiki_filter:Page 1 of 11 DSAR-8.3 Electrical Systems Station Distribution Rev 1 Safety Classification:                     Usage Level:
{{#Wiki_filter:Page 1 of 11 DSAR-8.3 Electrical Systems Station Distribution Rev 1 Safety Classification:
Safety                               Information Change No.:                 EC 69625 Reason for Change:         This section is being updated as part of the design and licensing basis reconstitution project.
Usage Level:
Preparer:                   M.Bakhit Fort Calhoun Station
Safety Information Change No.:
EC 69625 Reason for Change:
This section is being updated as part of the design and licensing basis reconstitution project.
Preparer:
M.Bakhit Fort Calhoun Station


DSAR-8.3                                       Information Use                                                     Page 2 of 11 Station Distribution                                                                                                         Rev. 1 Table of Contents 8.3   Station Distribution .............................................................................................................3 8.3.1 4.16-kV System .......................................................................................................3 8.3.1.1 Design Bases ..........................................................................................3 8.3.1.2 Description and Operation.......................................................................3 8.3.1.3 Design Analysis .......................................................................................5 8.3.2 480-Volt System ......................................................................................................6 8.3.2.1 Design Bases ..........................................................................................6 8.3.2.2 Description and Operation.......................................................................6 8.3.2.3 Design Analysis .......................................................................................7 8.3.3 Deleted ....................................................................................................................7 8.3.3.1 Deleted ....................................................................................................7 8.3.3.2 Deleted ....................................................................................................7 8.3.3.3 Deleted ....................................................................................................7 8.3.4 DC Systems ............................................................................................................7 8.3.4.1 Design Bases ..........................................................................................7 8.3.4.2 Description and Operation.......................................................................8 8.3.4.3 Design Analysis .......................................................................................9 8.3.5 Instrument AC System ............................................................................................9 8.3.5.1 Design Bases ..........................................................................................9 8.3.5.2 Description and Operation.....................................................................10 8.3.5.3 Design Analysis .....................................................................................11
DSAR-8.3 Information Use Page 2 of 11 Station Distribution Rev. 1 Table of Contents 8.3 Station Distribution.............................................................................................................3 8.3.1 4.16-kV System.......................................................................................................3 8.3.1.1 Design Bases..........................................................................................3 8.3.1.2 Description and Operation.......................................................................3 8.3.1.3 Design Analysis.......................................................................................5 8.3.2 480-Volt System......................................................................................................6 8.3.2.1 Design Bases..........................................................................................6 8.3.2.2 Description and Operation.......................................................................6 8.3.2.3 Design Analysis.......................................................................................7 8.3.3 Deleted....................................................................................................................7 8.3.3.1 Deleted....................................................................................................7 8.3.3.2 Deleted....................................................................................................7 8.3.3.3 Deleted....................................................................................................7 8.3.4 DC Systems............................................................................................................7 8.3.4.1 Design Bases..........................................................................................7 8.3.4.2 Description and Operation.......................................................................8 8.3.4.3 Design Analysis.......................................................................................9 8.3.5 Instrument AC System............................................................................................9 8.3.5.1 Design Bases..........................................................................................9 8.3.5.2 Description and Operation..................................................................... 10 8.3.5.3 Design Analysis..................................................................................... 11  


DSAR-8.3                               Information Use                           Page 3 of 11 Station Distribution                                                                     Rev. 1 8.3   Station Distribution 8.3.1     4.16-kV System 8.3.1.1   Design Bases The 4.16-kV system was designed to function under the environmental conditions defined in Section 8.1.1 , to provide power to the Spent Fuel Pool and other supporting auxiliaries.
DSAR-8.3 Information Use Page 3 of 11 Station Distribution Rev. 1 8.3 Station Distribution 8.3.1 4.16-kV System 8.3.1.1 Design Bases The 4.16-kV system was designed to function under the environmental conditions defined in Section 8.1.1, to provide power to the Spent Fuel Pool and other supporting auxiliaries.
8.3.1.2   Description and Operation General The 4.16-kV system comprises four, outdoor transformers; nonsegregated bus duct supply connections separately routed to each of the four main buses; a diesel-generator for emergency supply; and supply-bus, and load-feeder circuit breakers. The arrangement of these elements is shown in DSAR P&ID Figure 8.1-1.
8.3.1.2 Description and Operation General The 4.16-kV system comprises four, outdoor transformers; nonsegregated bus duct supply connections separately routed to each of the four main buses; a diesel-generator for emergency supply; and supply-bus, and load-feeder circuit breakers. The arrangement of these elements is shown in DSAR P&ID Figure 8.1-1.
Buses 1A1 and 1A2 are normally connected to unit auxiliary transformers T1A-1 and T1A-2, respectively; these transformers are supplied at 22-kV from main transformer T1. Buses 1A3 and 1A4 are connected to, respectively, house service transformers T1A-3 and T1A-4 for normal supply, and diesel-generators D-1 and D-2 for emergency supply. Transformers T1A-3 and T1A-4 are supplied from the 161-kV system.
Buses 1A1 and 1A2 are normally connected to unit auxiliary transformers T1A-1 and T1A-2, respectively; these transformers are supplied at 22-kV from main transformer T1. Buses 1A3 and 1A4 are connected to, respectively, house service transformers T1A-3 and T1A-4 for normal supply, and diesel-generators D-1 and D-2 for emergency supply. Transformers T1A-3 and T1A-4 are supplied from the 161-kV system.
Buses 1A3 and 1A4 supply plant 4.16-kV loads and all 480-Volt loads through three, double-ended 480-Volt load centers, each with three bus sections.
Buses 1A3 and 1A4 supply plant 4.16-kV loads and all 480-Volt loads through three, double-ended 480-Volt load centers, each with three bus sections.
Line 30: Line 34:
The systems associated with bus 1A3 and 1A4 are operated as separate systems. Interlocks prevent interconnection of these systems at the 480V level.
The systems associated with bus 1A3 and 1A4 are operated as separate systems. Interlocks prevent interconnection of these systems at the 480V level.
Station lighting transformers T1C-3A and T1C-4A can be fed from either bus 1A3 or 1A4. Normally T1C-3A is fed from bus 1A3 and T1C-4A is fed from 1A4. Special situations may require that both transformers be fed from the same bus. Interlocks on the feeder breakers make this possible without paralleling 1A3 and 1A4.
Station lighting transformers T1C-3A and T1C-4A can be fed from either bus 1A3 or 1A4. Normally T1C-3A is fed from bus 1A3 and T1C-4A is fed from 1A4. Special situations may require that both transformers be fed from the same bus. Interlocks on the feeder breakers make this possible without paralleling 1A3 and 1A4.
All four 4.16kV buses can be supplied from either the 22kV or 161kV sources.
All four 4.16kV buses can be supplied from either the 22kV or 161kV sources.  


DSAR-8.3                         Information Use                             Page 4 of 11 Station Distribution                                                                 Rev. 1 As arranged, 4.16-kV buses 1A1 and 1A3, have access to either the generator auxiliary transformer (T1A-1) or the house service transformer (T1A-3), while 4.16-kV buses 1A2 and 1A4 have access to either the other generator auxiliary transformer (T1A-2) or the other house service transformer (T1A-4).
DSAR-8.3 Information Use Page 4 of 11 Station Distribution Rev. 1 As arranged, 4.16-kV buses 1A1 and 1A3, have access to either the generator auxiliary transformer (T1A-1) or the house service transformer (T1A-3), while 4.16-kV buses 1A2 and 1A4 have access to either the other generator auxiliary transformer (T1A-2) or the other house service transformer (T1A-4).
Automatic control circuits are provided for transfer of each of the four 4.16-kV buses from their preferred to the alternate source. The buses are arranged in pairs as shown in P&ID Figure 8.1-1. The preferred source for house service bus 1A3 is the alternate source for unit auxiliary bus 1A1, and vice versa. A similar reciprocal relationship applies for house service bus 1A4 and unit auxiliary bus 1A2. Automatic transfers are not provided that would parallel any two supply transformers, which would result in available short-circuit current in excess of the switchgear capacity.
Automatic control circuits are provided for transfer of each of the four 4.16-kV buses from their preferred to the alternate source. The buses are arranged in pairs as shown in P&ID Figure 8.1-1. The preferred source for house service bus 1A3 is the alternate source for unit auxiliary bus 1A1, and vice versa. A similar reciprocal relationship applies for house service bus 1A4 and unit auxiliary bus 1A2. Automatic transfers are not provided that would parallel any two supply transformers, which would result in available short-circuit current in excess of the switchgear capacity.
One mode of automatic transfer, (Slow transfer) from the preferred to the alternate source, remains after permanent cessation of power operations. 'Slow' transfer depends on decay of the transformer secondary voltage and load shed rotating equipment and applicable lighting loads of the affected bus prior to connection to the alternate source.
One mode of automatic transfer, (Slow transfer) from the preferred to the alternate source, remains after permanent cessation of power operations. 'Slow' transfer depends on decay of the transformer secondary voltage and load shed rotating equipment and applicable lighting loads of the affected bus prior to connection to the alternate source.
Slow transfer is initiated by transformer secondary undervoltage relays; completion of a transfer is automatically inhibited by the following:
Slow transfer is initiated by transformer secondary undervoltage relays; completion of a transfer is automatically inhibited by the following:
: a. No alternate source voltage;
: a.
: b. Uncleared fault on the transferred bus;
No alternate source voltage;
: c. Failure of the preferred source circuit breaker to open (alternate source breaker cannot close until a 'B' contact on the preferred source breaker closes);
: b.
: d. Manually.
Uncleared fault on the transferred bus;
: c.
Failure of the preferred source circuit breaker to open (alternate source breaker cannot close until a 'B' contact on the preferred source breaker closes);
: d.
Manually.
In the event of a loss of offsite power, both 4.16-kV buses 1A3 and 1A4 are disconnected from their normal and alternate supply sources. Load shedding of motor and selected lighting loads connected to 4.16-kV and 480-Volt buses is initiated by undervoltage relays. Diesel-Generators are manually connected and loaded.
In the event of a loss of offsite power, both 4.16-kV buses 1A3 and 1A4 are disconnected from their normal and alternate supply sources. Load shedding of motor and selected lighting loads connected to 4.16-kV and 480-Volt buses is initiated by undervoltage relays. Diesel-Generators are manually connected and loaded.
Automatic starting of Diesel-Generators is normally administratively disabled.
Automatic starting of Diesel-Generators is normally administratively disabled.  


DSAR-8.3                               Information Use                           Page 5 of 11 Station Distribution                                                                   Rev. 1 A 4.16-kV bus can be connected to both transformers during manual, hot bus transfer. The manual hot bus transfer has both transformers connected for a limited period of time. Either both generator auxiliary transformers or both house service transformers have the capability of carrying the full station service load. Under normal conditions the load is divided between the two transformer systems (two 22-kV/4.16-kV and two 161-kV/4.16-kV transformers).
DSAR-8.3 Information Use Page 5 of 11 Station Distribution Rev. 1 A 4.16-kV bus can be connected to both transformers during manual, hot bus transfer. The manual hot bus transfer has both transformers connected for a limited period of time. Either both generator auxiliary transformers or both house service transformers have the capability of carrying the full station service load. Under normal conditions the load is divided between the two transformer systems (two 22-kV/4.16-kV and two 161-kV/4.16-kV transformers).
The 4.16-kV Switchgear is rated at 4.76-kV maximum voltage, metal clad, with 1200 ampere (load) and 2000 ampere (bus feeder) circuit breakers. Bus 1A1 and 1A3 have a 350 MVA interrupting rating, 1A2 and 1A4 have a rating of 250 MVA interrupting.
The 4.16-kV Switchgear is rated at 4.76-kV maximum voltage, metal clad, with 1200 ampere (load) and 2000 ampere (bus feeder) circuit breakers. Bus 1A1 and 1A3 have a 350 MVA interrupting rating, 1A2 and 1A4 have a rating of 250 MVA interrupting.
Unit auxiliary transformers T1A-1 and T1A-2 are outdoor units rated for 12/13.44/17.9 MVA, OA/OA/FA, 22-4.16-kV, and have a nominal 6 percent impedance.
Unit auxiliary transformers T1A-1 and T1A-2 are outdoor units rated for 12/13.44/17.9 MVA, OA/OA/FA, 22-4.16-kV, and have a nominal 6 percent impedance.
Line 50: Line 58:
Should loss of offsite power occur, bus undervoltage relays on the 4.16-kV bus and undervoltage relays on the 480-V load centers operate auxiliary relays to trip bus loads.
Should loss of offsite power occur, bus undervoltage relays on the 4.16-kV bus and undervoltage relays on the 480-V load centers operate auxiliary relays to trip bus loads.
8.3.1.3 Design Analysis The four bus arrangement described above is used to provide a flexible reliable power supply to the Spent Fuel Pool and other supporting auxiliaries.
8.3.1.3 Design Analysis The four bus arrangement described above is used to provide a flexible reliable power supply to the Spent Fuel Pool and other supporting auxiliaries.
The worst case single failure in the plant auxiliary power system is a fault on 4.16-kV bus 1A3 or 1A4 that is not cleared automatically and cannot immediately be cleared manually. If bus 1A3 is de-energized, its associated 480 volt buses 1B3A, 1B3B and 1B3C can be energized via the 1A4 side providing proper 480 volt breaker lineups have been performed.
The worst case single failure in the plant auxiliary power system is a fault on 4.16-kV bus 1A3 or 1A4 that is not cleared automatically and cannot immediately be cleared manually. If bus 1A3 is de-energized, its associated 480 volt buses 1B3A, 1B3B and 1B3C can be energized via the 1A4 side providing proper 480 volt breaker lineups have been performed.  


DSAR-8.3                                 Information Use                             Page 6 of 11 Station Distribution                                                                       Rev. 1 A slow transfer from the 22-kV to the 161-kV provides sufficient dead time to avoid possible motor damage. Slow transfers also are arranged to prevent transfer of a fault or transfer to a dead alternate source.
DSAR-8.3 Information Use Page 6 of 11 Station Distribution Rev. 1 A slow transfer from the 22-kV to the 161-kV provides sufficient dead time to avoid possible motor damage. Slow transfers also are arranged to prevent transfer of a fault or transfer to a dead alternate source.
8.3.2     480-Volt System 8.3.2.1   Design Bases The system arrangement shown in DSAR P&ID Figure 8.1-1 is based on maintaining reliable power to the Spent Fuel Pool and supporting auxiliaries.
8.3.2 480-Volt System 8.3.2.1 Design Bases The system arrangement shown in DSAR P&ID Figure 8.1-1 is based on maintaining reliable power to the Spent Fuel Pool and supporting auxiliaries.
8.3.2.2   Description and Operation The 480-Volt system arrangement is shown in DSAR P&ID Figure 8.1-1. The main 480-Volt buses comprise three, double-ended load centers, each with three bus sections. The center bus section of each can be tied to either adjacent bus section, but not both if the adjacent sections are energized from their associated 4.16-kV/480-V transformers. This is prevented by electrical control circuit interlocked bus-tie circuit breakers. The normal alignment of the 480-Volt buses is shown on DSAR P&IDFIG 8.1-1.
8.3.2.2 Description and Operation The 480-Volt system arrangement is shown in DSAR P&ID Figure 8.1-1. The main 480-Volt buses comprise three, double-ended load centers, each with three bus sections. The center bus section of each can be tied to either adjacent bus section, but not both if the adjacent sections are energized from their associated 4.16-kV/480-V transformers. This is prevented by electrical control circuit interlocked bus-tie circuit breakers. The normal alignment of the 480-Volt buses is shown on DSAR P&IDFIG 8.1-1.
Each center bus section is normally connected to the "preferred" adjacent bus section by means of a normally closed bus-tie circuit breaker as indicated in Figure 8.4-1. Thus the center bus sections are each part of one of the two separate systems, starting with 4.16-kV main buses 1A3 and 1A4, where station loads are divided.
Each center bus section is normally connected to the "preferred" adjacent bus section by means of a normally closed bus-tie circuit breaker as indicated in Figure 8.4-1. Thus the center bus sections are each part of one of the two separate systems, starting with 4.16-kV main buses 1A3 and 1A4, where station loads are divided.
Each double-ended load center group is provided with two d-c control power feeders, one from each d-c system (see Section 8.3.4) and a manual transfer switch to ensure availability of control power.
Each double-ended load center group is provided with two d-c control power feeders, one from each d-c system (see Section 8.3.4) and a manual transfer switch to ensure availability of control power.
The six load center transformers are throat-connected, 1000/1,333 kVA, dry-type, AA/FA, 4,160-480-Volt, delta-delta units, and provided with surge protection on the 4.16-kV side. The air circuit breakers are of the stored energy type.
The six load center transformers are throat-connected, 1000/1,333 kVA, dry-type, AA/FA, 4,160-480-Volt, delta-delta units, and provided with surge protection on the 4.16-kV side. The air circuit breakers are of the stored energy type.
The Spent Fuel Pool Circulating Pump Motors are powered from MCC-3A2 and MCC-4C2 which are supplied from 480 V load centers. Other motor control centers are also supplying power to equipment in support of the Spent Fuel Pool Cooling and other plant auxiliaries.
The Spent Fuel Pool Circulating Pump Motors are powered from MCC-3A2 and MCC-4C2 which are supplied from 480 V load centers. Other motor control centers are also supplying power to equipment in support of the Spent Fuel Pool Cooling and other plant auxiliaries.  


DSAR-8.3                             Information Use                               Page 7 of 11 Station Distribution                                                                       Rev. 1 8.3.2.3 Design Analysis Nine 480-Volt bus sections, three with access to bus 1A3 for supply, three to bus 1A4, and the three swing buses align to either bus 1A3 or 1A4, provide the distribution of loads (see DSAR P&ID Figure 8.1-1).
DSAR-8.3 Information Use Page 7 of 11 Station Distribution Rev. 1 8.3.2.3 Design Analysis Nine 480-Volt bus sections, three with access to bus 1A3 for supply, three to bus 1A4, and the three swing buses align to either bus 1A3 or 1A4, provide the distribution of loads (see DSAR P&ID Figure 8.1-1).
Provision of a dual d-c control power feed-manual transfer switch for each load center minimizes the consequences of a failure in the d-c control power systems. The manual transfer switches are located at the load centers.
Provision of a dual d-c control power feed-manual transfer switch for each load center minimizes the consequences of a failure in the d-c control power systems. The manual transfer switches are located at the load centers.
Selective fault protection is used throughout the 480-Volt system.
Selective fault protection is used throughout the 480-Volt system.
Available fault current levels are within the circuit breakers' or breaker/starters' interrupting capability.
Available fault current levels are within the circuit breakers' or breaker/starters' interrupting capability.
8.3.3     Deleted 8.3.3.1 Deleted 8.3.3.2 Deleted 8.3.3.3 Deleted 8.3.4     DC Systems 8.3.4.1 Design Bases The d-c systems are designed as the basic sources of energy for plant control and instrumentation in most categories, and to operate without interruption during adverse environmental conditions listed and referenced as general design bases in Section 8.1.1.
8.3.3 Deleted 8.3.3.1 Deleted 8.3.3.2 Deleted 8.3.3.3 Deleted 8.3.4 DC Systems 8.3.4.1 Design Bases The d-c systems are designed as the basic sources of energy for plant control and instrumentation in most categories, and to operate without interruption during adverse environmental conditions listed and referenced as general design bases in Section 8.1.1.
The capacity of the storage batteries in the d-c system is adequate for the operation of all necessary control and instrumentation devices in the event all 480v power is lost. See Section 8.4.2 for further discussion.
The capacity of the storage batteries in the d-c system is adequate for the operation of all necessary control and instrumentation devices in the event all 480v power is lost. See Section 8.4.2 for further discussion.  


DSAR-8.3                             Information Use                             Page 8 of 11 Station Distribution                                                                   Rev. 1 8.3.4.2 Description and Operation The d-c systems are diagramed in DSAR P&ID Figure 8.1-1. Each of the two systems comprises a 58-cell storage battery with each battery rated at a nominal 2062 ampere - hours at the constant eight-hour discharge rate, a battery charger, main fuses, a main distribution switchboard with circuit breakers and switches, local distribution panels, and feeders. A third battery charger can be used as a spare and can be connected to either d-c system. Spare battery charger d-c circuit breakers are mechanically key interlocked to prevent paralleling main buses.
DSAR-8.3 Information Use Page 8 of 11 Station Distribution Rev. 1 8.3.4.2 Description and Operation The d-c systems are diagramed in DSAR P&ID Figure 8.1-1. Each of the two systems comprises a 58-cell storage battery with each battery rated at a nominal 2062 ampere - hours at the constant eight-hour discharge rate, a battery charger, main fuses, a main distribution switchboard with circuit breakers and switches, local distribution panels, and feeders. A third battery charger can be used as a spare and can be connected to either d-c system. Spare battery charger d-c circuit breakers are mechanically key interlocked to prevent paralleling main buses.
The battery chargers are solid-state, rated 400 Amperes and are designed for constant voltage operation up to a nominal 380 Amperes and have a current limiting characteristic beyond the nominal 380 Amperes.
The battery chargers are solid-state, rated 400 Amperes and are designed for constant voltage operation up to a nominal 380 Amperes and have a current limiting characteristic beyond the nominal 380 Amperes.
The switchboard circuit breakers are rated to interrupt expected fault current. Battery fuses, main panel supply and feeder circuit breakers, and local panel feeder circuit breakers and fuses provide selective fault protection.
The switchboard circuit breakers are rated to interrupt expected fault current. Battery fuses, main panel supply and feeder circuit breakers, and local panel feeder circuit breakers and fuses provide selective fault protection.
Line 74: Line 82:
Each of the two d-c power supply systems is provided with condition and performance instrumentation in the control room as follows:
Each of the two d-c power supply systems is provided with condition and performance instrumentation in the control room as follows:
On control room d-c distribution panels (AI-41A for d-c system 1, AI-41B for d-c system 2):
On control room d-c distribution panels (AI-41A for d-c system 1, AI-41B for d-c system 2):
: a. Battery ammeter (charging current or discharge current)
: a.
: b. Battery voltmeter
Battery ammeter (charging current or discharge current)
: c. Main d-c bus voltmeter
: b.
: d. Battery charger, voltmeter and ammeter
Battery voltmeter
: e. Main d-c ground indication
: c.
: f. Ground Fault Voltmeters
Main d-c bus voltmeter
: d.
Battery charger, voltmeter and ammeter
: e.
Main d-c ground indication
: f.
Ground Fault Voltmeters  


DSAR-8.3                                 Information Use                             Page 9 of 11 Station Distribution                                                                       Rev. 1 On main control boards:
DSAR-8.3 Information Use Page 9 of 11 Station Distribution Rev. 1 On main control boards:
: a. Battery charger failure monitoring annunciator point for:
: a.
Battery charger failure monitoring annunciator point for:
: 1. Loss of a-c input
: 1. Loss of a-c input
: 2. Low d-c output voltage
: 2. Low d-c output voltage
Line 88: Line 103:
: 4. Charger failure (low output current)
: 4. Charger failure (low output current)
DC System Annunciation.
DC System Annunciation.
: 1. An undervoltage relay monitors the battery and bus voltage and will sound an alarm in the control room on low voltage.
: 1.
An undervoltage relay monitors the battery and bus voltage and will sound an alarm in the control room on low voltage.
Ground detection monitors both positive and negative buses for ground and will sound a separate alarm in the control room on detection of a single bus ground.
Ground detection monitors both positive and negative buses for ground and will sound a separate alarm in the control room on detection of a single bus ground.
System instrumentation/annunciation, together with administrative control will ensure that any abnormal condition, should it arise, will be detected and corrective action taken.
System instrumentation/annunciation, together with administrative control will ensure that any abnormal condition, should it arise, will be detected and corrective action taken.
8.3.4.3   Design Analysis Each switchgear section is provided with two feeders, one from d-c bus 1 and one from d-c bus 2, and a manual transfer switch, see P&ID Figure 8.1-1. Similar provisions are made for other essential control panels.
8.3.4.3 Design Analysis Each switchgear section is provided with two feeders, one from d-c bus 1 and one from d-c bus 2, and a manual transfer switch, see P&ID Figure 8.1-1. Similar provisions are made for other essential control panels.
8.3.5     Instrument AC System 8.3.5.1   Design Bases The a-c instrument system is designed to function without interruption in the event of natural disasters cited in Section 8.1.1.
8.3.5 Instrument AC System 8.3.5.1 Design Bases The a-c instrument system is designed to function without interruption in the event of natural disasters cited in Section 8.1.1.
Other design requirements include:
Other design requirements include:
: a. Deleted
: a.
: b. Inverter voltage regulation and total harmonic content contribution.
Deleted
: c. Inverter synchronous operation with the 480-V system as the reference source with automatic reversion to internal reference if the synchronous reference source is lost or if the reference source frequency is outside of the desired range.
: b.
Inverter voltage regulation and total harmonic content contribution.
: c.
Inverter synchronous operation with the 480-V system as the reference source with automatic reversion to internal reference if the synchronous reference source is lost or if the reference source frequency is outside of the desired range.  


DSAR-8.3                               Information Use                             Page 10 of 11 Station Distribution                                                                     Rev. 1 8.3.5.2 Description and Operation The a-c instrument system is comprised of seven separate buses.
DSAR-8.3 Information Use Page 10 of 11 Station Distribution Rev. 1 8.3.5.2 Description and Operation The a-c instrument system is comprised of seven separate buses.
Each instrument bus is supplied by a separate solid-state inverter from the d-c system, except for Instrument Bus #3 (IB-3) which is supplied from an independent uninterruptible power supply (IB-3U).
Each instrument bus is supplied by a separate solid-state inverter from the d-c system, except for Instrument Bus #3 (IB-3) which is supplied from an independent uninterruptible power supply (IB-3U).
As shown in Figure 8.1-1, instrument buses A, C, and 1 are supplied from d-c bus 1 and B, D, and 2 are supplied from d-c bus 2.
As shown in Figure 8.1-1, instrument buses A, C, and 1 are supplied from d-c bus 1 and B, D, and 2 are supplied from d-c bus 2.
Line 106: Line 125:
Instrument buses A and C, supplied from d-c bus 1, have a manual bus tie for use only when an inverter is out of service for maintenance. Buses B and D, supplied from d-c bus 2, are similarly arranged. Maintenance activities can also be performed on an inverter by transferring its instrument bus to its associated swing inverter without having to manually tie the instrument buses together.
Instrument buses A and C, supplied from d-c bus 1, have a manual bus tie for use only when an inverter is out of service for maintenance. Buses B and D, supplied from d-c bus 2, are similarly arranged. Maintenance activities can also be performed on an inverter by transferring its instrument bus to its associated swing inverter without having to manually tie the instrument buses together.
Each of the instrument inverters which supply power to the instrument buses also have a bypass source which supplies power to the bus if there is an inverter failure or inverter maintenance is necessary. In the event of inverter failure, the load on the inverter is automatically transferred to the bypass source. The bypass source is supplied with power from the 480 volt distribution system which is an interruptible source.
Each of the instrument inverters which supply power to the instrument buses also have a bypass source which supplies power to the bus if there is an inverter failure or inverter maintenance is necessary. In the event of inverter failure, the load on the inverter is automatically transferred to the bypass source. The bypass source is supplied with power from the 480 volt distribution system which is an interruptible source.
In addition to the bypass transformers, inverters 1 and 2 each have a dedicated test transformer which can supply convenience power to instrument buses 1 and 2, respectively, when the normal inverter/bypass power supply is unavailable.
In addition to the bypass transformers, inverters 1 and 2 each have a dedicated test transformer which can supply convenience power to instrument buses 1 and 2, respectively, when the normal inverter/bypass power supply is unavailable.  


DSAR-8.3                             Information Use                             Page 11 of 11 Station Distribution                                                                   Rev. 1 8.3.5.3 Design Analysis Each inverter reverts to an internal frequency reference when the system reference synchronization voltage source is lost or if the reference source frequency is outside of the desired range. This is an expected condition when the 480 Volt system is powered from the emergency diesel generators.
DSAR-8.3 Information Use Page 11 of 11 Station Distribution Rev. 1 8.3.5.3 Design Analysis Each inverter reverts to an internal frequency reference when the system reference synchronization voltage source is lost or if the reference source frequency is outside of the desired range. This is an expected condition when the 480 Volt system is powered from the emergency diesel generators.
The bypass transformers provide the alternate AC to the instrument buses and serve to supply any larger current demands due to start up or other overloads. The transformers act as an isolation to instrument buses and regulate the output voltage to reduce disturbances caused by power system faults and motor starting conditions associated with the 480 V distribution system. A bypass transformer is only connected to the associated instrument bus when the associated inverter static switch is operating in bypass mode..}}
The bypass transformers provide the alternate AC to the instrument buses and serve to supply any larger current demands due to start up or other overloads. The transformers act as an isolation to instrument buses and regulate the output voltage to reduce disturbances caused by power system faults and motor starting conditions associated with the 480 V distribution system. A bypass transformer is only connected to the associated instrument bus when the associated inverter static switch is operating in bypass mode..}}

Latest revision as of 20:35, 10 December 2024

Independent Spent Fuel Storage Installation Updated Decommissioning Safety Analysis Report, DSAR-8.3., Rev. 1, Electrical Systems, Station Distribution
ML20170A411
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Site: Fort Calhoun, 07100256  Omaha Public Power District icon.png
Issue date: 04/30/2020
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Page 1 of 11 DSAR-8.3 Electrical Systems Station Distribution Rev 1 Safety Classification:

Usage Level:

Safety Information Change No.:

EC 69625 Reason for Change:

This section is being updated as part of the design and licensing basis reconstitution project.

Preparer:

M.Bakhit Fort Calhoun Station

DSAR-8.3 Information Use Page 2 of 11 Station Distribution Rev. 1 Table of Contents 8.3 Station Distribution.............................................................................................................3 8.3.1 4.16-kV System.......................................................................................................3 8.3.1.1 Design Bases..........................................................................................3 8.3.1.2 Description and Operation.......................................................................3 8.3.1.3 Design Analysis.......................................................................................5 8.3.2 480-Volt System......................................................................................................6 8.3.2.1 Design Bases..........................................................................................6 8.3.2.2 Description and Operation.......................................................................6 8.3.2.3 Design Analysis.......................................................................................7 8.3.3 Deleted....................................................................................................................7 8.3.3.1 Deleted....................................................................................................7 8.3.3.2 Deleted....................................................................................................7 8.3.3.3 Deleted....................................................................................................7 8.3.4 DC Systems............................................................................................................7 8.3.4.1 Design Bases..........................................................................................7 8.3.4.2 Description and Operation.......................................................................8 8.3.4.3 Design Analysis.......................................................................................9 8.3.5 Instrument AC System............................................................................................9 8.3.5.1 Design Bases..........................................................................................9 8.3.5.2 Description and Operation..................................................................... 10 8.3.5.3 Design Analysis..................................................................................... 11

DSAR-8.3 Information Use Page 3 of 11 Station Distribution Rev. 1 8.3 Station Distribution 8.3.1 4.16-kV System 8.3.1.1 Design Bases The 4.16-kV system was designed to function under the environmental conditions defined in Section 8.1.1, to provide power to the Spent Fuel Pool and other supporting auxiliaries.

8.3.1.2 Description and Operation General The 4.16-kV system comprises four, outdoor transformers; nonsegregated bus duct supply connections separately routed to each of the four main buses; a diesel-generator for emergency supply; and supply-bus, and load-feeder circuit breakers. The arrangement of these elements is shown in DSAR P&ID Figure 8.1-1.

Buses 1A1 and 1A2 are normally connected to unit auxiliary transformers T1A-1 and T1A-2, respectively; these transformers are supplied at 22-kV from main transformer T1. Buses 1A3 and 1A4 are connected to, respectively, house service transformers T1A-3 and T1A-4 for normal supply, and diesel-generators D-1 and D-2 for emergency supply. Transformers T1A-3 and T1A-4 are supplied from the 161-kV system.

Buses 1A3 and 1A4 supply plant 4.16-kV loads and all 480-Volt loads through three, double-ended 480-Volt load centers, each with three bus sections.

The double-ended 480-Volt load centers permit feeding of the 480-V station auxiliary loads from either bus 1A3 or 1A4. The normal alignment for the 480-Volt load centers is shown in DSAR-FIG 8.1-1.

The systems associated with bus 1A3 and 1A4 are operated as separate systems. Interlocks prevent interconnection of these systems at the 480V level.

Station lighting transformers T1C-3A and T1C-4A can be fed from either bus 1A3 or 1A4. Normally T1C-3A is fed from bus 1A3 and T1C-4A is fed from 1A4. Special situations may require that both transformers be fed from the same bus. Interlocks on the feeder breakers make this possible without paralleling 1A3 and 1A4.

All four 4.16kV buses can be supplied from either the 22kV or 161kV sources.

DSAR-8.3 Information Use Page 4 of 11 Station Distribution Rev. 1 As arranged, 4.16-kV buses 1A1 and 1A3, have access to either the generator auxiliary transformer (T1A-1) or the house service transformer (T1A-3), while 4.16-kV buses 1A2 and 1A4 have access to either the other generator auxiliary transformer (T1A-2) or the other house service transformer (T1A-4).

Automatic control circuits are provided for transfer of each of the four 4.16-kV buses from their preferred to the alternate source. The buses are arranged in pairs as shown in P&ID Figure 8.1-1. The preferred source for house service bus 1A3 is the alternate source for unit auxiliary bus 1A1, and vice versa. A similar reciprocal relationship applies for house service bus 1A4 and unit auxiliary bus 1A2. Automatic transfers are not provided that would parallel any two supply transformers, which would result in available short-circuit current in excess of the switchgear capacity.

One mode of automatic transfer, (Slow transfer) from the preferred to the alternate source, remains after permanent cessation of power operations. 'Slow' transfer depends on decay of the transformer secondary voltage and load shed rotating equipment and applicable lighting loads of the affected bus prior to connection to the alternate source.

Slow transfer is initiated by transformer secondary undervoltage relays; completion of a transfer is automatically inhibited by the following:

a.

No alternate source voltage;

b.

Uncleared fault on the transferred bus;

c.

Failure of the preferred source circuit breaker to open (alternate source breaker cannot close until a 'B' contact on the preferred source breaker closes);

d.

Manually.

In the event of a loss of offsite power, both 4.16-kV buses 1A3 and 1A4 are disconnected from their normal and alternate supply sources. Load shedding of motor and selected lighting loads connected to 4.16-kV and 480-Volt buses is initiated by undervoltage relays. Diesel-Generators are manually connected and loaded.

Automatic starting of Diesel-Generators is normally administratively disabled.

DSAR-8.3 Information Use Page 5 of 11 Station Distribution Rev. 1 A 4.16-kV bus can be connected to both transformers during manual, hot bus transfer. The manual hot bus transfer has both transformers connected for a limited period of time. Either both generator auxiliary transformers or both house service transformers have the capability of carrying the full station service load. Under normal conditions the load is divided between the two transformer systems (two 22-kV/4.16-kV and two 161-kV/4.16-kV transformers).

The 4.16-kV Switchgear is rated at 4.76-kV maximum voltage, metal clad, with 1200 ampere (load) and 2000 ampere (bus feeder) circuit breakers. Bus 1A1 and 1A3 have a 350 MVA interrupting rating, 1A2 and 1A4 have a rating of 250 MVA interrupting.

Unit auxiliary transformers T1A-1 and T1A-2 are outdoor units rated for 12/13.44/17.9 MVA, OA/OA/FA, 22-4.16-kV, and have a nominal 6 percent impedance.

The house service transformers ratings are identical except that the voltage rating is 161-4.16 kV and the nominal impedance is 8 percent. With these transformer ratings the plant can be operated at maximum capacity (worst case plant loads) with only two transformers in service. One transformer must be associated with buses 1A1 and 1A3 and one transformer must be associated with buses 1A2 and 1A4.

Relay protection follows standard power plant practices in most respects.

Should loss of offsite power occur, bus undervoltage relays on the 4.16-kV bus and undervoltage relays on the 480-V load centers operate auxiliary relays to trip bus loads.

8.3.1.3 Design Analysis The four bus arrangement described above is used to provide a flexible reliable power supply to the Spent Fuel Pool and other supporting auxiliaries.

The worst case single failure in the plant auxiliary power system is a fault on 4.16-kV bus 1A3 or 1A4 that is not cleared automatically and cannot immediately be cleared manually. If bus 1A3 is de-energized, its associated 480 volt buses 1B3A, 1B3B and 1B3C can be energized via the 1A4 side providing proper 480 volt breaker lineups have been performed.

DSAR-8.3 Information Use Page 6 of 11 Station Distribution Rev. 1 A slow transfer from the 22-kV to the 161-kV provides sufficient dead time to avoid possible motor damage. Slow transfers also are arranged to prevent transfer of a fault or transfer to a dead alternate source.

8.3.2 480-Volt System 8.3.2.1 Design Bases The system arrangement shown in DSAR P&ID Figure 8.1-1 is based on maintaining reliable power to the Spent Fuel Pool and supporting auxiliaries.

8.3.2.2 Description and Operation The 480-Volt system arrangement is shown in DSAR P&ID Figure 8.1-1. The main 480-Volt buses comprise three, double-ended load centers, each with three bus sections. The center bus section of each can be tied to either adjacent bus section, but not both if the adjacent sections are energized from their associated 4.16-kV/480-V transformers. This is prevented by electrical control circuit interlocked bus-tie circuit breakers. The normal alignment of the 480-Volt buses is shown on DSAR P&IDFIG 8.1-1.

Each center bus section is normally connected to the "preferred" adjacent bus section by means of a normally closed bus-tie circuit breaker as indicated in Figure 8.4-1. Thus the center bus sections are each part of one of the two separate systems, starting with 4.16-kV main buses 1A3 and 1A4, where station loads are divided.

Each double-ended load center group is provided with two d-c control power feeders, one from each d-c system (see Section 8.3.4) and a manual transfer switch to ensure availability of control power.

The six load center transformers are throat-connected, 1000/1,333 kVA, dry-type, AA/FA, 4,160-480-Volt, delta-delta units, and provided with surge protection on the 4.16-kV side. The air circuit breakers are of the stored energy type.

The Spent Fuel Pool Circulating Pump Motors are powered from MCC-3A2 and MCC-4C2 which are supplied from 480 V load centers. Other motor control centers are also supplying power to equipment in support of the Spent Fuel Pool Cooling and other plant auxiliaries.

DSAR-8.3 Information Use Page 7 of 11 Station Distribution Rev. 1 8.3.2.3 Design Analysis Nine 480-Volt bus sections, three with access to bus 1A3 for supply, three to bus 1A4, and the three swing buses align to either bus 1A3 or 1A4, provide the distribution of loads (see DSAR P&ID Figure 8.1-1).

Provision of a dual d-c control power feed-manual transfer switch for each load center minimizes the consequences of a failure in the d-c control power systems. The manual transfer switches are located at the load centers.

Selective fault protection is used throughout the 480-Volt system.

Available fault current levels are within the circuit breakers' or breaker/starters' interrupting capability.

8.3.3 Deleted 8.3.3.1 Deleted 8.3.3.2 Deleted 8.3.3.3 Deleted 8.3.4 DC Systems 8.3.4.1 Design Bases The d-c systems are designed as the basic sources of energy for plant control and instrumentation in most categories, and to operate without interruption during adverse environmental conditions listed and referenced as general design bases in Section 8.1.1.

The capacity of the storage batteries in the d-c system is adequate for the operation of all necessary control and instrumentation devices in the event all 480v power is lost. See Section 8.4.2 for further discussion.

DSAR-8.3 Information Use Page 8 of 11 Station Distribution Rev. 1 8.3.4.2 Description and Operation The d-c systems are diagramed in DSAR P&ID Figure 8.1-1. Each of the two systems comprises a 58-cell storage battery with each battery rated at a nominal 2062 ampere - hours at the constant eight-hour discharge rate, a battery charger, main fuses, a main distribution switchboard with circuit breakers and switches, local distribution panels, and feeders. A third battery charger can be used as a spare and can be connected to either d-c system. Spare battery charger d-c circuit breakers are mechanically key interlocked to prevent paralleling main buses.

The battery chargers are solid-state, rated 400 Amperes and are designed for constant voltage operation up to a nominal 380 Amperes and have a current limiting characteristic beyond the nominal 380 Amperes.

The switchboard circuit breakers are rated to interrupt expected fault current. Battery fuses, main panel supply and feeder circuit breakers, and local panel feeder circuit breakers and fuses provide selective fault protection.

The systems are ungrounded and provided with ground detectors and alarms.

During normal operation, the battery charger floats on the bus, supplying d-c load demand up to maximum charger capacity, and at the same time keeps the battery fully charged. The battery assists in meeting peak demands greater than charger capacity. The charger is also used for applying an equalizing charge to the battery.

Each of the two d-c power supply systems is provided with condition and performance instrumentation in the control room as follows:

On control room d-c distribution panels (AI-41A for d-c system 1, AI-41B for d-c system 2):

a.

Battery ammeter (charging current or discharge current)

b.

Battery voltmeter

c.

Main d-c bus voltmeter

d.

Battery charger, voltmeter and ammeter

e.

Main d-c ground indication

f.

Ground Fault Voltmeters

DSAR-8.3 Information Use Page 9 of 11 Station Distribution Rev. 1 On main control boards:

a.

Battery charger failure monitoring annunciator point for:

1. Loss of a-c input
2. Low d-c output voltage
3. High d-c output voltage
4. Charger failure (low output current)

DC System Annunciation.

1.

An undervoltage relay monitors the battery and bus voltage and will sound an alarm in the control room on low voltage.

Ground detection monitors both positive and negative buses for ground and will sound a separate alarm in the control room on detection of a single bus ground.

System instrumentation/annunciation, together with administrative control will ensure that any abnormal condition, should it arise, will be detected and corrective action taken.

8.3.4.3 Design Analysis Each switchgear section is provided with two feeders, one from d-c bus 1 and one from d-c bus 2, and a manual transfer switch, see P&ID Figure 8.1-1. Similar provisions are made for other essential control panels.

8.3.5 Instrument AC System 8.3.5.1 Design Bases The a-c instrument system is designed to function without interruption in the event of natural disasters cited in Section 8.1.1.

Other design requirements include:

a.

Deleted

b.

Inverter voltage regulation and total harmonic content contribution.

c.

Inverter synchronous operation with the 480-V system as the reference source with automatic reversion to internal reference if the synchronous reference source is lost or if the reference source frequency is outside of the desired range.

DSAR-8.3 Information Use Page 10 of 11 Station Distribution Rev. 1 8.3.5.2 Description and Operation The a-c instrument system is comprised of seven separate buses.

Each instrument bus is supplied by a separate solid-state inverter from the d-c system, except for Instrument Bus #3 (IB-3) which is supplied from an independent uninterruptible power supply (IB-3U).

As shown in Figure 8.1-1, instrument buses A, C, and 1 are supplied from d-c bus 1 and B, D, and 2 are supplied from d-c bus 2.

Inverters A, B, C, D and Swing Inverters EE-8T and EE-8U are rated 7.5 KVA at 0.8 power factor, lagging at 120-volts +/- 2 percent, single phase.

Inverters 1 and 2 are rated 10 KVA at 0.8 power factor, lagging at 120-volts +/- 2 percent, single phase.

All instrument buses provide annunciation in the main control room upon detection of low bus voltage. Each inverter has its own annunciator point in the control room which is actuated when the inverter is in an off-normal condition.

Instrument buses A and C, supplied from d-c bus 1, have a manual bus tie for use only when an inverter is out of service for maintenance. Buses B and D, supplied from d-c bus 2, are similarly arranged. Maintenance activities can also be performed on an inverter by transferring its instrument bus to its associated swing inverter without having to manually tie the instrument buses together.

Each of the instrument inverters which supply power to the instrument buses also have a bypass source which supplies power to the bus if there is an inverter failure or inverter maintenance is necessary. In the event of inverter failure, the load on the inverter is automatically transferred to the bypass source. The bypass source is supplied with power from the 480 volt distribution system which is an interruptible source.

In addition to the bypass transformers, inverters 1 and 2 each have a dedicated test transformer which can supply convenience power to instrument buses 1 and 2, respectively, when the normal inverter/bypass power supply is unavailable.

DSAR-8.3 Information Use Page 11 of 11 Station Distribution Rev. 1 8.3.5.3 Design Analysis Each inverter reverts to an internal frequency reference when the system reference synchronization voltage source is lost or if the reference source frequency is outside of the desired range. This is an expected condition when the 480 Volt system is powered from the emergency diesel generators.

The bypass transformers provide the alternate AC to the instrument buses and serve to supply any larger current demands due to start up or other overloads. The transformers act as an isolation to instrument buses and regulate the output voltage to reduce disturbances caused by power system faults and motor starting conditions associated with the 480 V distribution system. A bypass transformer is only connected to the associated instrument bus when the associated inverter static switch is operating in bypass mode..

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