ML19253B812
| ML19253B812 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 10/17/1979 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Gammill W Office of Nuclear Reactor Regulation |
| References | |
| TAC-10968, NUDOCS 7910220270 | |
| Download: ML19253B812 (24) | |
Text
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SACRAMENTO MUNICIPAL UTILITY DISTRICT O 6201 s street, eox 15830, sacramento, Califomia 95813; (916) 45i o211 October 17, 1979 Mr. William Gammill Acting Assistant Director for Operating Reactors Projects Division of Operating Reactors U.S. Nuclear Regulatory Comission Washington,'D.C.
20555
Dear Mr. Gammill:
The August 8,1979, letter from the NRC to all Power Reactor Licensees (except Humbolt Bay) requested:
1.
A verification by analysis of the adequacy of Rancho Seco's offsite power system and the onsite electrical distribution system.
2.
A verification, by test, of the adequacy of 9,ancho Seco's offsite power system and the onsite electrical distribution system.
3.
A review of Rancho Seco's electrical power supply system to determine if there are any conditions which could result in the simultanecus or consequential 1oss of both required cir-cuits to the offsite network to determine if any potential exists for violation of GDC-17 in the regard.
4.
Immediate remedial action and prompt notification of the Comission with written followup in the event of a violation or patential violation of GDC-17 or voltage requirements of safety loads.
The responses to these requests are listed below:
1.
The analysis of Rancho Seco's offsite power system and the on-site electrical distribution system indicates that the District's existir.g systems will be adequate, with a normal plant line-up, down to the minimum expected switchyard voltage of 214ky when the mcdifications listed below are implemented:
a.
Change the leading sequence of the diesel generator roon M\\g supply and exhaust fans from Block two to Block three (Table 1).
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Mr. W. Gammill October 16, 1979 b.
Change the setpoint on tne existirg inverse time under-e voltage relays.
c.
Chaage the setpoint of the existing overvoltage relays.
d.
Modify plant operating procedures and technical specifi-cations to include operator responses and limiting con-ditions for operation for degraded voltage conditions.
A discussion of each modification is included in the response to guidelines contained in Enclosure I. The applicable guideline for each mod-ification is listed below:
Modifications Reference Guideline a
9 b
10 c
11 d
6 The above modifications will insure the adequacy of the Rancho Seco's offsite power system and the onsite electrical distribution system to supply safety-related loads under the conditions descrii ed in Encicsure I of this letter.
2.
The District's method of determining the adequacy of the offsite power system and onsite electrical system is based on a combination of test data and analysis.
The load data for the Class IE 4.16ky system and safety motors greater than 60 hp was based on actual field measurements (under simulated accident conditions, if applicable). The impedance data for transformers was based on the factory test results.
If test data was not available, the data used in the ayalysis was based on conservative engineering assumptions.
Refer to Enclosure I Response to Guideline 13 for a discussion of the assumptions made in the analysis.
The analytical re:ults were obtained using a computer load flow program.
The program has been checked to verify its accuracy.
It solves nodal admittance network equations by the accelerated Gauss-Seidel method.
A single full scale system test will not provide sufficient data to justify or verify the analytical methods and assumptions used in the analysis.
It is not practical and in scme cases not possible to simultaneously produce, in a test, all the conservative assumptions made in the analysis.
Listed be-low are three examples of assumptions made in the analysis that are impractical to implement in a test:
a.
The analysis assumes 214kv in the Rancho Seco switchyard.
The normal operating voltage range for the switchyara is 221kv to 236ky.
The start-up transformers are operating at the maximum tap and the District cannot lower the switchyard voltage to 214kv without seriously effecting the grid.
4 1150 382
- Mr. W. Gamill October 16, 1979 b.
The analysis assumes full operating load on the non class IE buses. The test would have to be run with the unit shut-down.. In this condition it is not possible to obtain full load on the non-safety related equipment.
For example, the concensate pumps would be operating at miniflow conditions instead of rated flow and load assumed in the analysis.
c.
The analysis assumes all safety related loads are operating at maximum design conditions encountered during a loss of coolant accident (LOCA). The upper dome air circulators and the reactor building emergency air coolers would be operating during a test at loads less than the load assumed in the analysis since the reactor building atmosphere would not be at a LOCA condition.
Therefore, it is not practical to perform a test at the conditions assumed in the analysis. The use of a proven computer program with actual measured test data combined with conservative assumptions provide the District with adequate assurance that the offsite power system and onsite distribution systems are adequate.
3.
The District has completed a partial review of Rancho Seco's electrical pcwer mpply for compliance to GDC-17.
The cases analyzed indicated
' hat the District s electrical power supply system is in compliance with GDC-17.
The District is still reviewing the possibility and consequences of a tower failure. The results of this review will be forwarded to the NRC upon its completion.
For information on the analysis performed for compliance to GDC-17 refer to Enclosure II of this letter.
4.
The District is taking imediate remedial action to implement the required modifications to insure operai. ion of safety equipment within the proper voltage range. Modifications a, b, and c will be completed by Novem-ber 5, 1979.
Completing these modifications will insure that the safety loads are adequetely protected for the maximum or minimum expected voltage. Modifi-cation (d) will be completed within 14 days after the District receives NRC approval.
Enclosure I of this letter is the District's response to the Guidelines contained in Enclosure 2 of William Gammill to Power Reactor Licensee's letter dated August 8, 1979.
Enclosure II of this letter is an evaluation of the District's offsite power supply system for compliance to GDC-17.
Sincerely yours, b
h$Y ohn J. Mattimoe Assistant General Manager and Chief Engineer 1150 083 Enclosures
ENCLOSURE I Response to Guidelines contained In Enclosure 2 of NRC's William Gamill to Power Reactor Licensees' letter dated August 8, 1979 g.
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Listed below is a response to each guideline listed in Enclosure 2
" Guidelines for Voltage Drop Calculations" of NRC's, William Gammill to Power Reactor Licensees, letter dated August 8, 1979.
GUIDELINE #1 Separate analyses should be performed assuming the power source to safety buses is (a) the unit auxiliary transformer; (b) the start-up trans-former; and (c) other available connections to the offsite network one by one assuming the need for electric power is initiated by (1) an anticipated trans-ient (e.g., unit trip) or (2) an accident, whichever presents the largest load demand situat'on.
RESPONSE TO GUIDELINE #1 The Rancho Seco electrical power system is described by the attached singlelinediagram(Sketch 1).
The District's analysis was performed assuming the power source for the safety buses was obtt'ned with following plant configuration (Case 1 is the normal operating configuration).
The District's analysis was performed assuming the power source for the safety buses was obtained with the following plant configurations.
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Case Description Reference Sketch 1A Bus 4A on start-up transformer #1 2
IB Bus 48 on start-up transformer #2 3
2 Bus 4A and 48 on start-up transformer #1 4
3 Bus 4A and 4B on start-up transformer #2 5
4A Bus 4A on start-up transformer #2 6
4B Bus 48 on start-up transformer #1 7
The unit auxiliary transformers are not an available source for the safety buses, and the above cases are all the connections available to the safety buses from the offsite network.
The transient assumed in the analysis is a loss of coolant accident (LOCA) with the reactor at 100 percent power coincident with a turbine-generator trip and a safety features actuation signal (SFAS) to both redundant safety systems. This transient produces the maximum load on the start-up transformers.
A turbine-generator trip will place non-safety buses 6A and 6B on start-up transformer 41 and non-safety buses 4C, 40, 4E1 and 4E2 on start-up transformer #2.
GUIDELINE #2 For multi-unit stations a separate analysis should be performed for each unit assuming (1) an accident in the unit being analyzed and simultaneous shutdown of all other units at that station; or (2) an anticipated transient in the unit being analyzed (e.g., unit trip) and simultaneous shutdown of all other units at that station, whichever presents the largest load demand situation.
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' 2-Enclosure I RESPONSE TO GUIDELINE #2 This guideline is not applicable to Rancho Seco.
Rancho Seco is a single unit station.
GUIDELINE #3 All actions the electric power system is designed to automatically initiate should be assumed to occur as designed (e.g., automatic bulk or sequential loading or automatic transfers of bulk loads from one transformer to another).
Included should be consideration of starting of large non-safety loads (e.g., condensate pumps).
RESPONSE TO GUIDELINE #3 The District's analysis assumed the following automatic actions occur coincident with the LOCA/ turbine-generator trip:
(a) Buses 6A and 6B transfer from unit auxiliary transformer #1 to start-up transformer 12.
(b) Buses 4C, 4D, 4E1 and 4E2 transfer from unit auxiliary trans-former #2 to start-up transformer #2.
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(c) A stand-by condensate pump is automatically started.
(d) The safety buses are sequentially loaded.
The loading sequence is indicated in Table 1.
Time zero is when the SFAS signal is received.
GUIDELINE #4 Manual load shedding should not be assumed.
RESPONSE TO GUIDELINE #4 Manual. load shedding was not assumed in the District's analysis.
GUIDELINE d5 For each event analyzed, the maximum load necessitated by the event and the mode of operation of plant at the time of event should be assumed in addition to all loads caused by expected automatic actions and manual actions permitted by administrative procedures.
RESPONSE TO GUIDELINE #5 The events the District analyzed provided the maximum load on the start-up transformers.
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Enclosure I.
The analysis assumed automatic starting of a stand-by condensate pump and.~ safety equipment due to an SFAS signal. The safety equipment automatic loading sequence is indicated in Table I.
It was assumed that the auxiliary feedwater pump motors were manually started after completion of the automatic sequential loading. The starting of these motors is an action permitted by administrative procedures.
GUIDELINE d6 The voltage at the tenninals of each safety load should be calculated based on the above listed considerations and assumptions and based on the assumption that the grid voltage is at the " minimum expected value". The
" minimum expected value" should be selected based on the least of the following:
a.
The minimum steady-state voltage experienced at the connection to the offsite circuit.
b.
The minimum voltage expected at the connection to the offsite circuit due to contingency plans which may result in reduced voltage from this grid.
c.
The minimum predicted grid voltage from grid stability analysis (e.g., load flow studies).
In the report to NRC on this matter the licensee should state planned actions, including any proposed " Limiting Conditions for Operation" for Technical Specifications, in response to experiencing voltage at the connection to the offsite circuit which is less than the " minimum expected value". A copy of the plant procedure in this regard should be provided.
RESPONSE TO GUIDELINE d6 The " minimum expected value" cf the grid voltage is 214kv and is based on the minimum steady-state voltage experienced at the connection to the offsite circuit.
The value of the voltages at the safety buses at the most distant (electrically) load during.this condition is shown on Sketches 2 through 7 for the cases the District analyzed.
The District is considering " Limiting Conditions for Operation" for the Technical Specifications similar to the paragraphs listed below:
a.
The reactor shall not be brought critical unless the switchyard voltage is greater than 216kv.
b.
If the switchyard voltage is equal to or less than 216kv, power operation may continue for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
If the switchyard voltage is not above 216kv within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the unit shall be placed in the cold shutdown condition.
If the switchyard voltage is re-stored to greater than 216kv unrestricted plant operation may be resumed.
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Enclosure I The District plans an operating procedure that will incorporate the following logic:
If the switchyard voltage is below 216kv both diesels will be started and plant operation may continue for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
If the voltage is not restored to greater than 216kv within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the unit will be placed in a cold shutdown condition.
If the voltage is restored to greater than 216kv within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, unrestricted plant operation may continue.
If both diesels do not start, the plant will be placed in a cold shutdown condition.
The District will supply the NRC a copy of the procedure within 14 days of approval by the NRC of the above logic.
GUIDELINE #7 The voltage analysis should include documentation for each condition analyzed of the voltage at the input and output of each transformer and at each intermediate bus between.the connection to the offsite circuit and the terminals of each safety load.
RESPONSE TO GUIDELINE #7 Sketches.2-7 indicate the voltages at each. intermediate bus between the connection to the offsite circuit and the terminals of the safety loads
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with the lowest steady state voltage.
GUIDELINE #8 The analysis should document the voltage setpoint and any inherent or adjustable (with nominal setting) time delay for relays which (1) initiate or execute automatic transfer of loads from one source to another; (2) initiate or execute automatic load shedding; or (3) initiate or execute automatic load sequencing.
RESPONSE TO GUIDELINE #8 The District has an overvoltage and undervoltage trip relay which will (1) initiate an automatic transfer of the safety buses from the offsite power source to the diesels and (2) initiate automatic loading shedding.
Automatic load sequencing is initiated by an SFAS signal and not by the voltage relaying.
The setpoint for the undervoltage relay is documented in the response to Guideline #10.
The setpoint for the overvoltage relay is documented in the response to Guideline #11.
GUIDELINE d9 The calculated voltages at the terminals of each safety load should be compared with the required voltage range for normal operation and start _ing of that load. Any identified inadequacies of calculated voltage require immediate remedial action and notification of NRC.
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Enclosure I RESPONSE TO GUIDELINE #o The District compared the calculated terminal voltages to that required for normal operation and N srting of each safety load.
The analysis identified inadequacies.
To correct the inadequacies, the District will make the following modifications:
1.
Change the loading sequence of the diesel-generator room supply and exhaust fans from block 2 to block 3 (Table 1).
2.
Limit reactor operation unless switchyard voltage is accept-able (See Response to Guideline #6).
The District's immediate remedial action is to complete modification (1) by November 5,1979, and modification (2) by the schedule outlined in Response to Guideline #6.
This schedule insures that the transmission system will be capable of starting and operating the safety loads at the minimum voltages the District expects in the Rancho Seco switchyard.
When the inadequacies were identified, the NRC was imediately notified by phone qn October 10, 1979, in a conversation between M. Fairtile of the NRC and R. Daniels of the District.
The justification for each type of load to operate at the calct, late voltages indicated on sketches 2 through 7 is given below.
This analysis assumes modifications (1) and (2) have been implemented.
Motors - For normal operation, the voltage data shown on sketches 2-7 show that some safety-related motors caould be operating below the nominal 90 percent mirimum voltage stipulated by NEMA MG 1.
Generally, the motors operating below this voltage are driving loads that are less than their name-plate horsepower. The District has performed an analysis thr* indicates con-tinuous operation at the voltage indicated is practical wit!
.; net less in motor life since the increased heating effects due to the reduced voltage are offset by the lighter than nameplate load.
For exceptions, where the motors are operating at a high load demand factor, motor life will be expended at a greater rate. However, this increased rate is acceptable since the total life expended is minor due to the limited time of operation anticipated at the reduced voltage level.
The District's safety related motors were qualified to start at 75 percent of rated voltage. The analysis determined that voltage above this value will be available during starting periods and the motors will start.
Motor Ocerated Valves - Motor operated valves are capable of oper-ating properly down to at least 345v (75 percent of 460) which is below the minimum voltage calculated.
Battery Charcers - The battery chargers were factory tested at rated load, at 140VDC, with an irout voltage of 432 volts (.94 of 460V).
The District has performed additional tests and calculations to verify that the battery chargers can operate at the minimum expected voltage of 386 volts %
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(.84 of 460). U '/
Enclosure I 6-Heat Tracino System - The heat tracing system for the safety-related pipes, tanks and valves containing boric acid consists of strip-type resistance heating tape, transformers, and thermostats. At the minimum veltage expected, the heat tracing system is capable of providing at least 91 percent of its required heat output. This is sufficient to maintain the required temperature. MCC Control Circuits - The District has verified by field test that the components in the control circuits of the MCC's can be operated at the minimum expected voltage. GUIDELINE #10 For each case evaluated the calculated voltages on each safety bus should be compared with the voltage-time settings for the undervoltage relays on these safety buses. Any identified inadequacies in undervoltage relay settings require immediate remedial action and notification of NRC. RESPONSE TO GUIDELINE #10 The District has compared the voltage-time settings of our existing undervoltage relays with the voltage requirements of the safety equipment. This comparison identified a potential inadequacy. The District will change the current undervoltage relay setpoint from 85 to 90 percent of 4160 to c6rrect the inadequacy. The immediate remedial action taken by the District will be to complete this modification by November 5,1979. The modification will improve the existing protection and provide addquate protection against degraded voltage conditions. The District has compared the calculated voltages on each safety bus with voltage-time settings for the undervoltage relays on these safety buses. The analysis indicates that the undervoltage relay should be set at 3744 volts (.9 of 4160 volts). The minimum expected voltage for the 4160 volt buses 4A and 4B is above.9 in all cases except when both safety buses are on start-up transformer #2 (Case 3). In this case, relay operation is possible causing transfer of at least one safety train to the stand-by diesel generator supply. Relay operation for this case is not an inadequacy and does not require any action by the District for the following reasor.s: a. Both safety buses on the start-up transformer #2 is a very abnomal plant line-up. The normal plant line-up is bus 4A on start-up transformer #1 and Bus AB on start-up transformer
- 2. Operation with both buses on start-up transformer d2 occurs when maintenance must be performed on the start-up transformer il system. Whenever possible all maintenance on this system is performed with the reactor in a cold shutdown condition.
There-fore this line-up is an available line-up for the safety buses but one that is rarely used with the plant in operation. b. The possible relay operation for this case is a correct response since the offsite system may not be capable of operating the safety equipment. O
Enclosure I ' 7-GUIDELINE #11 To provide assurance that actions taken to assure adequate voltage levels for safety loads do not result in excessive voltage, assuming the maximum expected value of voltage at the connection to the offsite circuit, a determination should be made of the maximum voltage expected at the terminals of each safety load and its starting circuit. If this voltage exceeds to maximum voltage rating of any item c. safety equipment immediate remedial action is required and NRC shall be notified. RESPONSE TO GUIDELINE d1l The District has performed a review of date on voltage in the P.ancho Seco switchyard. Based on this review, the maximum experienced switchyard voltage is 236.2kv. For the existing transfomation ratios (sketches 2-7) and assuming a no load condition, the maximum voltage is 4477 (107 percent of 4160V) on the 4.16kv system and 504V (110 percent of 460V). This voltage is equal to or less than the maximum voltage rating of any safety equipment. An analysis for each type of safety related equipment is listed below: R/ tors & Motor Ocerated Valves The 4160 volt motors are designea to operate at a maximum voltage of 4576 volts (110 percent of 4160 voltj, which exceed the maximum expected voltage of 4530 volts. The 460 volts motors, including motor operated valves have a maximum voltage rating of 506 volts (110 percent of 460 volts) which is greater than maximum expected voltage of 504 volts. Therefore, there are no cases for motors where the maximum expected voltage exceeds the maximum voltage rating for a motor. Battery Charcers The battery chargers a.e qualified to operate at full load with a maximum input voltage of 528 volts (114 percent of 460) which is above the maximum expected voltage of 504 volts. Heat Tracing System The heat tracing system for the safety related pipes, tanks, and valves containing boric acid consists of strip type resistance heating tape, transformers and thermostats. All of this equipment is qualified to operate at the maximum expected voltage of 504 volts. MCC Control Circuits The control voltage for each 480 volt MCC feeder circuit is cbtained from a feeder line tape through a 480 to 120 volt stepdcwn control power transforme r. The maximum /oltage rating for the most limiting component is 132 volts. The maximum expected voltage possible on the ccmponent is 126 volts -which is less than the maximum voltage rating. \\\\EO 09\\ 'L,
Enclosure I - Overvoltace Relay Setooint In the case the maximum expected voltage is exceeded the analysis indicates that the District's overvoltage relay should be set at 4493 volts (108 percent of 4160) which corresponds to a maximum of 110 percent of 460 volts. This setpoint is equivalent to a voltage of 237kv in the switchyard. With this setpoint, the relay is set to protect the safety related equipment. The relay is also set at a higher voltage than the maximum expected voltage and will not cause spurious trips. The District will chcnge the setpoint of the existing overvoltage relays by Ncvembar 5,1979. GUIDELINE #12 Voltage-time settings for undervoltage relays shall be selected so as to avoid spurious separation of safety buses from -ffsite power during plant startup, normal operation and shutdewn due to s.artup and/or operation of electric loads. RESPONSE TO GUIDELIflE #12 The setting for the undervoltage relay was selected to assure protection of the safety equipment as explained in tne response tu Guideline
- 10. The setting selected avoids spurious separation of the safety buses from the offsite power during plant startup, normal operation and shutdown due to starting and/or operation of loads.
GUIDELINE #13 Analysis documentation should include a statement of the assumptions for each case analyzed. RESP 0flSE TO GUIDELINE #13 For the s.;ses analyzed the District's assumptions have been included. The following statements describe the general assumptions used in the computer analysis. a. The compute 'eled running loads and motors as having a constant voit-ampere characteristic. b. Starting motors are modeled as having a constant impecance characteristic. c. The load data for the non-Class IE 4.16kv system (and subs'. cams) and safety motors greater than 60 hp ms based on actual fitld measurements (under simulated accident conditions, if applicable); for other loads, field test data, manufacturers' data and typical motor / load data were utilized. d. Impedance data for transformers was based on the actual nameplate data. e. Impedance data for bus duct was based on manufacturers published data. 1150 092
g. Enclosure I Impedance of cables was modeled for Class IE 4160V trans-former supply cables, MCC feeders and worst-case loads. Other loads were lumped together at their supply point. g. Cable impedance was calculated based on the actual circuit length and cable type. h. The impedance of switching equipment (switchgear, breakers, etc.) :s negligible and was not included. 1150 093
ENCLOSURE II Evaluation of the Rancho Seco Offsite Power System for Compliance To General Design Criter1on 17 I150 094
The NRC's August 8,1979, letter to all Reactor Licensees (except Humbolt Bay) requested the District "To review the electric power systems of your nuclear station to determine if there are any events or conditions which could esult in the simultaneous or consequential loss of both re-quired circuits to the offsite network to determine if any potential exists for violation of GCC-17 in this regard." The District has completed a partial review of the electrical power system for Rancho Seco and has determined that the District's electrical power supply system is in compliance with GDC-17. The basis for this con-clusion is contained in what follows. The power distribution system from the transmission network to the onsite safety related electrical distribution system consists of: a. Five overhead lines b. Start-up transformers #1, #2 and ~; clear service transformer c. Bus duct from the start-up transformers to the onsite safety related electrical distribution system. d. Pro + ve relays, circuit breakers, control panels, batteries, and er and control cables associated with the cperation of the o tribution system. The following assumptions were made by the District in determining events which could result in simultaneous or consequential loss of both re-quired ci rcuits. For a one line diagram of the Rancho Seco distribution system refer to Enclosure I sketch 1. a. All switchyard breakers are closed and in service. b. All five lines that connect the switchyard to the transmission system are in service.
- c. - Safety Bus 4A is connected to start-up transformer #1.
d. Safety Bus 4B is connected to start-up transformer #2. e. Only a single event or failtre is assumed to occur unless it could be demonstrated that the single event could lead to multiple failures. Based on the following assumptions, the District has analyzed the following events to determine if they could cause loss of both required circuits. FIRE It is possible for a single fire either in a control cabinet, cable tray or conduit to involve the control circuits for all the circuit breakers required for both offsite sources, and cause the circuit breakers to trip. However, this loss of power would only be temporary since the r'equired circuit 1150 09,3
Enclosure II ' 2-breakers can be quickly closed manually without any electrical power. The District has minimized to the extent practically the likeli-hood of this event by: 1. Using flame retardant cable for all cable between the plant and switchyard. 2. Installing a fire detection and supression system in the plant and switchyard where the circuits of concern are routed. 3. Providing a manual niethod of chasing the. circuit breakers. Therefore, this event is not a violation or potential violation of GDC-17. SEISMIC EVENT A design basis earthqua?e may cause the loss of both offsite sources. However, the District has designed and located equipment so as to minimize to the extent practical the likelihood of loss of both required circuits during a seismic event by including a seismic load in the design of supports for eau'pment required to be in service to provide offsite power. Therefore, loss of ooth required offsite power sources during an earthquake is not a potential violation or violation of GDC-17. RANDOM SINGLE FAILURES The District has analyzed the power distribution system from the transmission system to the onsite safety electrical distribution system for single failures tha.t can cause loss of both required offsite circuits. The review indicated that there are no single faliures that can cause the loss of both required effsite sources. This analysis. included seven items. a. Short circuits b. Breaker failures c. Switchyard battery failure d. Relay failures e. Transformer failures f. Lightning strikes TOWER FAILURES The District is still evaluating the possibility and consequences of tower failures. The results of the analysis and proposed remedial action will be supplied to the NRC as soon as they are available. 1150 096
TABLE 1 NUCLEAR SERVICE BUS (EACH) AUTOMATIC LOACING SEQUENCE Loading Sequence Quantity Description Block 1 - Energize at: 1 Decay heat pump (low pressure inj.) 0 + 0 sec 2 Reactor Building upper dome d!r circulators l Motor control center (miscellaneous load) 0 + 3 sec* 1 Makeup pump (high-pressure inj.) Block 2 - Energize at: 2 Reactor Building Emergency air cooler 0 + 16 see 1 Nuclear service cooling water pump Block 3 - Energize at: 1 Nuclear se vice raw water pump 0 + 26 sec 2 Diesel generhtor room supply and exhaust fans Block 4 - Energize at: 1 Reactor Building spray system including pump 0 + 300 sec
- Start of the make-up pump (high pressure inj.) is delayed 3 seconds to allow its beacing lube oil flow to get started 1150 397
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~~ ' ~ ~} ~,' SKETCH 2 l CASE 1 A BUS 4A ON START-UP TRANSFORMER NO.1 STEADY STATE AFTER SEQUENTIAL LOADING 214 KV SWITCHYARD VOLTAGE 220 KV SWITCHYARD STARTUP TR ANS. N O.1 214 KV 221 - 12.47 - 6.9 KV H TAP - 230 KV ww H WINDING - 38.6 MVA X WINDING - 10 MVA X Y TO 6.9 KV BUSSES 6A & 68 Y WINDING - 34.6 MVA 5.6 MVA TO CANAL PUMPING SUB 27.9 MVA 11.47 KV ww NUCLEAR SERVICE SUPPLY TP?.fiSFORMER 12.47-4.36 KV TM 7.5 MVA ESF SYSTEfst" 3.79 MVA, 4160 V BUS 4A 3324 V (.94 0F 4160) STATION SERVICE 4160 - 4 0 V MOTOR M TAP - 4260 V (.94 0F 4160) 1.12 MVA .37 MVA v 480 V BUS 3A 422 V (.92 0F 460) 416 V M OTO R (.90 CF 460) 480 V MCC 2A1 420 V (.910F 460) 409 V MOTOR (.89 0F 460) NOTES:
- 1. MOTORS CONNECTED TO A 41 GOV BUS ".RE RATED 41 GOV. THE 4LOV SYSTEM MOTORS ARE RATE 0 460V.
- 2. THE MOTORS SHOWN ARE ELECTRICALLY THE MOST OISTANT f.10 TOR FROM THE BUSSES SHOWN. ALL OTHER P.10 TORS ON THESE BUSSES WILL OPERATE AT A VOLTAGE BETWEEN THAT OF THE BUS, AND THAT 1150,i;9,9, 3
OF THE MOST DISTANT MOTOR. O [* , gT g
- W
~O I
- T E
SKETCH 3 CASE 1B BUS 4B ON START.UP TRANSFORMER NO. 2 STEADY STATE AFTER SEQUENTIAL LOADING 214 KV SWITCHYARD VOLTAGE 220 KV SWITCHYARD 214 KV H STARTUP TRANSFORMER NO.2 ~~ %w 221 - 4.36-4.3'. K'.' TAP &M&P H WIN 0 LNG - 42.G MVA Y Z Y WIN DING - 24 MVA Z WIN 0 LNG - 22.6 MVA, TO 4160V BUSSES 4E1 & 4E2 14.1 MVA 14.1 MVA o T0 4160 V SUSSES 4C & 40 3770 V ESF SYSTEM 4160 V BUS 48 3766 V (.31 dF 4160 VI'~ STATION SERVICE TRANS. X43B gg 3754 4160-400 V MOTOR m m TAP - 4260 V (.90 0F 4160) 1.12 MVA 1.06 MVA o 480 V BUS 38 400 V L87 0F 460 V) OTOR 85 0F 460) 480 V BUS 281 399 V L87 0F 460 V) 392 V NOTES: MOTOR L85 0F 460 V)
- 1. MOTORS CONNECTED TO A 4160V BUS ARE RATED 4160V. THE 480V SYSTEM MOTORS ARE RATED 460V.
- 2. THE MOTORS SHOWN ARE ELECTRICALLY THE MOST DISTANT MOTOR FROM THE BUSSES SHOWN. ALL OTHER MOTORS ON THESE BUSSES WILL Ol'ERATE AT A VOLTAGE SETWEEN THAT OF THE BUS. AND THAT llC]
I }.] I 0F THE MOST O!STANT N10 TOR. .. _. ~
a -~~~T M -~. m - CASE 2 ~ j BUS 4A & 4B ON STARTUP TRANSFORMER NO.1 STEADY STATE AFTER SEQUENTIAL LOADING i 214 KV SWITCHYARD VOLTAGE 220 KV SWITCHYARD 214 KV STARTUP TR ANS. NO.1 H 221 - 12.47 KV WW TAP - 230 KV mmmm X WINDING - 10 MVA 9.01 MVA X Y TO 6.9 KV BUSSES SA & 68 .TO CAN AL PUMPING SUB 11.37 KV 27.9 MVA WW NUCLEAR SERVICE m m SUPPLY TRANS. 12.474.36 KV 6.S9 MVA 7.5 MVA ESF SYSTEM 4160 V BUS 48 4160 V BUS 4A 3808 V 3803 V (.92.0F 4160T/) (.91 0F 4160 V) gg y (.910F STATION SERV. STATION SERV. 4160 V) TR ANS. X438 ww , TRAflS X41A WW 3796 4160-480V MOTOR . 4160-480V MOTOR mm (. F 4160 V) TAP - 4260 V TAP -4260 V TP 1.12 MVA 1.12 MVA .92 MVA 1.06 MVA 480 V BUS 3A 480 V BUS 3B 409 V 405 V (.89 0F 460 V) (.8_8.0 F' 460 V) 397 V (.86 0 F 460 V) f,03 V ~ MOTOR MOTOR S8 0F 460 V) 483 V MCC 2A1 480 V MCC 281 408 V 403 V (.89 0F 46C V (.88 0F 460 V) OTOR OTOR (.86 0F 460) (.8S OF 4CO) ~ NOTES:
- 1. MOTORS CONNECTED TO A 4160V BUS ARE RATED 4160V. THE 480V SYSTEM MOTORS ARE RATED 4 GOV.
- 2. THE MOTORS SHOWN ARE ELECTRICALLY THE MOST O!STANT MOTOR ll}}
()1 FROM THE BUSSES SHOWN. ALL OTHER MOTORS ON THESE BUSSES Ul WILL OPERATE AT A VOLTAGE BETWEEN THAT OF THE BUS, AND THAT 0F THE MOST DISTANT MOTOR.
CASE 3 s SKETCH 5 BUS 4A & B ON START UP TRANSFORMER NO. 2 STEADY STATE AFTER SEQUENTIAL LOADING 214 KV SWITCHYARD VOLTAGE ~ ' 220 KV SWITCHYARO 214 KV STARTUP TR Af'SFORMER NO.2 WW 221 - 4.36-1.36 Ki~ ~ ~ ~ &M&M TAP - 230 KV Y Z
- H WINDING -42.6 MVA
' YWINDING -24 MVA TO 4160V RUSSES 4E1 & 4E2 Z WINDING - 22.6 MVA 14.1 MVA 17.1 MVA 1P TO 4160V BUS 4C TO 4160V BUS 40 3720 V 3714 V ESF SYSTEM 4160 V SUS 4A 4160 V BUS 48 3719 V 3712 V (.89 0F 4160 V) (.89 0F 4160 V) STATION SERV. STATION SERV. TR ANS. X438 TRANS. X43A 3707 V TM 4160-480 V MOTOR 4160-430V MOTOR (.89 0F 4160 V) TAP - 4260 TAP - 4260 1.12 MVA 1.12 MVA . 3699 V .92 MVA (.89 0F 4160 V) 480 V BUS 3A 480 V BUS 3B 399 V_ 394 V (.87 0F 460 V)___ (.86 0F 460 V) MOTOR 393 V MOTOR (.85 0F 460 V) 386 V (.84 0F 460 V) 480 V MCC 2A1 480 V BUS 2B1 397 V 332 V (.86 0F 460 V) (.85 0F 460 V) [ 35 MOTOR MOTOR g 34 0F 460 V)
- 385 V NOTES:
f.84'0F 460 V)
- 1. MOTORS CONNECTED TO A 4160V BUS ARE RATED 4160V THE 480V SYSTEM MOTORS ARE RATE 0 4COV.
- 2. THE MOTORS SHOWN ARE ELECTRICALLY THE MOST OISTANT MOTOR FROM THE BUSSES SHOWN. ALL OTHER MOTORS ON THESE SUSSES WILL OPERATE AT A VULTAGE SETWEEN THAT OF THE BUS. AND THAT OF THE MOST OISTANT MOTOR.
1150 102
SKETCH 6 CASE 4A l BUS 4A ON START UP TRANSFORMER NO. 2 STEADY STATE AFTER SEQUENTIAL LOADING 214 KV SWITCHYARD VOLTAGE 220 KV SWITCHYARD H 'STARTUP TR ANS. NO. 2 wy 221 - 4.36-4.36 KV H WINDING - 42.S MV A Y Z Z WINDING - 22.6 MVA TO 4160V BUSSES 4E1 & 4E2 'YWINDING - 24 MVA 1_4.1 MVA 14.0 MVA I U I TO 4160V BUS 4C TO 4160V BUS 40 m 3777 V ESF SYSTEM 4100 V BUS 4A 3776 V TSiOF 3160 V) STATION SERV. TR ANS. X43A gy 4160-480 V 3763 V &M MOTOR TAP - 4260 V (.90 0F 4160 V) 1.12 MVA .97 MVA 480 V BUS 3A 404 V (.88 0F 460 V) 398 V (.87 0F 460 V) MOTOR 480V MCC 2A1 403 V (.88 0F 460 V) NOTES: 391 V
- 1. MOTORS CONNECTED TO A 4160V BUS ARE RATED 4160V. THE 480V
(.85 0F 460 V) M'OTOR SYSTEM MOTORS ARE RATED 460V.
- 2. THE MOTORS SHOWN ARE ELECTRICALL *' THE MOST DISTANT MOTOR FROM THE BUSSES SHOWN. ALL OTHER MOTORS ON THESE BUSSES WILL OPERATE AT A VOLTAGE BETWEEN THAT OF THE BUS, AND THAT OF THE MOST DISTANT MOTOR..
1150 103 i -i 3 ..... ~
SKETCH 7 CASE 4B BUS 4B ON START UP TRANSFORMER NO.1 STEADY STATE AFTER SEQUENTIAL LOADING 214 KV SWITCHYARD VOLTAGE 220 KV SWITCHYARD STARTUP TR ANS. N O.1 221 - 12.47 - 6.9 KV g TAP - 230 KV H WINDING - 36.6 MVA X WIN 0 LNG - 10 MVA &M&M Y WINDING - 34.6 MVd X, Y 5.72 MVA TO 6.9 KV BUSSES SA & 68 TO CANAL PUMPING SUB 27.9 MVA 11.43 KV NUCLEAR SERVICE aw SUPPLY TRANSFO RMER mm 12.47 - 4.36 KV 7.5 MVA 3.90 MVA TO ESF SYSTEM 4160 V BUS 48 D11 V
- (.94 0F 4160 V)
(.94 0F 416b V) TRANS.X 38 4160-480 V MOTOR TAP - 4260 V ^ 1.07 MVA 480 V BUS 38 418 V __ _.._ (.91 0F 460 V) 411 V. L89 0F 460V) MOTOR 480 V MCC 281 417 V i (.91 0 F 450 V) 410.V. (.89 0F 460 V) ~ MOTOR NOTES:
- 1. MOTORS CONNECTED TO A 4160V BUS ARE RATED 4160V. THE 480V SYSTEM MOTORS ARE RATED 460V.'
1 I
- 2. THE MOTORS SHOWN ARE ELECTRICALLY THE MOST GISTANT MOTOR FROM THE BUSSES SHOWN. ALL OTHER *.10 TORS ON THESE BUSGES WILL OPERATE AT A VOLTAGE BETWEEN THAT OF THE BUS, AND THAT OF THE MOST O!STANT ',10 TOR.
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