ML20127H196
| ML20127H196 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 06/14/1985 |
| From: | Jens W DETROIT EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| VP-85-0136, VP-85-136, NUDOCS 8506260238 | |
| Download: ML20127H196 (15) | |
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-e Wryne H. Jens
.,, Vee PreSdent Nuclear, Operations 1i f'
Fortru 2 Edison '. 6400 North Ds4 Highway m=r"-
June'14, 1985 VP-85-0136 Mr.. James G. Keppker Regional Administrator o< Region III V
U. S. Nuclear Regulatory Commission j
799 Roosevelt Road Glen Ellyn, Illinois 60137
Dear Mr.',
Keppler:
r References.
Fermi 2 1
NRC Docket No. 50-341 NRC h1' cense No. NPP-33
Subject:
Detroi Edison Response Inspection Report 50-341/85-15 This letter responds to the open item described in your Inspection Report No. 50-341/85-15.
This inspection was conducted by Messrs. S. DuPont, S. Guthrie, S. Stasek, T.
Tongue, and N. Chrissotimos on March 4 through 6, 1985.
We trust this letter satisfactorily responds to the open item described in the inspection report.
If you have questions regarding this matter, please contact Mr. Lewis l
Bregni, (313) 586-5083.
Sincerely, i
1 cca P. M. Byron
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N. J. Chrissotimos USNRC, Document Control Desk i
Washington, D.C.
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Mr. James G. Keppler June 14, 1985 VP-85-0136 l
Page 2 bcca F. E. Agosti R. W. Barr M.
L. Batch E.
R. Bosetti-W..F. Colbert L.
B. Collins O.
K. Earle-C. R. Gelletly W. J. Glasser E. P. Griffing W..R.
Holland J. W. Honkala S. J.
Latone
.R.
S. Lenart
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Marquardt/ Docket File (2)
W. E. Miller, Jr.
S. H. Noetzel J.
A. Nyquist G.
R. Overbeck T.
D. Pnillips J.
L. Plana J.
H. Plona j
E.
R. Preston L.
E. Schuerman F. T. Schwartz L. J. Simpkin G. M. Trahey i
A..E. Wegele Apprvoal Control (136 NOC)
Region III Chron File NRC File Secretary's Office (2412 WCB) l l
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THE DETROIT EDISON COMPANY P
d..i FERMI 2 II NUCLEAR OPERATIONS ORGANIZATION RESPONSE TO NRC INSPECTION REPORT NO. 50-341/85-15 DOCKET NO. 50-341
LICENSE NO. NPF-33 INSPECTION AT:
FERMI 2, NEWPORT, MICHIGAN INSPECTION CONDUCTED:
MARCH 4-6, 1985
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RESPONSE TO NRC INSPECTION REPORT 50-341/85-15 Description or Open Item 85-15-01 This open item involves two concerns with the Fermi 2 electrical distribution system.
The first concern is that the electrical distribution system, as constructed, does not appear to meet the requirement for two physically independent-circuits from the offsite transmission network to the onsite electrical distribution system, as specified in General Design Criterion 17.of 10CFR50 Appendix A.
The second concern is that the separation of the offsite power sources reduces plant. safety by increasing the chance of plant transients and challenges to safety systems due to a loss of either offsite' network.
Detroit Edison Response The Detroit Edison electrical distribution system design maintains separation through our offsite electrical system, so that our 120 kV and_345 kV switchyards are not tied together locally.
The 120 kV switchyard has three independent incoming lines, while the 345 kV switchyard has two independent incoming lines.
We feed one division of Class IE power via a transformer from the 120 kV-switchyard and the other division via a transformer from the 345 kV switchyard.
Therefore, each division of Class IE power is normally supplied by at least two (2) physically independent circuits from the transmission network.
This independence reduces the. possibility that offsite.AC power would.be lost, ther,eby reducing the. susceptibility of Fermi _2 to' station blackout.
This configuration goes well beyond the requirements of GDC 17 and its acceptance is documented in Section 8.1 of the Fermi 2 Safety Evaluation Report.. In addition, IEEE Standard-765-1983,~"IEEE Standard for Preferred Power Supply tor-Nuclear Power Generating Stations", shows and discusses several examples of an acceptable preferred power supply design.
Figures 2(a) and (b) of that standard illustrate a similar system to ours in that each class IE bus has a single feed from the non-class IE system with multiple lines feeding the non-class IE bus.
The only variation between the figures in the standard and the Fermi 2 design is that we transform the offsite transmission power after the non-class IE bus instead of before.
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RESPONSE TO NRC INSPECTION REPORT 50-341/85-15 Detroit Edison Response (Cont'd)
The inspector noted that the loss of either transformer would impose an undesirable transient on the unit, unnecessarily challenge safety _ systems and challenge the j
He indicated that station reliability could be enhanced by employing an automatic transfer between the two offsite power sources to provide feeds to each division of Class IE power.
Detroit Edison contends that the use of automatic transfers would reduce the reliability of our offsite power sources thereby reducing the inherent level of safety provided by our Class IE power system.
A summary of the historical basis for this position, which included evaluation of reliability and other considerations (etfecting both safety and economics),
follows.
For many years Detroit Edison power plant auxiliaries were supplied directly from the terminals of the generator by an auxiliary transformer and required another external source for startup of the unit.
After the generator was synchronized and capable of taking the load, the auxiliaries were transferred from the external source to the generator terminal auxiliary transformer.
Likewise, for a normal shutdown, the automatic throwovers transferred the auxiliaries to the external source.
This scheme, with its undervoltage relays, timers, interlocks etc., was ditficult to make entirely reliable.
As generating units increased in size, the hazards possible with throwovers and transfers greatly increased.
With the design of our Trenton Channel No. 9 Unit in 1966, this operating philosophy was reviewed, which led to a change in operatir.g philosophy:
the throwovers would be abandoned and the high voltage switchyard would be the source of supply to the auxiliaries.
An auxiliary (System Service) transformer so connected would prove as reliable as the generator transformer.
If the high voltage bus were not available the unit would not be available and therefore, the auxiliaries would not be required.
The System Service Transformer, fed from the high voltage switchyard has been used on the last ten generating units added to the Detroit Edison grid with very reliable success.
The change in philosophy is detailed in IEEE paper 31PP66-549.
During the initial design for the Fermi 2 plant, the use of a machine fed auxiliary transformer versus transmission system fed. transformer was again discussed.
It was concluded that'the use of a system service transformer 2
RESPONSE TO NRC INSPECTION REPORT 50-341/85-15 Detroit Edison Response (Cont'd)
(transmission system fed) offered the best advantages and thus was adopted as the acceptable design for the plant auxillaries because of:
o Simplicity of design, o
Less expensive, o
Better operating convenience, o
Good reliability Because Fermi 2 is a nuclear plant and General Design Criterion 17 requires " Electrical power from the transmission network to the onsite electric distribution system shall be supplied by two physically independent circuits... designed and located so as to minimize to the extent practical the likelihood of their simultaneous failure under operating and postulated accident and environmental conditions," our second feed was taken from the onsite 120 kV switchyard using the principles of the system service transformer design.
At that time, it was recognized that the loss of either the 120 kV switchyard or the 345 kV switchyard would most likely result in a unit trip.
However, this design was judged acceptable based on an evaluation of factors which could affect safety, reliability, and availability, as follows.
1.
Auxiliary power system integrity was considered good because most situations forcing unit shutdowns are associated with the units themselves.
2.
The elimination of transfers and auto-throwovers made it a simpler and safer system.
3.
Both high voltage buses are fed by multiple transmission lines.
4.
Spare transformers are available.
3
RESPONSE TO NRC INSPECTION REPORT 50-341/85-15 Detroit Edison Response (Cont'd) 5.
Failure probabilities were considered for the major components, including transformers, cables, and terminations.
A copy of the discussion notes for the March 19, 1971 design meeting documenting these considerations is available for your review.
Detroit Edison, Transmission Planning Group, nas determined the probability and duration for loss of the offsite power sources for the Fermi plant.
A copy of this calculation (July 20, 1981) is also available for your review.
Based on this calculation, the reliability of the offsite power feeds to Fermi 2 is considered to be acceptable.
Detroit Edison believes our method of providing power to the class IE divisional buses meets the requirement of GDC 17 for providing two independent offsite power sources and poses no undue challenges to safety systems.
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'IRENTCH CHANNEL NO. 9 - A OlANGE IN PHILOSOPHf -
k IN SUPPLIES TO AUXILIARIES Yh
,69 W. J. Campbell 4
Both of:
'1he Detzvit Ediscn Capany[b Member IEEE J. L. Voyles Detztit, Mich.
Member IEEE A paper recamended by the IEEE Po.er Gruup for presentation at the 1966 ASME/IEEE Joint Power Generation Ccriference, Denver, Colorado, September 18-22, 1966. Manuscript subnitted August 2,1966; made available for printing August 3,1966.
Price': $1.00 All Rights Reserved by (75f at meeting)
The Institute of Electrical and Electronics Engineers, sec (15f per copy additfoaal li 845 t,ast 47th Street first class mailing desired)
New York, N. Y.10017 (25f per copy additional if Litho in USA air mail is desired)
Paper No.
31 PP 66-5849 i
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TRENTON CMRNNEL No. 9 - A CHANGE IN PHILO10PHy - IN SUPPLIES TO AUXILIARIES i
2.,' ' -
W. J. Cag bell J. L. Voyles 1.
u-Moder IEEE Meeer IEEE
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THE DETROIT EDISON COMPANY
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SUMMARY
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The engineering of the electrical aux-This system is shown In Figure 1 Illery system for Trenton Channel No. 9 Is based on a mejor change In the philosophy of design-This plant was capable of supplying Its own Ing auxillary electrical systems. A single auxillarles. A gradual trend toward a-c power transformer connected to the unit high voltage for all auxillaries, with ties from both the bus will supply the major auxillarles for the transmission system and teroloal transformers unit. Major features of the auxtllary system was established in plants constructed at a later are described, date in the Detroit Edison system.
INTRODUCTION First Plant Expansion 7
The addition of the 500 ihr turbine The first expansion of the Trenton Channel
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generator No. 9 to the Trenton Channel Power Power. Plant occurred in 1950 and included two Plant will be the second major expansion of 100 N turbine generators supplied by four i
this plant. The engineering of the electrical headered boilers. The steam conditions of these aux 111ery system for this addition is based on units are 1380 psig and 950 F.
This addition a major change in the philosophy of. designing represented a substantial increase in unit slae 5
auxillary electrical systems. This change in and also unit auxillary load. Investigations philosophy is based on many of the same factors were made to determine the advisebility of i
that have been Igortant In the engineering and expanding the existing d-c system or providing selection of all power plant equipment, many of a new a-c euxillary system. With the added which have shown large engineering advances and power requirements, d-c power Investment costs changes over the years. Before discussing this were Increasing greatly so that It could not be
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change In philosophy, it would be desirable to justifled as a source of speed control. Alter-study the development of auxillery systens. A nating curreat power was less expensive and Its review of the existing Trenton Channel Power reliability had been Igroved because of the high j
Plant design provides a good example of aux-voltage transmission system that tied all power Illery system development In The Detroit Edison plants together. Thus, a-c power was' selected Cogeny system, for all auxillarles. The design of a c auxIlla-ry systems for these two units was based on EXISTING PLANT DESCRIPTION maintaining auxillary power to the unit for both ystem disturbances and possible problems in the gtransformer supplying the auxillary system.
l Original Installation The-first requirement was met by connecting aux-The original Installation at Trenton litary transformers to the generator terminals.
Channel included six 50 h turbine generators The second requirement was met by standby trans-and thirteen boilers which were costned to formers (called system service transformers) i supply steam to the turbine throttle at steam connected to the transmission system with auto-conditions of 400 psig and 725 F.
This part of throwavers from the auxillary transformer to the the plant was cogleted in the mid 1920's. The system service transformers, cenerator breakers i
plant was planned before the Introduction of were provided so that transfer of aux 111arles the Cogany's major high voltage transmission would not be required for each startup and shut-lines and was located in a remote area. Aux-down of the unit. This basic system is shown in lllery power was provided by house service Figure 2.
This system operated at 2400 v a c, generators at a voltage of 240 v d-c connected which was in use In the existing plant. and through a coninon house service bus. House provideql a convenient means of establishing the service power provided the reliability for the backup requirements previously described.
auntilaries and d-c power supply provided a suitable means of speed control for punes and Subsequent Develoon etj, fans. This plant was also one of the first en
.The Detroit Edison Cogany to burn pulverlaed Whatn this sectior was co g lete, the total f
fuel and a separate building was provided for capacity of Trenton Channel Power Plant was the pulveri Ing equipment. All coal handling 500 m. This represented about 30 per cent of equipment was driven by a-c setors with house the Detroit Edison system at that time so the service generators and one tie from the Cogeny's next expansion of the Cogany's power generation
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transmission system serving as the power supply.
facilities took place at two new power plant 1
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sites. Th2 unit sIra et these ow plcnts In.-
Eerlier Aust 11ery Systems accesso gradually to 325 PW and stsam conditions risa to 2400 psig 10$0/1000 F.
Thi unit scheme As shown previously, earlier power plcnt of boiler and turbine was applied to these new auxillary systems were usually one large Inter-4 units and many developments in pwer plant connected system with the power supplied from technology were made. The aux 111ery system house generators. When a-c pwer was supplieri
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voltage rose to 4I60 volts with the same basic for auxillaries, the auxillary system had requirements as the first expansion at the additional ties from the switching station which Trenton Channel Pwer Plant. The major change the generators supplied. These systems were in these later units was the elimination of the very expensive and the possibility existed that generator voltage breaker because of the tech-electrical trouble in the area of one generating nical problems in haridling large currents. This unit could spread to that of another unit' or development placed adde.d eghasis on the system that the whole plant could be cascaded down, service transformer because it then became necessary to transfer auxillaries for each start-This led to the adoption of the unit up and shutdwn of the unit. The system service system wheret,y the auxlilaries of each unit are transformer also provided back-up for the unit normally supplied directly from the terminals of auxillary transformers but failure of the system the unit's generator. It was reasoned then that service transformer would also jeopardize the trouble on the auxillaries of a unit should unit because the unit could not be restarted affect only that unit. However, with this type af ter a shutdown. Thus, backup was also re-of system, the auxillaries were required to be quired for the system service transformer. This started from another. source external to the unit.
backup was provided by Installing at least two Af ter the generator had been synchronized and was system servics transformers for each group of capable of taking on load, the auxillaries were units la a plant that had a conrion auxillary transferred from the external source to the system voltage, generator terminal source. Likewise on normal shutdowns, auto-throwovers transferred the aux-Second Plant Expansion at Trenton Channel IIIsries to the external source. The philosophy of operation was that fans, condensate pugs, The second plant expansion at the Trenton boller feed pugs etc., were required to be Channel Pcwar Plant will be the addition of
' operating even on forced shutdown. Numerous Unit No. 9 and the design will follow the papers in IEEE literature have been written Cogany and Industry practice of the unit describing how best to accogilsh these auto-turbine-generator and boiler Installation. The throwovers and transfers.
500 phe rating will double the nameplate rating of the plant. The unit is scheduled for service Throwovers and Transfers Make it vulnerable C'
in October of 1967. Steam conditions will be 2400 psig 1000/1000 F.
This scheme, with its under voltage relays, ~
timing relays, auxillary relays, transfer f
In developing the auxillary system for switches, Interlocks and auxillary contacts etc.,
j Trenton Channel No. 9. It was recognized that a is difficult to make entirely reliable. Redun-thorough review should be made of existing dancy bullt into the system also made it vulner-practices and philosophy in supplying power to able to human error, and equipment of ten was the auxillarles for this Installation. Previous damaged due to rialfunctionIng. As units further unit Installations have generator terminal increased in size, the hazards possible with transformers supplylr) the unit auxillaries.
throwovers and transfers greatly increased. It Startup, shutdown, and backup services are became Increasingly expensive to furnish such a i
provided by transformers fed from the power system with sufficient backbone In it to support plant's high voltage bus. *The gradual change the great inrush of power which occurs on these from house service supply to dependency upon auto-thrwovers.
the high voltage transmission system for unit auxillaries suggested that this revlow of the Questioning Ooeratine Practice philosophy of auxillary system supply could produce new concepts in the supply of auxillery This led Edison engineers to question our operating practice. Were auto-throwovers really power.
necessary? Was it really essential that the BASIC PHILOSOPHY DEVELOPMENT aux 111arles continue to be supplied on a unit being forced down? When a unit is forced dw n.
The continuity of output of a generating the fires and Ignition are always extinguished unit is directly dependent on the continuity of Immediately and since modern steam generators the aux 111arles which drl ne it, therefore, its have conraratively Ilttle residual heat stored reliability Is no greatsr than that of its In them, there is little need for r.ordensate auxilleries. Consequen*1y, designing a firm pugs, boiler feed pugs etc., to be kept and reliable source of power supply to the aux-operating. The fans of modern units have very Illpries has always been a prime consideration high inertia and they keep turning rapidly for of a power plant planning engineer.
some time af ter they lose their source of power.
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This in itself coupled with the effect of the Some small amou t of power would be required r
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sten would quickly clear the gasses from the for outage of the transformer for essential a-c steet generator. Also, on a restart, steam service and during transformer maintenance work, generators are always purged before refiring.
This power can be supplied by a small low 7
Reasoning thus, it became apparent that the unit voltage bus with auto-throwovers to another could be shut down safely on loss of auxillary source. This source can be obtained from power and little could be found tc justify auto-existing plant services if available, from out-thrswvers.
side plant connections, or from automatic start Diesel driven generatorm.
New Philosophy This system Is exceedingly sigle and This led to a change in operating phl-st rai ghtforward. When costs are cogared to losophy. Auto-throwovers would be abandoned.
previous practices, the resultant savings If a unit was forced down, It would be shutdown become substantial. For a single unit Instal-completely. On restart, the auxillarles would lation at an existing plant.* the savings result i
be started properly In sequence. A revlow of from the elimination of the generator terminal b
shutdowns of generating units revealed that transformers, connections from these trans-outages were caused by troubles within the formers, auto-throwovers etc. If transformer l
turbine generator, steam generator, valves, reliability remains questicnable, the single I
exciter etc., and rarely, If ever, In the unit Installation W uld require two system generator transformer or the unit high voltage service or startup transformers because failure bus. It was reasoned -- why not select the of a single transformer Installation would unit's high voltage bus as the source of supply result in ultimate shutdown of the unit. There to the aux 111arles? An aux 111ary transformer are, of course, added costs and losses In the so connected would prove as reliable as the generator transformer, but these are small In generator transformer. If the unit high voltage the Increme tal cost of the transformer and in bus were not ave 11able, the unit would not be capitalized losses when conpared to the savings available and the auxillarles would not be mentioned above, required. This connection would still be con-sidered a unit system of supply to the aux-For the large multi-unit plant, it should -
111eries because the unit high voltage bus can also be recognized that the savings of this plan be considered as part of the unit. Maintenance would diminish because the costs of startup
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on the transformer can easily be accomplished transformers and bus connections would be spread with scheduled and unscheduled outages of the between several units.
unit.
TRENTON CHANNEL No. 9 AUXILIARY SYSTEM With the basic auxillary power system requirements fulfilled by a single trans-As a result of the revisions in basic former, the only remaining question is that of philosophy, the unit auxillaries for Tren, ton transformer reliability as it relates to the Channel in. 9 will be served from one trans-entire unit rellability. The auxillary trans-former connected to the unit high voltage bus I
former rellability is essentlally the same as and located close to the pwer plant well beside the generator transformer. Generator trans-the generator transformer as shown on Figure 3.
former reliability has been depended on where There will be no throwovers or transfers of the the common Industry practice has been to Install power supply to main auxlllaries. The ellel-l a single three phase transformer to step up the nation of transfers relieves the operating generator voltage to the system high voltage personnel of a major operating step during each j
bus. This same dependency is extended to the startup and shutdown and they are enthusiastic auxtllary transformer for this auxillary system.
about this simplification in operating procedure.
I Spare generator transformers have not been
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carried for The Detroit Edison Company system, goller Feed Punes and Motor Driven AuxIllarles but this policy is being reviewed within the Michigan Power Pool. Costs of a spare generator The economic study of the various means of
- transformer to cover many pool units could be supplying boiler feed pun, power (motors with shared on a pool basis. It is also planned to hydraulle couplings, shaf t driven pumps with study auxillary transformers for large units on hydraulle couplings and turbine driven pugs i
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the same basis, with Inherent speed control) resulted In the selection of two half size turbine-driven, Basic Conclusions boller-feed pugs for this unit. This relleved the auxillary system of a large amount of load.
As a result of this philosophy development, All other aux 111arles (fans, pumps, compressors, the basic auxillary power requirements can be etc.) are driven with a-c squirrel cage motors satisfied by a single transformer connected to with flow or volume control accoglished by E
the unit high voltage bus. No backup or throw-other means. A list of these main auxillaries l
overs are required. All major unit auxillaries is shown in Table I.
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low voltcge winding to llalt this va riatisn ts l*,
Aasillery System Valt*ges _
plus er cinus 10 p2r cent.
The auxillary system voltage was selected ct 4160 volts. The elimination of transfers The transformer will receive Iquise and
(; l and throwovers made ties to the existing 2400 corone tests as acceptance checks on the manu-facture of the transformer, system unnecessary and the amount of auulliery
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load for Unit ho. 9 could be handled easily at 4160 volts. Motors above 200 hp will be fed Auxillary Switchgear and Basic Relaying f
directly f rom this 4160 v system. The smaller Protection actors, lighting and other services will be Standa'rd 4.16 kv 250 Mva. metal clad supplied at 480 volts.
switchgear wl:1 be used for the two main aux-lilary Lusses. The Igedence of-the transformer Auxillary Transformer and secondary cables will limit the fault duty A single auxillary transformer has been to the rating of the 5reakers. The maximum fault has been calculated as follows:
speelfled with one high voltage winding at 123 kv, and two low voltage windings at 4160 MONENTARY FAULT AT 1/2 CYCLE volts. The rating will be 22.5/30 Mwa, OA/FA.
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Because the high voltage bus varies from 120 kv g
to 132 kv, the transformer will be equipped with M tors 4,6 load tap changing (LTC). The LTC equipment has been selected to maintain 4160 volts on the auxillary bus, regardless of the actual system TOTAL ASYMMETRICAL FAULT voltage or the load on the transformer. By controlling the secondar,y voltage "through the N S02 + W OO2 = $8,500 an s Iron", a single low voltage tap changer will
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control both low voltage windings at the same INTERRUPTING FAULT AT 4 CYCLES time. The control of the secon.dary voltage d-c a -c allows the use of standard motors on all aux-Illaries. By establishing the initial voltage Transformer 27,400 8,100 before starting at 104 per cent of motor voltage Motors 400~
400
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, 00 by LTC regulation, the motor voltage een start-Ing will be above 90 per cent. The LTC equip-ment will be regulated by hand.
TOTAL ASYMMETRICAL FAULT
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The inedance of the transformer was spect-d27,8002 + 11,5002 = 27,800 ag s fled as follws on the 22.5 Mva base of the transformer.
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a ers are rat d 4,000 amps ZH-X 11.0%
momentary and 35,000 ags interrupting. The
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switchgear will be in an Isolated room with g
2 c ncrete flo rs above and below. No pipes will U -X 22*0%
cross the switchgear and the room incoming air 1 2 will be filtered. All pwer and control cables 5
This will provide a zero leg on the equiv-wl I enter the switchgear f rom below. This alent circult of the transformers which becomes:
arrangement will provide a dustless and dripless environment for ti e switchgear, thus providing r
' greater reliability.
g Previous 4160 y systems have been solidly 11.C%
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grounded. This practice has been changed for Trenton Channel No. 9 to a resistor grounded Mg Na system which limits the ground current to 600 Instantamous sensithe gmuM relays l
mps.
With this equivalen't Igedance diagram, supplied by toroldal CT s will be furnished on ce a st fauhs on W v nstems motors on one low voltage winding will not eac er.
affect the switchgear rating for the other origirate as ground faults, this system will winding. The Ig edance was also required to 8*IY
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have a tolerance of 7.5 per cent which is better limit the fault f rom spreading to phase-to-phase than the 10 per cent normal t91erance of a three or to an aults.
,r winding transformer, Feeder circult overcurrent protection will The low voltage LTC equipment also varies be provided by overcurrent and Instantaneous 3 the Ig edance considerably when the Impedance relays In two phases, with remote anneters g
is corrected to the actual voltage being main-provided in the third phase. On motor circuits.
toined on the secondary of the transformer. To the overcurrent relay pickup will be 173 per Inhlblt this igedance variation the trans-cent of m tor full load current. An instan-(..
fo.rmer has been provided with a special series I
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g teneous current relay will be provided for alarm m.
Ofp main oli pug s Indication on motor circuits, with pickup at n.
Bfp turning gear motors
([~ 120 per cent of motor full load current. The o.
Bfp oil dump valves f
instartaneous alarm relay will provide many p.
Booster pug, fire protxtion
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advantages over thermal relays in that it will er provide advance warning, will be easier to *.est Additional protection Is provided to many of and adjust, and will be checked on each motor the services on the essential bus by duplicate
- start, motors with feeds from other 480 v busses. Aia, a small automatic start Diesel-generator is Control. Let Down and Essentlet P m er provided as a standby sou~e for comunications; an emergency battery charger is provided from the With the single auxillary transformer plant d-c bus; and a second unit source is supplying the main auxillarles for the unit, the provided for the boiler control, need remains for some small amount of pwer for control, let down and essential functions.
Other Electrical Features Control power is required to operate switch-Several other electrical features of Unit gear, unit protective systems, annunciators, No. 9 should be mentioned where past practice has sequence events recorders, fire sprinkler systems been modified or even considerably changed.
etc. This power Is furnished by a unit battery.
The battery will be a 130 v lead-calclum type The turbine generator Is a tandem-cogound, slaed for alght hour duty.
four-flow machine. thus departing from the cross-cog ound machine Installed with the last nine Let down power is required to protect the units on The Detroit Edison Comany system. The unit for a coglete loss of the a-c system. This generator will have a water-cooled stator and power will be provided from the existing plant hydrogen-cooled rotor operating at a maximum d-c bus at 240 v., and will feed emergency pressure of 45 psig. The shaf t-driven exciter bearing oil pugs for the main turbine generator will include an a-c generator and sl!! con rectl.
and the two boller-feed pug turbines. The plant flers with an amplldyne voltage regulator. No d-c bus serves the emergency oil pugs of the spare exciter will be provided, but a spare bank existing eight units at the plant and also the of silicon rectifiers will be provided. An boiler and turbine auxillaries of the original electrohydraulle governor will control the six units. House generators provide power to tu rbi ne.
A' programed automatic startup control
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the d-c bus, thus providing Independent protec-system has been added to the turbine-generator tion to the emergency motors of all units in the electrohydraulle control system.
plant.
4, The generator bus Is rated 18,000 amperes Essentist power is provided at 480 v with at 22,000 volts. The bus will be welded aluml-two sources and an automatic throwover. The two num and forced-air cooled.
sources are necessary to maintain power during maintenance work on the auxillary transformer.
All 4160 y power cables will have butyl and The two sources are from the unit transformer, neoprene Insulation and will be run in ladder and from the existing plant. With two sources, type trays. The aux 111ery transformer cables an automatic throwover was easily added and will be made up of 2-1500 Mem cables per phase other desirable a-c loads fed frorr this bur. The and wlit bs transposed to balance the igedance following loads are served from the essential bus:
and eliminate negative sequence currents. Three conductor, triplexed, non shielded cables will ne e ers to news and transkmers, 1.
Maintenance All 600 y power cables for motor 'cf rcults a.
30% of welding circuits will als have butyl and neoprene Insulation and b.
30% of plant lighting c.
Coal handling for units 7, 8 & 9 will be run in ladder type trays. Multi-conductor control cables will be PEPVC type with d.
Elevator 15 mils of polyethelyne and 30 mits of polyvinyl chloride. Cables entering switchgear, motor 2.
Essentla,'
control centers and control boards will enter f r m below to protect the electrical equipment a.
Soller air heaters b.
Boller electronic control f r m dripping water.
c.
Control battery charger The boiler control equipment will be com-d.
Communications plately electric with all burner and boiler e.
Clock feeds control functions controlled from the unit con-f.
Excitation bias supply trol room. Sequence events recorders and print-g.
Generator stator cooling pugs ers will provide vital Information about off-h.
htg electrohydraulle control pug normal conditions and emergency situations.
I.
Mtg turning gear motors J. Mtg hydrogen vacuum pug k.
Mtg hydrogen seal oil pug 1.
Mtg auxiliary suction oil puq 5
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TAal'E I CONCLUSIONS
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The design of the auxillary electrical Trenton Channel No. 9
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system for Trenton Channel No. 9 Is based on a Auxillary Transformer Loads mejor change In the philosophy in the design of electrical supply to the suulliaries. The basic
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promise of this philosophy is that no damage East Auxillary tus will result from the loss of the unit's major electrical sources, thus leading to the conclu-ston that backup sources of power are not 3 Condenser Circulating Pugs 500 hp 1 Induced Draf t Fan required to protect the unit. One transformer 3500 hp 1 Forced Draf t Fan C !.p to feed the unit's auxillarles which is connected 8 Coal Mills to the generator high voltage bus satisfies this 800 hp 1 Coal Handling Feeder conclusion.
Conveyor Motor 900 hp Based on these conclusions, the major aux
- Transformer 750 kva litery electrical system for Trenton Channel No.
Transformer 500 kva 1 480 y feeder 9 will include one transformer supplying the main auxillaries of the unit. The transformer will Precipitator Transformer 1000 kva be connected to the unf t's high voltage bus, thus standby Transformer 1500 kva providing an exceedingly sigle system. Major auxillary bus transfers an'd auto-throwovers have West Auxillary Bus been eliminated. Power for smaller essential 2 Ceneral Service Pugs 400 hp services and for maintenance work when the trans-former is down for service is provided by an 4 Boller Circulating Pumps 700 hp essential 480 v bus with dual feeds from the i Induced Draf t Fan 3500 hp i Forced Draft Fan 1750 hp.
unit transformer and the existing plant.
2 480 v Feeders The Detroit Edison Company considers the Precipitator Transformer 1000 'kva engineering of Trenton Channel No. 9 auxillary sus 1 Transformer 1500 kva system to be a forward step in the design of Bus 2 Transformer 1500 kva 2 Heater Drains Pugs 450 hp power plant auxillary systems.
3 Condenser Condensate Pugs 250 hp
.I Station Air Compressor 350.hp D3
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