910 POST: PORT WASHINGTON POWER PLANT FEATURES Transactions A.I.E.E.

Discussion good engineering, for little should be left to pure opinion or

Alex D. Bailey: While Mr. Post's paper possibly affords personal preferences unless these actually are justified by theopportunity for discussion regarding certain detailed features of economics of the case.

station desig, iThe decision to install 1 boiler per turbine is justified fully bvstation design, it is important primarily becanse it embodiesthe... .. . . . w ~~~~~~theoperating experiences of ma.ny plants. The writer has beenbest thought in station design, though it originated 4 or 5 years . w

ago. The design of this station shows quite conclusively the an advocate of this system for years. The size of the units at

value of simplification, which offers the greatest opportunity for Port Washington and the high pressure and temperatures em-

reduction in investment cost. With the improvement which has ployed are the outstanding characteristics of this 1 boiler per

been made in the reliability of both steam generating and turbine turbine plant.equipment in the last few.yearsl of s n .is In selecting boiler pressures, the engineers of this plant had

equipmeganingte las the advantage of complete records of the 1,200-lb plant at Lake-rapidly gaining favor.aSo far as the 1,200-lb turbine units are concerned, the per- side Station. In view of the excellent performance at this plant,

formance record ofal turbines for 193 s tt te 1 b one is not surprised at the decision to use this pressure at Portformance record of all turbines for 1932 shows that the 1,200-lb ahntn atclrywe tevroscs nlssmiunits are fully as reliable as those operating at lower pressures. Washigton, partocularly when thevarnous cost analyses indi-The 4 high pressure units at Lakeside have a particularly good a '

record as all 4 ofthem are betterthantheaverage.are based upon 60 per cent load factor. One may question thisrecord as al 4 Of them are better thlan thle average.In the controversial question of the unit system versus bin assumption, for in the past, the average load factors of station

system,the design apparently was based largely on reliability equipment over their whole useful life falls greatly below thissystem, figure. It is evident that a long operating life is assumed aswhic Jaturallyn,Speakingabstpractly fm t a indicated by a rate of 13 per cent for annual fixed charges. IfE,.J. Billin,s: Speaking abstractly from the standpointofPort Washington is to be the base load station of the system, thenthe manufacturer of power station equipment, a customers Lakeside will be relegated to peak loads and its fine performanceevaluation of bids is apt to be fraught with uncertainties and sur- records accordingly will suffer. What is the basis for the selec-

prises to the bidder. When, as presented in this paper, the custo- tion of 60 per cent annual load factor?mer fearlessly gives out details of the evaluation for a secondary Mr. Post takes pains to justify the use of 825 deg F steam and-iluton by the engineering public, it iS certainly a PrOgreSSiVeevaluatio by t e pr reheat temperatures. The writer believes that even higherstep in the direction of equitable evaluation of bids.Although the author stresses the point that the design has been meratr coulbe fully justified. It is certain that special'

worked out strictly for local conditions and that for other con- mtealswil be uo 82deg Fhantbe additional cost ofditions or other locations the design might have been radically materi fr25t 50 deF erftemperaturesshould not havedifferent, there still remains the possibility that some of the be very grea h the mance station would' . 1 1..1 . ~~~~~have been improved. One may expect stations operating atpremises will be accepted more literally by a portion of the engi-neering public than is really intended or justified. This is sta,ted 1,000 deg F within a few years.neeringparticublarireferenthatiy prte of justh perd.eain wi the In view of the increasing use of slag bottom furnaces with high

rates of heat release, the decision to use dry bottom furnaces withboiler and combustion equipment. To illustrate:aboinlTbleIrth dfiitand unquestionableipment. fixedchargaite a heat release of only 15,000 Btu per cu ft will arouse much com-In Table IV the definite and unquestionable fixed charge item mn.Oeaigrcdsofthrsainwthmdaerts.. .11 1 1 .............. . |. . ment. Operating records of other stations with moderate rateson the added cost of the bent tube boiler with large furnace is of heat release such as Lakeside, Avon Beach, and Ashtabula,shown to be more than offset by a series of operating credits any a

l

one of which is subject to a variety of conflicting opinions. Sup- s ain ten and highincy. The d o tore-pose, for example, that the radiant superheaters and reheaters did tam this construction at Port Washington appears to be con-not work out quite as anticipated, and instead of having a furnace servative.maintenance credit over tbe high heat release slag tap furnace of The choice of the bin and feeder systems in place of the unit$5,700 per year the situation was reversed exactly and the system also is contrary to present trends. This paper affords ancr,edi becamea debit uppose, rete same an, the opportunity to the advocates of the two systems to discusscredit of $3,900 per year fOr better furnace availability became thoroughly their merits and disadvantages in the light of recenta debit instead. Thus, the margin of $9,763 per year over and operating results.above the fixed charge debit of $12,783 and in favor of the bent The selection of bent tube boilers with 5 stages of bleeding andtube boiler with large furnace might work out to be something air preheaters continues Lakeside practice. From theoreticalentirely different even to the point of changing the economics considerations, this is the proper arrangement of heat recoveryof the design se ec dtd. apparatus in spite of the increasing use of high pressure econo-Whe an engineering evaluation brings two quite radically mizers.

diferent designs so close together in worth to the company that Other writers have pointed out the savings.in power to thetedifferentdesigs measureda,soinethein worthintermsotheo rdvt boiler feed pump that may be secured by pumping cold ratherthe difference is measured, as in this ease, in terms of the order than hot water. The Port Washington plant probably is the firstof 1 per cent of the annual fixed and operating charges, then the

t pl hsie npatc.Ti ed oteueo leedesigner might well make his selection purelv on the basis of to apply this idea in practice. This leads to the use of 3 bleederwhich design he thinks will give him, his management, and his heaters under full 1,600-lb boiler feed pressure and their per-operators the greatest amount of satisfaction during the life of formance will be followed with interest. In designing thesethe equipment. heaters as shown in Fig. 3 a new idea of sub-cooling the con-

If more power station designers would present as freely as has densate is introduced which Mr. Post claims will improve plantthe author of this paper their line of rea,soningf for evaluation by economy by i4 per cent. One is led to question why advantagethe engineering public it would do much to sta,bilize fea,tures of has not been taken of providing more counter-current flow a.tdesign onwhich there is now a considera,ble divergence of opinion, the steam entrance to take advantage of the superheat in theA. G. Christie: Milwaukee's power pla,nts from old Oneida, steam at certain of the upper heaters, to lessen or possibly over-

Street to Lakeside have aJll been noted for their contributions come entirely the terminal difference of the leaving feed water.towards advancing the art of steam station design and operation. While many savings are given in the paper, the writer did notThe new Port Washington Sta,tion adheres to this tradition a,nd notice any sta,tement of the expected overall performance of theMr. Post's excellent paper will be studied in detail by power station in Btu per kwhr. Such a statement would be of wideplant designers a.nd opera.tors. One is impressed with the pain- interest as undoubtedly it would establish a new standard forstaking considera,tion given to a,ll equipment a,nd pa,rticula,rly steam stations.by the complete dollar analysis applied to each decision. Tbis is In Table VI the station peak capacity is valued at $75 per

September 1933 POST: PORT WASHINGTON POWER PLANT FEATURES 911

kilowatt. Is one to infer that this is the estimated cost of the our studies also have indicated that neither vertical nor horizontalnew Port Washington Station? isolation is justified economically when compared with the latest

I. E. Moultrop: The design of the Port Washington Station designs of non-isolated construction.described in the paper again points out the results that can be R. C. Powell: The studies for the design of the proposed plantobtained by careful engineering study and intelligent economic for the San Joaquin Light and Power Corporation at Herndon,analysis. While we may not agree with all of the conclusions confirm, in general, the conclusions arrived at by Mr. G. G. Post,advanced in the paper we know that at least the decisions are viz., that a single boiler and turbine installation operating atbacked by the best engineering judgment. Many of us agree on 1,250 lb pressure and 850 deg F maximum temperatures for pri-the selection of the economical pressure for the new station, and mary superheat and reheat is the best economically, all thingsit is hoped that the authors accomplish what they predict as a considered, and is as reliable as lower pressures and temperatures.result of the steam temperature selected. Due to favorable climatic conditions, both the boiler and tur-As we raise the operating steam temperature nearer and nearer bine together with some of the heaters at Herndon were to be

the limit of the available materials of construction, the control installed outdoors. The capacity for Herndon (75,000 kw maxi-of the steam temperature becomes increasingly important. It mum) approximated that of Port Washington.would be interesting to receive the operating results and to com- Mr. Post's statement regarding inconvenience in operationpare them with the design expectations as shown by curve 1. and maintenance for the vertical compound unit is not confirmedIf the authors are able to obtain these flat steam temperature by the experience at Station A after 22Myears operation with thecharacteristics, they will have solved the major problem that has type where the high pressure units are mounted on the low pres-retarded the adoption of steam temperatures above 750 deg F, sure generator. So far as can be determined to date, such unitsand will have gone a long way toward justifying the abnormally have neither operating nor maintenance disadvantages.large furnaces used in their design. Mr. Post's statement as to an investment saving of $250,000We have recently made a careful study of the design of a new with 1 boiler over 2, checks very closely with an estimated saving

high pressure reheat station and our investigation showed a lower at Herndon of $225,000.cost per unit of capacity for the cross-compound turbines with Mr. Post's conclusions as to the relative costs of bent andconstant back pressure on the high pressure turbine as compared straight tube boilers are confirmed by our studies, but experiencewith the straight tandem-compound design. Furthermore, by at Station A with straight tube boilers does not confirm his con-the use of multiple-valve high and low pressure turbines and the clusions that straight tube boilers are deficient in water storageproper heat balance arrangement, the same economy can be ob- and circulation, or do not furnish dry steam even when forcedtained above 60 per cent of full load and the difference in economy severely, also, that there is any difficulty as regards water wallbetween the two designs is only 1.3 at 45 per cent of full load. The connections or in the removal of suspended solids. At Station Aconstant back pressure design has much to recommend it, and the load on a turbine unit has been increased from 10,000 kw toshould not be discarded without careful study of all the advan- 50,000 kw in approximately 35 seconds, with very little dis-tages and disadvantages. turbance as regards pressure, temperature, or change in drum

It is believed that The Milwaukee Electric Railway & Light water level.Company is the only large utility still using the large "lazy Undoubtedly, the use of coal would have considerable influenceflame" furnace with low heat release. Most new installations are upon the selection of boiler equipment, but, at least with oil anddesigned for a heat release of twice that used in the Port Wash- gas fuel, the higher investment for a bent tube low heat releaseington design and our studies indicate that the higher heat furnace is not justified. Nevertheless, the cost difference is notrelease designs should be cheaper to build. It will be interesting great and Mr. Post is sound in sticking to something that histo hear later whether the lower furnace maintenance costs have own experience has proved so successful.justified this greater investment. The writer fully agrees as to the advantages of high pressureWe must admit that the control of steam temperatures by heaters, although for somewhat different reasons than given. The

means of desuperheaters is not all that could be desired, but it experience at Station A with 1,600-lb pumps taking water atis workable and offers one solution of the problem. approximately the temperature given by Mr. Post, viz., 430 deg FThe difficulties with, and high maintenance costs for economi- has been very excellent with no difficulty due to varying tem-

zers mentioned in the paper were true of the designs of 5 years peratures. There is, as mentioned, somewhat better economy byago, but the designs now offered by the manufacturers have pumping at lower temperature, but the real advantage is in the,eliminated most of the objectionable features. We feel that the simplicity of one pump as against two in series.economizer is an economical form of heat absorbing surface and Philip Sporn: The conclusions as regards the mercury steamhas a place in the design of high pressure installations which cycle, or even the less tried Benson cycle, most certainly arecannot economically be replaced by the air heater or more boiler decisions that are justified fully in the light of the present avail-surface. able knowledge as to the success, plus or minus, of each of these

In view of the results being obtained in many stations with two methods of generation. It is, however, open to questionthe unit system of pulverized coal firing, mnany of us cannot whether the conclusion to adopt the 1,200-lb, 825-deg reheatagree with the statements in regard to the comparative merits cycle was reached after exhausting all other possibilities. Forof this system in comparison with the bin system. We question example: although a comparison was made with the 600-lbespecially the accuracy of the statement that in commercial reheat cycle, no figures are presented for the 600-lb, 825 degoperation the bin system will show 2.1 per cent better station non-reheat cycle. If any figures were developed in this connec-economy than the unit sy,4stem. We do not believe that this tion, theywouldbemostinteresting.statement can be substantiated. In connection with the various phases of the heat cycle andThe design of the high pressure extraction heaters used is the effect of fixed charges on them, Mr. Post uses aJ figure for

extremely interesting and shows a marked improvement over fixed charges of 13 per cent. While this perhaps is adequate, itdesigns used in the past. This design seems to provide a, sturdy might be pointed out that with money taken at 7 per cent andpiece of equipment that should be free from troubles and should taxes and insurance at 1 per cent, a total of 5 per cent is allowednot be unduly expensive to construct. The arrangement for for depreciation and/or obsolescence. Under certain conditionsundercooling the heater drips is an outstanding development. 5 per cent might not be sufficient. It is interesting, too, thatOur studies confirm the conclusions of the author that outdoor the savings in fuel figured on the basis of a unit fuel1 covt of

iron-clad switches and structures are more expensive for 25,000 $3.80 per ton, would show up entirely differently if tlhe fiCxedvolts than indoor or combination indoor-outdoor designs. But charges involved in the mining of fuel were taken into considera-

912 POST: PORT WASHINGTON POWER PLANT FEATURES Transactions A.I.E.E.

tion. This, of course, was not necessary in connection with the further thought desirable and/or necessary to supplement thatPort Washington Station, but obviously it has to be taken into by battery service. It would appear that this was a refinementconsideration in a not uncommon case where a plant and coal that could justify itself only in extreme conditions.mine are operated as a unit. Again, from the broad national G. G. Post: In his discussion, Mr. E. J. Billings makes twoeconomic standpoint, it has a very definite significance. suppositions in referring to Table IV, one that if the radiantThe conclusions and the report of the results of the battle of superheaters and reheaters did not work out quite as anticipated

storage vs. unit system of fuel firing are extremely interesting, but the furnace maintenance credit of $5,700 per year over the highit is not quite certain that the battle has been fought entirely on heat release slag tap furnace might become a debit, and thefair grounds. It will be noted, for example, by referring to Table other, that for the same reason the credit of $3,900 per year forVI, that the burden of excess investments of the storage system better furnace availability might also become a debit. Admit-in the amount of $59,112 is compensated by capitalizing the peak tedly, there might be differences of opinion in various engineer-capacity resulting from the smaller electrical demand, at the rate ing phases of a plant of new design, such as this, but in the 2of $75 per kilowatt. The writer wonders whether a consideration examples cited by Mr. Billings, The Milwaukee Electric Rail-of the entire system as a unit, rather than only this particular way and Light Company feels that it has made no rash assump-station would not show that the difference in capacity required tions for the bases of its calculations. The company has been aby the 2 fuel firing systems could not be met several times over co-developer of radiant heat absorbing surfaces since 1923 andby excess capacity in the form of overload capacity on running has at its disposal actual operating records and accurate data onturbines, or in the form of standby capacity in idle turbines; such surfaces, to say nothing of the experiences gained throughcapacity that would go unused as a result of the saving in capacity their use. Actual furnace maintenance costs (including waterat this particular plant. If that is the case, it is obvious that the and steam walls) on the 4 high pressure boilers at Lakeside dur-credit of $44,400 is not quite a sound credit. ing the twelve-months' period ending July 1933, were $10,437The electrical phases of the plant with the 3-system of busses for 306,593 tons of coal burned, or 3.40c. per ton. The figure

are extremely interesting, but one wonders whether all the switch- includes any and all replacements, none having been changed toing end of the bus work involving a single unit really was con- capital or depreciation accounts.sidered indispensable before the final decision was made toward As to availability, mention was made in the paper of the 93.7its installation. It would be interesting to find out whether a per cent which these 4 boilers averaged during 1932. To date noscheme was considered which utilized 3-winding transformers for comparable record for a boiler with a high heat release slag tapthe main power group having a 26.4-kv winding on the low side, furnace has been found. In making the calculation for avail-with a 22-kv auto-tap on this winding, and 132-kv winding on ability, it was assumed that the high heat release furnace wouldthe high side. If this did not give proper phase relations, a have an availability of only 2.5 points below that of the low heatstraight 3-winding transformer could be used. With a 3-winding release furnace:-87 2 per cent against 90 per cent.transformer it would of course be possible to make the 22-kv Mr. A. G. Christie inquired as to the basis for the selection ofside delta and the 26.4 and 132-kv windings Y, with the idea of 60 per cent annual load factor for the various calculations in thefurnishing the present as well as future local power requirements paper. Sixty per cent annual load factor was selected because itat 26.4 kv. This would eliminate entirely the 22-kv switching is expected that Port Washington will be operated at this loadand have the further advantage of not subjecting the generators factor without detrimental effects to the economy at Lakeside.to any hazards that may result from feeding directly into over- High availability, proved possible by the Lakeside high pressurehead transmission lines from the generator terminals. Again, units, will assist in obtaining the 60 per cent load factor. Con-Mr. Post shows reactors behind all the 22-kv breakers, a further ditions at Lakeside, which will be the secondary plant of Theitem of expense. It is obvious that the elimination of the 22-kv Milwaukee Electric Railway and Light Company's system afterbus would have eliminated the necessity for these. As far as the Port Washington is in operation, are different than would ordi-effect on the short circuit capacity of the other voltages is con- narily be expected because there the 1,200-lb cycle capacity iscerned, they might have been handled by higher reactance trans- only 40 per cent of the total station capacity, the remaining 60formers properly distributed among the 3 windings. In trans- per cent being straight 300-lb equipment, some of which is overformers of this size it is no great burden to obtain reactances up 10 years old.to 22 per cent. It would be interesting to find out whether such a In providing load for Port Washington, the load will in effect bescheme was considered and what were the reasons against its transferred from the comparatively inefficient 300 lb section atadoption. Lakeside. This will tend to improve Lakeside's overall stationKeeping in mind that a great deal of money is expended in economy, but also because of having to transfer a small amount

switching, one wonders whether a scheme of tying together the from its 1,200-lb cycle during low load periods, Lakeside's overallauxiliary transformer to the main generator winding without a station economy has been considered as remaining the same. Thislow tension switching was considered and why this was not is reasonable especially in light of the fact that partial-load heatutilized. For example, we have operated our Deepwater Plant consumption on the Port Washington 1,200-lb cycle (compoundthat way for almost 3 years without any difficulty, and would operation) will be better than it is at Lakeside (constant backduplieate such an arrangement today. pressure). The transfer of load will not be as great as it may

In connection with the splitting of the auxiliary load in 3 seem at present because by the time Port Washington goesgroups, namely, 2,300 volts alternating current, 480 volts alter- into operation the load on the system as a whole will havenating current and direct current, and the drawing of the line increased.of demarcation between the two alternating current voltages at In Mr. I. E. Moultrop's opinion, the 2.1 per cent better stationapproximately 100 horse power, one is inclined to ask whether economy for the storage system over the unit system cannot be550 volts was considered and if so, what the reasons were against substantiated. For Port Washington's design with its singleits adoption. Most low tension switching equipment in the 480 boiler-single turbine, its large air heater without economizer, itsvoltage rating permits safe operation at 550 volts, and further- radiant superheating and reheating surfaces, its higher steam andmore, with the newer olilless switching equipment, the economic reheat temperatures (850 deg F maximum), and its mill dryinglimit of the lower voltage is closer to 250 horsepower than 100 with flue gas, and for conditions under which the station is ex-horse power and permits a considerable saving by the elimination peeted to operate, each one of which enhances the difference, theof the 2,300-volt switching equipment. Again, it would be 2.1 per cent is conservative. In order to show how this total wasinteresting to find out why direct current service was adopted for arrived at, the results of ca.lculations for the component itemsthe operation of turbine-room elevators, etc., and why it was follow:

September 1933 POST: PORT WASHINGTON POWER PLANT FEATURES 913

Reliability "demand charge" feature of electric service rates. In general,An outage or an interruption on any one of the 4 unit mills considered for load cannot be put on a system without providing station ca-

the Port Washington installation would necessitate an immediate transferof load to older equipment in another station where the heat consumption pacity to carry it.would be 2,500 Btu per kilowatt-hour power and coal would cost 66c. per Another point mentioned is the omission from the compari-ton more. Obviously, the economics of the case dictate operating Port sons of a table showing figures for the 600-lb, 850 deg F stationWashington to its greatest possible extent. A statement by a company operating without reheat. It was omitted because calculationsusing both the unit and the storage system on an equal basis points out thatin three months' operation it was necessary, due to difficulties with unit showed that the 600-lb station with reheat efected a $16,100mills, to reduce the load on the station from 5,000 to 12,000 kw on 7 different larger net annual saving than did the 600-lb station withoutoccasions. Should only 0.5 per cent of Port Washington's total possible reheat, and therefore, the former was selected in making thegeneration have to be transferred in a year, because of interruptions, to the comparison with the 1,200-lb cycle. Space did not permitpoorer equipment whose heat consumption is 20 per cent poorer than Port . compari sh12- cyc Spaer didnotuperWashington's, an 0.1 per cent loss in station economy would result. prmiting this comparison nor many other nterestng studies

made for the Port Washington station.Storage Unit Concerning the electrical features, reference to Fig. 5 willMill Drying _Reduced flue gas losses indicate that there is in reality but one bus in the station, thisDue to 6 per cent of the flue gas discharged to stack at150 being the 22,000-volt bus. The 26.4-kv and 132-kv busses aredeg F instead of at 350 degF ............... percent ...0.35 0 for transfer purposes only. All switching is intended to be done

Due to greater mean temperature difference and greater at 22-kv and transformers are in effect portions of individualheat absorption in air heater...............per cent... 0.40 transmission lines. It was thought desirable to provide a 22,000-

Total gain ........................... per cent. ..0 .75 volt bus to effect economies in switching and to permit industriesCoal vent loss ........................... per cent... 0.25 that might locate in the vicinity of the plant to connect directly

to the bus bars without the need of transformation. This isimportant when it is remembered that such industrial load might

Temperature Variation amount to as much as 150,000 kilowatts. The use of a 22,000-a. Coal feed variations without hand adjustments per cent. . 0 10 volt bus dictated the use of reactors in all the lines except thoseb. Variation inCO 2 ........................ percent... 0 1.7c. Variation in radiant heat absorption .......... per cent ... 0 20 supplying the transformers stepping up to 132 kv. Reactors ared. Change in reheat temperature, (deg F).. . 0 50 not necessary in the leads of the 132-kv transformers because thee. Effect on station economy (1 per cent per 80 deg F on phase conductors are isolated. At the Lakeside plant, 10 over-

reheat alone) ...... per cent loss... 0.6 head transmission lines operating at generator voltage are con-

Pressure Variation nected to the station bus through only a few hundred feet ofa. Boiler pressure variation ................ lb/sq in... 5 50 underground cable and since no trouble has been experienced web. Operating pressure. lb below popping point lb/sq in. 50 95 do not believe there will be any hazard in similarly connectingc. Lesser operating pressure.lb/sq in.45d. Efsect on station economy . per centloss.... 0.6 overhead transmission lines at Port Washington.AirEffeat Pormsation cnomy. per cent loss. 0.6

In the auxiliary service 480 volts was used because this is theA.r Quantityofrforoomai used for tempering air throughauxiliary voltage at Lakeside and also is a standard voltage on

b. mi percente.mpering the company's system. The division between 2,300 volts and

b. Resulting effect on flue gas exit temperature, deg F 12 480 volts was made at 100 hp because in the first unit of thec. Corresponding effect on boiler efflciency. ..per cent loss. .. 0.3 station it would have cost $5,300 more to have made it at 250 hp.

Summary The switching arrangement shown for the first unit is tem-Greater reliability ..................0 . 1 per cent porary in some respects but is such that it can easily be changedMill drying gains .0.5 per cent to conform to the expected ultimate arrangement. Three-wind-Temperature variation gains .0. 6 per cent ing transformers for the main power group were considered butPressure variation gains. 0. 6 per centBetter air heater performance . .3 per cent were not adopted because no ultimate saving could be effected.

We have always considered it desirable to install oil circuitTotal advantage of storage system ...... 2. 1 per cent breakers between generator leads and auxiliary transformers so

as to permit the disconnection of such transformers without inter-Mr. Philip Sporn takes exception to capitalizing the value of ruption to service. The station is being built to operate at a high

the greater kilowatt demand of the unit system motors at the availability factor and in our opinion the relatively small addi-time of the station peak, maintaining that the extra or over- tional expense for disconnecting the auxiliary transformer wasrating capacity of this station, or of others on the system, would justified.be sufficient to absorb the small increase in demand created by Direct current service was adopted for certain equipment andthese motors. While the argument may at first seem reasonable backed up with a battery because this system will be used forand it may be difficult to allocate certain station capacity to reserve excitation and for driving the pulverized fuel feedersindividual loads, it must be admitted that some station capacity supplying coal to the furnaces. It is very desirable in case ,ofis required, even for a load as small as that of a residential con- system disturbances to be able to control the fires accurately insumer. That this is recognized generally, is attested by the order to restore service more promptly.