military standard definitions applicable to speed...

MIL-sTw7aA17 March 1958

SUPERSEDINGMlLS~17824 Match 195s

MILITARY STANDARD

DEFINITIONS APPLICABLE TO SPEED-GOVERNING

OF ELECTRIC GENERATOR SETS

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OFF$CEOf THE ASSISTANT SECRETARYOF DEFENSEWASHINGTON 25, 0. c.

Supply and I@stics 17 March 1968

Defkdtians Applicable to Speed-Governing of Electric Generator ~

ML-S’NM78A

L This standard has been approvwi by the Departme]~t of Defenseand is mandatory for use by the Departments of the Amy, the Navy, andthe Air Force, effective 17 April 1958.

2 In accordance with established prwedure, tlw G.:ps of Engineers,the Bureau of Ships, and the Air Force l!n”;e hen Mlgnzted as Army-\’avy-.4ir Form eus Lodiam of this SWLJ:,,,;

3. Recommended corrections, additions, m= d~~!etions shoI.IM be ad-dressed to the Wmdardimtion Division, O~Cc c,: :1:, .>~~:~:arl &clr:=r:iof D#fense (Supply md Logidics j, Washington 25, D. C.


MlL-STD-l 78A17 Morch t9$8

1. SCOPE

2. REFERENCED DOCUMENTS

3. DEFINITIONS

4. ALPHABETICAL LISTINGS OF TERMS WHICH ACCORDING TOTHIS DOCUMENT ARE NONSTANDARD

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MU4TD-178A17 Murdl 19s8

) L SCOPE

This standard covers definitions of termsapplicable primarily to complete primemover driven generators and to mechanicaland electrical speed-governing of generatorsets where the ratio of prime mover speedto generator speed remains constant. Withincertain limitations, which are obvious, thisstand may also be used for generator setswhere the ratio of prime mover speed togenerator speed varies.

2. REFERENCED DOCUMENTS

2.1 The following standard, of the issuein effect on date of invitation for bids, forms3 part of this standard.

FED-STD-5 — Standard Guides for

w Preparation of Item

)

Descriptions by Gov-ernment Suppliers.

3. DEFINITIONS

3.1 Average. Average is the quantityfound by dividing the sum of ail quantitiesby the number of quantities. Example: theaverage of 3, 5, and 10 is 6. For the purposesof this standard the terms average and meanare used synonymously.

3.2 k speed. Base speed is the speedrepresented by the midpoint of the steady-state speed regulation band at rated pow*eroutput (see also, mean governed speed (3.7 )and midspeed (3.9) ).

3.3 Deadband. Deadband is the total speedchange 1~-ithin which the speed-go~erningsystem makes no measurable correction tothe setting of the go7+-ernor-controlled de-‘.-:CWS.swh as fwi-n-,wt’r;ng equipment.

stability of speed which is evidenced byforced oscillation of the speed about a meanvalue where the amplitude of the oscillation(periodic maximum deviation from the meanvalue) exceeds the specified limits for thesteady-stat e governing speedband. An ob-served condition of hunting is described ‘bythe frequency and amplitude of the osciUa-tion. The amplitude is expressed in percentof rated speed.

3.5 Load detector.A load detdor is adevice which senses load, or a quantity pr-portional thereto, and delivers a signal out-put proportional to load.

%6 Mean. Mean is the quantity found bydividing the sum of all quantities by thenumber of quantities. Example: The meanof S, 5, and 10 is 6. For the purmaes of thisstandard the terms mean and average areused synonymously.

3.7 Mean governed speed. Mean governedspeed (see figure 1) is the average speed thatoccurs in a given period during which a gen-erator set is operating under any sustainedcondition of electrical load with the speed-governing system in control. It is the arith-metic mean of all the instantaneous valuesof speed occuring during the period underconsideration.

3.8 Mean speed-power curve. The meanspeed-power curve is the relationship be-tween mean governed speed and power out-put of the generator set.

3.9 Midspeed. I’klidspeed k the averagespeed obtained from the maximum instanta-neous speed and the minimum instantaneousS])(?sd iM!lUd&d ill tlit! ObSC!l’V@?d S@?dbi31d

(see figure 1), of a generator set when OPcrating under conditions of strady=state elec-:ricfil load.

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MAIO-W$A97 m 1-

Cmua la speed above the midapeed ~at the aaxmd opemthg condition incident toa sudden decreaee between two giveA St--6tati electrical lode. It is expressed in per-cmt d r8td @peed, ma:

(a) For a load decrease equal to ratedpower output:

So=l=k-&n,

Where:

n, = rated speed.

(100)

na = midspeed at zero power output.

n- =: maximum momentary . speedincident to a sudd~n andcomplete loss of load fromconditions at rated spmland a steady-s+tate electricalbad equal to rated pcwevoutput.

(b) For a load decrease !ess than ratedpower output:

nmar- n,so=—n,

Where:

n, = rated s~.

(100)

n. = midspeed at the secondstate electrical bad,

n~,= = maximum momentary

steady-

Speedincident to a sudden reduc-tion between two steady-atate loads.

%11 Iblomeniary mderapeed. Momentaryu?dfwsp?wl !!lee flw~re 31 is thr ?nnxi-,’:m

momentary decrease in speed below the rnid-speed occurring at the second opmti~g con-dition incident to a sudden increase betweentwo given steady-state electrical loads, It isexpresd

2

in percent of rated speed, thus:

Su - ‘~:n=:~- (100)n,

Where:

n, = rated speed.

m = midspeed at the eecond deady-8* elcwtski loa4L

blm = minimum momentary speed ia-cident to a sudden IncreaaehWeen two steady-state elec-tricalloada.

0.12 Obswved epeedbaA& Observed speed-k,~[? is the speed-time enve]ope having up-per And lower speed values represented bythe maximum and minimum instantaneousspeeds which occur during a sample time in-ter-t al t nroughout which the specified condi-tluns pi”eva;; and so chosen that a repm-wfi:al i$*(BSe(’tion of t! !3 act u:.1 instrument?“ace of th+. ~peed-time function % mverad.The o~scrved spesdband is described narzBs-tiveiy by ~tsting the deviation of these upperand lower speed values from the midspeed,where the amplitude of dev%tion is expressedin percent of rated speed.

3.13 Powe.o output. Power output is thefl~t ~]~1’i”;ai power ?.hfit is oht a ined fromthe gencrah ~?”set. k is t)w e)ectric~ 1 poweroutput at the generator term inala after d-ductions have been made for the electrical?(lwer ::sed i)y any auxiliar]es that by agree-ment are Ccrisidered to function in e?fect asessential par~~ of the basic generfitor set.

3.14 Prescribed ~pedmnd. Prescribedspeedband is a speed-time envelope havingupper and lower s-d limits which repre-sent, respectively, the values of the maximumand minimum instantaneous speeds to beused w*hendetermining the instant of termi-;..I:.I..IA4IA’r~~~k~ry .Jllu i:. kll”cd. Tl!e ‘;&ll.itiof thew lim.jts are specified by means of anamplitude wi~ich is taken with respecl to ;hemidspeed of the observed speedband. Thisamplitude is expressed in percent of ratedspeed.

3.15 Rated Power output. Rated power

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output is the mandactuwr’a stated or guar-anteed net eiectdd POW- (kwJ OUtPUtthat is obtainable continuously from the gen-erator set when it is functioning at ratedspeed under the specified operating condi-tions.

3.16 Rated s- For alternating-cu=ntgenerator sets, ratd speed applies to thespeed which produces rated frequency. Fordirect+mrent generator sets, rated 8PAapplies to the identiflcatiop plate designvalue of speed for rated power output.

3.17 Recovery time. Recovery time is thattime which elapses between the instantwhen load starts to change and the instantwhen the speed reaches a certain state ofrecovery following a given sudden change inthe steady-state electrical load on a genera-tor set. It is the time in seconds from instantof change from the initial load condition tothe instant when the decreasing oscillationof speed finally enters a prescribed speed-band.

)3.18 Speed. The term speed as used her~in

refers to rotational speed (usually in revo-lutions per minute).

3.19 Speed changer. The speed changeris that portion of a speed governing systemwhich provides means for changing the meangoverned speed of the operating generatingset while the generator set is in operation.

3.20 Speed control mechanism. The speedcontrol mechanism includes all equipment,such as relays, servo-motors, pressure orpower amplifying devices, levers, linka~,valves and associated interconnectio~~ ~tween either or both the speed detector andload detector and the fuel-metering @W~Prnent in the case of internal combustion ~-gine generator sets, the valves in the case ofturbine generator sets, and the basic motorin the

.3.21

case of motor-generators.

Speed detector. A speed detector is

MlL~17SA17um

a devioe which senses aped, or a quantityproportional thereto, and delivers a signaloutput propotiiowl either to speed or tothe deviation of speed from a reference value.

322 Speed deviatk Sped deviation isa maximum departure of speed from mid-speed of the initial observed speedbandwhich occurs during transient response re-sulting from stated upsetiiw cxmditimmSpeed deviation is expressed in percent ofrated speed. S- deviations above rnid-speed of the initial observed apesdband mpositive and speed deviations below mid-speed of the initial observed speedband arenegative. When used without further quali-fications, operation with adjustments set forrated conditions and step changes in genera-tor load impedance is implie&

3.23 Speed drift. Speed drift is the totalamount of variation of the mean governedspeed with time under steady-state operatingconditions. For specified conditions andperiod of time, speed drift is expressed inpercent of rated speed.

3.24 S@-~V_ed syum. A speeci-gaverned system is a generator set or amotor-generatur as defined in Standard FED-STD-5, less the speed-governing system

3.25 Speed-governing _. ‘I’he 8peed-goveming system generally consists of aspeed detedm or such combinations as thespeed and bad detectors, and the neeeaswymechanism required to tranamit the speedcorrective action from either or both detec-tors to the fuel-metering equipment of aninternal combustion engine generator set,the valvea in the case of ● steam turbinegenerator set, or the -ic mtior in ~case of a motor-generator. It may also in-clude such devices as a speed changer and aspeed regulation changer.

3.26 Sped regulation changer. ‘I%espedregulation changer is that portion of the

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MIL-sT&17eA?7 “Mordl WSo

speed governor system which providesmeans for changing the steady-state speedregulation of the generator set.

3.27 Stability. Stability ia that property ofthe speed-governing system which causes itto develop restnring forces among its elec-trical and mechanical eknicmta.

348 Steady-sta@ electrical loacL Steady-statc electrical load on a generator set is anyelectrical power demand having a constantmean value although it may have either orboth the following:

(a) Random deviations not exceedinga specified value such as plus orminus 0.25 pel*cent of ratedpower output

(b) Periodic deviations not exceeding aspecified value such as plus or

minus 0.1 parcent of rated poweroutput.

3.29 Steady-state governing speedban&Steady-state governing speedband is a speed-time envelope l;aving upper and lower speedvalues represented by the maximum andminimum instantaneous speeds which oc-cur under given steady-state operating con-ditions with the speed-~ overning systemfunctioning. The limits for the steady-stategoverning speedband are defined by an am-plitude which is taken with respect to themidspeed of the observed speedband. Thistmplitude is expressed in percent of rated-*

3.30 Steady-state incremental speed regu-~tion. Steady-state incremental speed regu-

~ation is the rate of change of speed withrespect to power output under comiit ions ofsteady-state electrical load. It is representedhv the slope of the tangent to the meanspeed-power curve at the point of power out-put under consideration. When used v “:!:the qualification “steady-s”~te ~nc remen::?!speed regulation referred to rated speed” ‘:

is implied that the tangent is establishedfrom a segment of a speed-power curve ob-tained with the mean governed speed forthe point of power output under comidera-t ion set at rated speed by means of the speedchanger. Steady-state incremental speed reg-ulation is expressed in percent of rded speedwhen the dificrcnce in sp~, c~prc~d inpercent of rated speed, between any twopoints on the defined tangent is divided bythe difference in the corresponding powerkve !s at these points expr~ed as a fractionof rated power output. It may be expressednmt hwrmt ‘caliy in percent as f o!lows:

It, =PC (n, - n,) (100)

n, (Pl - l?:)

Where:

n, = rated speed,

n, - rhd speed corresponding tu thelarger power level P,.

n. = speed corresponding to the lesserpower level Pg.

P. =: rated power output.

d’

3.31 Steady-state operating conditimwStF:;dj”-state operating conditions exist whenthe qenPmt or set ip functioning with anyinf?uences thtit are variable coming withinw]:, limits that may hatre ken specified forstead j--state operation, or, if no limits havebeen specified, are as nearly constant as ispractically possible.

3.:32 Steady-state speed regulation. Steady-sw.te speed re~ulation is the change in mid-speed, expressed in percent of rated speed,u“hen the potvw”output of the driven genera-tm. is ~educed from rated power output toZt’!’[}pov-e:”output with fixed wtf.ings of all:{djustmcnts of the speed-governing system.[“I~less otlmwise i:~dimted, the fixed .set-tinps l~f :Idjustrnents are such that basesyed Nnd Mtwl speed coincide. Speed I-egu-10””.,?.;ll~ ;< L*..~~~ideredpositive u-hen the speeda- zeru :~~1~1tJI. output IS grcnter than thespeed at rzted power output.

4 )


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.

) =~w=$etim-d’Staady-state aped regulation band is theband formed by the parallelogram of mini-mum area which circumscribes, betweenaero and rated power outp~ the group ofmean speed-power cnnms, obtained in suchmanner as to establish the bounds of opera-tion of the generator set under the control-ling infhwme of the speed-governing sy8-tem for given conditions of adjustment,limits of environmental conditions, andmodes of operation of the generator set. It iudesignated in terms of speed spread (ex-pressed in percent of rated speed) and slope(expressed in percent of 100 percent speedregulation ). When the term is used withoutfurther qualification, operation in accordancewith applicable specifications with adjust-men~~ set for rated conditions is implied.

4. ALPWkBB’XKXL LISTING W TERMSWMXCH ACCORDXNG TO THIS DOCU-MENT, ME NONSTANDARD

1

4.1 Alphabetical listings of terms, whichaccording to this standard are nonstandardare as follows:

(a) -I? WlltiO]-8H 3.26.

(b) Frequemcy of dither~ 8.27.

(c)

(d)

(e)

(f)

(IO

(h)

(i)

Frequency regulation-see 3.82.

Momentary undera~~ 3.11.

Speed droop control++ee 8S6.

Speed governor actuating xnecha~nism-see 8.iW.

Speed governor ekment+we 35and 3.21.

Steady speed regulation–--see 3.32

Copies uf this skmiard for Milim u- may beobtained as indicstui & the f~ to tbe Izdexof Military Specification and St4UArd*

Both the title and the identimrqg qmhol numbershould be stipulated When requesting copkw ofMilituy stsndamh

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I STANDARDIZATION DOCUMENTIMPROVEMENTPROPOSAL OMB~p~~OVd

NO. 22.R2SS

INSTRUCTIONS: me purpose of this form is to soltcit benefscmi Comtnenta which wdl help schieve procure-ment of suitable products at reasonable cow ●nd muttmum dda). or wtll otherwise enhonce use of the document.DoD contractors, government scttvttles. or m-uf~cturers /vend- who ●e prospective suppliers of the productare invtted to submit comment. to the government. Fold ~m Ames on reverse sIdo, staple in comer, ●nd send toprepmring ●ctivtt y. Comments submitted on thisform do not conmstute or im~ly ●uthertsat ion to waive ●yportion of the referenced document(ol or to ●mend conwactuel requirements. Att8ch ●ny pertinent data whichmay be of use in tmprov;ng this Iiocum=t. If there ●e sddlti ‘nsl aapers, ●ttsch to form sad plmce both m MenveJope ●ddressed ,0 areodrmg ●ct~vity.

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Man~nt Office (ATTN: PD:PL)Bu21dSng lS7-3,Washingtm Navy Yardwashington, DC 20374

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