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The New Information System for the National Dispatching Centre at the Swedish State Power Board
SYS;:'';';L
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Tit:; ];Al'IOEAL DISPA'l'C:HI1lG
C~ITn 2
AT ':'lfu S,r::DISH S'l'Al.'L
Lars Gustafsson
Jo~~
PO ·.i~;{
BOARD
Lindqvist
Swedish State Po~er 30ard (SSPB ) V,-~ 11 inC'by,
ABSTRAcr First i s gi ven an account of th ,~ =esponsibilities of the Dispatch Centre with some back0rou:-.0. in fo.c.l a tion about the pO 'J er sys tem. Then follo~s a deriv at ion of the concept of the inf ormation systems funct i onal des i ;'"11 . I\Casons arc c iven for the effort to Cet a hiGh dcGree of inteGration and f l exibili ty i n the sys tem. 'r he system cons ists of a real t i me part and also an off-r eal time part (p la.!mins and statistics). These are Go inS to be int cGrated and the t,·;o databases fully coop ati be l. Eost of the report is devoted to the real time part, '.;hich has a bie in put of on-lin e data frol:: the »o;[er system . A ,lea',,)' amount of dat a is entered r:: anually to tile real t i me COI:lputer syster.; (2 :mJ S i gr:1a 9, ~2 bits, 1 60 K core each). !lence there is a sophisticated r.J a.!"l/ r.Ja~h ine coor.mnication systerJ . F inally is Given an account of the development plans for the nearest futur e , ',{hi ch a none; other th inss in c ludc the i mplementation of a real time state estimator . 1. 'l'm.: S',;;;;D IS11 PO',r,e;R BILITI J..;S 010' 3SPB
SYST~';
AND TIll.:
R~SPWS I
1.1. The install ed cauacity wit h i n the Swedish Po,..;er Sys tem is about 1 9000 l,!',{. Of this 65,: i s hydroelectric pOI·rer and 35,; thernal po\·f er. 'r he the rmal pOHer p lants cons is t of condense units, back pressure units, nuclear units and c asturbines. rl'ne S·vle d i sh gr i d cyste~ is composed of 400 kV lin es (6 770 km) anu. 220 kV lines ( 5 166 km), 10 synchronous condensers, 0 seri es c a pac i tors a!1.d ) ) shunt reactors. 'l 'he transforr:~er cap a c i ty connected to the system a~l ounts 'Co 26 000 : ,~vA . 'l'he s yste m, ',:h i ell is in terconnec ted with several region al systens in J\leden fo r 1 30 kV and 70 kV , has about 100 nodes. I t i s als 0 i n terconnec te-d I! i til the ,;rid sys t ems in Denr:;al.' k , I: or-.my a.!ld }' inland .
The averaGe al1nual increaoe of pO',i cr COnS lU:1ption i n S,·!eden i s so far s u p,:Josed to be about ~~ . The extension of the power system has to correspond ;;ith the i ncrease of the ccnsunpL ion . The incrcaGe 0; ins t aIel c apacity is primarily to be covered by nuclear po~e r. The constru ct i on 0:" ;"l in e nuclear uni ts Hith a~o tal -: a pa c ity 0:'" .) ):0 I~·. j is ~ oinc or;. . ::otic\?able is also the planned. i ncrease in in;;talled
Slfeden
,: apaci ty in hydro pO'.-ler i7lainly fo r peak load cov e race . The need for transmissio n capacity is pri~a rily to be covered by rul extens ion of the cfOO l:V systeill . An 800 kV system may hO'dever co;ne in operat ion about 1980. About 45:~ of the installed capac ity and most of the g r i d system belon~ to the SSPB . SSPB is rcsponsible for the operat i on of the crid sys t ep.! anu. for the inte rcOimex i ons 'xith the ile i ehbouring cow1tri es and also for the operation of the po;.;er stations belonc inG t o SSPB . An o,:Jerat inG d.epar t;'1 ent at t h e ilead quart e r s in Jtockholr:; a.~d its control room for dispatchine; - Power Cont rol - are responsible for the fol10l'l inG' functions: Opera tin g planninG', direction and supervision of the production system of SSFB - Opera t ion of the Swedi sh c ri d system i nclud ing load control ,vo ltac e reGulation, d irecti on of circuitbr eaker opcra t ions , permission to lin e outaGe and other maintcnance \{ork , sccurity supervis i on and system restoration after d isturbances - Su?erv isi on of the Nordic interconnexions - ?requence and time control - ACree!Jent s a bo u t exci.anses of ter:;porary pOI·: er (econorc i c pOI'f er exchanc c 1. ',:i tl; the 1: ord i c countr i es and I:i t h co!:!pan i es '.-/i th in Sweden 1. 2 . 'i'he 3\{ed ish pO',fer sys tem is c r o\,inc; rapidly in size an d co~plexity . ~ 3pec ially the installation of big nuclear unit s in the southern part of the system Gives r is e to a lot of ne',,' 9rob1e:.; s . Accidental trippin ,,: of this biG un i ts (900 K~ 197J, 1 200 - 1 500 ~~ dur ing 1 900's) calls f or rul increased need for operat in s reserve, ',;hi c h at evc:..'Y oonent DUS t be de f i ned in s ice, allocation and respon.:;e tine. 7he increase in short-circuit currents calls
for neH supe rvi s i on and pla;-.::.i nC routines. -:"he concentration of JJO'./er produ ct i on to big power st a tions in the s outh and mi ddl e of t~e country nay a t out aGes and d i sturbCl.nces c aus e 135
great chanGes in the load flo\1 of the systeo ..,hich necessitates rapid actions from Power Control. The chane;e froo a by hydroelectric po-.rer dominated system to a syster:: dominated by therrr,al pouer \-/ith bi G tl ifference s in marGinal production costs during the 24 hours of day and niGht increases the dem~~d for more accurate "llannine; and control . The short term re -;ul :J.t i on of the hydroelectric ,o', ler, Hl',i ch fro~: a:1 e c onor.-.ic point of' vie',' is very compli-
ted to ~ 30 million. To- day the return from the system is at least $ 60 million. Of the capitalized return roughly 60; come from normal state (pO\'fer production 25>~ , power pool cooperation lo;~ and operating reserve 255~) and the rest from the remaining states, alert, emergency and restoration. (As to the meaning of the four power system states see appendix 1) •
c~te1 ,
The investment cost for the real time system is no',-/ estimated to ~ 22 million . From this sum 20 to 25,: are dataprocessing and 5O;~ data acquisition.
~ il]
be of g reat
i ~portallce
for a ratio-
n al use of the pOHer system. At last the great irr.portance of the pOl.,er cooperation in S"'eden and in Nordel oUGht to be mentioned . The value of exchanGed tempcral~ pO'.ler between SSPB and other power companies in llordel has ar:lOunted to I"lore than ;;: 100 million/ year. This pOWer e):change is mos tly made up on an hourly basis by agreerJents between the dispatchroor::s. The impor tance of these pO~fer exchanGes uill prob ",i.lly continue to grO\l because of the remaininG d i rference in pOKer systerr.s , delays in the installation of new plants, increase in system size and increase in generation costs. (Hef 1) . A power systeE like the Swedish one is very dynamic, becam:e of the variations in \>;atersupply and because of the location in the middle of the ncrdic pOKer system , which leads to that a e:reat part of the "surplus" or "shortage" of po',,'er in \>That so ever area has an influence in this system. To this ,le r,Q;J have to add the "disturbances" of different kinds caused by the behavior of the ~i 6 nuclear units. AGainst this backcrounC: it is obvious that the claim to.pon the informat ion system for operatinc: planning ru1d direction and supervision of the pOl·rer system IT.ust be gre at \·ri th respect to the treat importance the operatior. of the pO'.·rer syster.: has fcr the econor;:y of the pO\ler cOIr.pany anc'. the fur:ction of the society . I f the soals hi el: reliability, GOoe. ecor.cmy and hiGh quality of electri c i ty shall be reached it seems therefore necessary to Give t!,e POller COl:trol the best possible equipoent . 2.
TIt.; nL'i'Uiill
I~ROJ·j
'i'he system is expected to be operational during fall 1975. (Ref 2) •
3.
THE CONCBPT OF TIDAS
3.1.
Integration from a functional point of
vie\{.
and interrelated goals for the dispatching activities at the control centre are good reliability, economy and quality of the delivery from the existing power system, here divided into 3 interrelated parts , production system, transmission system and pO\{er exohanges . Since predictive information (planning, scheduling, probing and so forth), real time information (indications, instantaneous values, logging, direct ordering, control ••• ) and "hat \-Ie call evaluation or follo\v-up information (statistics, reports ••• ) no doubt form a continuity in time it \'Ias natural to define TIDAS as an information system supporting all relevant decision makers \-lith adequate information from the 3 types of information to fulfil the main goals for the entire pover system . Fi[;Ure 1 is an attempt to visualize all the activities going on in a complete dispatch system . One can think of 27 boxes (activities) vith information running in between them . (Only one box indicated in fig 1) . Such a complete information system consequently also calls for a fourth kind of information , support or servioe information, keeping track of all the instructions, rebUlations, agreements , remaindErS and so on .
l~ ain
'l'IDAS the initiatinG studies we decided to divide the system into t\-IO integrated parts , one real-time part and one "off-real-time" part. '"'he latter consistinc of statistics, accounting, week ly ru1d seasonal plannin& and other evaluation study proerarrunes .
Fro~
froo ,·:tat is stated above one ca.!'). see the need of a !!;oc.e rn information system for "Power Control" . In 1969 the Board. decided to start the develoFment work of such a systec . From the beginnint; it was obvious that the sys te m l-:ad to be very flexible i n desisn , because of the most chancinG ccnditions under \Thich the ne'..' syste::! l:ad to func:t ior. durinc; its liiltime . Therefore the newest achievements in informaticn system theory and hard~,are developn.er..t as ~ell had to be used . It was dec i ded to Give priority to the real ti~e part of the system . ~ost of \That is said in thiG report ~reats this part of the information syster.: . '"'he benefit of the real time system
~'fas
estima-
) . 2.
DesiGn aspects
?ro!J "Ihat is earlier mentioned one can see that the new informat ion system had to be bui~ flexible to be able to reflect the changes in the pO\·/er system development and meet new requirer::lents from the dispatcher. This means modularity and an expression for this is among other things the two databases in the tvo systems. These t,IQ databases \-Till be fully eompatibel for easy exchange of data in bet,.een them and for easy access to both of them . In both cases we
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strive for a high desree of indeper. ':'.ence bet\,:een the base and its application proe;rannes to be able to easy reallocate or chance the data or to add new progra!:1LleS for instance. The 01freal-time sys terl "ill be runninc in our general purpose computer system.
bac:C up. l'here are t,,·o fi/;ed head 0.iscs (6 !:B each) ru1Ci one dual spindel removable disc (2 x 2,~ ~:B) at eacl-1 sys~er:.. Sor..e ,le-vices are sha:::-able, meanin,; that they CBI. be connected to bott of the syste'-1s by prosrar::controlled peripheral switches.
In ~hat follows only the real time part of TIDAS "ill be treated and it .dll be refe:::-red to as TIDAS for short.
The :7lan/machine subsystei:..l consists of -t co:-~so les "here 3 norn~lly are connected to the online systC:'l and the fourt::. to the bac]:-up systeLl (fiG 3 ). ;;;ach console has tHO u.isplays (nondedicated) and th e dispatcher nor;nally COHl!r.unicates \.:ith the cO!l:puter syste:n via these displays. 7he !:lain tasks of the SUbsystem are to p:esent information according to predefined forillats ar.l.G. to input data to the computer system. ', ;11en sui table the COl:1puter Gubsys tern Gives c uiding directiO!lG to the dispatcher' to facili tate his '. . ork and. reduce the possibili t ~r for r.listakes. );he displays are colou:c seraiGraphical. The \;ays for the fourth display to be used are:
For natural reasons 'f IDA::; consists of tHO ,'lain systens, the data acquisition syste:J aI!d the data proceseinc system with a carefully defined logical interface in bet1-leen. In the c.ata acquisition system there is a messaGe s1{itchinc network comprising 22 mino:::- process COI:lputers. In 1976 there will be transmitted some 850 indications and 750 digital or analc:.:-ue values online from the pouer and transoission system to the data processine system at the control centre in Stockholm. The data acquisition system is treated in ref 3. In a project of this size ry to carefully penetrate renents before we started '.4e have already indicated lity. Other requi:::-ements
*
High system reliability
*
Continuous round the clock operation
*
The information systen shall sinplify the every day \lork for the dispatcher
*
The DP-system shall be easy to learn ruld easy to use
*
'~uick
*
(;han{J=s in mes shall
- "on line CPU mode" is used. as back up for the consoles in the dispatchinG room
\Ie found it necessathe goals and requithe design VIork. the need for flexibiare for instance:
- "back up CPU !:lode" is used for procrarr: testil::;, traininG, deI:lonst:::-ations and display libra;:y f.1aintenance All vital parts in the systen are doubled to red.uce the ri:;k for (lis turbance8. ,];he cOLlffiunication subsysterr. acte as the inte:::face between the computer subs~rstern at o~e hruld ar..d the Y.lan-machinc-systcm a.l'1d front end at the other hand. It consists of one basic \mi t 8Il;. (coru:lU!1ication interface assembler) to 1iilich t he COr.lputcrs are connected at t'do separate pOl'tS. The connection of the links to the front end and wan-machine-system to the CIA are separa te channelprocesso.rs, uhich take care of SOE12 commur~ication l) roc edures and t:lessaCE: ouf;,."erin5. 0acr: channelpJ..'oc8330~ can ir.iividuall.:r be connected to each por.Jc •
alarr.linc and processing <:!.a tabas c, displays a;ld pro,:;:camhave to 1;)0 i!:l?leTi!~nt(.:·ci d urir~ {; up
t~e
time From the goal hierarc~y '\.:e lear-J1ed lc·r i r:s t al l88 ti1at there had to be a cood ;.: an/ n,ac~l i n0 '~8r.:
".
..
'.2he system so .f tHare con.sists of tlle sta.."1dara.. o~eI'atin D sys:e:-. (fron :·~DS and not treate(} hel:-e) and some add ed a:,_d very ir.portant nodules c!.esicned by Tn,; from fu.'1ctiona1 require:1cnts Civen by 3SP:9. r~lhe nodules are divi ,i ed i::1 three main parts accol.'""dinG to their functi()!:s. 7he first part is a com::>ler;:.ent io the sta.nda::d cperatin£ systes (OS Addition) to =~:e tlle data processinG ~it the processin~ requireDen~s, set by ti1e pO'. ;er systeL' , t[;e second is the r:.an/ uac1:ir~e :;l ~'laGer a.!-1L.. the thirc.. is the c..atB. base f,ja::ac er •
:::u.'1ication syste;:; a!1d that .,!e :,a(, to buy a dedicated corr.puter system for this 0'.,-lin0 an ,:;' real-time p~oceSS-3u::>er\l"isc)j.:·:r syste::1. ",:0 als:) learned thB.-: as to the applications 1,','e ~ l ac.. to give priority to develop;Jir,c all tile every-day inforQation routines that arc chara=te=istic for the dispatcher's ~ork. It was also decided not fr03 the beciru;in; to diccnsion t~e systeD fer direct control li~:c AGe and LE'C. Em,ever, it is believed thOlt these routines will be icpleoenteJ. about 1950.
::; .1. ':'h.!::.S::..)_Aiii,tlY2 consists of seve~'al submodules amonG th e !:!o:::;J~ i!.1ro.::~ant are
Hard\"are consists of co:nputel' su'JsyS t"::1 , I:1a:.:/ machine sUbsys:e:-: a..Tld cOr.lo'7lunication St'i.Dsys~e::. (fiG 2). The cOGputer subsystem is a dual co:::puter-syste~ \·;itt two XJS SIGLA 3 ec:ui~?e:: at present with 160 K words of core each. One computer is on-line and the other acts as a
:'r:c failover func"tic!l. It is ::'esponsible :or s~;itchinG a co~pute= fro~ on-line ~cde to back-ur- :wde (and. vice versa) il: case of a serious n:alflU1ction 01" deGradation in the online systeD
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The real-time scheduleI.'. It has a number of features .Ihich g ives the user programmes t he c apability to start afte r a ce r t ai n ~ount of time or at a certain time of the d ay and run either "single shot" or at a cyclic basis. There are also facilitie s to inspec t d i f ferent scheduleI.' queues and for instance ab ort an initiated programme . It i s poss ibl e for a programme in the on-line system to schedule a programme in the back-up system ("extended on-line pro gramme ") and so on . - The on-line int egration function. This module g ives the facility t o modify and add new r e al-time software in to the system ,~h i le it is operating. 5 . 2 . ll~-Ba£h!n~ ~a~~e£._ This compri ses a I1/M-supervisor and 6 submodules each containing 1-10 programmes. The operator communi cates wi th the l·ijM-supervisor via one functional and one alphanumerical keybo ard. The supervisor schedules the other H/11-submodules and/or the application-programmes depending on selected function. One of the largest submodul es is the Display Compiler. This al ways executes in the back-up CPU. From the fourth conso le the operator can, by use of the Display Compil er , do one or more of gene rate ne" displays modify existinG displays re move existing disp lays The displays contain two sets of i nformation : background ru1d dynam ic fie l d . At cOffipilation the background i s defined and stored on the disc. For the dynamic fields the data base r eferences are stored. Then ac tual values are at run-time either obt ained from t he data base or prepared by an application programme.
5. 3. ~a!a_b~s~ ~~a£e£. All i nformat i on about tl:e power system as il".stantaneous neasurement values, technical data, limit s values , planning, and so on, is stor ed in the data base. The data are stored in the core memory or on different types of dis cs independent of application proGrammes . The data base will from the beginning cont ain about one million data . In the bacl< up computer there is a copy of the on-line data base. The back-up data base i s updated continuously from the' on line computer in such a Hay that a slip of max i mum 30 s is per mit ted . Figure 4 g ives an id~~ of the situation of the data base in the systeffi .
J2CTS hav e got an unique number , an identificati on nu.l11Jer ( I D). Nany TYP;::S have more than one data per OBJ~CT , for instance the various hourly me anvalues in the stat i stical reports. The se are separated ,.. i th the aid. of an ;SL;:J:~;'l' nurr,ber . ~-l hen callinG the data base the rl'Yp~ number , the ID number and the i<:L.L;licllT nur"ber ar e i ndicated . It i s also poss ible to call a group of ID: s ano! or a Group of :O:Lc;l-La-i'l'S and also all ID: s and/or all i.::L.:.l·2;i'TS . The d a ta base manage r consists of four submodules: the data base superv i sor , the data base structure tables , the data base compiler and the stored i nformat ion . The data base supervisor has a number of tasks . The most i mportant are Rece ive and queue up the read and ·..rrite calls from the ap:!?lication programmes . '.i'he queue is ordered accord inc to the priority of the calling programme - Compute the storage address and media ,fith the aid of the structure tables and datatransport to and from the calling proG'l.'am Accompl i sh checks , for instanc e TYPJ-interference protect ion The data base tables contain all the informatien necessary for the supervisor to compute the phys i cal addresses. The tables are core resident with copies on discfiles . It is possible to update the tables by use of the data base comp il e r. The data base compiler. Those files used at the generation of the structt~e tables are created by batch runs wit h punched cards as input. Changes in the data base structure , s u ch as add i tions of TYPES a~d OBJ8CTS , are first implemented in the back-up computer . ';[hen the restructuring i s comp l eted a "fail-cver" is executed and the same r est ruct uring is done i n t he opposite system. The online functions are not d is turbe d when th i s procedure is carried out . stored information. Data may be stored in core memory, fast random access disc (llitD ) and disc . Every TYPE is stored phys i cally as an ent ity . The selection of storaGe media i s g iven by the frequency calls and response r equir ements . The major portion of the i nstantaneous data is stored in core . The heavy parts of the base as statist i cs and plans for several days are stored on ilAD .
6. A key concept in the da t a base structure is the "TYPE ". A "TYPI:;" is a group of data , :-or instance a ctual station out put for all hydro pO\{er stations or nomi nal voltage for all transformers . ~ a ch TYP~ has Got an unique number. At present there are some 500 'i'yr:s divided in 19 registers. TYP;;;S \'T ithin the same file concern d ata for same kind of OBJ~CTS , for instance lines , reactors, g as turb i nes , po~er exchanges and so on. In 8ach file all OB-
THE TIDAS APPLICA'l'IONS
6 . 1 . F irst phase . Accord i ng to plans some 100 dif f erent routines will be i mplemented at the time the computer systerr. will be installed, that is fall 1975 . ROUGhly one tJ:ircl r e:-ers to c l assical process routines lik e alar~l andlin g , l ogging , indication mon itoring . The Hork at POwer Contro l is cllarac terized by buyi nG' and sellinG' ter.lporary pO,ler . Acreeoents
138
~ r ~ set ~ur i nG meet i n~~ or te l ep hone cal l s. These oean~ a l ot of cruIual data i nput to the conputer v i a displays concern i nG the~e acree!::cnt~ . 'i"l i ~ also me a ns a lot of qu ery rout i nes cO:lcern i n..; the 3cancl i navian co-operation and. other pOHer e;·:chan::;e . '~'here are query facil it i es far stat i ono reservo i rs, restr i ctions , 1ir.: i tations 0: dif."'fcrent kinds but a l so for unu3 (>'.1. ":I ater pO';ler and sp i nn i nG' reserve . r:2hc que~'ies cancern ooL!: ac ~ ual s ~ate , plans ruld sta~istic:-; . r~hc ?l"csentat i on miGht be numer i c a l There are ['unctions for the Ol"o r ,:; :co.? l-liGal. lcrinc or c ea3ure inforJ ~ o.t i on , for remainJers a:-,::' ,~o 0:--.2 8ub - ~oal has been to Get rid of all "Ci1e pa;:>el.' ar.d folder hand li n.:; in the ccnt ::- cl ro e ;:: .
0" .
Also calculatin~ routines are i nvolved i n this :irst phase fo r instance for the hourly load , tl:2 il:flo·,,. , ac ti vc reserve , SSPB po\;er balance . It can be i:lcn~ i on C' d that on l y O , 2/~ of the content in the dat a base are d i rectly forHarded on line values and. indicat i ons . ?he rest is infor~-:at i or. e i ther uer i vec', from the on line d ata or, I-Ihicl: is the .:;reatest part , manu a ll y i n put data .
a:vl have nO\l d ec i d e d wh ich wa y t o go in thc b eGinning of the li fe of TI DAS. ',le s tar t t he SE cal cul a t i ons by trans:or~ i nG the measur ed v a l ues t o li ne c urr ents . The me~lod i s good fo r t;H; convercei1ce a:-1<1 p r events from me a suring error aud i tion and reproduct i on . ~:Q',;ever
on:e the ::',et'lod work h a s been don e an d the bas i c a l eor i th ~ s a re developed there i s a r::~jo!' step iz;tp l er;te:tt i nc tiles" i n the r eal -time computer system . S" i s a key f u.'l ct i on fo r th e furt:lcr applications i n TI DAS . I ts role i s to ,!lrocess the "ra~-l" r::e a sure -i i nfor ma t i on of H\, ' s , EVAr ' s and k-" s i nto a more cons i stent (st a te var i ables ) and r el i n.ble (Baci dat a reffio'led and least squ ares f it y i e l ds the opt i ma l state est ir,1a te ) form . I n des i gn ing the r e al-ti me se; it i s practical to sp li L i t u p i n r ouc;h l y fo ur part~ :
1 . Data prep a ration , da t a base i nte r fac e 2 . 3ad data detect i on ~ .
Least square
est i~at i on
t . Calculati on of l oad flo\,'s ~he
manpo'",er spent for .:icsib11 and i r;l:'1 pr;; en ta tion of the firs t applicat i on phase i s ~Iore than ,j.O r.tanyears . ar:"lOtLTlt of
Jecond ~)hase .
10 1 above h a s ma i nly to do with the in tegra t ion oi the state est i wator a l Gorit hms i n t he real- tir.le sys t em , a nd 2- 1\ 3.l:'e bas i cally al go rit hms .
G.2 .
S ta te est i mat i on has been found j u st i f i ed of n!'..l¥ reasons s u ch as for examp l e
a . ?oGs i b l e cav i nG's i n meaD u rement :;:;ysten . All interest i nG quru1t i ties for mon i torinG and cont r ol nust not be me a sured , s i nce they all can be cal cul ated from the state est i mate b.
I~pl'oved
accuracy cor.rpa r ed to the r.:easure-
I.lents
c.
~ore
efficient Bad Data Detect i on is poss i b-
le d . State variab l es a r e needed by other appl i cations and can not b e obtai ned usin.:; trad i t iona l LI'- teclmiqu es I n the early beGinni nG tte discuss i ons focused very r.:uch on a) wId b) bu t :-,reno'..,. !:lO r e cO!1cent:;:ate d on c) . Nost of the reports on Power System S;:; (re f 4) have so far dea l t ma i nly wi th the =athematic al and ne t hodoloC i cal aspects . -,:e l:ave founl t~lat the cLo iGe 0: rr:et11oQ for S~ is ·: !or:1;liGated . Tile oes t :.le t hod is po·,·:e .:- ~3yS tcr.1 (icpend ~nt . ~e have carried ou t a ere a t deal of s i!'lUlation -::alculat i ons for th i s evaluat i n.:; ·.lo=k
1he ::;,::; nas h a d a g r e a t i mpact on the J:le a s ur ewen t system conf i GUration of 'rI DAS , L e . the loc a t ion of t he meas u r i ng po i nt . A cood confi Gu r a t ion i s often Inore important than i::tproved oeasurement acc u racy . Furt h e r mor e , du e to the stru c ture of the TI DAS t r a.!lsm i ssio!1 s y stem ",.he r e min i computers , concentra tors are mon i tor i ng the mea"ure:nent g a theri ng i n a ,Seo::;raph i cal i\ren. , thc confi g u r a t i on i s becomi nG mo r e complex . It has been a 60al that the loss of a cO!1centra tor mu st not affect state est i mat i on of the rest of the )ower syste~. The real tine S:::; is schecluled to be operat i onal spr i nG 1976 . Operators Load }'loH . I ntrod u c i nG Opera t ors L1-' in t he 7 I DAS system is a quite natural step _ Firstly I-Ie rea l ly have the need f or i t , secondly it fits i n to the cenera l idea o f ~1an/",ach i ne dialot,ue -"hic;1 i s established in '~IDAS . Operators L? is a tool for the operator to analyse the conseque!1ces 0!1 the system of for example diffel'ent l oad/ ceneration patte r ns , d i ffe r ent transw i ssioll sys tern confi Q trations , s u dden load chanGes , ••• etc . 'r he O.,era tors :""''C '"i l l be used !l'ai nly for p l l'l.nn i n.; and study purposes , p:::oduct i o:1 al~ (t J:laintel:ance pI o.nn':'n . .,;, , pO'.:cr exchance n e Gotiat i ons , secur i ty assessme!1t~ hencc th i s appl i catio!1 activity is :ituated in both t~c !:'eal- t i r:1e l)art and. ~ile off ~-'~a l- t:!.De part of TIDAS as well . .-~,.: ~ C
'-"o'u+io'" '"Il - ·o~ i· l · '- is ;lcre ·,Jell :~no1,!'n (tra-~l·OOlt.:L1 i s :0 d.esi ;.ITI ar. in~() ra(!~ive sj-ster.l :.'0:1.' t21e user to bui l d up inp u t
~.~ti~r.;l .. LFY ~~t
139
th;
data to the LP via CRT's. The system must be c apable to retrieve or store away sets of data, t o modify or to buil d up completely new cases ami to e xecute t h e LF in the most simple and efficient ,;ay. The desiGTI will be very much focused u pon the needs of the operator and on making the us e of the system as simple as possible. The g oal Hill be to leave as little on the input data preparation to the user as possib l e and still retain full flexibility. The implementation is planned for 1977.
vclved and SSPB put efforts in the \vork of developpine methods that can be used in operation. In introducing the state estimation routine we think "le have solved the data input problem. The requirement~ for operation supervision of the stability is to get a result of the calculations within 15 minutes. As of the operation plannin g a result would be sufficient within 2 hours or some1ihat more. Production planning. The aim of the first phases of TIDAS is to cover the most urgent need for assistance to the dispatch engineers.
6 . ) . Third phase. As s es3inc the security for a stable pOl1er system is a function that often :Jeans a test system for specifically and beforehand ch03en continGencies; a deterDinistic approach that can not judge the probability for the systeD to fail. Furthermore for these continGencie s one oft en tests only the actual states of the po'"er system, which means that the correcting measures taking tirJe to achieve will affect quite another status of the pO\ler system.
The real-time routines described above will be an important link bet1.. een existing lone term and short term plannine routines and the today use d system for frequency control which is the last step in the optimization process. A sophisticated program has earlier been developed for short term optimum economic scheduline of a combined thermal and hydroelectric poHer system. This he.s hOHever not been used currently because of the frequent need for rescheduline and the comprehensive data preparation. The later problem ,.,ould be solved by means of the data base in TIDAS. It has ho\.. ever also been sho'vm that it is difficult to get results from the optimization ,.,hich ./ell enough corresponds \dth the real situation.
The above has led to the decision trying to implement a security assessment routine which is proba bilistic and predictive (ref 4). Furthermore \le 'v.-ill take into account the relation bet\leen the secUl'ity assessment routines and operation planning (fig 5). \le intend to use a function which 11e call the Security Function shortly defined as follows. It is the probability for violatinG the system security as a function of the nearest future reearding the actual pouer system status and future unscheduled events.
Compared partly .dth the great amount of efforts needed fcr this kind of automatized optimization and also the difficulty in considering adequately the complicated reality 've therefore nOH (lo not think that a programme for a total optimization is the best solution. It seems better to have a set of simulation programmes for relevant parts of the power system by means of which it would be possible for the dispatchers to compare different measures from economic and technical points of view and choose the best solution (ref 1 and 4).
The implementat ion of the Security Function requires a develOllment of and integration ,dth some other routines for example: - Estimation of actual power system status - Load forecast for actual time peri.od - -"conomical operat ion p lalmine for ac t ual tiDC p e riod
The first phases of TIDAS do not involve EDC or AGe. Because of the especial frequency regulation system and free loadflow between the power companies in Nordel EDC or AGC have so far not been justified. Depending on the development of the po" er system towards a greater portion of thermal pOKer this opinion may change. The first studies of the power system from this aspects have just started. The TIDAS-system has such a design that it shall be possible to include EDC and AGC ,.,ith comparatively small additional investments in hardware and software modifications.
- Se lc c tion of r e levant lis t of ev ents (of the biC amount of all poss ible events one have to sele c t t hos e uhi ch e ive a si Gnificant contribution to til e Se curity Function) - :C;sti mation of the s tochasti c behavior of the p01Jer sys te m compon en ts fro m hi s t orical (main l y ) ope rat i on data - Ls tab li shi nG of a stocha s ti c mode l in ord er t o a c hiev e the pr obabili t ie s of future pos s ible stat es
7. Cons truct i on of r e l ev ant con tinGenc y evaluation mcthods ',ie p la.."YJ. for introducing the proba bilistic c uri t y as ses sm ent r ou t ine in 1978 .
Sur;r,lARY
Up till now most of our attention has been paid to the objective of keeping the power system at normal state as long as possible. In the future "le have the ambition to pay more attention to the remainine three states.
se-
AssessinG the s tabili ty . There i s a nced f or bett er as se ss i n.:; the stability in ope ration in a [ e\; y ears . The r e is a lot of probl ems in-
A dispatc h information system will never be completed. We do not believe in a fully auto-
140
ffiated system. A dialoe ical and advisory int e rplay system between man and machine oug ht to be a goal worthwhile to strive for.
(1) Gustafsson, L. and Norlir"
L., "Optif.lization of The Production in a Hydro-Therl.:al Pm,er SysteIJ", ',10 RLD }lO',,'':..;] (; OHF:m~:C;'; , );oscow 1968
(2) Gustafsson, L. and Lindqvist, J., "J:'iclasan Intee rated Information Syst c !:: for Dispatching on a National level", U1nL :D ~. J A7A-PROCZSSnw C ONF :,rt~,H C~ , I';ad!'id 1;1 1";
( 3) Jerlhac;cr. , 'l'. and Leancle r, B., "A L e ssa;e
Ale r t
~";t at e .
Hel p d i srat.c h !.:l!.. . U E:) s taf : t o i IT!8.!'"~ d rettu"~-l t o nO !";.: v.l s tat '2 il l
pose constraints a r-;i nir:n.ir:l t ioe.
EJ.1erc enc y e T- ate. De l p c1i. s~l at c t C' r an.cl 2~aff to prevent to spread o f th e emere ency, to ~jnimi ze th c extent an d d uration of di s turb cillcc . l~e !::. toratior.
stat e . Ee lp tl is p cic he!.' a!IG staff to return to ncrffial in a :;- ini~u ~ t i ne .
Note, that for eac h s tate some information proce s sin c routines a r e r e al-tiP.le a nc. ot h ers "of f real tim(!". F or instance a typical rout i. n e to s up p ort th e dispatc he r d urins emerc ency stat e i s an. o f f-real time one , nal!'ec ly Dis t urbar:ce ~rainin c SysteQ.
Swi tcllinc NchiOrk Desic::nt>c, [or Da t a. COI:"Jlmnication and Renote Control", CIGHE, 1974
Quality
(4) Bubenko, J., Anders son, i'; ., Nord ar.lycke, I., Pctterss on, L.O., ·.{aern, B. an d otlH.'l.'s, "Power System Simulation", (book), D ~P1 . OF i:L;';C'l'HIC PO\/ER SYST",1-1S l::l!G., ,lOYAL DlST. 0:<' 'h ClI., Stockholm, 197~
Economy
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.
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I
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I
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(
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: ~(fiS
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APPENDIX 1
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PO';/ER SYST.::J'; S'.l'ATg S From ideas e iven by L. Kirch Eay e r ar.c. others '"e have derived !, state s of the IJo'" e r syste m, viz. normal, alert, emergency and. restoraticn. Eore precise c..efin .~ tion s e.re no',' under c.evelopment. Beam-fhile \-,' e u s e tL e foll oH inC morEe' heuristic one's. Normal state: All customer de Qan o,s (loac" fr( ,quency, voltag e, stability) ar e !:let an d. ne a pparatus or line are overloaded.. Di sp <-.tcher strives for operating po\o[er sys tev. at J7iinimtUil cost wi thi,: r estri c ti on s a.r:d ac co r J inL: t o a t:reements. '1 'here ar e n o i r,I-·enuir.::; cl.l e rcen cie s . Swi tc h inc 'O e,y t ake plac e.
"F IG 1
O-system comput .... s
Alert state: As lik e normal state t ut a p ot ential emergency has been detected.
OISC
LI:!er e:;ency state: Customer (J e man ('"s ar c' :, c t ~e t. Apparatus are overload e d, o scillati o n ::; ::-,i :;ht appear. Prequency an d /cr VC.l 1; :l.gc no t satisf'atory.
SWitch
Restoration state: ~he emerGency st.a tc j , a~. been stabilized. There l!li g ht be ov e rl oade d apparatus or customer d e~ aLds not s erved. Dispatcher strives for restorin c t h e },o,:e r s ~' stG!:1 .
Mog
to~
SWitch
Hog topo Cord reo
Subgcals for information processin G r ou t ine s used for actual state are:
SWitch
Int.doc. for time Shoring
Normal state. ;~ elp c. is p atciler ared s ':.af~' to keep system at n c rmal condi1;i on s a s lOLG a s possible.
141
storoge
rim.
No rma Uy to on.: lln e s y stem
Ma" machine system Intarfoc:e
I I
Alarmun lt
Disp l a y g~rato r
Of T Interf oc:e
I I
Dat a Bas e
App lica tion Programme s
Oo t at rons mi SS ion system
I
J
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~/ User
I I
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Powe r system
I
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r-
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Op era t ing s yst.m a nd OS Add it ion
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POSI'l'IOl;
l'II~
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Overview : de scri bing relations between Security Assessment and Operation Planning ,..-----....., Figure 50
Security Probing ~y.,
Economy
I
S.curity Supervi sion
Conf irmation of actual produc:t1Otl plan
sec~~rt~ "'">+.!!R..,.."",,,,,,,-,,,,,,on,,,,,-,a,,,"_ _", leveL safe? No
I
0
Operation Plann ing
Actuol stat. Contr"Ot occord ina
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hew plan
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,.,
,------1
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I ;t;~tiC' I
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lion
---'-,
Restoration of the
I I
~ ~w~r":y~t~ J
operation statistlC:s
Security evaluation
Figure 5 b Security Supervision: Continously the actual state is evaluated to determine whether the power system is safe or not. If the system is safe the reserves are governed according to plans and security prooing is done at appropriate point of times. Securit~
PTobing: Derived from the actual state the actual productlon plan is evaluated for sufficient security levels for future time. If out af limit a new productian plan is created. Otherwise the production plan is used. 0eeration Planning: Sets llmits for utllization of ring the planning period. valid the power system is unscheduled even t s, (i.e. rity).
the economical and technical the power system resources duIf the planning assumptions are safe and con manage reasonable maintain the set level af secu-
Security Evaluotion: Processes operotion statistics according to security requirements. It generates information needed for security probing and operation planning. 142
:~O]
Tit:; ];Al'IOEAL DISPA'l'C:HI1lG
C~ITn 2
AT ':'lfu S,r::DISH S'l'Al.'L
Lars Gustafsson
Jo~~
PO ·.i~;{
BOARD
Lindqvist
Swedish State Po~er 30ard (SSPB ) V,-~ 11 inC'by,
ABSTRAcr First i s gi ven an account of th ,~ =esponsibilities of the Dispatch Centre with some back0rou:-.0. in fo.c.l a tion about the pO 'J er sys tem. Then follo~s a deriv at ion of the concept of the inf ormation systems funct i onal des i ;'"11 . I\Casons arc c iven for the effort to Cet a hiGh dcGree of inteGration and f l exibili ty i n the sys tem. 'r he system cons ists of a real t i me part and also an off-r eal time part (p la.!mins and statistics). These are Go inS to be int cGrated and the t,·;o databases fully coop ati be l. Eost of the report is devoted to the real time part, '.;hich has a bie in put of on-lin e data frol:: the »o;[er system . A ,lea',,)' amount of dat a is entered r:: anually to tile real t i me COI:lputer syster.; (2 :mJ S i gr:1a 9, ~2 bits, 1 60 K core each). !lence there is a sophisticated r.J a.!"l/ r.Ja~h ine coor.mnication systerJ . F inally is Given an account of the development plans for the nearest futur e , ',{hi ch a none; other th inss in c ludc the i mplementation of a real time state estimator . 1. 'l'm.: S',;;;;D IS11 PO',r,e;R BILITI J..;S 010' 3SPB
SYST~';
AND TIll.:
R~SPWS I
1.1. The install ed cauacity wit h i n the Swedish Po,..;er Sys tem is about 1 9000 l,!',{. Of this 65,: i s hydroelectric pOI·rer and 35,; thernal po\·f er. 'r he the rmal pOHer p lants cons is t of condense units, back pressure units, nuclear units and c asturbines. rl'ne S·vle d i sh gr i d cyste~ is composed of 400 kV lin es (6 770 km) anu. 220 kV lines ( 5 166 km), 10 synchronous condensers, 0 seri es c a pac i tors a!1.d ) ) shunt reactors. 'l 'he transforr:~er cap a c i ty connected to the system a~l ounts 'Co 26 000 : ,~vA . 'l'he s yste m, ',:h i ell is in terconnec ted with several region al systens in J\leden fo r 1 30 kV and 70 kV , has about 100 nodes. I t i s als 0 i n terconnec te-d I! i til the ,;rid sys t ems in Denr:;al.' k , I: or-.my a.!ld }' inland .
The averaGe al1nual increaoe of pO',i cr COnS lU:1ption i n S,·!eden i s so far s u p,:Josed to be about ~~ . The extension of the power system has to correspond ;;ith the i ncrease of the ccnsunpL ion . The incrcaGe 0; ins t aIel c apacity is primarily to be covered by nuclear po~e r. The constru ct i on 0:" ;"l in e nuclear uni ts Hith a~o tal -: a pa c ity 0:'" .) ):0 I~·. j is ~ oinc or;. . ::otic\?able is also the planned. i ncrease in in;;talled
Slfeden
,: apaci ty in hydro pO'.-ler i7lainly fo r peak load cov e race . The need for transmissio n capacity is pri~a rily to be covered by rul extens ion of the cfOO l:V systeill . An 800 kV system may hO'dever co;ne in operat ion about 1980. About 45:~ of the installed capac ity and most of the g r i d system belon~ to the SSPB . SSPB is rcsponsible for the operat i on of the crid sys t ep.! anu. for the inte rcOimex i ons 'xith the ile i ehbouring cow1tri es and also for the operation of the po;.;er stations belonc inG t o SSPB . An o,:Jerat inG d.epar t;'1 ent at t h e ilead quart e r s in Jtockholr:; a.~d its control room for dispatchine; - Power Cont rol - are responsible for the fol10l'l inG' functions: Opera tin g planninG', direction and supervision of the production system of SSFB - Opera t ion of the Swedi sh c ri d system i nclud ing load control ,vo ltac e reGulation, d irecti on of circuitbr eaker opcra t ions , permission to lin e outaGe and other maintcnance \{ork , sccurity supervis i on and system restoration after d isturbances - Su?erv isi on of the Nordic interconnexions - ?requence and time control - ACree!Jent s a bo u t exci.anses of ter:;porary pOI·: er (econorc i c pOI'f er exchanc c 1. ',:i tl; the 1: ord i c countr i es and I:i t h co!:!pan i es '.-/i th in Sweden 1. 2 . 'i'he 3\{ed ish pO',fer sys tem is c r o\,inc; rapidly in size an d co~plexity . ~ 3pec ially the installation of big nuclear unit s in the southern part of the system Gives r is e to a lot of ne',,' 9rob1e:.; s . Accidental trippin ,,: of this biG un i ts (900 K~ 197J, 1 200 - 1 500 ~~ dur ing 1 900's) calls f or rul increased need for operat in s reserve, ',;hi c h at evc:..'Y oonent DUS t be de f i ned in s ice, allocation and respon.:;e tine. 7he increase in short-circuit currents calls
for neH supe rvi s i on and pla;-.::.i nC routines. -:"he concentration of JJO'./er produ ct i on to big power st a tions in the s outh and mi ddl e of t~e country nay a t out aGes and d i sturbCl.nces c aus e 135
great chanGes in the load flo\1 of the systeo ..,hich necessitates rapid actions from Power Control. The chane;e froo a by hydroelectric po-.rer dominated system to a syster:: dominated by therrr,al pouer \-/ith bi G tl ifference s in marGinal production costs during the 24 hours of day and niGht increases the dem~~d for more accurate "llannine; and control . The short term re -;ul :J.t i on of the hydroelectric ,o', ler, Hl',i ch fro~: a:1 e c onor.-.ic point of' vie',' is very compli-
ted to ~ 30 million. To- day the return from the system is at least $ 60 million. Of the capitalized return roughly 60; come from normal state (pO\'fer production 25>~ , power pool cooperation lo;~ and operating reserve 255~) and the rest from the remaining states, alert, emergency and restoration. (As to the meaning of the four power system states see appendix 1) •
c~te1 ,
The investment cost for the real time system is no',-/ estimated to ~ 22 million . From this sum 20 to 25,: are dataprocessing and 5O;~ data acquisition.
~ il]
be of g reat
i ~portallce
for a ratio-
n al use of the pOHer system. At last the great irr.portance of the pOl.,er cooperation in S"'eden and in Nordel oUGht to be mentioned . The value of exchanGed tempcral~ pO'.ler between SSPB and other power companies in llordel has ar:lOunted to I"lore than ;;: 100 million/ year. This pOWer e):change is mos tly made up on an hourly basis by agreerJents between the dispatchroor::s. The impor tance of these pO~fer exchanGes uill prob ",i.lly continue to grO\l because of the remaininG d i rference in pOKer systerr.s , delays in the installation of new plants, increase in system size and increase in generation costs. (Hef 1) . A power systeE like the Swedish one is very dynamic, becam:e of the variations in \>;atersupply and because of the location in the middle of the ncrdic pOKer system , which leads to that a e:reat part of the "surplus" or "shortage" of po',,'er in \>That so ever area has an influence in this system. To this ,le r,Q;J have to add the "disturbances" of different kinds caused by the behavior of the ~i 6 nuclear units. AGainst this backcrounC: it is obvious that the claim to.pon the informat ion system for operatinc: planning ru1d direction and supervision of the pOl·rer system IT.ust be gre at \·ri th respect to the treat importance the operatior. of the pO'.·rer syster.: has fcr the econor;:y of the pO\ler cOIr.pany anc'. the fur:ction of the society . I f the soals hi el: reliability, GOoe. ecor.cmy and hiGh quality of electri c i ty shall be reached it seems therefore necessary to Give t!,e POller COl:trol the best possible equipoent . 2.
TIt.; nL'i'Uiill
I~ROJ·j
'i'he system is expected to be operational during fall 1975. (Ref 2) •
3.
THE CONCBPT OF TIDAS
3.1.
Integration from a functional point of
vie\{.
and interrelated goals for the dispatching activities at the control centre are good reliability, economy and quality of the delivery from the existing power system, here divided into 3 interrelated parts , production system, transmission system and pO\{er exohanges . Since predictive information (planning, scheduling, probing and so forth), real time information (indications, instantaneous values, logging, direct ordering, control ••• ) and "hat \-Ie call evaluation or follo\v-up information (statistics, reports ••• ) no doubt form a continuity in time it \'Ias natural to define TIDAS as an information system supporting all relevant decision makers \-lith adequate information from the 3 types of information to fulfil the main goals for the entire pover system . Fi[;Ure 1 is an attempt to visualize all the activities going on in a complete dispatch system . One can think of 27 boxes (activities) vith information running in between them . (Only one box indicated in fig 1) . Such a complete information system consequently also calls for a fourth kind of information , support or servioe information, keeping track of all the instructions, rebUlations, agreements , remaindErS and so on .
l~ ain
'l'IDAS the initiatinG studies we decided to divide the system into t\-IO integrated parts , one real-time part and one "off-real-time" part. '"'he latter consistinc of statistics, accounting, week ly ru1d seasonal plannin& and other evaluation study proerarrunes .
Fro~
froo ,·:tat is stated above one ca.!'). see the need of a !!;oc.e rn information system for "Power Control" . In 1969 the Board. decided to start the develoFment work of such a systec . From the beginnint; it was obvious that the sys te m l-:ad to be very flexible i n desisn , because of the most chancinG ccnditions under \Thich the ne'..' syste::! l:ad to func:t ior. durinc; its liiltime . Therefore the newest achievements in informaticn system theory and hard~,are developn.er..t as ~ell had to be used . It was dec i ded to Give priority to the real ti~e part of the system . ~ost of \That is said in thiG report ~reats this part of the information syster.: . '"'he benefit of the real time system
~'fas
estima-
) . 2.
DesiGn aspects
?ro!J "Ihat is earlier mentioned one can see that the new informat ion system had to be bui~ flexible to be able to reflect the changes in the pO\·/er system development and meet new requirer::lents from the dispatcher. This means modularity and an expression for this is among other things the two databases in the tvo systems. These t,IQ databases \-Till be fully eompatibel for easy exchange of data in bet,.een them and for easy access to both of them . In both cases we
136
strive for a high desree of indeper. ':'.ence bet\,:een the base and its application proe;rannes to be able to easy reallocate or chance the data or to add new progra!:1LleS for instance. The 01freal-time sys terl "ill be runninc in our general purpose computer system.
bac:C up. l'here are t,,·o fi/;ed head 0.iscs (6 !:B each) ru1Ci one dual spindel removable disc (2 x 2,~ ~:B) at eacl-1 sys~er:.. Sor..e ,le-vices are sha:::-able, meanin,; that they CBI. be connected to bott of the syste'-1s by prosrar::controlled peripheral switches.
In ~hat follows only the real time part of TIDAS "ill be treated and it .dll be refe:::-red to as TIDAS for short.
The :7lan/machine subsystei:..l consists of -t co:-~so les "here 3 norn~lly are connected to the online systC:'l and the fourt::. to the bac]:-up systeLl (fiG 3 ). ;;;ach console has tHO u.isplays (nondedicated) and th e dispatcher nor;nally COHl!r.unicates \.:ith the cO!l:puter syste:n via these displays. 7he !:lain tasks of the SUbsystem are to p:esent information according to predefined forillats ar.l.G. to input data to the computer system. ', ;11en sui table the COl:1puter Gubsys tern Gives c uiding directiO!lG to the dispatcher' to facili tate his '. . ork and. reduce the possibili t ~r for r.listakes. );he displays are colou:c seraiGraphical. The \;ays for the fourth display to be used are:
For natural reasons 'f IDA::; consists of tHO ,'lain systens, the data acquisition syste:J aI!d the data proceseinc system with a carefully defined logical interface in bet1-leen. In the c.ata acquisition system there is a messaGe s1{itchinc network comprising 22 mino:::- process COI:lputers. In 1976 there will be transmitted some 850 indications and 750 digital or analc:.:-ue values online from the pouer and transoission system to the data processine system at the control centre in Stockholm. The data acquisition system is treated in ref 3. In a project of this size ry to carefully penetrate renents before we started '.4e have already indicated lity. Other requi:::-ements
*
High system reliability
*
Continuous round the clock operation
*
The information systen shall sinplify the every day \lork for the dispatcher
*
The DP-system shall be easy to learn ruld easy to use
*
'~uick
*
(;han{J=s in mes shall
- "on line CPU mode" is used. as back up for the consoles in the dispatchinG room
\Ie found it necessathe goals and requithe design VIork. the need for flexibiare for instance:
- "back up CPU !:lode" is used for procrarr: testil::;, traininG, deI:lonst:::-ations and display libra;:y f.1aintenance All vital parts in the systen are doubled to red.uce the ri:;k for (lis turbance8. ,];he cOLlffiunication subsysterr. acte as the inte:::face between the computer subs~rstern at o~e hruld ar..d the Y.lan-machinc-systcm a.l'1d front end at the other hand. It consists of one basic \mi t 8Il;. (coru:lU!1ication interface assembler) to 1iilich t he COr.lputcrs are connected at t'do separate pOl'tS. The connection of the links to the front end and wan-machine-system to the CIA are separa te channelprocesso.rs, uhich take care of SOE12 commur~ication l) roc edures and t:lessaCE: ouf;,."erin5. 0acr: channelpJ..'oc8330~ can ir.iividuall.:r be connected to each por.Jc •
alarr.linc and processing <:!.a tabas c, displays a;ld pro,:;:camhave to 1;)0 i!:l?leTi!~nt(.:·ci d urir~ {; up
t~e
time From the goal hierarc~y '\.:e lear-J1ed lc·r i r:s t al l88 ti1at there had to be a cood ;.: an/ n,ac~l i n0 '~8r.:
".
..
'.2he system so .f tHare con.sists of tlle sta.."1dara.. o~eI'atin D sys:e:-. (fron :·~DS and not treate(} hel:-e) and some add ed a:,_d very ir.portant nodules c!.esicned by Tn,; from fu.'1ctiona1 require:1cnts Civen by 3SP:9. r~lhe nodules are divi ,i ed i::1 three main parts accol.'""dinG to their functi()!:s. 7he first part is a com::>ler;:.ent io the sta.nda::d cperatin£ systes (OS Addition) to =~:e tlle data processinG ~it the processin~ requireDen~s, set by ti1e pO'. ;er systeL' , t[;e second is the r:.an/ uac1:ir~e :;l ~'laGer a.!-1L.. the thirc.. is the c..atB. base f,ja::ac er •
:::u.'1ication syste;:; a!1d that .,!e :,a(, to buy a dedicated corr.puter system for this 0'.,-lin0 an ,:;' real-time p~oceSS-3u::>er\l"isc)j.:·:r syste::1. ",:0 als:) learned thB.-: as to the applications 1,','e ~ l ac.. to give priority to develop;Jir,c all tile every-day inforQation routines that arc chara=te=istic for the dispatcher's ~ork. It was also decided not fr03 the beciru;in; to diccnsion t~e systeD fer direct control li~:c AGe and LE'C. Em,ever, it is believed thOlt these routines will be icpleoenteJ. about 1950.
::; .1. ':'h.!::.S::..)_Aiii,tlY2 consists of seve~'al submodules amonG th e !:!o:::;J~ i!.1ro.::~ant are
Hard\"are consists of co:nputel' su'JsyS t"::1 , I:1a:.:/ machine sUbsys:e:-: a..Tld cOr.lo'7lunication St'i.Dsys~e::. (fiG 2). The cOGputer subsystem is a dual co:::puter-syste~ \·;itt two XJS SIGLA 3 ec:ui~?e:: at present with 160 K words of core each. One computer is on-line and the other acts as a
:'r:c failover func"tic!l. It is ::'esponsible :or s~;itchinG a co~pute= fro~ on-line ~cde to back-ur- :wde (and. vice versa) il: case of a serious n:alflU1ction 01" deGradation in the online systeD
137
The real-time scheduleI.'. It has a number of features .Ihich g ives the user programmes t he c apability to start afte r a ce r t ai n ~ount of time or at a certain time of the d ay and run either "single shot" or at a cyclic basis. There are also facilitie s to inspec t d i f ferent scheduleI.' queues and for instance ab ort an initiated programme . It i s poss ibl e for a programme in the on-line system to schedule a programme in the back-up system ("extended on-line pro gramme ") and so on . - The on-line int egration function. This module g ives the facility t o modify and add new r e al-time software in to the system ,~h i le it is operating. 5 . 2 . ll~-Ba£h!n~ ~a~~e£._ This compri ses a I1/M-supervisor and 6 submodules each containing 1-10 programmes. The operator communi cates wi th the l·ijM-supervisor via one functional and one alphanumerical keybo ard. The supervisor schedules the other H/11-submodules and/or the application-programmes depending on selected function. One of the largest submodul es is the Display Compiler. This al ways executes in the back-up CPU. From the fourth conso le the operator can, by use of the Display Compil er , do one or more of gene rate ne" displays modify existinG displays re move existing disp lays The displays contain two sets of i nformation : background ru1d dynam ic fie l d . At cOffipilation the background i s defined and stored on the disc. For the dynamic fields the data base r eferences are stored. Then ac tual values are at run-time either obt ained from t he data base or prepared by an application programme.
5. 3. ~a!a_b~s~ ~~a£e£. All i nformat i on about tl:e power system as il".stantaneous neasurement values, technical data, limit s values , planning, and so on, is stor ed in the data base. The data are stored in the core memory or on different types of dis cs independent of application proGrammes . The data base will from the beginning cont ain about one million data . In the bacl< up computer there is a copy of the on-line data base. The back-up data base i s updated continuously from the' on line computer in such a Hay that a slip of max i mum 30 s is per mit ted . Figure 4 g ives an id~~ of the situation of the data base in the systeffi .
J2CTS hav e got an unique number , an identificati on nu.l11Jer ( I D). Nany TYP;::S have more than one data per OBJ~CT , for instance the various hourly me anvalues in the stat i stical reports. The se are separated ,.. i th the aid. of an ;SL;:J:~;'l' nurr,ber . ~-l hen callinG the data base the rl'Yp~ number , the ID number and the i<:L.L;licllT nur"ber ar e i ndicated . It i s also poss ible to call a group of ID: s ano! or a Group of :O:Lc;l-La-i'l'S and also all ID: s and/or all i.::L.:.l·2;i'TS . The d a ta base manage r consists of four submodules: the data base superv i sor , the data base structure tables , the data base compiler and the stored i nformat ion . The data base supervisor has a number of tasks . The most i mportant are Rece ive and queue up the read and ·..rrite calls from the ap:!?lication programmes . '.i'he queue is ordered accord inc to the priority of the calling programme - Compute the storage address and media ,fith the aid of the structure tables and datatransport to and from the calling proG'l.'am Accompl i sh checks , for instanc e TYPJ-interference protect ion The data base tables contain all the informatien necessary for the supervisor to compute the phys i cal addresses. The tables are core resident with copies on discfiles . It is possible to update the tables by use of the data base comp il e r. The data base compiler. Those files used at the generation of the structt~e tables are created by batch runs wit h punched cards as input. Changes in the data base structure , s u ch as add i tions of TYPES a~d OBJ8CTS , are first implemented in the back-up computer . ';[hen the restructuring i s comp l eted a "fail-cver" is executed and the same r est ruct uring is done i n t he opposite system. The online functions are not d is turbe d when th i s procedure is carried out . stored information. Data may be stored in core memory, fast random access disc (llitD ) and disc . Every TYPE is stored phys i cally as an ent ity . The selection of storaGe media i s g iven by the frequency calls and response r equir ements . The major portion of the i nstantaneous data is stored in core . The heavy parts of the base as statist i cs and plans for several days are stored on ilAD .
6. A key concept in the da t a base structure is the "TYPE ". A "TYPI:;" is a group of data , :-or instance a ctual station out put for all hydro pO\{er stations or nomi nal voltage for all transformers . ~ a ch TYP~ has Got an unique number. At present there are some 500 'i'yr:s divided in 19 registers. TYP;;;S \'T ithin the same file concern d ata for same kind of OBJ~CTS , for instance lines , reactors, g as turb i nes , po~er exchanges and so on. In 8ach file all OB-
THE TIDAS APPLICA'l'IONS
6 . 1 . F irst phase . Accord i ng to plans some 100 dif f erent routines will be i mplemented at the time the computer systerr. will be installed, that is fall 1975 . ROUGhly one tJ:ircl r e:-ers to c l assical process routines lik e alar~l andlin g , l ogging , indication mon itoring . The Hork at POwer Contro l is cllarac terized by buyi nG' and sellinG' ter.lporary pO,ler . Acreeoents
138
~ r ~ set ~ur i nG meet i n~~ or te l ep hone cal l s. These oean~ a l ot of cruIual data i nput to the conputer v i a displays concern i nG the~e acree!::cnt~ . 'i"l i ~ also me a ns a lot of qu ery rout i nes cO:lcern i n..; the 3cancl i navian co-operation and. other pOHer e;·:chan::;e . '~'here are query facil it i es far stat i ono reservo i rs, restr i ctions , 1ir.: i tations 0: dif."'fcrent kinds but a l so for unu3 (>'.1. ":I ater pO';ler and sp i nn i nG' reserve . r:2hc que~'ies cancern ooL!: ac ~ ual s ~ate , plans ruld sta~istic:-; . r~hc ?l"csentat i on miGht be numer i c a l There are ['unctions for the Ol"o r ,:; :co.? l-liGal. lcrinc or c ea3ure inforJ ~ o.t i on , for remainJers a:-,::' ,~o 0:--.2 8ub - ~oal has been to Get rid of all "Ci1e pa;:>el.' ar.d folder hand li n.:; in the ccnt ::- cl ro e ;:: .
0" .
Also calculatin~ routines are i nvolved i n this :irst phase fo r instance for the hourly load , tl:2 il:flo·,,. , ac ti vc reserve , SSPB po\;er balance . It can be i:lcn~ i on C' d that on l y O , 2/~ of the content in the dat a base are d i rectly forHarded on line values and. indicat i ons . ?he rest is infor~-:at i or. e i ther uer i vec', from the on line d ata or, I-Ihicl: is the .:;reatest part , manu a ll y i n put data .
a:vl have nO\l d ec i d e d wh ich wa y t o go in thc b eGinning of the li fe of TI DAS. ',le s tar t t he SE cal cul a t i ons by trans:or~ i nG the measur ed v a l ues t o li ne c urr ents . The me~lod i s good fo r t;H; convercei1ce a:-1<1 p r events from me a suring error aud i tion and reproduct i on . ~:Q',;ever
on:e the ::',et'lod work h a s been don e an d the bas i c a l eor i th ~ s a re developed there i s a r::~jo!' step iz;tp l er;te:tt i nc tiles" i n the r eal -time computer system . S" i s a key f u.'l ct i on fo r th e furt:lcr applications i n TI DAS . I ts role i s to ,!lrocess the "ra~-l" r::e a sure -i i nfor ma t i on of H\, ' s , EVAr ' s and k-" s i nto a more cons i stent (st a te var i ables ) and r el i n.ble (Baci dat a reffio'led and least squ ares f it y i e l ds the opt i ma l state est ir,1a te ) form . I n des i gn ing the r e al-ti me se; it i s practical to sp li L i t u p i n r ouc;h l y fo ur part~ :
1 . Data prep a ration , da t a base i nte r fac e 2 . 3ad data detect i on ~ .
Least square
est i~at i on
t . Calculati on of l oad flo\,'s ~he
manpo'",er spent for .:icsib11 and i r;l:'1 pr;; en ta tion of the firs t applicat i on phase i s ~Iore than ,j.O r.tanyears . ar:"lOtLTlt of
Jecond ~)hase .
10 1 above h a s ma i nly to do with the in tegra t ion oi the state est i wator a l Gorit hms i n t he real- tir.le sys t em , a nd 2- 1\ 3.l:'e bas i cally al go rit hms .
G.2 .
S ta te est i mat i on has been found j u st i f i ed of n!'..l¥ reasons s u ch as for examp l e
a . ?oGs i b l e cav i nG's i n meaD u rement :;:;ysten . All interest i nG quru1t i ties for mon i torinG and cont r ol nust not be me a sured , s i nce they all can be cal cul ated from the state est i mate b.
I~pl'oved
accuracy cor.rpa r ed to the r.:easure-
I.lents
c.
~ore
efficient Bad Data Detect i on is poss i b-
le d . State variab l es a r e needed by other appl i cations and can not b e obtai ned usin.:; trad i t iona l LI'- teclmiqu es I n the early beGinni nG tte discuss i ons focused very r.:uch on a) wId b) bu t :-,reno'..,. !:lO r e cO!1cent:;:ate d on c) . Nost of the reports on Power System S;:; (re f 4) have so far dea l t ma i nly wi th the =athematic al and ne t hodoloC i cal aspects . -,:e l:ave founl t~lat the cLo iGe 0: rr:et11oQ for S~ is ·: !or:1;liGated . Tile oes t :.le t hod is po·,·:e .:- ~3yS tcr.1 (icpend ~nt . ~e have carried ou t a ere a t deal of s i!'lUlation -::alculat i ons for th i s evaluat i n.:; ·.lo=k
1he ::;,::; nas h a d a g r e a t i mpact on the J:le a s ur ewen t system conf i GUration of 'rI DAS , L e . the loc a t ion of t he meas u r i ng po i nt . A cood confi Gu r a t ion i s often Inore important than i::tproved oeasurement acc u racy . Furt h e r mor e , du e to the stru c ture of the TI DAS t r a.!lsm i ssio!1 s y stem ",.he r e min i computers , concentra tors are mon i tor i ng the mea"ure:nent g a theri ng i n a ,Seo::;raph i cal i\ren. , thc confi g u r a t i on i s becomi nG mo r e complex . It has been a 60al that the loss of a cO!1centra tor mu st not affect state est i mat i on of the rest of the )ower syste~. The real tine S:::; is schecluled to be operat i onal spr i nG 1976 . Operators Load }'loH . I ntrod u c i nG Opera t ors L1-' in t he 7 I DAS system is a quite natural step _ Firstly I-Ie rea l ly have the need f or i t , secondly it fits i n to the cenera l idea o f ~1an/",ach i ne dialot,ue -"hic;1 i s established in '~IDAS . Operators L? is a tool for the operator to analyse the conseque!1ces 0!1 the system of for example diffel'ent l oad/ ceneration patte r ns , d i ffe r ent transw i ssioll sys tern confi Q trations , s u dden load chanGes , ••• etc . 'r he O.,era tors :""''C '"i l l be used !l'ai nly for p l l'l.nn i n.; and study purposes , p:::oduct i o:1 al~ (t J:laintel:ance pI o.nn':'n . .,;, , pO'.:cr exchance n e Gotiat i ons , secur i ty assessme!1t~ hencc th i s appl i catio!1 activity is :ituated in both t~c !:'eal- t i r:1e l)art and. ~ile off ~-'~a l- t:!.De part of TIDAS as well . .-~,.: ~ C
'-"o'u+io'" '"Il - ·o~ i· l · '- is ;lcre ·,Jell :~no1,!'n (tra-~l·OOlt.:L1 i s :0 d.esi ;.ITI ar. in~() ra(!~ive sj-ster.l :.'0:1.' t21e user to bui l d up inp u t
~.~ti~r.;l .. LFY ~~t
139
th;
data to the LP via CRT's. The system must be c apable to retrieve or store away sets of data, t o modify or to buil d up completely new cases ami to e xecute t h e LF in the most simple and efficient ,;ay. The desiGTI will be very much focused u pon the needs of the operator and on making the us e of the system as simple as possible. The g oal Hill be to leave as little on the input data preparation to the user as possib l e and still retain full flexibility. The implementation is planned for 1977.
vclved and SSPB put efforts in the \vork of developpine methods that can be used in operation. In introducing the state estimation routine we think "le have solved the data input problem. The requirement~ for operation supervision of the stability is to get a result of the calculations within 15 minutes. As of the operation plannin g a result would be sufficient within 2 hours or some1ihat more. Production planning. The aim of the first phases of TIDAS is to cover the most urgent need for assistance to the dispatch engineers.
6 . ) . Third phase. As s es3inc the security for a stable pOl1er system is a function that often :Jeans a test system for specifically and beforehand ch03en continGencies; a deterDinistic approach that can not judge the probability for the systeD to fail. Furthermore for these continGencie s one oft en tests only the actual states of the po'"er system, which means that the correcting measures taking tirJe to achieve will affect quite another status of the pO\ler system.
The real-time routines described above will be an important link bet1.. een existing lone term and short term plannine routines and the today use d system for frequency control which is the last step in the optimization process. A sophisticated program has earlier been developed for short term optimum economic scheduline of a combined thermal and hydroelectric poHer system. This he.s hOHever not been used currently because of the frequent need for rescheduline and the comprehensive data preparation. The later problem ,.,ould be solved by means of the data base in TIDAS. It has ho\.. ever also been sho'vm that it is difficult to get results from the optimization ,.,hich ./ell enough corresponds \dth the real situation.
The above has led to the decision trying to implement a security assessment routine which is proba bilistic and predictive (ref 4). Furthermore \le 'v.-ill take into account the relation bet\leen the secUl'ity assessment routines and operation planning (fig 5). \le intend to use a function which 11e call the Security Function shortly defined as follows. It is the probability for violatinG the system security as a function of the nearest future reearding the actual pouer system status and future unscheduled events.
Compared partly .dth the great amount of efforts needed fcr this kind of automatized optimization and also the difficulty in considering adequately the complicated reality 've therefore nOH (lo not think that a programme for a total optimization is the best solution. It seems better to have a set of simulation programmes for relevant parts of the power system by means of which it would be possible for the dispatchers to compare different measures from economic and technical points of view and choose the best solution (ref 1 and 4).
The implementat ion of the Security Function requires a develOllment of and integration ,dth some other routines for example: - Estimation of actual power system status - Load forecast for actual time peri.od - -"conomical operat ion p lalmine for ac t ual tiDC p e riod
The first phases of TIDAS do not involve EDC or AGe. Because of the especial frequency regulation system and free loadflow between the power companies in Nordel EDC or AGC have so far not been justified. Depending on the development of the po" er system towards a greater portion of thermal pOKer this opinion may change. The first studies of the power system from this aspects have just started. The TIDAS-system has such a design that it shall be possible to include EDC and AGC ,.,ith comparatively small additional investments in hardware and software modifications.
- Se lc c tion of r e levant lis t of ev ents (of the biC amount of all poss ible events one have to sele c t t hos e uhi ch e ive a si Gnificant contribution to til e Se curity Function) - :C;sti mation of the s tochasti c behavior of the p01Jer sys te m compon en ts fro m hi s t orical (main l y ) ope rat i on data - Ls tab li shi nG of a stocha s ti c mode l in ord er t o a c hiev e the pr obabili t ie s of future pos s ible stat es
7. Cons truct i on of r e l ev ant con tinGenc y evaluation mcthods ',ie p la.."YJ. for introducing the proba bilistic c uri t y as ses sm ent r ou t ine in 1978 .
Sur;r,lARY
Up till now most of our attention has been paid to the objective of keeping the power system at normal state as long as possible. In the future "le have the ambition to pay more attention to the remainine three states.
se-
AssessinG the s tabili ty . There i s a nced f or bett er as se ss i n.:; the stability in ope ration in a [ e\; y ears . The r e is a lot of probl ems in-
A dispatc h information system will never be completed. We do not believe in a fully auto-
140
ffiated system. A dialoe ical and advisory int e rplay system between man and machine oug ht to be a goal worthwhile to strive for.
(1) Gustafsson, L. and Norlir"
L., "Optif.lization of The Production in a Hydro-Therl.:al Pm,er SysteIJ", ',10 RLD }lO',,'':..;] (; OHF:m~:C;'; , );oscow 1968
(2) Gustafsson, L. and Lindqvist, J., "J:'iclasan Intee rated Information Syst c !:: for Dispatching on a National level", U1nL :D ~. J A7A-PROCZSSnw C ONF :,rt~,H C~ , I';ad!'id 1;1 1";
( 3) Jerlhac;cr. , 'l'. and Leancle r, B., "A L e ssa;e
Ale r t
~";t at e .
Hel p d i srat.c h !.:l!.. . U E:) s taf : t o i IT!8.!'"~ d rettu"~-l t o nO !";.: v.l s tat '2 il l
pose constraints a r-;i nir:n.ir:l t ioe.
EJ.1erc enc y e T- ate. De l p c1i. s~l at c t C' r an.cl 2~aff to prevent to spread o f th e emere ency, to ~jnimi ze th c extent an d d uration of di s turb cillcc . l~e !::. toratior.
stat e . Ee lp tl is p cic he!.' a!IG staff to return to ncrffial in a :;- ini~u ~ t i ne .
Note, that for eac h s tate some information proce s sin c routines a r e r e al-tiP.le a nc. ot h ers "of f real tim(!". F or instance a typical rout i. n e to s up p ort th e dispatc he r d urins emerc ency stat e i s an. o f f-real time one , nal!'ec ly Dis t urbar:ce ~rainin c SysteQ.
Swi tcllinc NchiOrk Desic::nt>c, [or Da t a. COI:"Jlmnication and Renote Control", CIGHE, 1974
Quality
(4) Bubenko, J., Anders son, i'; ., Nord ar.lycke, I., Pctterss on, L.O., ·.{aern, B. an d otlH.'l.'s, "Power System Simulation", (book), D ~P1 . OF i:L;';C'l'HIC PO\/ER SYST",1-1S l::l!G., ,lOYAL DlST. 0:<' 'h ClI., Stockholm, 197~
Economy
/' .... -:-:. -
---~ :---l
.
I
I
I
I
I
- - --{'
•
(
«
R.fiobilit, I
P
: ~(fiS
into.: /' / /
F,
infO.,,,;....
-------).....:.. - - - r - - ,/'/
/// -
--~-
..... /
APPENDIX 1
"m
- -~ ....... /
. . . .,. - - - -,...-
/' /'
---~---.,.......
r
; nfo. /' .,/,...
-
-
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,.,../
PO';/ER SYST.::J'; S'.l'ATg S From ideas e iven by L. Kirch Eay e r ar.c. others '"e have derived !, state s of the IJo'" e r syste m, viz. normal, alert, emergency and. restoraticn. Eore precise c..efin .~ tion s e.re no',' under c.evelopment. Beam-fhile \-,' e u s e tL e foll oH inC morEe' heuristic one's. Normal state: All customer de Qan o,s (loac" fr( ,quency, voltag e, stability) ar e !:let an d. ne a pparatus or line are overloaded.. Di sp <-.tcher strives for operating po\o[er sys tev. at J7iinimtUil cost wi thi,: r estri c ti on s a.r:d ac co r J inL: t o a t:reements. '1 'here ar e n o i r,I-·enuir.::; cl.l e rcen cie s . Swi tc h inc 'O e,y t ake plac e.
"F IG 1
O-system comput .... s
Alert state: As lik e normal state t ut a p ot ential emergency has been detected.
OISC
LI:!er e:;ency state: Customer (J e man ('"s ar c' :, c t ~e t. Apparatus are overload e d, o scillati o n ::; ::-,i :;ht appear. Prequency an d /cr VC.l 1; :l.gc no t satisf'atory.
SWitch
Restoration state: ~he emerGency st.a tc j , a~. been stabilized. There l!li g ht be ov e rl oade d apparatus or customer d e~ aLds not s erved. Dispatcher strives for restorin c t h e },o,:e r s ~' stG!:1 .
Mog
to~
SWitch
Hog topo Cord reo
Subgcals for information processin G r ou t ine s used for actual state are:
SWitch
Int.doc. for time Shoring
Normal state. ;~ elp c. is p atciler ared s ':.af~' to keep system at n c rmal condi1;i on s a s lOLG a s possible.
141
storoge
rim.
No rma Uy to on.: lln e s y stem
Ma" machine system Intarfoc:e
I I
Alarmun lt
Disp l a y g~rato r
Of T Interf oc:e
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Oo t at rons mi SS ion system
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Powe r system
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Overview : de scri bing relations between Security Assessment and Operation Planning ,..-----....., Figure 50
Security Probing ~y.,
Economy
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S.curity Supervi sion
Conf irmation of actual produc:t1Otl plan
sec~~rt~ "'">+.!!R..,.."",,,,,,,-,,,,,,on,,,,,-,a,,,"_ _", leveL safe? No
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hew plan
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Restoration of the
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operation statistlC:s
Security evaluation
Figure 5 b Security Supervision: Continously the actual state is evaluated to determine whether the power system is safe or not. If the system is safe the reserves are governed according to plans and security prooing is done at appropriate point of times. Securit~
PTobing: Derived from the actual state the actual productlon plan is evaluated for sufficient security levels for future time. If out af limit a new productian plan is created. Otherwise the production plan is used. 0eeration Planning: Sets llmits for utllization of ring the planning period. valid the power system is unscheduled even t s, (i.e. rity).
the economical and technical the power system resources duIf the planning assumptions are safe and con manage reasonable maintain the set level af secu-
Security Evaluotion: Processes operotion statistics according to security requirements. It generates information needed for security probing and operation planning. 142