5 RSS System Model. Figure 10: Device Model Flowchart

Transcription

1 5 RSS System Model The omplete model to test the opertion of the RSS onsists of two prts: the existing rely system model to dpt nd the RSS model. Both systems re modeled in Mtl. The existing relys re modeled so they re expliitly told when to trip for fult. The RSS model is omplete model, nd uses tul MTP dt to perform rely lultions. Trip signls from the existing relys trigger the RSS into tion. This signl is supplied y n uxiliry ontt from the existing rely. The generl flow of the system model is shown in Figure 10. For eh smple of n MTP se study, the model sets trips from existing relys (in the Fultsys routine), performs supervision of the existing relys (in the RSS routine), nd sets ny reker trips. The model ontinues until ll smples of the se study re exhusted. Reding one smple t time permits time synhroniztion etween the existing rely models nd the RSS. Red One Smple nd of Cse? N Fultsys RSS Set Brekers Y nd Figure 10: Devie Model Flowhrt 5.1 Brekers Breker sttus is determined y series omintion of ny reker opertions provided y existing relys nd from the RSS. The rekers modeled tke 1 yle to open. Setting reker to trip initites the reker filure rely sheme. This sheme works on timer. As long s the reker should trip, nd remin losed, the reker filure timer inrements every smple. When this vlue rehes the timer setting, the reker filure sheme sends trip signl to ll rekers inluded in the reker filure sheme. When the reker opens, the reker filure timer is reset to xisting rely models The existing relys re expliitly told whih fults to trip for. It is ssumed tht the relys lwys work orretly for ll fults within their zone of protetion. Hidden filure modes hnge the zone of protetion. The Fultsys routine tests the existing rely models. Bsed on informtion supplied for the test se, the routine heks to see if the fult uses ny relys to trip. This inludes the effets of ny hidden filure modes. The routine returns the stte of ll existing relys to the min progrm. very MTP se hs swith to identify fult ineption. No rely opertes until this swith loses. 19

2 Trnsmission lines, rekers, nd trnsformers re ll ojet types in the Mtl ode. h ojet hs method routine to test the relys ssoited with the devie. h ojet lso ontins list of rekers to trip should the devie operte. The methods follow the protetion shemes listed in Tle 14. The Fultsys routine tests the existing rely model. Bsed on informtion supplied for test se, the routine heks to see if the fult uses ny relys to trip. This inludes the effets of hidden filure modes. Tle 14: xisting Protetion Shemes Line Protetion Phse Ground Primry Step-Distne Step-Distne Bkup Diretionl Comprison Bloking Phse Comprison Bloking Bkup Phse Comprison Bloking Diretionl Overurrent Trnsformer Protetion Phse Ground Primry Differentil Differentil Breker Filure Protetion Phse Ground Primry Overurrent Breker Filure Overurrent Breker Filure Tle 15: Model Operting Timer Settings for Relys Rely Operting Time (yles) Zone 1 2 Zone Timer setting (0.3 se * 60 Hz) Zone Timer setting (0.6 se * 60 Hz) Diretionl Comprison Bloking Timer setting (0.3 se * 60 Hz) Phse Comprison Bloking 1.5 Diretionl Overurrent Time Dil Setting (0.4 se * 60 Hz) Trnsformer Differentil 1 Breker Filure 1 Other Devies Contts 0.5 Brekers 1 The methods used to test existing relys re ll similr. h method determines if the fult is in the operting diretion, nd if this speifi rely is operting under hidden filure mode. The next step determines if the fult is within the rely zone of protetion. For some relys, the informtion needed to determine this is the distne to the fult, in perent of line length. For other relys, the informtion needed is the stedy stte fult urrent mgnitude in seondry mps. If the fult is in the zone of protetion, the method strts timer. This timer models the length of time the tul rely tkes to reognize nd operte for fult. Tle 15 lists the operting time for eh existing rely model. One this timer expires, the method returns trip signl. 20

3 The existing rely system models require the following informtion: Fulted line, lotion of fult in perent of line length, nd whether it is phse or ground fult. Relys tht work on fult urrent mgnitude, suh s overurrent relys, require stedy-stte fult urrent vlue. The Fultsys routine tests the existing rely model. For eh line, trnsformer, nd reker, the routine heks to see if the fult is in the zone of protetion for the rely, or whether hidden filure uses the fult to e within the rely zone of protetion. 5.3 RSS Model The RSS is the model of the susttion omputer implemented in Mtl. The inputs to the model re supplied y the existing rely model, nd y MTP. Anti-lising filter of the System Opertor Commnd TerminlBlok TripBlok Progrm Proessing Rely Trips To Trip Contts DtBuffer VoteLogi Settings LineBkr BkrBkr Line Logi Line Prot Settings Line Brekers Breker Brekers Figure 11: RSS Shemti 21

4 voltge nd urrent wveforms re modeled in MTP. The RSS smples wveforms t 12 times per yle, s represented in the MTP model. The existing relys provide trip signls to trigger the RSS into tion. The RSS hs three operting modes: Norml, mergeny, Out of Servie. These modes only supervise relys t the lol susttion. For ny rely, ny one of these modes must return trip result for 3 onseutive smples to llow devie opertion. This ensures the reliility of the fult lultion Generl Flow The RSS ontinuously smples nd stores voltge nd urrent wveforms for ll devies. To simulte time flow through the fult se, the model tully works step y step through n rry of smple dt. This hieves time synhroniztion etween the existing relys, the RSS, nd the rekers. The RSS works on trip signls, whih enter through TerminlBlok. h element in TerminlBlok represents ontt input from speifi protetion sheme for speifi devie. When trip signl enters, the RSS hooses n lgorithm sed upon whih of the three operting modes the RSS is in: Norml, mergeny, or Out of Servie. The RSS lwys opertes in Norml mode, with two exeptions. An externl ommnd from the system opertor n ple the RSS in mergeny mode. An externl ommnd from the system opertor n ple the RSS in Out of Servie mode s well, or the RSS n ple itself in Out of Servie mode due to omponent filure. Communitions signls from the system opertor, nd the RSS self-test, re modeled s user input. Norml mode determines performs hidden filure supervision for ny protetion sheme with trip signl. To perform the hidden filure supervision, the lgorithm retrieves informtion for this line stored in Settings. Settings ontins the type of hidden filure supervision sheme to use, nd the tul rely settings for this sheme. The speifi supervision lgorithm uses the rely settings to perform fult lultion. If the fult is in the zone of protetion for the sheme, the routine inrements the Trip sttus in TimerBlok orresponding to this protetion nd devie y one. If the fult is outside the zone of protetion, the lgorithm resets the Trip sttus in Timerlok to zero. Three onseutive suessful fult lultions re neessry to tully trip reker, so the vlue of Trip must equl three to tully send trip output signl. When the vlue of Trip rehes three, the TripBlok output ontt is set to trip for ll rekers ssoited with this devie. mergeny mode lso determines whih speifi protetion shemes for speifi devies hve trip signls. First, this routine retrieves the logi informtion of the vote sheme for this line, stored in VoteLogi. If the logi sheme in VoteLogi hs three or more protetions, the routine pplies the logi sheme. If t lest two protetion shemes for the line inluded hve trip signls, the vote logi sheme deides there is trip. For trip, the routine inrements Trip in TimerBlok for this line. Otherwise, Trip is reset to zero. As in Norml mode, there must e three onseutive suessful vote lultions to tully set n output trip. When the vlue of Trip equls three, the TripBlok output ontt is set to trip for ll rekers ssoited with this line. Lines or devies tht don't hve logi sheme stored in VoteLogi, suh s trnsformers nd rekers, re pushed into norml mode hidden filure supervison. Out of Servie mode models the sitution where the RSS is removed from servie. This n our due to filure of the RSS during self-test, removl due to mintenne, et. In this se, the TripBlok output ontt is set to trip ll rekers. 22

5 5.3.2 Hidden Filure Supervision This setion desries in detil the implementtion of ll hidden filure supervision Trip Signl Perform rely lultion Get V & I wveforms for this rely Trip? Yes Clulte V & I phsors No Blok Trip Allow Trip Get rely settings for this hidden filure supervision nd Figure 12: Generl Hidden Filure Algorithm shemes. All shemes follow the sme generl progrm flow s illustrted in Figure Zone The Zone lgorithm models distne rely using mho irle hrteristi. The lgorithm is used extly s is for the Step-Distne supervision method, nd is uilding lok for other supervision methods. The Zone lgorithm is lled one for eh zone of distne 1 yle Fourier Trnsform Clulte 6 equtions Chek Rely Zones Return Trip Signl Figure 13: Distne Rely Algorithm rely. This lgorithm n hndle rely zones tht operte instntneously or operte on oordintion timer. The si lgorithm is the sme in either se. The lgorithm lultes 6 impedne equtions, nd ompres eh of these equtions to the zone setting. 23

6 The routine first uses the 12 most reent dt smples for every urrent nd voltge wveform to perform the one yle Fourier trnsform. The resulting fundmentl phsors for the voltges nd urrents re used to in the 6 fult impedne equtions. I I I I I I I + mi 0 I + mi 0 I + mi 0 (m is the zero sequene ompenstion ftor, defined s: Z0 Z Z 1 1 ). The lgorithm then ompres the 6 impednes to the zone reh setting. If ny of the 6 impednes re within the mho irle, the lgorithm returns trip. For ses where the rely zone uses oordintion timer, the lgorithm is performed twie. The first instne verifies fult still exists, nd the seond instne supervises the zone time y verifying the fult existed to tully strt the timer. The first lultion is performed extly s ove, using the 12 most reent smples to onvert to phsors. If this lultion returns trip, inditing fult urrently exists, the lgorithm runs seond time. In this se, the lgorithm srolls kwrds through the stored dt smples for n mount of time equivlent to the timer setting. The 12 previous smples from this point in the uffer re used to determine the phsors nd lulte the fult impedne. For exmple, if the timer setting is 0.3 seonds, the dt from [ 0.3se 60 yles 12 smples = ]216 smples previous is used. se yle If this seond lultion returns trip, then the whole lgorithm returns trip. Tle 16 shows the required settings for the Zone rely. Atul settings for eh line re shown in Appendix IV. Tle 16: Zone Rely Settings Setting Positive sequene impedne Zero sequene impedne Mximum torque ngle Zone reh setting Timer setting Units rdins seonds AelZ The AelZ routine is Zone 1 extension sheme, used to supervise hidden filure modes tht depend on rrier signls. This routine first performs zone 1 (under-rehing) distne lultion, using the Zone lgorithm. If this lultion returns trip, the whole lgorithm returns trip. If this distne lultion doesn't return trip, the routine wits for speified length of time nd performs zone 2 (over-rehing) distne lultion. This time is stored in TimerBlok. If this zone 2 lultion returns trip, the whole lgorithm returns trip. very smple inrements the timer in TimerBlok. 24

7 Zone 1 lultion Trip? No Timer Zone 2 lultion Return Trip Signl Yes Figure 14: Zone 1 xtension Algorithm Tle 17: AelZ Rely Settings Setting Positive sequene impedne Zero sequene impedne Mximum torque ngle Zone 1 reh setting Zone 2 reh setting Dely timer setting Units rdins seonds DirOC The DirOC routine performs voltge nd urrent polriztion to use with diretionl Ineut 1 yle Fourier No Ipolr = I HS + I LS All Soures? Yes I 0 V 1 yle Fourier 3 0 lultion Torque qutions Diretion Result Figure 15: DirOC Rely Algorithm overurrent relys. Current polriztion uses the neutrl urrent from the high side nd low side grounded-wye windings of the three-winding trnsformers. It uses t lest one, ut n use more trnsformers s soure for the polrizing urrent. All the relys in this system use oth trnsformers s polrizing urrent soures. The 12 most reent smples re used for the neutrl urrent wveforms. These smples re onverted to phsors using one yle Disrete Fourier Trnsform. The high side neutrl urrent is refleted to the low side se. The lgorithm lso mthemtilly mthes ny differene etween the high side nd low side CT rtios. The polrizing urrent is the sum of ll the high side nd low side neutrl urrents. Voltge polrizing ompres the zero sequene line voltge to the zero sequene line urrent. The lgorithm uses the 12 most reent smples of the zero sequene urrent nd the line 25