Research of PD on-line Monitoring System for DC Cable

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1 Reserch Jourl of Applied Scieces, Eieeri d Techoloy 7(2): , 2014 ISSN: ; e-issn: Mxwell Scietific Oriztio, 2014 Submitted: Mrch 23, 2013 Accepted: My 10, 2013 Published: Jury 10, 2014 Reserch of PD o-lie Moitori System for DC Cble 1 Du D-Pe, 1 Qi Wei-Qi, 1 Liu Ho-Ji, 1 Zh Yu-Ji, 1 Ye Ku, 1 Che Xu d 2 Ye Hi-Fe 1 Beiji Electric Power Reserch Istitute, Beiji, , Chi 2 Deprtmet of Electricl Eieeri, Shhi Jio To Uiversity, Shhi, , Chi Abstrct: I order to moitor the isultio of XLPE cble of ril system, O-lie Prtil Dischre (PD) Moitori System pplied for 1500V DC cbles of Shhi Trctio Substtio is described, icludi its hrdwre d softwre structure. After istlled, this system successfully detected oe PD sil. The results demostrted tht this system worked stbly d relibly. Keywords: DC cble, o-lie moitori, prtil dischre, trctio substtio INTRODUCTION Ril trsporttio, oe of the public trsporttio tools, is directly relted to the sfety of psseers. My fctors ifluece its opertio sfety. Power supply is oe of the mi fctors d its key system is DC power supply. Thus moitori the sfety sttus of DC cble is very importt. Prtil dischre is the mi reso of the cble isultio i. O-lie PD sil moitori is effective method for diosis of cble isultio (Zhou et l., 2009; Hiqi et l., 2009). Commo Prtil dischre detectio methods iclude differetil, directiol coupli d electrometic coupli. The electrometic coupli method does ot hve to set coupli cpcitor i the hih-volte side to obti PD sil, so mesuri circuit does ot hve direct electricl coectio, which c successfully suppress oise (Mi-Jie d Y, 2012). This system detects prtil dischre sil i the method of electrometic coupli, imi t evluti the cble isultio coditio. This system uses the widebd curret sesor d hih-speed dt cquisitio crd to obti prtil dischre sils; uses the dt system d the lysis d diosis system for cquisitio d cotrol of sils d lysis of dt; filly mke comprehesive evlutio o dischre of the cble d ive effective wri of the cble which is possible to hve isultio problems. HARDWARE OF SYSTEM Fiure 1 shows the hrdwre structure of the olie dischre moitori system for subwy DC cble. The system is divided ito three prts icludi the widebd curret sesor, sil distributio box d server. The widebd curret sesor is istlled i the uderroud cble. The sil distributio box d server re istlled i the collectio server cbiet i cotrol room. Widebd curret sesors: As i Fi. 2, the widebd curret sesor is istlled i the uderroud cble. The sesor s structure looks like pliers, brii coveiet disssembly d istlltio. Usully, six cbles mke up roup, ech of them covered by curret sesor. There re five roups i totl. The sesor hs iterl electrometic coupli metic core d mplifyi d filteri module. Becuse the bd of city ril DC cble dischre sil is wide, ri from tes of khz to tes of MHz d there is lre mouts of brodcst iterferece sil (Fe et l., 2006; Hshmi et l., 2011), this system choose the Roowski Coil to cquire prtil dischre sils i its bd. Amplifyi d filteri module hs 2 built-i lo switches. It hs fuctio of 4-level mplifyi. Bsed o the mplitude of smpli sil, we c mificte it by softwre either 10 times or 100 times. It retly simplifies the frot-ed cquisitio module d improves the stbility d relibility of the system to iterte metic core d mplifyi d filteri module with the sesor. Fiure 3 shows the mplitude-frequecy chrcteristic curve of sesor. The smpli frequecy bd of sesor is 1.6 to 10 MHz. The mplitude-frequecy respose curve is flt i this bd, cosistet with the eed of system moitori. Sil distributio box: Fiure 4 shows the hrdwre fuctio of system. The umber of subwy substtio cble is eerlly 25 or so. I order to leve some mri d prevet emerecy of moitori lies, the hrdwre system is desied with 30 cbles. At preset, the system c support up to 30 prtil dischre sil cquisitio. I order to simplify the structure of system d reduce the cost, we use oly 1 piece of 4-route Correspodi Author: Du D-Pe, Beiji Electric Power Reserch Istitute, Beiji, , Chi 263

2 Res. J. Appl. Sci. E. Techol., 7(2): , 2014 Fi. 1: System hrdwre structure throuh the prllel port. Four chels of sil re trsmitted to the dt cquisitio crd ech time. Fi. 2: Sesors istlltio dirm Server: As i Fi. 4, hih-speed dt cquisitio crd is istlled i the server. Acquisitio crd hs 4 mutullyidepedet A/D coversio chel, processi the mplified lo sil i diitl wy d stori the results i memory. Chels sychroize with ech other by clock d trier bus. This method c esure ech chel to be triered d recorded t the sme time. Bckroud processi softwre reds dt from the specific chel throuh system bus d cotrols the prmeters d stte of cquisitio chel. The server cbiet is istlled o the scee s i Fi. 5: The prtil dischre sil collected by curret sesor is trsmitted throuh shieldi lie to the sil distributio box d server for processi. Fi. 3: Amplitude-frequecy chrcteristics of sesor hih-speed dt cquisitio crd, we eed sil distributio box to llocte chels for 30 dischre sils. Ech time 4 chels of sils re trsmitted. There re 5 lo switches i sil distributio box, cotrolli 30 chels, respectively. The lo multiplexer is cotrolled by the bckroud softwre 264 SOFTWARE OF SYSTEM The olie cble moitori softwre system is composed of dt cquisitio d cotrol system d the lysis d diosis system. The whole structure is show i Fi. 6. Dt cquisitio d cotrol: Dt cquisitio d cotrol system mily icludes prmeter setti, smpli cotrol d self-diosis module. Prmeter setti module hs fuctio to set prmeter, dt store formt, pth d so o. Smpli cotrol module is mily used to complete the commuictio betwee computer d dt cquisitio crd, cotrolli the smpli chel of cquisitio crd d executi the correspodi smpli commd. Self-diosis module is resposible for moitori server d etwork. Whe the system is borml, it reset immeditely d utomticlly.

3 Res. J. Appl. Sci. E. Techol., 7(2): , 2014 Fi. 4: Hrdwre fuctio block dirm () Fce (b) Bck Fi. 5: O-site istlltio of moitori ceter ti se dt cquisitio r e te m p r l p li m c o tro s Softwre of System lf se o sis i -d Fi. 6: System softwre structure diosis system d si c e ti c tio i re o sis i p ro m tu -j e x tr i r d fe w As i Fi. 7, disply iterfce for dt cquisitio d cotrol prorm is used to disply the time domi wveform, dt file iformtio d smpli stte of smpli dt. Ech dt file hs its correspodi specific cble. Click the file me d the iterfce will disply the correspodi time domi wveform of smpli dt. Dt diosis d lysis: Dt lysis d diosis system mily icludes the ti-jmmi processi, feture extrctio, diosis d wri module. Ati-jmmi processi: Ati-jmmi processi module is mily used to suppress the 265

4 Res. J. Appl. Sci. E. Techol., 7(2): , 2014 Fi. 7: Dt cquisitio prorm widow Fi. 8: Fierprit of DC prtil dischre bckroud oise d lie coupli oise i oriil testi dt. Vrieties of oises exist i the PD moitori field. Typicl iterfereces re divided ito three cteories: white oise, discrete spectrum iterferece d pulse iterferece. These iterfereces hve hue differece i time-frequecy chrcteristics betwee them. It is touh to elimite the iterferece with sile method, so differet filteri methods should be used ccordi to the type of iterferece (F d Ci, 2007). Therefore, this system uses three techiques of 266

5 Res. J. Appl. Sci. E. Techol., 7(2): , 2014 fuzzy loic PD sils 1st type of feture 2d type of feture tred lysis Cluster method evlutio similr sil Fi. 9: Flow chrt of PD diosis Fi. 10: Alrm widow of the moitori system wvelet filteri, FFT filteri d eurl etwork filteri to, respectively suppress the typicl iterfereces. Dischre feture extrctio: At preset, the olie moitori system for subwy cble prtil dischre extrcts two PD chrcteristic prmeters. The first oe mesures the dischre level, mily used to lyze the developmet tred of dischre. I totl, 9 feture prmeters reextrcted, icludi the mximum vlue, the 267 vere vlue of dischre pulse d pulse umber etc. The secod oe shows the dischre mode, mily used to lyze the stbility of dischre mode. I totl, 22 feture prmeters re extrcted, icludi skewess d projectio etc., used to build the PD fierprit, s i Fi. 8. Diostic ssessmet d prewri: The diosis d tretmet of PD is firly complex, requiri combitio of professiol kowlede d itelliet diosis techiques. Yers of reserch shows tht, i curret coditio, it is

6 Res. J. Appl. Sci. E. Techol., 7(2): , 2014 CONCLUSION Good site opertio coditio proved tht this system c relize olie moitori of the cble isultio stte, retly reduci the security risks of power supply system. This system hs the followi chrcteristics: Fi. 11: PD sil d its frequecy spectrum impossible to use sile method to complete prtil dischre diostic tsk. A vriety of techoloy is eeded to build comprehesive diosis system. I order to et more ccurte evlutio results, we eed to lyze two kids of feture prmeters seprtely, s i Fi. 9. The first type of feture prmeters is mily used for tred lysis, combied with fuzzy loic to evlute the severity d determie the stbility of the dischre level. The secod type of feture prmeters is mily used for similrity lysis, combied with clusteri method to cluster d lyze similr sil d determie the stbility of dischre mode. Accordi to the fil evlutio coclusio, moitori system sed wri iformtio for cbles tht exceed the lrm threshold. As i Fi. 10, red dots, which pper i the moitori lrm iterfce, idicte tht cble my hve problem i isultio d it eeds further sfety ispectio. SITE OPERATION At preset, the subwy DC prtil dischre olie moitori system desied by our reserch roup hve bee successfully istlled i severl Shhi subwy trctio substtios. Accordi to the survey, they re rui i ood coditio. Duri the opertio of moitori system, it successfully detected dischre borml sils i oe cble. The time-domi wveform d spectrum re show i Fi. 11. After osite ispectio, cble isultio deteriortio ws cofirmed. The workers replced the cble d the disply of moitori system recovered. Itertio of mplifier d sesor simplifies the istlltio process d effectively improve the relibility of frot rui. Sychroous cquisitio of 4 chels c support olie moitori of 30 cbles, fully ble to meet the curret eeds of Shhi subwy sttio cble moitori. Comprehesive use of vrious itelliet lorithms o cble dischre diosis c ive effective erly wri iformtio of the cble which hs isultio problem, esuri the sfety of power system opertio. ACKNOWLEDGMENT This study is supported by Ntiol Hih Techoloy Reserch d Developmet Prorm (863 Prorm) uder Grt No. SS2012AA REFERENCES F, H. d J. Ci, A probe ito the bckroud iterferece of the testi system for PD i power cbles [J]. Elect. Wire Cble, 2: Fe, Y., Y. F d Y. Xu, Study of oise reject techique for PD o-lie moitori o cble joit [J]. Hih Volt. E., 32(7): Hiqi, N., C. Xio-Li, A. Cvllii, G.C. Motri d Z. Yo, Experimetl reserch o prtil dischre t HVDC volte d idetifictio of PD source [J]. Hih Volt. E., 35(7): Hshmi, G.M., M. Lehtoe d M. Nordm, Clibrtio of o-lie prtil dischre mesuri system usi Roowski coil i covered-coductor overhed distributio etworks [J]. IET Sci. Mes. Techol., 5(1): Mi-Jie, Z. d Z. Y, Preset situtio of XLPE power cble prtil dischre o-lie detectio d discussio [J]. Elect. Wire Cble, 4: Zhou, C., M. Michel, D.M. Hepbur d X. So, O-lie prtil dischre moitori i medium volte uderroud cbles [J]. IET Sci. Mes. Techol., 3(5):