Research on detection system of heat faults based on multi-sensor information fusion

Transcription

1 Avalable onlne Journal of Chemcal and Pharmaceutcal Research, 204, 6(4):36-4 Research Artcle ISSN : CODEN(USA) : JCPRC5 Research on detecton system of heat faults based on mult-sensor nformaton fuson Junhua Xong,2, nglng Wang, Halan Shen and Chao Yun 2 Department of Electrc Power, North Chna Unversty of Water Resources and Electrc Power, Zhengzhou, Chna 2 School of Mechancal Engneerng and Automaton, Behang Unversty, Bejng, Chna ABSRAC Amng at the dfferent samplng rates of multple sensors for the real-tme detecton system of heat faults n hgh-voltage equpment n substaton, the step by step predcton fuson algorthm based on synchronous samplng data was used to rapdly calbrate the locaton of thermal faults. And a new method that usng nfrared thermal mager together wth CCD (Charge Coupled Devce) camera and wreless sensor networks was proposed to mplement heat faults detecton. he energy harvestng technque was employed to obtan solar energy, whch acheved the ndependent power supply of sensor nodes. he expermental results n a substaton showed that the system proposed n ths paper could effectvely detect overheatng faults of the transformers and could mprove the operaton relablty of the electrcal equpment.. Key words: Mult-sensor nformaton fuson;heat faults;step by step predcton fuson algorthm;nfrared thermal mager;wreless sensor network INRODUCION Wth the development of modern power ndustry nto the hgh voltage and large capacty, hgh requrement of the power equpment mantenance was requred to ensure the safe and effcent operaton of electrcty producton. he thermal effect of electrcal equpment was the crtcal cause of many faults and abnormal phenomenon, therefore, temperature detecton of the electrcal equpment was a necessary means to ensure the relable operaton of the electrcal equpment []. At present, the specal methods used for measurng heatng defects of hgh-voltage equpment manly ncluded two categores: the one was usng nfrared thermal mager for non-contact measurement, and the other was usng a varety of wreless detecton devce for contact measurement [2]. Currently, the method usng the nfrared temperature measurement technology to detect heat faults has been wdely used n power system. Most of whch was hand-held nfrared devces. In recent years, the nfrared and vsble lght camera have been nstalled at the cradle head, and acqured automatcally and crcularly the nfrared thermal mager of electrc equpment n the substatons under the control of montorng computer [3].Whle utlzng the nfrared thermal mager of fxed poston to measure, the accuracy of the measurement was largely nfluenced by factors such as the background radaton, measure dstance, ambent temperature, etc. Furthermore, there were blnd areas where nfrared thermal mager cannot detect, for nstance, resstance of other apparatuses, apparatus located n electrc cupboard, etc. he strong electromagnetc felds produced by hgh voltage nterfered wth rado wave badly, therefore, t was necessary to choose an approprate frequency when usng the wreless devce to montor the condton of electrcal equpment. ZgBee wreless sensor network have many features: low cost, short-tme delay, the unlcensed bands, hgh safety, low power consumpton, and the network was the deal soluton to solve the heatng problem of real-tme and onlne detecton of hgh-voltage equpment [4]. Wth the rapd development of power ndustry, the labor ntensty of the mantenance personnel of power equpment 36

2 Junhua Xong et al J. Chem. Pharm. Res., 204, 6(4):36-4 has been ncreasng and the use of a sngle sensor to detect equpment heatng defects cannot guarantee the stable runnng. he technology of mult-sensor nformaton fuson was adopted to enhance the survval ablty of the montorng system. Smultanety, the system had better fault correcton capablty due to the nformaton redundancy between the dfferent sensors. he coverage abltes of tme and space could be expanded through the complement and combnaton of the detecton abltes of tme and space between dfferent sensors. SRUCURE OF HE DEECIONSYSEM OF HEA FAULS Installng the nfrared thermal mager at the substatons scene of the temperature measurement became possble for ts prce had fallen sharply. he fxed nfrared thermal mager cannot nspect the blnd area, therefore, a new method that the nfrared thermal mager was put together wth ZgBee wreless sensor network was put forward to realze the real-tme and onlne detecton of the hgh-voltage equpment. he detecton system of heat faults for hgh-voltage equpment was shown n fgure. No. substaton router coordnator nfrared thermal mager CCD camera upper computer cradle head stepregon Ethernet No. 2 substaton No. n substaton sensor node detecton area remote PC Fg. Structure of detecton system In fgure, the nfrared thermal mager was set on the controllable dgtal cradle head, and was nstalled at the framework of the equpment accordng to the actual poston of the substaton and the effectve dstance of temperature measurng of nfrared thermal mager. he montorng angle or the exact locaton of the focus devce could be adjusted manually wth the montorng system. he pre-set ponts could also be checked automatcally wth the settngs of the montorng platform parameters. Whle automatcally nspectng, all the measured parts of electrcal equpment were scanned wth nfrared thermal magery to fnd out the hot abnormal areas. hen, the accurate temperature of the abnormal parts and the key testng equpment were measured and the heat spectrogram was taken. Imagng parameters of CCD camera was smlar to the nfrared thermal mager. Controllable cradle head was the postonng devce to capture the photos, whch was controlled by a prncpal computer through the RS-485 transmsson sgnal. Accordng to the program nstructons, cradle head selected the correspondng anchor pont, whch not only supported and nstalled the ntegrated cameras and thermal magers, but also could expand vson feld of the CCD cameras and nfrared thermal magers. Cradle head could rotate a 330 n the horzontal drecton, and could ptch a ±30 n the vertcal drecton. ZgBee wreless sensor network n fgure was desgned based on the IEEE techncal standard and ZgBee network protocols. he sensor node n the fgure could measure the heatng temperature and send the wreless data. he router could transmt wreless data, and the network coordnator could send the recevng data to the upper computer [6]. he upper computer communcated wth the remote computer n real tme and realzed the remote detecton through the specal cable of the power system. In order to manage the heat defects of hgh-voltage equpment n multple cross-regonal substatons centrally, the remote PC made a two-way communcaton wth the upper computer of each substaton through the Ethernet. hen, the remote fault analyss and database management for the PC from dfferent IP addresses could be realzed. he transformer substaton was a powerful source of electromagnetc nterference, therefore t would produce some electromagnetc nterference under the normal or fault condtons. In ths paper, electromagnetc compatblty was one of the key ssues when desgnng the temperature sensor nodes, whch was drectly contacted wth hgh-voltage equpment. he nterferental sgnal frequency manly concentrated from 20kHz to 30MHz n the substatons, therefore ths frequency band was avoded and 2.4GHz frequency was used to transfer the wreless data. In general condtons, the unwanted sgnal could not nterference the sensor node.he sensor nodes desgned n ths paper, whch had been tested by a measurng and testng centers n Chna, could meet the electromagnetc compatblty requrements of substaton ntellgent electronc devces [7]. MUI-SENSOR INFORMAION FUSION AND HE LOCAING OF FAIL POIN he procedure of mult-sensor nformaton fuson Wth the rapd development of power ndustry, the labor ntensty of the power equpment mantenance personnel 37

3 Junhua Xong et al J. Chem. Pharm. Res., 204, 6(4):36-4 was ncreasng and the use of a sngle defect detecton to detect equpment heatng defects cannot guarantee the stable runnng. he technology of mult-sensor nformaton fuson was proposed, whch can enhance the survval ablty of the montorng system. At the same tme, due to the nformaton redundancy between the dfferent sensors, the system has better fault correcton capablty. he coverage abltes of tme and space can be expanded through the complement and combnaton of the detecton abltes of tme and space between dfferent sensors. Infrared detecton technology was a knd of observaton technology that used nfrared detectors to collect the heat dstrbuton nformaton of equpment under the nfrared radaton status, and then converted nto vsble mages. It could realze the observaton of temperature dstrbuton n the large area, and temperature measurement at the fxed pont of local defects [8]. However, the nfrared thermal mager created an mage of dfferent temperature dstrbuton, therefore, t could not show the geometrcal shapes of the parts at same temperature. When the observed equpment n the complex stuatons, such as t was blocked by other equpment, or t was set n the electrc cabnet, etc., t was hard for observers to determne the locaton of the heat source through nfrared thermal mages quckly and accurately [9]. In ths system, wreless temperature measurement sensors on the key equpment that could not be able to be observed by the nfrared thermal mager were nstalled, and the nfrared thermal mager and CCD optcal sensors as well as ZgBee wreless sensor network were appled to the thermal fault detecton.he system dsplayed thermal energy dstrbuton of the measured target through nfrared thermal mages, and dsplayed the complete shape and accurate poston of measured target n the vsual mage forms. he thermal fault could be located fast and accurately wth the regstraton of nfrared thermal mage and vsble lght mage and the fuson of the hot faults nformaton together wth the nformaton obtaned by the wreless temperature sensors. he procedure of mult-sensor nformaton fuson was shown as fgure 2. the measured electrc equpment nfrared mage collecton mage segmentaton CCD mage collecton mage segmentaton temperature collecton of wreless sensor node wreless data acquston of the coordnator feature extracton feature extracton mage regstraton by phase correlaton remove maxmum mean flter step by step predcton fuson algorthm fault locaton Fg.2 Flow chart of mult-sensor nformaton fuson he regstraton of nfrared thermal mage and vsble lght mage, as well as the accurate locatng of the fault ponts on the nfrared mage was the hot research felds of the electrcal equpment fault detecton[0]. hs system adopted the Phase Correlaton Algorthm [] for mage regstraton. Assume that the mage f( x, y) could produce the mage f2( x, y) wth the translaton of the x ( n,.e. f 2( x y x, y) f ( x d, y d ) () And the correspondng Fourer transform was shown as the equaton of (2): F2 ( u, F ( u, exp( j2 ( dxu d y) (2) he power spectrum n the frequency feld was shown as the equaton of (3): * F ( u, F ( u, 2 exp( j2 ( d u d )) * F ( u, F ( u, v x y 2 Where, the symbol * represented phase conjugaton. Impulse functon of x d, y d ) ( x y (3) could be obtaned by 38

4 Junhua Xong et al J. Chem. Pharm. Res., 204, 6(4):36-4 the nverse transformaton of power spectrum. here were obvous peaks n the poston offset and we could get the translaton of the two mages. Experments showed that f the speed of ths method was faster, t would have a better relablty and a hgher accuracy. he step by step predcton fuson algorthm Mult-sensor nformaton fuson system could be dvded nto two categores: synchronous and asynchronous sensor system. radtonal fuson algorthm usually was based on whch all knds of test data were measured and arrved at the same tme, so called measure of synchronzaton. he data of the mult-sensor fuson must be on the condton that the dfferent sensors were observed at the same tme and on the same entty. In ths paper, the research objectve was a dynamc system of multple sensors that had the dfferent samplng rates. By usng a step by step predcton fuson algorthm [2], the data of nfrared sensors and CCD sensors could be fused wth the data of wreless RF sensors to locate heat defects ponts of the electrc equpment rapdly. We set mult-sensor dynamc system as shown n the equatons of (4) and (5): x( k ) ( x( w( (4) z ( H( x( v (,,2,..., N (5) In the equaton of (4), the nteger of k was a dscrete tme varable, and k 0 ; x ( n was the state vector; n n ( R was the system matrx; w ( n was the system process nose, whch was zero mean and whte nose sequence, and E{ w( w ( j)} Q(, k, j 0 (6) kj And n the equaton of (6), Q( was nonnegatve defnte matrx. After regsterng the nfrared and vsble lght mage, we fused the average flterng data of rado frequency sensors. herefore, the step by step fuson flterng algorthm had two sensors wth dfferent samplng rates to observe P characterstcs of the target. In the equaton of (5), z( was the value of x( observed by the sensor; P n P H( R was measurng matrx; v ( was a zero mean whte nose sequence, and E{ v ( v ( l)} (,, j,2,..., N; k, l 0 j (7) j kl And n the equaton of (7), ndependent of each other. ( R was postve defnte matrx. Assume that x (0), w(, v (,2) and were k z ( ) [ z (), z (2),..., z ( ] z k [ z (), z (2),..., z ( ] (8) (9) z k ( ) In the above equatons, was the gather of measurng sequence set of the sensor n the tme of, k z 2,,k. was the gather of measurng sequence set of the two sensors n the tme of, 2,,k. xˆ ( k he essental dea of the step by step flterng was that f the global estmated value of x( and the P( k correspondng error covarance n the tme of k all had been obtaned, we could use the local observatons n the tme of k+ together wth the Kalman flter to estmate the x( k ) n turn, thus to obtan the global xˆ ( k k ) P( k k ) estmated value and the correspondng error covarance. 39

5 Junhua Xong et al J. Chem. Pharm. Res., 204, 6(4):36-4 he results and analyss of the fuson algorthm Amng at the wall bushng whch was easy to occur current caused heat faults n the substaton, the wreless temperature measurng devce had been nstalled at the bushng jont n the No. 2 transformer n a substaton to obtan the three-phase bushng contact temperature. And the lve vdeo mages were acqured by the nfrared thermal mager and the CCD camera. After the mage regstraton, the data were fused wth the contactng temperature of the x( 0) x three-phase wall bushng obtaned by the coordnator. Suppose that the ntal state was 0, and the ntal covarance matrx was P0 E{[ x(0) x0][ x(0) x0] }. And gven that fuson cycle was 60s, and that nfrared and, wreless sensor samplng perod respectvely was 2, and 20s, 2 0s, then we could get fuson results of the dfferent tme shown n table. From the results, the temperature rse of phase C was obvously hgher than the other two phases, therefore suspectng t has defect. After repeated measurement, the temperature was stll hgh. It was found that the casng jont of phase C had oxdaton wth nspecton of the No. 2 transformer bushng. By analyss, we found that the conductve part of wall bushng and the busbar was the terrble oxdaton because the wall bushng and the busbar were alumnum conductors and copper conductors wthout copper alumnum transton n the jont termnal. After dealng wth the oxdaton and recoverng the power, the testng for temperature rsng of phase C was normal. he experment results showed that the step by step predcton fuson algorthm had a good effect on the target state estmaton. ntal tme t( C) category wreless temperature measurement data nfrared temperature measurement data ab. Results of data fuson 9:00 envronmental temperature 20.4 C 4:00 envronmental temperature 29.3 C A B C A B C data fuson results A B C CONCLUSION he temperature detecton of the hgh-voltage electrcal equpment has become a practcal problem about the safe operaton of the electrcal equpment n the power system, whch needs to be solved pressngly. he temperature detecton of the hgh-voltage electrcal equpment has become a practcal problem about the safe operaton of the electrcal equpment n the power system, whch needs to be solved pressngly. It was crucal sgnfcant to enhance the relablty of electrcal equpment and to ensure the safety and stable operaton of power system. Based on the on-lne detecton of heat faults of mult-sensor nformaton fuson, t could not only solve the problem that some parts of electrcal equpment was unable to be nspected by usng on-lne nfrared thermal mager sngly, but also t could be equpped wth wreless temperature sensor on the key equpment to locate the thermal fault ponts quckly. Energy capture technology was used to collect solar energy and provde heat energy for equpment, whch had solved the problem of ndependent power supply of the sensor nodes. he system could be mproved durng practcal applcaton to have greater practcal value and realstc sgnfcance. Acknowledgments he authors wsh to thank Zhengzhou Scence and echnology Bureau n Chna for contract 2PPGG358-5, whch named Research on montorng system of thermal defects onlne based on nformaton fuson, under whch the present work was possble. REFERENCES [] ZHAO Zhen-bng, GAO Qang, YUAN Jn-sha, et al. Hgh Voltage Engneerng, pp , vol.8, no.8,

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