Evaluation Analysis of Transformer Substation Radiation on Surrounding Environment

Transcription

1 6 rd Internatonal Conference on Engneerng Technology and Applcaton (ICETA 6) ISBN: Evaluaton Analyss of Transformer Substaton Radaton on Surroundng Envronment Ynmng Zhang North Chna Electrc Power Unversty, Baodng, Hebe, Chna Pengju Wang Dongbe Unversty of Fnance and Economcs, Dalan, Laonng, Chna ABSTRACT: At frst, ths thess screened out the ndexes to evaluate the radaton that transformer substaton has on the surroundng envronment. Secondly, t conducted nondmensonalzaton and made grey relatonal analyss of the evaluaton ndexes and results to obtan the judgment matrx. Then, ths thess used fuzzy-analytcal herarchy model to obtan ndex weght and obtaned the man evaluaton ndexes at last, provdng theoretcal foundaton for the analyss of the radaton that transformer substaton has on the surroundng envronment. Keywords: transformer substaton, radaton, herarchy analyss, grey relatonal analyss INTRODUCTION Transformer substaton s a place to change voltage. In order to reduce energy loss durng power transmsson, hgh voltage needs to be used n dstance transmsson. In Chna, normal dstance transmsson voltage wthn km s kv whle kv wll be needed for a further dstance. Transformer substaton s used to reduce voltage and transmt t ndoor. In urban areas or boundares, kv transformer substaton reduces voltage to kv and transmts t to kv transformer substaton. The rest can be done n the same manner; kv transformer substaton reduces voltage to kv and transmts t to transformer substatons around communtes. Then, voltage wll be reduced to 8/v, and thus, resdents can use the voltage. Therefore, the swtch center of every cty power supply system s transformer substaton. However, current transformer substatons are facng the problem of constructon. More and more people are aganst buldng transformer substatons nsde the cty. They are manly worred about radaton threat. In fact, ths threat s very weak. Even f voltage of a transformer substaton s very hgh, ts radaton may be even lower than that of a cellphone. In order to further analyze the radaton problem of transformer substaton and elmnate people s msunderstandng, ths thess appled nondmensonalzaton, grey relatonal analyss, and fuzzy-analytcal herarchy model to make scentfc analyss on ths problem. GREY RELATIONAL ANALYSIS Accordng to the selected data (see Table ), ths thess obtaned the relaton between each ndex and the evaluaton results by research. As there was no obvous relaton between each ndex and scores of evaluaton results, ths thess made pcture processng on these data and obtaned the followng scatter dagram (See Fgure ). Fgure. Scatter dagram. 6

2 At the begnnng, ths thess obtaned a model wth herarchcal structure by makng the problem herarchcal and systematc. Then, the problem was conssted of processed decomposton elements. Based on element property and relaton, the elements formed multple herarches among whch crterons control- Irradated area Dfferent populatons Heat dsspaton Table. Each ndex and scores of preferred schemes. Magnetc feld Envronmental temperature and mosture Electrc feld Electromagnetc wave Total feld Evaluaton result Specfc analyss procedures of grey relatonal analyss are as follows: () Decde comparson objects (evaluaton objects) and reference array (evaluaton standards). Set there are m evaluaton objects and n evaluaton ndexes. The reference array s xn={xn(k) k=,,,n} and the comparson array s x ={x(k) k=,,,n}, =,,,m. () Confrm correspondng weght of each ndex value. Herarchy analyss can be used to confrm the weght of each ndex. w = [w, w,, w n ] and w k (k=,,,n) refers to the correspondng weght of No. k ndex. () Calculate grey relatonal coeffcent: k xkx k max max xkx k k max max mn mn k x k x k x k x k k In whch k refers to the relatonal coeffcent between techncal statstcs and comparson herarchy. mn mn x k x k and max max x k x k refer k k to the two-stage mnmum dfferental and the two-stage maxmum dfferental respectvely. In general, the bgger coeffcent ρ s, the hgher resoluton rato wll be; the smaller ρ s, the lower resoluton rato wll be. (4) Calculate grey weghted relaton. The calculaton formula of grey weghted relaton s r w k, n k n whch r refers to the grey weghed relaton of No. evaluaton object to ts deal object. () Analyze evaluaton objects. Accordng to the obtaned values of grey relaton, we sorted all evaluaton objects and obtaned ther relatonal sequence. The results show that evaluaton results are proportonal to relatonal sequence. As there were dfferent dmensons contaned n the data of Table, we needed to calculate the same dmensons of data durng calculaton process. Thus, we used nondmensonalzaton to process these data. The followng method was appled for converson: Set the orgnal number sequence as X=(x(),x(),,x(n)). Then, the ntalzed sequence s x() xn ( ) X (,,, ) x() x(). Therefore, t s obvous that the ntalzed sequence cannot meet the requrement of nondmensonalzaton. See detals n Table. Table. Processed data. Irradated area Dfferent populatons Heat dsspaton Magnetc feld Envronmental Temperature and mosture Electrc feld Electromagnetc wave Total feld Evaluaton result Then, ths thess conducted grey relatonal analyss of the eght ndexes of the radaton that transformer substaton has on the surroundng envronment. The formulas of relatonal analyss are as follows: s s s n n s s s x s s s k k n k x k x k x n x n k x ns x k x n The followng results were obtaned from grey theory software: Preferred Scheme Irradated area. Dfferent populatons.68 Heat dsspaton.68 Magnetc feld.4 Magnetc feld.8 Electrc feld. Total feld.4 Total feld.8 FUZZY-ANALYTICAL HIERARCHY MODEL

3 lng related elements of lower herarches were composed of hgher herarches. The model manly ncludes three herarches: ) The top herarchy There s only one element n ths herarchy. As t s the preset target for analyss of excellent desgn scheme, t s also called the target herarchy. ) The ntermedate herarchy Ths herarchy s composed of several herarches. As t contans all the crterons and sub-crterons, t s also called the crteron herarchy. ) The bottom herarchy Ths herarchy s composed of all methods to realze the target. It s also called the scheme herarchy (or measure herarchy). In general, herarchy quantty of the model can be free selected. However, t s closely related to the dffculty level of the problem you want to solve. It s wdely known that for each herarchy, t s better to keep the element quantty controlled by each element of the model less than nne. If t exceeds nne, too many elements n control can make t hard to make parwse comparson and judgment.. Construct judgment matrx Accordng to the quanttatve trend shown n the fractonal change of herarchcal structure, we have found there were three crteron factors whch led to the changes. However, durng the trade-off process of decdng target, the proportons of the factors correspondng to all the crterons n the crteron herarchy were dfferent. Therefore, ths thess appled weght analyss to process these eght ndexes. It s hard to make quanttatve analyss of the proporton that nfluental factors of fracton amount possess n the total populaton. Besdes, too many nfluental factors can result n neglgence or ncomprehensve consderaton and make t mpossble to thoroughly thnk about the mpact that each factor has on one element. Thus, we may obtan data of lttle mportance or a seres of conflctng data. In order to avod the error, we assume that a kg stone can be broken down nto n peces. We can measure the weghts of all the peces and set them as w,,w n. Now, please ask someone to estmate the proporton that weght of these n peces that n the total weght (do not let hm know the weght of each pece). It s not only hard for hm to gve an accurate proporton; but s also very lkely for hm to provde contradctory data. Assume we need to compare the nfluental degrees that n factors X={x,,xn} have on Z, how to provde relable data? Saaty et al. have suggested to make parwse comparson among the factors to establsh parwse comparson matrces, that s to take two factors x and xj. Use aj to express the rato between the nflucencal degrees that these two factors have on Z. Use A=(aj)n n to express all comparson results. A refers to the parwse comparson judgment matrx between Z-A (abbrevated as judgment matrx). It s easly to see that f the rato between the nfluental degrees that x and xj have on Z s aj, the rato between the nfluental degrees that xj and x have on Z shall be a j. aj Defnton If matrx A=(aj)n n can meet () aj>, () a j (,j =,,,n), t s called a postve and aj negatve matrx (easy to see a=, =,,n). Ths thess used scale (-) and recprocal to obtan the value of aj. Scale,4,6,8, Recprocal Table. Connotaton of scales. Connotaton By comparson, the two factors contan the same mportant. By comparson, the former s slghtly more mportant that the latter. By comparson, the former s obvously more By comparson, the former s much more By comparson, the former s extremely more It refers to the medan of adjacent judgment mentoned above. If the mportance rato between factor and factor j s aj, the mportance rato between factor j and factor s aj = / aj. Accordng to psychologcal analyss, we have found that the segmented herarches cannot be too many; or they wll weaken our judgment and thus make t more complcated to judge. By conductng actual experment, ths thess studed the accuracy of our judgment n stuaton wth multple dmensons. The results show that to scales are approprate. It should be ponted out at last that t s generally necessary to make parwse comparson judgment for nn tmes. Some regard t s enough to compare all elements wth one element and thus only (n-) tmes of comparson wll be approprate. The weakness of ths means s obvous. Once a judgment s wrong, the whole sequence obtaned wll be wrong. Moreover, there wll always have mnor wrong judgments n nn quanttatve analyss system. tmes of comparson can provde more nformaton. A reasonable sequence can be derved from repeated comparson from dfferent perspectves.. Consstency check of judgment matrx max n () Calculate consstence ndex CI: CI n () Search for correspondng average random con- 8

4 sstency ndex RI. Saaty provded the values of RI to n=,, as shown n Table 4. Table 4. RI Value. n RI Random method was appled to buld sample matrces to obtan the values of RI: extract numbers randomly from to and ther recprocals to construct straght recprocal matrces to obtan the average value of the largest egenvalue ' ' n max. Defne RI max. n CI () Calculate consstency rato CR: CR. When RI CR <., t s regarded as the consstency of the judgment matrx s acceptable; or, approprate modfcaton wll be needed for the judgment matrx.. Modelng The scorng judgment matrces were obtaned accordng to relatons between each ndex and the evaluaton results: Table. Scorng Judgment Matrces Establsh herarchy structure (see Fgure ): Fgure. Analytcal herarchy structure chart. Use matlab software to calculate the scorng weght of each nfluental factor of the data gven n Table 6. See Table for the results. Table. Weght result Result analyss Accordng to the results obtaned n the above analytc herarchy process, t can be seen that the factors wth hgh weght nclude total feld, electromagnetc wave frequency, electrc feld, and magnetc, showng that these four factors can be used to analyze the radaton that transformer substaton has on the surroundng envronment.. Applcaton Accordng to the four ndexes, ths thess conducted electromagnetc radaton survey on the kv power transmsson lne between No. tower and No. tower n Bnshu West Road of unversty town n Xqng Dstrct of Tanjn. See the dstrbuton graph as follows: Irradated area Dfferent populatons Heat dsspaton Magnetc feld Table 6. Relevant data. Envronmental temperature and mosture Electrc feld Electromagnetc wave Total feld Evaluaton result

5 Table 8. Measurement results. No. Electrc Feld Magnetc Feld Total Feld Intensty X Y Z X Y Z Electrc Feld Magnetc Feld Among whch, between No.4 pont and No.8 pont, there s an nterval of 8m between every two ponts; and between No.8 pont and No.8 pont, there s an nterval of 4m between every two ponts. The heght above ground s m wth temperature of C and humdty of 8 C. See measurement results n Table 8. Result analyss: below the kv power transmsson lne between No. tower and No. tower of Bnshu West Road s a pavement. The dstance between the lne and the pavement s long. The power frequency electrc feld and magnetc feld below the lne can both meet correspondng natonal standards. See the dstrbuton of power frequency electrc feld as follows: CONCLUSIONS Ths thess frst establshed eght evaluaton ndexes for the problem, and then constructed fuzzy-analytcal herarchy model based on t. By applyng MATLAB software, four man evaluaton ndexes whch nfluenced evaluaton results were obtaned: electromagnetc feld, electromagnetc wave frequency, oscllaton nature, and contnuous rradaton tme. At last, t conducted electromagnetc radaton survey on the kv power transmsson lne between No. and No. towers on the Bnshu West Road of unversty town n Xqng Dstrct of Tanjn. The obtaned results can meet correspondng natonal standards. REFERENCES [] Lu, D.G. & Gao, J.J.. Analyss of kv transformer substaton electromagnetc radaton nfluence on envronment. Journal of Shenyang Lgong Unversty, (6): -8. [] Gu, X.Y. 8. Emprcal research on transformer substaton electromagnetc radaton nfluence on envronment. Electrcal Engneerng, (8): [] Zheng, Y. & L, G.M.. Analyss of transformer substaton electromagnetc nfluence on envronment. Envronment, (S): -. [4] Fu, Y.D.. Exploraton and analyss of transformer substaton electromagnetc nfluence on envronment--takng Qngnan transformer substaton as an example. Envronmental Scence and Management, (): -8. [] Chen, B.C., Wu, H.T. & Xu, M.F. 4. Envronment mpact analyss of urban ndoor transformer substaton electromagnetc radaton. Envronmental Scence and Management, (): 8-8. [6] Zhao, H., Luo, H., We, R.H. & Zeng, J.T. 6. Influence of urban hgh voltage transformer substaton electromagnetc radaton on surroundng resdent lfe and envronment. Guangdong Electrc Power, (): -. [] Huang, C.F. & Wu, J.P.. Methods of montorng envronment electromagnetc radaton. Envronmental Study and Montorng, (4):