Substation Noise Research Based on Geometric Divergence

Transcription

1 6 3 rd Internatonal Conference on Engneerng Technology and Applcaton (ICETA 6) IBN: ubstaton Nose Research Based on Geometrc Dvergence Ru u, Yun Fu, Chundong, Zhe h, hshen Guan & Jun Zhao tate Grd aonng Electrc Power Company, henyang, aonng, Chna ABTRACT: wth ncreasngly straned urban land resources, fully sealed substaton wth hgh ntegraton level has become the manstream scheme for kv power dstrbuton network. Therefore, ths thess manly studes the nose problem of prefabrcated dstrbuton substaton, amng to solve the nose nterference of fully sealed compact substaton. Ths thess ntroduces the computatonal formulas of nose attenuaton frstly. Then, t establshes the computng model of substaton attenuaton based on geometrc dvergence n combnaton of the theory for sound propagaton n meda. At last, t offers computaton to the nose propagaton of pont sound source, plane sound source, and global sound source of substaton respectvely; and concludes the attenuaton relatonshps between nose and dstance n dfferent sound sources. Keywords: nose; prefabrcated dstrbuton substaton; geometrc dvergence; plane sound source INTRODUCTION Wth contnuous mprovement n urban constructon, quantty of kv substaton s n rapd ncrease. Thus, there s a contradctory relaton between urban land use and substaton quantty. Therefore, fully-sealed substaton wth hgh ntegraton level has become the manstream scheme for kv power dstrbuton network. Ths thess manly studes the nose problem of prefabrcated dstrbuton substaton. Many predecessors have made great contrbuton to solve substaton nose problem, among whch: In 4, Yang Gao made deep analyss of the low frequency characterstcs and propagaton laws of substaton equpment nose n theory and proposed nose management plan n hs Predctve Research on ound Feld Features and Nose Dstrbuton of ubstaton, provdng techncal support for future substaton optmzaton desgn []. In 4, Xueyun Ruan establshed acoustc model to predct transformer nose based on outdoor half- open spatal coherence vrtual source n hs Predcton Theory of Coherent Acoustc Feld Nose and Research on ts Applcaton n Hgh-voltage DC Transmsson ystem, contanng great sgnfcance n mprovng the nose predcton of DC exchange staton []. In, Haozheng We studed the formaton mechansm of the man nose source equpment nose nsde hgh-voltage DC convertor staton and made separaton amendment on supermposed nose of complex sound feld n hs Research on Audble Nose Predcton ystem n Hgh-Voltage DC Transmsson ystem, provdng mportant reference proof for the nose predcton calculaton of hgh-voltage DC convertor staton [3]. In 4, ang Huang dd dgtal exchange of dsplacement-superposton accordng to several sample data from the same dscharge source n hs Research on the emdefnte Relaxaton uccessve Approxmaton Postonng Methods of ubstaton Partal Dscharge ources. He used fourth-order cumulant to obtan tme dfference and effectvely restraned nose whle mprovng NR [4]. Based on predecessors research, ths paper frstly ntroduces the computatonal formula of nose attenuaton. Then, t combnes the propagaton theory of sound n meda to establsh the substaton nose attenuaton computng model based on geometrc dvergence. astly, t calculates the nose propagaton of pont sound source, plane sound source, and global sound source of substaton respectvely; and obtans the attenuaton relaton between nose and dstance n dfferent sound sources, amng to contrbute to solvng the nose nterference problem exstng n fully-sealed compact substaton. 59

2 NOIE ATTENUATION CACUATION In combnaton of the propagaton characterstcs of sound, t can be known that vbraton of sound source can cause vbraton of surroundng meda molecules. Then, the vbraton can cause vbraton of other meda molecules. Thus, vbraton of sound source can be propagated outwards n form of wave beam. Durng the propagaton process, scatterng, refracton, and dffracton can occur due to sheldng. As a result, energy wll be gradually attenuated durng propagaton. Wth ncrease n dstance, sound wll be reduced. Accordng to actual stuaton, the energy attenuaton of sound durng propagaton can be manly dvded nto the followng parts: geometrc dvergence, ground absorpton, atmospherc absorpton, sheldng acoustc absorpton, and many other attenuaton factors. Therefore, n the entry nose calculaton of substaton, the method to calculate the sound pressure level at predcton pont r away from sound source after varous attenuaton s shown n Formula () gven below: p ( p dv atm bar gr msx r) ( r) ( A A A A A ) () In formula (), p(r) refers to the weghtng A sound pressure level at r away from sound source, db. Adv refers to the nose attenuaton caused by geometrc dvergence, db. Aatm refers to the nose attenuaton caused by atmospherc absorpton, db. Abar refers to the nose attenuaton caused by acoustc sheldng, db. Agr refers to the nose attenuaton caused by ground effect, db. Amsx refers to the nose attenuaton caused by other factors, db. In Formula (), there s nterrelaton between the attenuaton caused by atmospherc absorpton Aatm and frequency of sound wave, gas molecule densty, and degree of actvty. Related research have manfested the formula to calculate the attenuaton at the pont r away from sound source caused atmospherc absorpton as shown n Formula () gven below: A atm a( r r ) () Among whch, r refers to the propagaton dstance (m) from sound source to predcton pont; r refers to the propagaton dstance (m) from sound source to reference pont; and a refers to temperature, humdty, and wave frequency functon. Atmospherc attenuaton coeffcents can be obtaned n Outdoor Acoustc Attenuaton. ee Table shown as below for common reference data.. heldng dffracton attenuaton process heldng nose attenuaton Abar refers to the obvous acoustc wave energy attenuaton caused by reflecton, projecton, and dffracton that sound makes n propagaton whle encounterng materals wth hgh densty, such as walls or boards. ee Fgure gven below for the propagaton path after acoustc wave encounters sheldng. Fgure. Propagaton path of acoustc wave after encounterng sheld. ee Formula (3) gven below for the method to calculate the nose attenuaton caused by fnte-long sheldng: Table. Attenuaton coeffcent table of absolute musc absorbed n atmosphere. Attenuaton coeffcent of atmospherc absorpton db/km Temperature () Relatve humdty Md-frequency of octave band Hz

3 A lg (3) bar 3 N 3 N 3 N3 In Formula (3), N, N and N3 refer to Fresnel numbers of whch the computatonal methods are related to the lengths of three propagaton paths. The three propagaton paths are the shortest dstances between sound source and predcton ponts as shown n Fgure gven below: dffracton dstance of predcton pont to the las sheld. e refers to the dffracton dstances of multple sheldng between boundares. d refers to the dstance from sound source to predcton pont. When sound propagates along the ground, due to the nfluence from complex ground-surface condtons, the followng computatonal formula s generally appled to calculate the nose attenuaton caused by ground effect: A gr hm (7) r r Among whch, r refers to the dstance between sound source and predcton pont; hm refers to average ground clearance; and hm= (hs+hr)/. If t s calculated that Agr s negatve, the calculaton shall take Agr =. 3 ETABIHMENT OF GEOMETRIC DIVER- GENCE NOIE ATTENUATION MODE Fgure. Dffracton paths whle acoustc wave gong through sheldng. Computatonal formula of Fresnel number: N / (4) Among whch, refers to No. path dfference: O OR R (5) λ refers to wave length. λ = c / f and c refers to sound velocty. Under normal condtons, the propagaton velocty of sound n ar c = 34m/s s selected n whch f refers to acoustc wave frequency. Fgure 3. Dffracton path of acoustc wave whle encounterng multple sheldng. Accordng to the multple sheldng as shown n Fgure 3, Formula (6) shall be appled to calculate dffracton path dfference. d e d d (6) O OR In Formula (6), d O refers to the dffracton dstance of sound source to the frst sheld. d OR refers to the Geometrc nose attenuaton s manly caused by ncrease of propagaton dstance. There are three man types of sound source: pont sound source, lne sound source, and plane sound source. When sound source vbrates, elastc objects surround the sound source wll also vbrate and the surroundng ar molecules wll also vbrate. Thus, sound source s propagated n form of acoustc wave. The wave equaton of plane acoustc wave s as follows: p p p p (8) x y z c t In Formula (8), c refers to sound velocty and s taken as 34m/s; t refers to tme (unt: s); and p refers to sound pressure (unt: pa). From Formula (8), t can be seen that sound pressure s the functon of space (x, y, z) and tme t and s descrbed as p(x, y, z), meanng the change law of sound pressure at some locaton. Accordng to some pulsaton sphercal sound wave wth even surface, the sound radaton pressure at locaton r away from center of sphere s as follows: p ck p( r, t) cos( t kr) Q cos( t ) r 4r kr (9) Among whch, Q refers to strength of sound source and Q=4πa u ; ω refers to angular frequency and ω=πf; k refers to wave number and k=ω/c; and ρ refers to ar densty wth unt of kg/m 3. As the range of sound pressure s wde, the logarthm of the specfc value between effectve sound pressure and standard sound pressure s generally appled to calculate sound pressure. ee Formula () gven below for the method to calculate sound pressure: 5

4 P p p lg lg () p p Among whch, p refers to effectve value of tested sound pressure; and p refers to standard sound pressure. Accordng to geometrc dvergence attenuaton of omndrectonal sound source, the calculaton method s gven n Formula () as follows: A dv lg( r / r ) () In Formula (), r refers to the dstance from predcton pont to sound source whle r refers to the dstance from reference pont to sound source. Accordng to the cube structures of transformer and hgh-voltage reactor nsde substaton, the propagaton space of nose s a half free feld. Except the base, all the other fve surfaces are nose radant surfaces. Ths thess abstracts cubc equpment such as transformer nto cubod mathematcal model as shown n Fgure 4 gven below: Fgure 4. chematc dagram of sound radaton of transformer. Accordng to the plane sound source structure of Fgure 4, energy superposton prncple can be used to obtan the acoustc level. ee Formula () gven below for the sound energy densty at p: w W D ds ds 4r 4 r Therefore, the acoustc level of pont p s W p lg ds 5 r (3) (4) 8 frequency band sound pressure values are generally used to descrbe nformaton about sound source nsde substaton. ee Table for the correspondng wave lengths under barometrc pressure. Table. Acoustc wave lengths correspondng to each frequency under standard atmospherc pressure. Frequency (Hz) Wave length (m) In combnaton of Table, t can be known that wave length of low frequency band s close to transformer dmenson. After acoustc wave exceeds 5Hz, ts wave length s much less than transformer dmenson. Therefore, ths thess concludes attenuaton of plane sound source as attenuaton of acoustc wave dffracton. Assume a plane sound source s dmenson of a b, the method to calculate the sound feld formed on predcton pont r on the other sde surface of the machne accordng to the dfferental ds on plane sound source s shown n Formula (5) gven below: jk cu( s) j j (5) P ( r ) ( ) V ( ) DG( kr) ds kr kr Among whch, u(s) refers to vbraton velocty of mcro-facet element, m/s. 3. Numercal ntegraton of computng model In combnaton of the fact that there s ntegral computaton n both Formula (4) and Formula (5), ths thess takes numercal ntegraton n form of numercal value. In defnte ntegral of functon, Newton-Vortex formula s manly used to calculate the sometry of node dstrbuton, ncludng trapezod formula and mpson formula. Ths thess takes trapezod formula for ntegral soluton. et the coordnates of cubc center as (x, y, z), cubc dmenson as a b c, and the coordnates of spatal mdpont as (x, y, z ); then, Formula (4) can be turned nto a b c x y z W lg a b c 5 x y z ( x x ) ( y y ) ( z z ) (5) dxdydz In combnaton of compound trapezod formula, respectvely dvde ntegral sectons a a, b b, c c x,x y,y z,z nto m, n and p equal parts. Thus, the step sze of each secton s: a b c h, g, l (6) m n p Therefore, set functon f ( x, y, z) ; ( x x y y z z ) ( ) ( ) then, Formula (5) can be turned nto Formula (7) as follows n accordance wth trapezod formula: m n p W hgl lg[ 5 8 In Formula (7): A A A f ( x, y, z)] j k (7) 5

5 Computng model Results of pont sound source computaton Results of plane sound source computaton Computng model of substaton Table 3. Close-range geometrc dvergence results of dfferent sound sources. Weghtng sound pressure level /db Dstance between predcted postons and sound source /m(heght s m) (, m) A (, n) A j (,,, m ) (,,, n ) A k (, p) (,,, p ) Therefore, n combnaton of the Formula (7) shown above and accordng to the computatonal model for near-feld nose of substaton, set dmenson of some transformer n substaton as (5m m 4m). Accordng to the model and calculaton formulas gven n ths thess, take the step sze as.. ee Table 3 for the geometrc attenuaton results for approxmate dstance of the computatonal model: Nose attenuaton trends as shown n Fgure 5 gven below can be obtaned accordng to computed results of Table 3. In combnaton of Fgure 5, t can be known that the attenuaton speed of pont sound source s the hghest. In the nose attenuaton trend wthn 4m away from sound source, attenuaton speed of substaton computng model s lower than those of pont sound source and plane sound source. sound pressure Dstance from sound source Fgure 5. chematc dagram of geometrc dvergence attenuaton of substaton computng mode. 4 CONCUION Calculaton model of pont sound source urface acoustc source model ubstaton calculaton model Ths thess frstly studes the sheldng dffracton propagaton mode of nose and provdes the propagaton stuaton when acoustc wave encounters sheldng. The acoustc wave energy loss caused by reflecton, projecton, and dffracton of acoustc wave whle encounterng hgh-densty materals, such as walls or boards, can be huge durng sound propagaton process. Then, ths thess establshes geometrc dvergence nose attenuaton model based on geometrc dvergence model prncples and the man reasons of geometrc nose attenuaton; and has obtaned the calculaton formula of nose attenuaton wth dstance ncrease whch contans great sgnfcance n solvng nose nterference problem of fully-sealed compact substaton. REFERENCE [] Gao, Y. 4. Predctve Research on ound Feld Features and Nose Dstrbuton of ubstaton. North Chna Electrc Power Unversty. [] Ruan, X.Y. 4. Predcton Theory of Coherent Acoustc Feld Nose and Research on ts Applcaton n Hgh-Voltage DC Transmsson ystem. Hefe Unversty of Technology. [3] We, H.Z.. Research on Audble Nose Predcton ystem n Hgh-Voltage DC Transmsson ystem. Hefe Unversty of Technology. [4] Huang,. 4. Research on the emdefnte Relaxaton uccessve Approxmaton Postonng Methods of ubstaton Partal Dscharge ources. Hefe Unversty of Technology. [5], W.H. 5. Research on Predcton and Control Technques of Hgh-Voltage ubstaton Nose Polluton. Guangdong Unversty of Technology. [6] N, Y. Zhou, B. Pe, C.M. & Zha, G.Q. 4. Analyss of nterference patterns of acoustc wave around kv extra-hgh voltage parallelng reactor. Hgh Voltage Engneerng, : [7] Xang, N. 9. Mechansm and Control tudy of Trans-Regonal Power Grd s ow Frequency Oscllaton. Wuhan Unversty. [8] Yang, M. 4. Research on Nonlnear Characterstcs of Ferromagnetc Resonance Overvoltage and Its Flexblty Restrant trategy. Chongqng Unversty. [9] Fan, X.P.,,., Huang, C.J., u, J.W., Chen, M. & Deng, Q. 4. Analyss and control of kv substaton nose polluton. Nose and Vbraton Control, 5: -4. [] Wang, Y.D., Xu,.W. & hen, J... Predctve study of substaton envronmental nose. Envronmental Engneerng, : [] Zheng, Y.. tudy of Human s ubjectve Feelngs on ubstaton Nose and Its Voce Control Methods. Zhejang Unversty. [], X.X., Yang, C.P. & Jang, W. 8. Captal asset prcng model based on nvestor s sentment behavors. Journal of Qngdao Unversty (Natural cence Edton), (4):