Influence and Correction from the Human Body on the Measurement of a Power-Frequency Electric Field Sensor

Transcription

1 s Artcle Influence orrecton from Human Body on Measurement a Power-Frequency Electrc Feld Sensor Dongpng Xao *, Huatong Lu, Qang Zhou, Yutong Xe Qchao Ma State Key Laboratory Power Transmson Equpment & System Securty New Technology, hongqng Unversty, hongqng , hna; @cqu.edu.cn (H.L.); @cqu.edu.cn (Q.Z.); [email protected] (Y.X.); [email protected] (Q.M.) * orrespondence: [email protected]; Tel.: Academc Edtor: Debbe G. Senesky Receved: 4 March 206; Accepted: 3 June 206; Publhed: 0 June 206 Abstract: Accordng to operatng specfcatons extng nstruments, techncans must be located far from nstruments to elmnate nfluence occupancy on a spatal. Neverless, n order to develop a portable safety protecton nstrument wth an effectve warnng functon for workng staff n a hgh-voltage envronment, t necessary to study nfluence an approachng on measurement an to correct measurement results. A sngle-shaft nstrument called Type LP-2000, whch was developed by our research team, used as research object n th study. Frst, we explan prncple measurement descrbe capactance effect produced by. Through a oretcal analys, we show that measured value decreases as a approaches. r relatonshp lnearly proportonal. n, rato dentfed as a correcton coeffcent to correct for nfluence proxmty. concluson drawn from oretcal analys proved va smulaton. correcton coeffcent k b =.800 obtaned on bas lnear fttng smulated data. Fnally, a physcal experment performed. When no present, we compare results from Type LP-2000 measured wth Narda EFA-300 smulated value to verfy accuracy Type LP For case an approachng, correcton coeffcent k b * =.9094 obtaned by comparng data measured wth Type LP-2000 to smulated value. correcton coeffcent obtaned from experment (.e., k b *) hghly constent wth that obtaned from smulaton (.e., k b ). Two expermental programs are set; under se programs, exctaton voltages dtance ponts are regulated to produce dfferent ntenstes. Usng k b =.9094, corrected measurement ntensty can accurately reflect orgnal envronmental ntensty, maxmal error less than 6% n all data comparons. se results verfy effectveness our proposed method. Keywords: power-frequency ; portable measurement; nfluence; correcton coeffcent; lnear fttng. Introducton Strong s ext around hgh-voltage al equpment. Extng research shows that strong power-frequency s have potental harmful effects on health safety []. refore, relevant nsttutons nternatonal organzatons have developed stards or have recommended lmtatons regardng power-frequency s for general publc power system practtoners, as shown n Table [2 6]. Here, spatal n absence any object consdered. Sensors 206, 6, 859; do:0.3390/s

2 Sensors 206, 6, Table. Exposure lmts regardng power-frequency s developed by relevant nsttutons nternatonal organzatons. Name Publh Tme Frequency (Hz) INIRP 200 E (kv/m) Occupatonal Exposure Publc Exposure IEEE NRPB EU INIRP Internatonal ommson on Non-Ionzng Radaton Protecton. 2. IEEE Insttute Electrcal Electroncs Engneers. 3. NRPB Natonal Resources Plannng Board. 4. EU European Unon. However, power system practtoners are lkely to be exposed to strong s n a short amount tme because r hlng hgh-voltage al equpment. Excessvely strong ntenstes result n dcomfort panc for practtoners, such effects are harmful to personal safety can lead to doperaton [7 9]. If practtoners can be equpped wth a portable safety protecton nstrument that can measure ntensty a workng area n real tme sue a safety precauton, n safety health practtoners n workplace can be ensured. Our group has been workng toward th objectve. Several power-frequency nstruments are avalable for commercal purposes [0]; y nclude Narda EF seres Germany, PMM Italy, A France. In addton, many research teams have studed developed nstruments for specal purposes [ 3]. Most current nstruments requre bracng probe wth an nsulated bracket; y also requre techncans to be far away from probe to avod nfluence proxmty on measurements [4]. However, warnng devces developed by our team need to be carred by workng practtoners, who thus become nevtably nvolved exert a potental effect on measurements. Electrc ntenstes measured n real tme are used as man ndex safety precauton. Meanwhle, orgnal envronmental ntensty subjected to exposure lmts nfluence durng measurement are nterestng topcs that are worth explorng. nfluence on measurement has attracted ncreasng attenton n recent decades. In [5], extence a was proposed to make spatal change n a certan range. In [6], changes n dtrbuton on dfferent parts when was olated from ground were demonstrated. In [7], proportonal relaton between undtorted dtorted at certan ponts on surface a model was presented. However, se studes only showed that occupancy leads to dtorton spatal s; y dd not focus on nfluence proxmty on measurement ways to correct measured results. In present work, we buld an equvalent crcut that explans prncple measurement on bas a sngle-shaft nstrument called a Type LP-2000 [8], whch was ndependently developed by our research team. n, smulaton va Anst/Maxwell conducted. nfluence on a plate capactor dcussed oretcally, followed by a proposal a correcton coeffcent for nfluence on measurements. In laboratory, generated by dfferent exctaton voltages n absence a measured wth a Type LP-2000 Narda

3 Sensors 206, 6, EFA-300. numercal comparon error analys measured data smulated data verfy Sensors 206, correct 6, 859 measurement Type LP reafter, s are measured wth 3 3 a portable Type LP-2000 that fxed on an ndvdual s arm under two sets expermental programs. corrected corrected values values obtaned by byusng real-tme measured values multpled by correcton coeffcent are compared wth orgnal n n smulaton envronment; errors are subsequently analyzed Equvalent rcut Analys Influence Human Body Body on on Electrc Feld Measurement Electrc Feld Measurement 2.. In Absence a Human Body 2.. In Absence a Human Body core Type LP-2000 compres a couple metal polar plates that can be seen as a capactor. core Type LP-2000 compres a couple metal polar plates that can be seen as a capactor. Inductve charges wth same frequency appear on metal plates when Inductve charges wth same frequency appear on metal plates when put nto alternatng. n, nduced voltage can be measured. relaton between put nto alternatng. n, nduced voltage can be measured. relaton nduced voltage ntensty at pont lnearly proportonal when between nduced voltage ntensty at pont lnearly physcal dmenson planar plate capactor suffcently small [8]. proportonal when physcal dmenson planar plate capactor suffcently small [8].. UU = DĖ DE () () two polar plates U. where D dtance between two polar plates U Ė are E are nduced nduced voltage voltage ntensty ntensty n phasor n form phasor respectvely. form respectvely. equvalent equvalent crcut crcut system system for for obtanng obtanng nduced nduced voltage voltage shown shown n n.. + jω jω M R U U -. Equvalent crcut system.. Equvalent crcut system. In, nduced voltage equvalent to a voltage source U wth angular frequency ω, In, nduced voltage equvalent to a voltage source U. wth angular frequency ω, nherent capactance plate capactor, M nherent capactance plate capactor, capactance capactor, M capactance capactor, R R nput nput restance restance crcut, crcut, U. U output output voltage. voltage. refore, refore,. + R( + ) UU = ` jωr p M ` q. U jωr (2) By By furr processng crcut, crcut, RMS RMS value value U Urms U rms U can be can obtaned. be obtaned. RMS value RMS Uvalue crms. U : Ucrms U b : ` ω2 R 2 p ` M q 2 U rms U ω ωr R ( rms (3) + M) Urms = U (3) rms ωr By combned Equatons () (3), we obtan RMS value Erms, that,. E rms = +ω R ( + ) M DωR U rms (4)

4 Sensors 206, 6, By combned Equatons () (3), we obtan RMS value E rms, that, b ` ω2 R 2 p ` M q 2 Sensors 206, 6, 859 E rms U DωR rms 4 (4) 3 In In measurement measurement crcut, crcut, capactance capactance at at nf-level nf-level much much larger larger than than nherent nherent capactance capactance,,.e.,.e., M >> M >> ; ; thus, thus, Equaton Equaton (4) (4) can can be be smplfed smplfed to to where where K a rato rato coeffcent coeffcent wrtten wrtten as as b ` ω2 2 2 R ω R M K = DωR b ω R `ω2r 2 M 2 E M rms = U rms DωR rms (5) (5) KU = KU rms rms (6) (6) In Equaton (5), ω, R, R,,, M, M, D are areall allfxed values; thus, K a constant. When parameters crcut are all fxed, ntensty n locaton parallel-plate capactve proportonal to to output voltage.. ntensty ntensty E rms Erms observaton pont pont can can be be obtaned obtaned by by U Urms In In ase ase an an Approachng Approachng Human Human Body Body In In practcal practcal measurements, measurements, when when an an ndvdual ndvdual approaches approaches s, s, measured measured ntensty ntensty changes changes because because possesses possesses complex complex tsues. tsues. relatve relatve d d constant constant lvng lvng tsue tsue n n a power frequency power frequency envronment envronment about about , conductvty 5 0 6, conductvty about about S/m S/m [9]. [9]. can can be be regarded regarded as as a conductor; a conductor; refore, refore, charges charges gar gar on on ts ts surface surface as as t remans t remans n n,, such such accumulaton accumulaton affects affects spatal spatal dtrbuton dtrbuton orgnal orgnal [20]. [20]. relatonshp relatonshp between between plate plate capactor capactor shown shown n n Body Polar A Polar B D d 2 2. Relatonshp between polar plates capactor. 2. Relatonshp between polar plates capactor. In 2, PolarA PolarB are two polar plates capactor, D dtance between In two 2, plates, Polar A wth Polar gap B are flled wth twoepoxy polar plates resn. dtance capactor, between D dtance between PolarB two d, wth plates, an ar wth medum gapn flled mddle. wth epoxy resn. wth dtance PolarA between wth PolarB form equvalent Polar B dcapactors,, wth an ar medum 2, respectvely. n mddle. equvalent wthcrcut Polar A wth Polar system B form n case equvalent an approachng capactors, 2, respectvely. shown n equvalent 3. crcut system n case Accordng an approachng to 3, M much larger shown than n ; 3. refore, E rms = = KU +ω R ( + ) b * rms M 2 * U rms ( ) + DωR (7)

5 Sensors 206, 6, ω R ( + ) M 2 Kb = (8) Sensors 206, 6, 859 DωR ( ) jω jω U jω 2 jω M 3. Equvalent crcut system n case an approachng. 3. Equvalent crcut system n case an approachng. Equaton (7) shows that when parameters are fxed, Kb a constant, output Accordng voltage to 3, remans M much proportonal larger thanto ; refore, at pont. By comparng Equatons (5) (7), we b observe that M + 2 > M ()/( + ) <, Kb > K. `ω2 Moreover, we note that U*rms < Urms f Erms constant. R E In or words, measured nduced voltage rms 2 p M` 2 q 2 decreases when a approaches DωR p q U rms. Wthout correcton, (7) ` measured ntensty becomes K b U smaller rms than physcal truth. In sum, correcton coeffcent kb can be defned as where K b also a rato coeffcent wrtten as b Kb kb = (9) ` ω2 R K 2 p M` 2 q 2 K b Thus, spatal ntensty n DωR absence p q (8) ` a can be obtaned by usng ntensty measured wth portable Type LP-2000 n real tme multpled by correcton Equaton coeffcent (7) shows kb. that when parameters are fxed, K b a constant, output voltage remans proportonal to at pont. 3. Smulaton By comparng Analys Equatons (5) (7), we observe that M + 2 > M ( )/( + ) <, K b > K. Moreover, we note that U * rms < U rms f E rms constant. In or words, measured nduced voltage decreases 3.. Smulaton whenmodel a Settng approaches. Wthout correcton, measured ntensty becomes smaller than physcal truth. smulaton model set up wth stware Anst/Maxwell, most smulaton In sum, correcton coeffcent k parameters are set on bas physcal b can be defned as experment condton shown n Secton 4. Dfferent ntenstes are produced when dfferent levels snusodal voltage wth k power-frequency are appled to power transmson b K b (9) K lne. In smulaton model, power transmson lne a copper conductor wth a dameter 4 mm a dtance 22 cm from Thus, spatal ntensty n absence a can be obtaned by usng ground. Observaton pont P at same level as conductor at 53 cm from conductor n ntensty measured wth portable Type LP-2000 n real tme multpled by horzontal dtance. correcton coeffcent k smulaton model b. plate capactor shown n 4. two polar plates are made 3. copper, Smulaton Analys measure 50 mm n length, 36 mm n wdth, mm n dtance. fllng medum epoxy resn. center concdent wth observaton pont P. 3.. Smulaton In addton, Model Settng condton bottom boundary set as groundng, boundary condtons or fve surfaces are set as balloon boundary wth al potental set smulaton model set up wth stware Anst/Maxwell, most smulaton to zero at nfnty durng smulatng. parameters are set on bas physcal experment condton shown n Secton 4. Dfferent ntenstes are produced when dfferent levels snusodal voltage wth power-frequency are appled to power transmson lne. In smulaton model, power transmson lne a copper conductor wth a dameter 4 mm a dtance 22 cm from ground. Observaton pont P at same level as conductor at 53 cm from conductor n horzontal dtance. R + * U -

6 Sensors 206, 6, smulaton model plate capactor shown n 4. two polar plates are made copper, measure 50 mm n length, 36 mm n wdth, mm n dtance. fllng medum epoxy resn. center concdent wth observaton pont P. Sensors 206, 6, opper Sensors 206, 6, opper opper Epoxy opper 4. Smulaton model. 4. Smulaton model Smulaton Results Analys n Absence a HumanEpoxy Body In addton, condton bottom boundary set as groundng, boundary 5 shows fve smulated spatal dtrbuton surroundng condtons or surfacesresults are setas balloon boundary wth al potental observaton pont Pdurng before placng under same exctaton 4.after Smulaton model. set to zero at nfnty smulatng. voltage condtons. 3.2.Smulaton SmulatonResults Results Analys Analysnn Absence AbsenceaaHuman HumanBody Body shows shows smulated smulated results spatal dtrbuton surroundng results spatal dtrbuton surroundng observaton P before after placng under under same same exctaton exctaton observaton pontpont P before after placng voltagecondtons. condtons. voltage P P P P (a) (b) 5. Electrc spatal dtrbuton surroundng observaton pont P (no nfluence a ). (a) Before placng ; (b) after placng. 5 shows that pont P evenly (a) orgnal surroundng observaton (b) dtrbuted. After placement, at four corners 5.5.Electrc spatal surroundng observaton pont PP(no nfluence aa become sgnfcantly dtorted enhanced, whereas surface outsde polar Electrc spataldtrbuton dtrbuton surroundng observaton pont (neld nfluence ). (a) Before placng ; (b) after placng. plates slghtly enhanced [2,22]. at observaton pont P stll even, whereas ). (a) Before placng ; (b) after placng. ntensty decreases relatve to orgnal value because sheldng effect 5 shows that orgnal surroundng observaton pont P evenly polar plates. 5 shows that orgnal surroundng observaton pont P evenly dtrbuted. placement results, at 0four Erms Table 2After shows smulated orgnal corners after dtrbuted. After placement, at fourecorners become become sgnfcantly dtorted enhanced, whereas surface outsde polar placng at pont whereas P when dfferent levers exctaton voltage arepolar generated. sgnfcantly dtorted enhanced, surface outsde plates plates slghtly enhanced [2,22]. at observaton pont P stll even, whereas slghtly enhanced [2,22]. at observaton pont P stll even, whereas 2.ntensty decreases relatvevalues to orgnal value because sheldng effect Table omparon pont because P before after placng ntensty decreases relatve to orgnalatvalue sheldng effect polar plates. polar plates. (drven by dfferent voltages). Table 2 shows smulated results orgnal E0 Erms after Table 2 shows smulated results orgnal E0 Erms after placng at pont P2when dfferent levers voltage are22generated. Us (kv) exctaton placng at pont P when dfferent levers exctaton voltage are generated. E0 (kv/m) Erms (kv/m) Table 2. omparon values at pont P before after placng (drven by dfferent voltages). data n Table 2 are lnearly ftted, as shown n 6. Us (kv)

7 Sensors 206, 6, Table 2. omparon values at pont P before after placng (drven by dfferent voltages). U s (kv) E0 (kv/m) Erms (kv/m) data n Table 2 are lnearly ftted, as shown n 6. Sensors 206, 6, E0 (kv/m) Sensors 206, 6, E0 (kv/m) Erms (kv/m) 4 6. Relaton curve values at pont P before after placng 3 6. Relaton curve values at pont P before after placng E.4.6 (kv/m) rms 6 shows that a lnear relaton exts between Erms E0. r relaton can be expressed 6. Relaton curve values at pont P before after placng mamatcally 6 showsasthat a lnear relaton exts between Erms E0. r relaton can be expressed. mamatcally as E0 = k0 Erms 6 shows that a lnear relaton exts E0 between k0 ErmsErms E0. r relaton can be expressed coeffcent between E0 Erms. Here, k0 = wheremamatcally k0 correcton as where k0 correcton coeffcent between E0 Erms. Here, k0 = E0 = k0 Erms 3.3. Smulaton Result Analys n ase an Approachng Human Body (0) (0) (0) 3.3. Smulaton Analys n between ase Ean Approachng correcton coeffcent 0 Erms. Here, k0human = Body whereresult k0 We assume that heght approachng ndvdual 76 cm. Gven that ndvdual s shoes are thckness nnsulatng assumed to be 2 mm durng smulaton We assume that heght approachng ndvdual 76 cm. Gven that ndvdual s 3.3. olated, Smulaton Result Analys ase materals an Approachng Human Body so that person does not drectly come nto contact wth ground. smulaton fxed shoes are olated, thckness nsulatng materals assumed to be 2 mm durng We assume that heght approachng ndvdual 76 cm. Gven that ndvdual s on person s arm, ts center come located pont P, wth smlar to ground. that shown n 5. so that person does not drectly ntoatcontact fxed shoes are olated, thckness nsulatng materals assumed to be 2 mm durng smulaton 7a shows dtrbuton surroundng conductor. so that person not drectly come nto ground. shown fxed on person s arm, does ts center located atcontact pontwth P, smlar to that n 5. on7b shows arm, partally detal at surroundng to. person s tsenlarged center located pont P, smlar that shown n 5. 7a shows dtrbuton surroundng conductor. 7a shows dtrbuton surroundng conductor. 7b shows7b partally enlarged detal surroundng. shows partally enlarged detal surroundng. (a) (a) (b)(b) 7. Electrc dtrbuton n n case. Surroundng 7. Electrc dtrbuton casean anapproachng approachng. (a) (a) Surroundng 7. Electrc dtrbuton n case an. approachng. (a) Surroundng conductor; conductor; (b) surroundng. (b) surroundng conductor; (b) surroundng. 3. omparon measured values values at after approach a a Table Table 3. omparon measured at pont pontppbefore before after approach (drven by dfferent voltages). (drven by dfferent voltages). Us (kv) Us (kv) Erms (kv/m) Erms (kv/m) E*rms (kv/m) E*rms (kv/m)

8 Sensors 206, 6, Table 3. omparon measured values at pont P before after approach a (drven by dfferent voltages). U s (kv) E rms (kv/m) E* rms (kv/m) Sensors 206, 6, As shown n 7, spatal dtrbuton outsde dtorted furr n As case shown an n approachng 7,, spatal whereas dtrbuton outsde between dtorted polar pates furr n evenly case dtrbuted. an approachng, whereas between polar pates evenly Table dtrbuted. 3 shows smulaton results before after approach a Table 3 shows (.e., E rms smulaton E* rms results respectvely) at pont P when before dfferent after levels approach exctaton a voltage are generated. (.e., Erms E*rms respectvely) at pont P when dfferent levels exctaton voltage are generated. data n n Table 3 are lnearly ftted, as shown n n Erms (kv/m) E * rms (kv/m) 8. Relaton curve ntensty at P before after approach a. 8. Relaton curve ntensty at P before after approach a. 8 shows that after approach, ntensty at observaton pont 8 shows decreases that after but proportonal approach to that before, approach ntensty. atth stuaton observaton explaned pont decreases n aspect but proportonal prncple that n Secton before2. approach lnear relaton between. Erms stuaton E*rms can be explaned expressed n as aspect prncple n Secton 2. lnear relaton between E rms E* rms can be expressed as * E rms = k b E E rms () () rms where kb k b correcton coeffcent regardng nfluence on on measurement; t t same same as as that that n n Equaton (9). (9). Here, k b kb = =.800. onsderng dual nfluence,, we we can can correct correct ntensty ntensty measured measured wth wth portable portable Type LP-2000 Type twce LP-2000 on twce bas on Equatons bas (0) Equatons () to(0) reflect accurately () to reflect orgnal accurately envronmental orgnal envronmental Expermental Verfcaton 4.. Expermental Result Analys n Absence a Human Body 4.. Expermental Result Analys n Absence Human Body expermental platform composed a voltage regulator, step-up transformer, conductor expermental platform composed a voltage regulator, step-up transformer, conductor nsulator shown n 9. Narda EFA-300 a portable Type LP-2000 are used as nsulator shown n 9. Narda EFA-300 a portable Type LP-2000 are used as measurement devces. techncal charactertcs equpment are shown n Table 4. measurement devces. techncal charactertcs equpment are shown n Table 4. b rms

9 4. Expermental Verfcaton 4.. Expermental Result Analys n Absence a Human Body expermental platform composed a voltage regulator, step-up transformer, conductor nsulator shown n 9. Narda EFA-300 a portable Type LP-2000 are used as measurement devces. techncal charactertcs equpment are shown n Table 4. Sensors 206, 6, (a) (b) 9. Expermental measurement (n absence ). (a) Measurng workste 9. Expermental measurement (n absence a ). (a) Measurng workste Narda EFA-300; (b) workste Type LP Narda EFA-300; (b) workste Type LP Table 4. Techncal charactertcs expermental equpment. Name voltage regulator transformer EFA-300 LP-2000 Techncal haractertcs nput: 220 V wth power frequency adjustable range: V rated capacty: 0 kva rated capacty: 0 kva rato: 200 measurable frequency range: 5 Hz 32 khz measurable range: 0. V/m 200 kv/m measurable frequency range: 5 Hz khz measurable range: 20 V/m 200 kv/m In absence a, comparons are conducted among measured result E LP-2000 Type LP-2000, measured result E EFA-300 Narda EFA-300, orgnal E 0 obtaned va stmulaton. errors are defned as stattcal data error analyses are shown n Table 5. e E LP-2000 E 0 E 0 ˆ 00% (2a) e 2 E EFA-300 E 0 E 0 ˆ 00% (2b) Table 5. Measurement data stattcs stmulaton experment error analys (n absence a ). U s (kv) E 0 (kv/m) E LP-2000 (kv/m) E EFA-300 (kv/m) e (%) e 2 (%) shows fttng curve based on data n Table 5.

10 ELP-2000 (kv/m) EEFA-300 (kv/m) e (%) e2 (%) Sensors 206, 6, shows fttng curve based on data n Table 5. (a) (b) Relaton Relaton curves curves related related to to exctaton exctaton voltage voltage varaton varaton (n (n absence absence a ). ). (a) (a) urves urves ntensty; ntensty; (b) (b) curves curves error. error. Gven nterference produced by or equpment n laboratory, certan errors Gven nterference produced by or equpment n laboratory, certan errors emerge between measured ntensty stmulaton results. However, value emerge between measured ntensty stmulaton results. However, value measured by Type LP-2000, n general, relatvely close to stmulaton value value measured by Narda EFA-300. refore, accuracy Type LP-2000 verfed Expermental Results Analys n ase an Approachng Human Body Sensors 206, 6, Regulatng Exctaton Voltages Electrc Feld measured by Type LP-2000, n general, relatvely close to stmulaton value value measured by Narda showsefa-300. that Type refore, LP-2000 accuracy fxed Type on LP-2000 arm verfed. ndvdual at a horzontal dtance 53 cm from conductor. Dfferent ntenstes can be generated by regulatng 4.2. exctaton Expermental voltages Results Analys conductor. n ase uncorrected an Approachng measurement Human data Body E LP-2000 Type LP-2000 orgnal E 0 n stmulaton are lted n Table Regulatng 2 shows Exctaton that uncorrected Voltages measured Electrc Feld ntensty n case an approachng shows less than that Type orgnal LP-2000 ntensty. fxed on Furrmore, arm ndvdual an approxmately at a horzontal lnear dtance relaton exts 53 between cm from m. conductor. lnear coeffcent Dfferent can be obtaned ntenstes by lnear fttng, can be.e., generated k b * =.9094, by whch regulatng close to exctaton k b =.800 voltages as obtaned n conductor. stmulaton. uncorrected error results measurement from electromagnetc data ELP-2000 Type nterference LP-2000 n expermental orgnal envronment. E0 n stmulaton are lted n Table 6. LP Measurng workste Type LP-2000 (n case an approachng ).. Measurng workste Type LP-2000 (n case an approachng ). Table 6. Uncorrected data stattcs wth dfferent exctaton voltages (n case an approachng ). Us (kv) E0 (kv/m)

11 Sensors 206, 6, Measurng workste Type LP-2000 (n case an approachng ). Table 6. Uncorrected data stattcs wth dfferent exctaton voltages (n case an approachng Table 6. Uncorrected ). data stattcs wth dfferent exctaton voltages (n case an approachng ). U s (kv) Us (kv) E 0 (kv/m) E0 (kv/m) E LP-2000 (kv/m) ELP-2000 (kv/m) shows fttng curve based on data n Table measurement lnear fttng E0 (kv/m) E LP-2000 (kv/m) Relaton curve curve stmulaton uncorrected expermental data (n case case an an approachng ). measured result corrected to obtan correspondng E* LP-2000 by usng correcton coeffcent k b * = comparon between corrected measured data E* LP-2000 orgnal E 0 shown n Table 7. Table 7. orrected data stattcs wth dfferent exctaton voltages (n case an approachng ). U s (kv) E 0 (kv/m) E* LP-2000 (kv/m) error (%) Table 7 shows that measured result Type LP-2000 after correcton accurately reflects actual ntensty n envronment that maxmal error less than 6% Regulatng Dtances between Measurng Pont onductor As most expermental condtons are kept dentcal to those n prevous experment exctaton voltage conductor set to 2 kv, dfferent ntenstes can be obtaned at dfferent ponts by regulatng dtances between pont conductor, as shown n 3. corrected measured data E* LP-2000 are obtaned by usng correcton coeffcent k b * = orgnal E 0 n smulaton correspondng error values are lted n Table 8.

12 As most expermental condtons are kept dentcal to those n prevous experment exctaton voltage conductor set to 2 kv, dfferent ntenstes can be obtaned at dfferent ponts by regulatng dtances between pont conductor, as shown n 3. corrected measured data E*LP-2000 are obtaned by usng correcton Sensors 206, coeffcent 6, 859 kb* = orgnal E0 n smulaton correspondng 2 4 error values are lted n Table 8. d L LP Electrc measurements n dfferent dtances (n case an approachng ). 3. Electrc measurements n dfferent dtances (n case an approachng ). Table 8. orrected data stattcs wth dfferent measurement dtances (n case an approachng ). Table 8. orrected data stattcs wth dfferent measurement dtances (n case an approachng ). dl (cm) E0 (kv) E*LP-2000 d L (cm)(kv) Eerror 0 (kv)(%) E* LP-2000 (kv) error (%) Table 8 also shows that corrected ntensty measured by Type LP-2000 constent wth orgnal ntensty n envronment that maxmal error less than 5%. 5. onclusons nfluence on measurement was nvestgated by usng Type LP-2000 sngle-shaft developed by our research team. results obtaned from prncpal model, smulaton, physcal experment showed that as an ndvdual approached, measured ntensty became less than orgnal envronmental ntensty n absence a ; however, both m were proportonal. orgnal envronmental ntensty was obtaned by usng ntensty measured wth portable Type LP-2000 n real tme multplyng ts value by defned correcton coeffcent. correcton coeffcent k b obtaned n smulaton was.800, correcton coeffcent k b * obtaned n experment was.9094; two values can be consdered approxmately equal. Two expermental programs were establhed; under se programs, exctaton voltages dtance ponts were regulated to produce dfferent ntenstes. Usng k b * =.9094, corrected measured ntensty accurately reflected orgnal envronmental ntensty, maxmal error was less than 6% n all data comparons. se results verfy effectveness our proposed correcton method. Addtonally, sngle-shaft proposed n th study may be more sutable for generated by transmson lnes than for that generated n substaton. refore, 3D measurement wll be explored n our future research. Acknowledgments: Th work was supported by Natonal Natural Scence Foundaton hna (NSF ), Fundamental Research Funds for entral Unverstes (06205DJXY50008).

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