SIM International Comparison of 50/60 Hz Energy ( )

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1 SIM Internatonal Comparson of 50/60 Hz Energy (00-007) Tom Nelson, Nen Fan Zhang, and Nle Oldham (NIST), René Carranza and Sergo Campos (CENAM), Maro Monge (CONACYT), Harold Sanchez (ICE), Ana Mara Franco (INMETRO), Lucas Lllo (INTI), Robert uarte (INTN), Eddy So (NRC), Carlos Sauders (SENACYT), Henry Postgo (SNM), Carlos Favero (UTE) Abstract: Results of the Inter-amercan Metrology System (SIM) nternatonal energy comparson are presented. Partcpatng countres were Argentna, Brazl, Canada, Costa Rca, El Salvador, Mexco, Panama, Paraguay, Peru, Uruguay, and the Unted States. Keywords: SIM, Internatonal comparson, Energy, travelng standard. Introducton The Inter-amercan Metrology System (SIM) sponsors perodc nternatonal comparsons of electrcal unts mantaned at Natonal Metrology Insttutes (NMIs) n the Amercas. The frst SIM electrcal comparson was conducted n the late 990s and used dgtal multmeters as travelng standards wthn the fve sub regons n SIM to measure ac and dc voltage and current and dc resstance []. At about the same tme, NIST was plotng the Consultatve Commttee for Electrcty and Magnetsm CCEM-K5 comparson of 50/60 Hz electrc power [] that ncluded NMIs n North and South Amerca. As a follow-up to the K5 comparson, NIST was selected to plot the SIM comparson of 50/60 Hz electrc energy, descrbed below. The plan s to lnk to CCEM-K5 so that more NMIs n the Amercas wll be ted to the key comparson database mantaned by the Internatonal Commttee of Weghts and Measures, CIPM [3]. After consultaton wth other NMIs, NIST metrologsts decded to perform the comparson at 50 and 60 hertz. Three ponts were selected to test the ampltude and phase measurng capabltes of the NMIs: 0 volts and 5 amperes at power factors.0, 0.5 lead (ld), NMI s used n ths document to denote the laboratory responsble for energy standards wthn each country partcpatng n the comparson. 0.5 lag (lg), where lead (capactve) ndcates that the current leads the voltage and where lag (nductve) ndcates that the current lags the voltage. A lst of partcpatng laboratores s gven n Table. Table. Lst of partcpants, NMIs, and measurement dates. Laboratory Measurement date NIST, USA August 00 May 007 ICE, Costa Rca July 003 SENACYT, Panama August 003 CONACYT, El Salvador November 003 CENAM, Mexco June 006 NRC, Canada May 007 INMETRO, Brazl February 004 UTE, Uruguay Aprl 004 INTN, Paraguay August 004 SNM, Peru Aprl 005 INTI, Argentna July 006 Two travelng standards (Radan model RM-) were used to reduce the tme requred to complete the comparson. These nstruments are ac-power-to-frequency or energy-to-pulse converters based on the tme-dvson-multpler operatng prncple. Wth 0 V and 5 A appled at.0 power factor, the nomnal output frequency of the converters s Hz. Coeffcents of voltage, current, and power factor for these standards are neglgble (less than 5 parts n 0 6 ) over a range of ±0. % of these parameters. Partcpants were asked to mantan a ±0. % tolerance. Temperature coeffcents are also neglgble n the range of 3 C ± 3 C. Humdty nfluences are more dffcult to measure. Partcpants were asked to record the ambent temperature and humdty. Identfcaton of commercal equpment s not ntended to mply recommendaton or endorsement by NIST, nor s t ntended to mply that the equpment s necessarly the best avalable for the purpose.

2 Some laboratores reported results n percentage regstraton, wth uncertantes n percent of readng. Others reported results as errors n ppm, µw/w, µwh/wh, µj/j (all equvalent to parts n 0 6 ), wth uncertantes n the same unts. Some reported values n terms of readng and others n terms of full scale (appled VA). All values were converted to errors and standard uncertantes n parts n 0 6 of readng. These normalzed results are gven n Table. Table. Reported Errors x,k and Standard Uncertantes u,k (n parts n 0 6 of readng), where denotes the NMI and k denotes the test pont. Travelng standard Hz 50 Hz.0 0.5ld 0.5lg.0 0.5ld 0.5lg NMI u, u, 3 u, 3 4 u, 4 5 u, 5 6 u, 6 NIST ICE SENACYT CONACYT CENAM NRC Travelng standard NIST INMETRO UTE INTN SNM INTI Analyss The travelng standards were measured at NIST before the comparson began, when the comparson was completed, and at several ponts durng the comparson. ependng on the standard and the test frequency, NIST performed up to 00 ndependent measurements at each test pont from 00 to 007. Snce two travelng standards were used and measured at dfferent NMIs, the comparson was treated as two ndependent loops wth the plot laboratory (NIST) as the common lnk. The sngle loop analyss and notaton used n ths comparson s based on that descrbed by Zhang et al. n reference 4. In ths case, for each test pont n th the j loop ( j =, ), we assume that a smple lnear regresson model 3 holds for measurements made by NIST, 3 The use of a lnear model was questoned by CENAM but based on the dstrbuton of NIST measurements, t was consdered the best compromse. X ( j) = α ( j) + β( j) t ( j) + ε ( j) () k k k for k =,... K j. The average of { tk ( j), k =,..., Kj} s t ( j). The average of X k s X. We further assume that the random error, ε ( ) j, has a zero mean and an uncertanty k u ( j ) for NIST. For the other laboratores ( ), measurements are taken at tme t ( j) and the correspondng model s X ( j) = α ( j) + β( j) t ( j) + ε ( j) () =,..., I j, where the random error has a zero mean and a standard uncertanty of u ( j) for =,... I j and I j s the number of labs n the th j loop. Snce the Type B uncertantes of the NIST measurements are the same for all tme perods,

3 as n reference 4, the regresson parameters for th the j artfact are estmated by: ( j) = K j k = β ( t k( j) t( j))( Xk( j) X( j)) (3) K j k = ( t ( j) t ( j)) k α ( j) = X ( j) β( j) t ( j) (4) =,..., I j. The correspondng uncertantes and the covarance terms are obtaned usng eq.5-8 of reference 4. The comparson reference value (CRV) at an optmal tme * ( ) th t j s, for the j loop: I j CRV ( j) = w ( j) X ( j) (5) t * ( j) = I j * where t ( j) = w( j) t( j) and w( j) = I j k = k = u ( j). (6) u ( j) We use the smplfed symbol CRV() to ndcate the CRV for the st loop, usng travelng standard 5058 and CRV() to represent the CRV for the nd loop, usng travelng standard The regresson components, CRVs and ther uncertantes are gven n Table 3. u CRV Results from partcpants that obtan energy traceablty from other NMIs or laboratores were not used n the CRV computaton. Table 3. Regresson parameters, CRV, and ucrv (n parts n 0 ). Standard 60 Hz 50 Hz lead 0.5 lag lead 0.5 lag α() β() CRV() u () CRV α() β() CRV() u () CRV From reference 4, the degree of equvalence of the th th laboratory, e.g., n the j loop ( j =, ) relatve to the CRV n the correspondng loop s the dfference j ˆ j ˆ j t j CRV * CRV, ( ) = α( ) + β( ) ( ) ( j) j =,. (7) The uncertanty of ths dfference s gven n reference 4 (eqs. 3 and 33). The dfferences () and uncertantes ( u ) are gven n Table 4. 3

4 Table 4. egrees of equvalence and the correspondng uncertantes (n parts n 0 6 ). 60 Hz 50 Hz CRV() usng travelng standard ld 0.5lg.0 0.5ld 0.5lg NMI u u u u u u NIST CENAM NRC CRV() usng travelng standard NIST INMETRO UTE INTI The degrees of equvalence between pars of natonal measurement standards n the same loop, e.g., the th j ( j =,), s defned as the dfferences k, ( j, j) = ( j) ( j), CRV k, CRV * ( j) β( j) t ( j) CRV( j) = α + * [ αk ( j) β( j) t ( j) CRV( j) + = α ( j) α ( j) k ] (8) when k. The correspondng uncertanty s gven n reference 4 (eq.36). However, when the two non-plot labs are n two dfferent loops, e.g., the th lab n the frst loop and the kth lab n the second loop, measurements of the lnkng lab, NIST, are used. The degree of equvalence s calculated as follows: Par-wse tables of equvalence are gven, wth uncertantes, n Appendx A, where a negatve sgn ndcates that the NMI on the left of the table s lower than the NMI on the top of the table. 3. Conclusons Results of the frst SIM nternatonal comparson of 50/60 Hz energy have been presented. In several cases the degrees of equvalence exceed the estmated uncertantes. However, problems have been dentfed and these ponts wll be rechecked va blateral comparsons to resolve the dfferences. The measurements took fve years to complete, much longer than orgnally antcpated. Shppng, customs, and testng delays were the man problems. These must be addressed before the next comparson. k, (, ) = () () [ () ()], CRV, CRV k, CRV, CRV = (,) (, ), k, where (,), and (,) k, are the par-wse degrees of equvalence between the th lab and NIST for the frst loop and the kth lab and NIST for the second loop, respectvely. The standard uncertanty of k, (, ) s gven by (9) u = u + u k, (,),(,) k,(,) (0) 4

5 References [] H. Sanchez, J. Coff, H. Laz,. Bennett, H. Ferrera, R. Ortega, N. Oldham, and M. Parker, "SIM Comparson of Electrcal Unts," Proc. Metrologa-000 Conference, ec 4-7, 000, Sao Paulo, Brazl, (ec 000) [] N. Oldham, T. Nelson T, N. F. Zhang and H. K. Lu 003 CCEM-K5 Comparson of 50/60 Hz Power Metrologa 40, Tech. Suppl.0003 [3] Gudelnes for CIPM Key Comparsons 999 (Appendx F to Mutual recognton of natonal measurement standards and of calbraton and measurement certfcates ssued by natonal metrology nsttutes) Techncal Report Internatonal Commttee for Weghts and Measures [4] N. F. Zhang, H. K. Lu, N. Sedransk and W. E. Strawderman, Statstcal analyss of key comparsons wth lnear trends, Metrologa Partcpatng NMIs and Author Contact Informaton Natonal Insttute of Standards and Technology (NIST), Gathersburg, M, USA, thomas.nelson@nst.gov Insttuto Costarrcense de Electrcdad (ICE), San José, Costa Rca, hsanchez@ce.co.cr Insttuto Naconal de Metrologa, Normalzaçao e Qualdade Industral (INMETRO), uque e Caxas, Brasl, amfranco@nmetro.gov.br Insttuto Naconal de Tecnologa Industral (INTI), Buenos Ares, Argentna, ldl@nt.gov.ar Insttuto Naconal de Tecnología, Normalzacón y Metrología, INTN, Asuncón, Paraguay, metrologa@ntn.gov.py Natonal Research Councl of Canada (NRC), Ottawa, Ontaro, Canada, Eddy.So@nrccnrc.gc.ca Secretaría Naconal de Cenca, Tecnología e Innovacón (SENACYT), Panamá, Repúblca de Panamá, csauders@senacyt.gob.pa Servco Naconal de Metrología (SNM), Lma, Perú, hpostgo@ndecop.gob.pe Admnstracón Naconal de Usnas y Trasmsones Eléctrcas, Montevdeo, Uruguay, dslomovtz@ute.com.uy Centro Naconal de Metrología (CENAM), Querétaro, Méxco, rene.carranza@cenam.mx Consejo Naconal de Cenca y Tecnología CONACYT, San Salvador, El Salvador, maroamonge@hotmal.com 5

6 Appendx A. Par-Wse Tables of Equvalence 60 Hz,.0 power factor (n parts n 0 6 ) fferences NIST ICE SENACYT CONACYT CENAM NRC INMETRO SNM INTI Standard uncertantes NIST ICE SENACYT CONACYT CENAM NRC INMETRO SNM INTI

7 60 Hz, 0.5 lead (capactve) power factor (n parts n 0 6 ) fferences NIST ICE SENACYT CONACYT CENAM NRC INMETRO SNM INTI Standard uncertantes NIST ICE SENACYT CONACYT CENAM NRC INMETRO SNM INTI

8 60 Hz, 0.5 lag (nductve) power factor (n parts n 0 6 ) fferences NIST ICE SENACYT CONACYT CENAM NRC INMETRO SNM INTI Standard uncertantes NIST ICE SENACYT CONACYT CENAM NRC INMETRO SNM INTI

9 50 Hz,.0 power factor (n parts n 0 6 ) fferences NIST CENAM INMETRO UTE INTN INTI Standard uncertantes NIST CENAM INMETRO UTE INTN INTI

10 50 Hz, 0.5 lead (capactve) power factor (n parts n 0 6 ) fferences NIST CENAM INMETRO UTE INTN INTI Standard uncertantes NIST CENAM INMETRO UTE INTN INTI

11 50 Hz, 0.5 lag (nductve) power factor (n parts n 0 6 ) fferences NIST CENAM INMETRO UTE INTN INTI Standard uncertantes NIST CENAM INMETRO UTE INTN INTI