1、g44g40g40g40g3g54g87g71g3g38g24g26g17g20g21g22g140g16g21g19g20g19g11g53g72g89g76g86g76g82g81g3g82g73g3g44g40g40g40g3g54g87g71g3g38g24g26g17g20g21g22g16g21g19g19g21g12g3g44g40g40g40g3g42g88g76g71g72g3g73g82g85g3g55g85g68g81g86g73g82g85g80g72g85g3g47g82g86g86g3g48g72g68g86g88g85g72g80g72g81g87g3g44g40
2、g40g40g3g51g82g90g72g85g3g9g3g40g81g72g85g74g92g3g54g82g70g76g72g87g92g3g54g83g82g81g86g82g85g72g71g3g69g92g3g87g75g72g55g85g68g81g86g73g82g85g80g72g85g86g3g38g82g80g80g76g87g87g72g72g3g44g40g40g40g22g3g51g68g85g78g3g36g89g72g81g88g72g3g49g72g90g3g60g82g85g78g15g3g49g60g3g20g19g19g20g25g16g24g28g28g
3、26g15g3g56g54g36g3g3g22g3g36g88g74g88g86g87g3g21g19g20g19g38g24g26g17g20g21g22g55g48IEEE Std C57.123-2010 (Revision of IEEE Std C57.123-2002) IEEE Guide for Transformer Loss Measurement Sponsor Transformers Committee of the IEEE Power +1 978 750 8400. Permission to photocopy portions of any individu
4、al standard for educational classroom use can also be obtained through the Copyright Clearance Center. iv Copyright 2010 IEEE. All rights reserved. Introduction This introduction is not part of IEEE Std C57.123-2010, IEEE Guide for Transformer Loss Measurement. During an earlier revision of Clause 8
5、 and Clause 9 of IEEE Std C57.12.90TM, IEEE Standard Test Code for Liquid-Immersed Distribution, Power and Regulating Transformers, which describe the measurement of no load and load loss, respectively, it was realized that there was a need for a guide that would explain in more detail the accuracy
6、requirements, test code procedures, various test methods available, methods to diagnose test anomalies, and the procedures for calibration and safety. Notice to users Laws and regulations Users of these documents should consult all applicable laws and regulations. Compliance with the provisions of t
7、his standard does not imply compliance to any applicable regulatory requirements. Implementers of the standard are responsible for observing or referring to the applicable regulatory requirements. IEEE does not, by the publication of its standards, intend to urge action that is not in compliance wit
8、h applicable laws, and these documents may not be construed as doing so. Copyrights This document is copyrighted by the IEEE. It is made available for a wide variety of both public and private uses. These include both use, by reference, in laws and regulations, and use in private self-regulation, st
9、andardization, and the promotion of engineering practices and methods. By making this document available for use and adoption by public authorities and private users, the IEEE does not waive any rights in copyright to this document. Updating of IEEE documents Users of IEEE standards should be aware
10、that these documents may be superseded at any time by the issuance of new editions or may be amended from time to time through the issuance of amendments, corrigenda, or errata. An official IEEE document at any point in time consists of the current edition of the document together with any amendment
11、s, corrigenda, or errata then in effect. In order to determine whether a given document is the current edition and whether it has been amended through the issuance of amendments, corrigenda, or errata, visit the IEEE Standards Association web site at http:/ieeexplore.ieee.org/xpl/standards.jsp, or c
12、ontact the IEEE at the address listed previously. For more information about the IEEE Standards Association or the IEEE standards development process, visit the IEEE-SA web site at http:/standards.ieee.org. v Copyright 2010 IEEE. All rights reserved. Errata Errata, if any, for this and all other sta
13、ndards can be accessed at the following URL: http:/standards.ieee.org/reading/ieee/updates/errata/index.html. Users are encouraged to check this URL for errata periodically. Interpretations Current interpretations can be accessed at the following URL: http:/standards.ieee.org/reading/ieee/interp/ in
14、dex.html. Patents Attention is called to the possibility that implementation of this guide may require use of subject matter covered by patent rights. By publication of this guide, no position is taken with respect to the existence or validity of any patent rights in connection therewith. The IEEE i
15、s not responsible for identifying Essential Patent Claims for which a license may be required, for conducting inquiries into the legal validity or scope of Patents Claims or determining whether any licensing terms or conditions provided in connection with submission of a Letter of Assurance, if any,
16、 or in any licensing agreements are reasonable or non-discriminatory. Users of this guide are expressly advised that determination of the validity of any patent rights, and the risk of infringement of such rights, is entirely their own responsibility. Further information may be obtained from the IEE
17、E Standards Association. Acknowledgments A number of the Working Group members contributed to the text of this guide. Special acknowledgment is, however, due to Dr. Ed So and Messers Bill Henning, L. S. McCormick, Bertrand Poulin, Ramsis Girgis for providing specific sections of the text of this doc
18、ument. Finally, the chairman acknowledges that most of the text on load-loss measurement (Clause 3 of the guide) was taken from the IEEE paper “Measurements of Transformer Losses” B10aauthored by Sam Mehta. aInformation on references can be found in Annex A. vi Copyright 2010 IEEE. All rights reserv
19、ed. Participants At the time this guide was submitted to the IEEE-SA Standards Board for approval, the Loss Tolerance with its voltage coil on the winding side of the current coil. The average-voltage responding voltmeter should be used to set the voltage. Also, measured values need to be corrected
20、in order to account for the effect of voltage harmonics on the magnetic flux in the core and hence on both the hysteresis and eddy current loss components of iron losses. The hysteresis loss component is a function of the maximum flux density in the core and is practically independent of the flux wa
21、veform. The maximum flux density corresponds to the average value of the half-cycle of the voltage waveform (not the rms value). Therefore, if the test voltage is adjusted to be the same as the average value of the desired sine wave of the voltage, the hysteresis loss component will be equal to the
22、desired sine-wave value. The eddy current loss component of the core loss varies approximately with the square of the rms value of the core flux. When the test voltage is held at rated voltage with the average-voltage voltmeter, the actual rms value of the test voltage is generally not equal to the
23、rated value. The eddy current loss in this case will be related to the correct eddy current loss at rated voltage by a factor k given in Equation (8.2) of Clause 8 of IEEE Std C57.12.90, and IEEE Std C57.12.91. This is only correct for voltage waves with reasonably low distortion. If, however, the v
24、oltage wave is so distorted that the value of k is larger than a certain limit value set by the standard, the average voltmeter readings will not be correct, and the voltage wave is then considered not suitable for use. Clause 8 of IEEE Std C57.12.90 and IEEE Std C57.12.91 limit the total correction
25、 of core loss due to this effect to 5%. where from Figure 5 as follows F is a frequency meter W is a wattmeter AV is an average-responding, rms-calibrated voltmeter A is an ammeter V is a true rms voltmeter IEEE Std C57.123-2010 IEEE Guide for Transformer Loss Measurement 10 Copyright 2010 IEEE. All
26、 rights reserved. Figure 5Connections for no-load loss test of a single-phase transformer As mentioned in 8.3 of IEEE Std C57.12.90 and IEEE Std C57.12.91, “actual per-unit values of the hysteresis and eddy current losses P1and P2should be used in the waveform correction factor (P1 + kP2)1.” A simpl
27、ified approach to obtain values of P1and P2for specific core steel at a specific induction utilizes the frequency dependence characteristics of these two components. P1is linearly proportional to frequency while P2is proportional to the square of the frequency. By knowing the specific loss values of
28、 the core steel at two different frequencies, the values of P1and P2can be obtained at any desired frequency. For example, if a particular core steel has loss values (at a specific induction level) of 1.26 W/kg and 0.99 W/kg at 60 Hz and 50 Hz, respectively, then 221(60)k (60)k 1.26 += (5) and 221(5
29、0)k (50)k 0.99 += (6) Hence, -21101.38 k = (7) and -4210 1.20 k = (8) IEEE Std C57.123-2010 IEEE Guide for Transformer Loss Measurement 11 Copyright 2010 IEEE. All rights reserved. Therefore, the hysteresis loss at 60 Hz = k1(60) = 0.828 W/kg, and the eddy loss at 60 Hz = k2(60)2= 0.432 W/kg. And, t
30、herefore, 657.01.260.861=P(9) and 343.026.140.02=P (10) or 0.343 657) 0.-(12=P (11) 3.5.3 Impact of a high source impedance In order to demonstrate how critical the magnitude of the source impedance is to an accurate no-load loss measurement, consider the following examples, which show the voltage a
31、nd current of a transformer first excited with a low impedance source, and then repeated with a high impedance source. The numbers at the left of each image constitute the harmonic content of each trace plus some of the key parameters calculated for each curve. Figure 6 shows a measurement using a l
32、ow impedance source, which gives a nearly pure sine-wave voltage. Figure 7 shows a measurement (for the same transformer) for a high impedance source, causing the measured voltage to become distorted (THD = 15%). For this case, even with this much distortion, the Vavediffers from Vrmsby only 0.7%, a
33、nd the corresponding ANSI waveform voltage correction would be less than 1%. Yet, the measured no-load loss in this case was 7% lower than that measured for the sinusoidal voltage. This 7% difference is, however, in part due to not having the same test conditions. Taking into account the effect on n
34、o-load losses of the 1.5% difference in the average voltages between the two test conditions of Figure 6 and Figure 7, the corrected measured no-load loss of Figure 7 would be about 3%4% lower than that measured for the sinusoidal voltage of Figure 6. Although the magnitude of the no-load loss diffe
35、rence in this case may be acceptable, this example demonstrates that the Vrms/Vaveratio is not always a good indicator of the real distortion of the voltage. More importantly, the waveform correction alone would not be sufficient to account for the effect of the high impedance source. As will be des
36、cribed in 3.7.3, the connection of the average voltmeter can also be very critical to the accuracy of the no-load loss measurements. Also with such a distorted voltage waveshape, other factors such as the wattmeter sampling rate and phase-angle error can have a significant influence on the accuracy
37、of the measurements. The clipping of the current wave peaks by a digital wattmeter circuit during measurement of no-load loss with a highly distorted current wave (when the transformer core is excited near saturation) can be an additional source of a measurement error. This can typically occur at 10
38、5% and 110% excitation measurements. IEEE Std C57.123-2010 IEEE Guide for Transformer Loss Measurement 12 Copyright 2010 IEEE. All rights reserved. Freq. Amplitude PhaseHz Amps Deg60 7.600 -192.0180 0.700 -287.0300 2.400 -216.0420 0.600 -81.0540 0.000 0.0660 0.100 0.0780 0.000 0.0900 0.000 0.01020 0
39、.000 0.0I_rms = 5.674 AmpsPo meas. = 34.3 kWPo Corr. = 34.3 kWCURRENTFreq. Amplitude PhaseHz kV Deg60 9.100 161.0180 0.000 0.0300 0.000 0.0420 0.000 0.0540 0.000 0.0660 0.000 0.0780 0.000 0.0900 0.000 0.0 1020 0.000 0.0Vrms = 6.435 kVV_ave = 6.435 kVMax volt = 9.099kVMax flux=0.0241kVSec(ActualMax f
40、lux=0.0241kVSec(based on V_Ave)VOLTAGETHD = 0%Figure 6Excitation voltage and current waveshapes for a low impedance source CURRENTFreq. Amplitdue PhaseHz Amps Deg60 7.700 -189.0180 0.800 -297.0300 9.100 -296.0420 0.900 -200.0540 0.100 -144.0660 0.000 0.0780 0.000 0.0900 0.000 0.01020 0.000 0.0I_rms
41、= 8.472 AmpsPo meas = 31.4 kWPo corr = 31.6 kWFreq. Amplitude PhaseHz kV Deg60 8.800 153.0180 0.100 -36.0300 1.300 -30.0420 0.200 69.0540 0.000 0.0660 0.000 0.0780 0.000 0.0900 0.000 0.01020 0.000 0.0Vrms = 6.292 kVV_ave = 6.340 kVMax volt=9.658 kVMax flux=0.0238 kVSec(Actual)Max flux=0.0238 kVSec(b
42、ased on V_ave)VOLTAGETHD = 15%Figure 7Excitation voltage and current waveshapes for a high impedance source In cases where the source impedance is so large that the voltage waveshape exhibits more than two zero-line crossings, the no-load loss measurements can be even more erroneous. This is due to
43、the incorrect reading of the average voltmeter, caused by the operating principle of the averaging voltmeter which is commonly based on a rectified waveform. Figure 8 shows a more distorted voltage waveshape (THD = 18%) but still with two zero-line crossings. In this case, the average voltmeter read
44、ing is still representative of the peak flux. Conversely, in Figure 9, where the voltage waveshape is highly distorted (THD = 29%) and there are more than two zero-line crossings, the actual average voltmeter reading is significantly lower than the Vrms. The maximum flux calculated from the average
45、voltage is different from the actual peak flux. In such a case the test is definitely not valid. In fact, there is a greater danger than just measuring erroneous no-load losses under these conditions. As the average voltmeter reading is being set to the desired voltage, in this case, the peak voltag
46、e appearing across the transformer terminals may reach values in excess of the dielectric withstand of the insulation system, possibly resulting in the failure of the transformer. This is demonstrated below in Figure 9, where the average voltmeter reading was 13.966 kV (101.2% of the 13.8 kV rated v
47、oltage), while the actual peak voltage was 26.356 kV (135% of the 19.5 kV rated peak voltage). It is always a good practice to monitor the peak voltage during the no-load loss test to avoid abnormal operating conditions. IEEE Std C57.123-2010 IEEE Guide for Transformer Loss Measurement 13 Copyright
48、2010 IEEE. All rights reserved. Freq Amplitude PhaseHz kV Deg60 20.695 -109.8180 0.107 -47.5300 0.933 18.6420 3.467 -92.3540 0.848 -114.3660 0.461 -147.3780 0.253 173.5900 0.000 0.01020 0.000 0.0V_rms = 14.869 kVV_ave = 14.526 kVMax volt = 23.142 kVMax flux=0.0544 kVSec(Actual)Max flux=0.0545 kVSec(
49、based on V_aveVOLTAGETHD = 18%Figure 8High impedance source with greater distorted voltage waveshape Freq Amplitude PhaseHz kV Deg60 20.243 -115.3180 3.877 26.4300 2.669 -115.5420 2.583 -47.7540 1.927 -86.3660 1.165 -128.4780 0.529 -168.4900 0.000 0.01020 0.000 0.0V_rms = 14.899 kVV_ave = 13.966 kVMax volt = 26.356 kVMax flux=0.0504 kVSec(Actual)Max flux=0.0524 kVSec(based on V_ave
