CLC/TR 50462:2008

Introduction
1 Scope
2 Normative references
3 Definitions
4 Symbols
   4.1 General symbols
   4.2 Symbols for uncertainty
5 Power measurement, systematic deviation and uncertainty
6 Procedures for no-load loss
   6.1 General
   6.2 Model function for no-load losses at reference conditions
   6.3 Uncertainty budget
7 Procedures for load loss
   7.1 General
   7.2 Model function for load loss at reference conditions
   7.3 Uncertainty budget for measured power P[2] referred to
        rated current
   7.4 Uncertainty budget for reported load loss
8 Three-phase calculations
   8.1 Power
   8.2 Reference voltage (current)
9 Reporting
   9.1 Uncertainty
   9.2 Traceability
10 Estimation of corrections and uncertainty contributions
   10.1 Ratio error of instrument transformers
   10.2 Phase displacement of instrument transformers
   10.3 Power meter
   10.4 Voltage measurement in no-load loss
   10.5 Ampere meter in load loss measurement
   10.6 Correction to sinusoidal waveform
   10.7 Winding temperature h at load loss test
   10.8 Winding resistance
Annex A (informative) Example of load loss uncertainty evaluation
        for a large power transformer
      A.1 Introduction
      A.2 Transformer rating
      A.3 Measuring method and instrumentation used
      A.4 Model of the measurand
      A.5 Results of the measurements
      A.6 Uncertainty of load loss
      A.7 Estimates of the single contributions to the uncertainty
Annex B (informative) Example of load loss uncertainty evaluation
        for a distribution transformer
      B.1 Introduction
      B.2 Transformer rating
      B.3 Measuring instrumentation
      B.4 Model of the measurand
      B.5 Results of the measurements
      B.6 Uncertainty of load loss
      B.7 Estimate of the single contributions to the uncertainty
          formation
Annex C (informative) General rules for the uncertainty estimate
      C.1 The basic concepts
      C.2 Measurements, estimates and uncertainties
      C.3 Evaluation of the input quantity uncertainties
      C.4 Evaluation and expression of the expanded uncertainty
Annex D (informative) Sensitivity coefficients for uncertainty
        contributions due to phase displacement correction of
        measurements at low power factor
      D.1 Introduction
      D.2 Sensitivity factors
Annex E (informative) Model function for load loss temperature
        correction
      E.1 General
      E.2 Model function
      E.3 Sensitivity coefficients
      E.4 Estimation of temperature during load loss test
      E.5 Simplified analysis
Annex F (informative) Measurement of winding resistance
      F.1 Description of the measurement
      F.2 Inductive voltage drop
Bibliography

This Technical Report illustrates the procedures and criteria to be applied to evaluate the uncertainty affecting the measurements of no load and load losses during the routine tests on power transformers. Even if the attention is especially paid to the transformers, the document can be also used for the measurements of reactor losses, when applicable.