Calibration of Test Systems for Measuring Power Losses of Transformers

Two years of development work by ASEA Electric, under the auspices of the Industrial Research Associate Program of the National Bureau of Standards, has resulted in a verifiable method of determining overall accuracy of test systems used in the measurement of transformer losses. This technical achievement is important to the industry because of the present trend towards lower power factors which makes loss measurements exceedingly difficult with desirable test system accuracy that is traceable. The technical details of this work are presented in NBS Technical Note 1204 (over 100 page document). The intent of this IEEE paper is to present the basic principles embodied in the Technical Note. A calibration system for accuracy verification and alignment of test systems is described. Methodologies and data for evaluating accuracy of test systems are summarized. The details elaborated upon in this paper represent a way to determine the accuracy of the overall test system for measuring transformer losses as well as that of the principal components of such a system.