Test equipment and its effect on the calibration of instrument transformers

Abstract

State-approved test centres in Germany supplying accuracy tests for instrument transformers must, in the future, provide measurement uncertainty budgets for their quality management systems. In this work, the cause of ratio error and phase displacement of instrument transformers are therefore discussed. The traceability to the national standards of PTB, the attainable uncertainty, and the permitted error limits of test equipment for testing instrument transformers are presented. Finally, an example of an uncertainty budget for a current transformer of the class 0,2 S is given.Published by Copernicus Publications on behalf of the AMA Association for Sensor Technology.

Metrological characterisation of current transformers calibration unit for accurate measurement

“…Based on the available information, it can be argued that in today's calibration activities, CT manufacturers, testing labs, energy companies, and other related enterprises remain using commercially available means of comparing. When calibrating CTs with an accuracy class of 0.2S, the contribution to the total measurement uncertainty, obtained via the admissible tolerance, from the use of the measuring bridge can be more than 90 % of the contribution of all the influencing variables when determining the RE value of 480 µA/A [15].…”

Modeling Stray Capacitances of High-Voltage Capacitive Dividers for Conventional Measurement Setups

“…In addition to the standards for ITs, there is also extensive related literature with available documents that try to address most of the issues that may affect their correct operation. For example, in [9][10][11][12][13], the effects of temperature on ITs are described; in [14][15][16][17][18][19][20], several modeling methods and procedures are presented, for both CTs and VTs (in both time and frequency domain); finally, [21][22][23][24][25][26] discuss specifically the ITs uncertainty under rated or off-nominal conditions of the grid.…”