UNCERTAINTY EVALUATION OF THE DISSIPATION FACTOR IN THE CALIBRATION OF PRECISION CAPACITANCE STANDARDS

This paper presents a methodological and metrological approach to thecalibration of precision capacitance standards with respect to the dissipation factor (loss factor) at the State Primary Standard of Electrical Capacitance and Dissipation Factor. The relevance of the study is driven by the need to ensure high accuracy measurements of capacitance and loss parameters in capacitors widely used in measurement systems and instrumentation, power engineering, telecommunications, and, in particular, electrical insulation testing equipment. The dissipation factor is an important characteristic of dielectric materials and capacitorsdetermining the level of energy losses in the dielectric and significantly affecting the accuracy of complex impedance measurements, as well as the results of electrical insulation diagnostics. A measurement system used for the calibration of precision capacitance standards with respect to the dissipation factor is presented, and its operating principle is described. A mathematicalmeasurement model has been developed that accounts for the main contributors affecting the determination of the dissipation factor, including measuring bridge parameters, quadrature signal errors, frequency and supply voltage instability, and parasitic losses in the measurement circuit. The measurement model equation is presented, and the physical meaning of its individual components is discussed in detail. Particular attention is devoted to the analysis of measurement uncertainty sources and the development of an uncertainty budget for the calibration procedure. An example is provided for calculating the combined standard uncertainty and expanded uncertainty of the calibration result for a precision capacitance standard with respect to the dissipation factor. The obtained results may be used in the development of calibration procedures for capacitance standards based on the dissipation factor and in ensuring the metrological traceability of capacitor parameter measurements to the State Primary Standard. References 20, figures 5, table 1.