Calibration of the Measuring Systems

Abstract

From the technical point of view, worldwide trade of goods requires internationally accepted test and calibration procedures, accredited testing and calibration laboratories and traceability of measurements to national or international standards of measurement. A short introduction into the themes like IEC standards, accreditation and traceability is followed by presenting the main calibration methods and circuits for the approval of measuring systems used in high-voltage and high-current tests. The scientific and technological fundamentals of test and measurement methods are mainly elaborated in CIGRE working groups and other organisations. The qualification and approval of a measuring system and its components takes place in the course of a large number of acceptance tests and checks which are documented in the record of performance. The preferred calibration method is the comparative measurement of the measuring system with an accurate reference system at high impulse voltages or currents. As an example, the arrangement of the comparison measurement at high impulse voltages is shown. Hereby, the scale factor and the measurement deviations for the time parameters are determined as well as their linearity. The short- and long-term behaviour and dependence on other influence quantities can be determined applying methods that are common in the low-voltage measurement technique. As an alternative to the comparison method, the dynamic behaviour of an impulse voltage divider can be judged by evaluating its step response in the relevant reference level epoch. Several methods for calibrating digital recorders are presented.