A calculable impulse voltage calibrator

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Doctoral thesis (monograph)
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Acta polytechnica Scandinavica. El, Electrical engineering series, 109
This thesis describes the principle, design, construction, and uncertainty analysis of a calculable impulse voltage calibrator. The calibrator can be used as a primary reference for impulse voltage measurements. The calibrator generates lightning impulses (LI) with known peak value (UP), front time (T1), and time to half value (T2); or switching impulses (SI) with known peak value (UP), time to peak (TP), and time to half value (T2). The peak voltages of the constructed devices range from 50 mV to 1000 V. The calibration of impulse voltage measuring equipment is required both by high voltage and quality standards, and the gap between the best measurement accuracy available at National Metrology Institutes; the accuracy that is required in high voltage testing has been very narrow. The only way to improve the situation is to lower the measurement uncertainty levels in the National Metrology Institutes. In this work, the traceability of the peak and time parameter values is based on the modelling of the circuit, and the calculation of these parameters according to network theory. This calculation is based on the calibrated component (resistor and capacitor) values of the impulse circuit. The uncertainty in the peak values is low, as the peak value is not sensitive to changes in the component values of the circuit. The estimated uncertainties for lightning impulse calibrators are 0,05% for peak value, 0,5% for front time, and 0,3% for time to half value. For switching impulses the corresponding uncertainties are 0,1%, 0,4% and 0,3%. The calibrators based on this work have been used for calibration work at Helsinki University of Technology, and as a transfer reference in an ongoing worldwide round-robin test.
high voltage, impulse voltage, calibration
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