Abstract: A method for measuring at least one electrical parameter of the operation of a p-phase power line, p being a positive integer, arranges respective sensing apparatus to sense at least one of the voltages and currents associated with each phase of the power line. Analog-to-digital conversion apparatus is used to digitize the response of each sensing apparatus, thereby to generate corresponding digital responses. A digital computer is used to correct each digitized response of the analog-to-digital conversion apparatus for non-linearities, gain errors and phasing errors in the responses of the sensing apparatus and for non-linearities and gain errors in the responses of the analog-to-digital conversion apparatus. The computer is used to high-pass digitally filter each digital response that has been corrected, in order to suppress any attendant direct term.

Abstract: An effective-value converting circuit comprising a rectifier circuit of which four arms are composed of diodes to rectify an a-c input, a temperature compensating diode connected between the output terminals of the rectifier circuit in series with a plurality of resistance elements for principally determining break points, a resistance element whose one terminal is connected with one output terminal of the rectifier circuit and whose other terminal is connected with the other output terminal of the rectifier circuit through an integrating capacitor so as to determine the fundamental inclination of a broken line, and series circuits consisting of inclination-determining resistance elements and diodes connected respectively between the integrating capacitor and the individual voltage-division points of the inclination-determining resistance elements.