Basic principles of creating a digital high-voltage measuring current transformer with absolute electrical strength

Abstract

The article describes the prerequisites for the creation а high-voltage measuring current transformers with near-absolute electric strength and wide dynamic range that can provide precision requirements for both commercial metering of electricity and relay protection equipment and can be used for any voltage classes. The necessity for developing small-sized digital current transformers of wide range of measurable currents with absolute electric strength and low price, which would allow them to be used for any voltage class operating in a wide range of measurable currents has been justified. The article reviews the hardware implementation of such a measuring transducer. It was proposed to perform a current transformer in the form of two independent blocks, that is - a measuring block and a substation. The measuring unit is located directly on the current-carrying conductor, and the receiving substation unit is located in the immediate proximity to the measuring unit, thus assuring the electrical strength of the system. To increase the range of measured current values, adaptable instrumental amplifiers have been proposed, which, along with the double-circuit Rogowski coil and passive integrator, can be rearranged to solve a wide range of current measurement tasks. The article shows that it is expedient to separate digital streams of current measurements directly after the Rogowski coil integrator; the integrator being of the passive type. Such solution makes it possible to provide by relatively low costs the necessary signal transform parameters that satisfy the requirements of both commercial electricity metering and the relay protection equipment of substations