Output characteristic of the remote transformer current transducer for rural electrical networks

Abstract

The advantage of the new remote transformer current transducer is that the magnetic flux each time passing through the turns of the multi-turn core directs electromotive force in the measuring winding, i.e. the total electromotive force in the measuring winding of the new device is several times greater than the electromotive force in the measuring winding of its prototype. It was established that the quality factor of the measuring circuit is approximately several times higher than the quality factor of the solenoid-type transducer. When measuring the unbalance of currents in a three-phase line, an electromagnetic sensor is installed under each phase, and their measuring windings are interconnected according to the open delta scheme. An analytical expression for the output characteristics of the new remote transformer current transducer with a multi-turn core has been obtained, taking into account the distribution of the parameters of their electric and magnetic circuits. It has been shown that with an increase in the attenuation coefficient of the magnetic field in the magnetic circuit, the slope of the output characteristic of the transducer decreases, which is explained by an increase in the magnetic leakage flux from one turn of the multi-turn core to another, which is partially involved in creating electromotive force in the measuring winding. It has been shown that if in structural schemes the processes occurring in automatic system are displayed in the form of a set of serially, parallel and mixed-connected standard links, then in the parametric structural schemes of the transducer, further decomposition of standard links is performed to the parameters of resistance, inductance, capacitance and their corresponding inverse parameters of conductivity, inductance and rigidity of chains of different physical nature, as well as before physical effects and phenomena, the so-called physical and technical effects within a chain of one physical nature and between two chains of different physical nature. It has been established that such a decomposition, firstly, allows in more detail, before an elementary transformation, reflecting in parametric structural schemes the processes occurring in the transducer; secondly, it allows revealing all possible influences of internal and external disturbances on the parameters and coefficients of intrachain and interchain physical and technical effects, and thirdly, it allows relatively easily obtaining analytical expressions for studying the static, dynamic and metrological characteristics of the transducer. The linear section of the output characteristic of the new current transducer has been determined. By the method of magnetic field modeling, an analytical expression for the converted current corresponding to the upper limit of the boundary of the linear section of the output characteristic of the new remote transformer current transducer has been obtained.