Power Supplies for Electronic High-Voltage Measuring-Current Transformers

Resumo

A power supply for electronic high-voltage measuring-current transformers with extraction of energy from the measured current that flows through a high-voltage line has been considered. A magnetic core of the supply transformer from the windings of which the necessary power is extracted is mounted on the line for this purpose. When the line current changes over a wide range, the supply transformer should have a quickly saturated magnetic core. It has been shown that, to reduce the losses and decrease the loading of the elements of a power-supply circuit in a wide current range, a ballast load should be introduced in the circuit of a secondary winding. Three variants of the ballast load have been compared: resistive, capacitive, and in the form of a transistor-current limiter. The results of simulations in the VisSim software have been considered for all three variants, as well as for the case of absence of a ballast load in the power-supply circuit. The simulations were carried out for the lowest and highest measured currents, as well as for the line short-circuit mode. The results of simulations have shown the advantages of a power supply based on a saturated transformer with a transistor-current limiter. A variant of a circuit of a transistor-current limiter has been suggested.