DEVICE FOR PROTECTION AGAINST SHORT CIRCUITS IN DEAD ZONE OF OUTDOOR SWITCHGEARS OF HIGH OR ULTRAHIGH VOLTAGE ELECTRIC POWER FACILITIES - IN SECTIONS BETWEEN CURRENT TRANSFORMERS AND SWITCHES

摘要

The invention is related to relay protection against short circuits in the dead zone between current transformers and switches in outdoor switchgears of power plants and substations. On a high or ultrahigh voltage potential for each phase, there are two transmitting modules installed at the ends of the protected section and interconnected by means of a fibre-optic communication line. On the ground potential, there is a re-receiving module connected by radio channels with both transmitting modules and connected by means of a fibre-optic communication line to a combined control station. Each of the transmitting modules includes a power supply unit, a measuring converter consisting of a current sensor and a null-indicator, a modem consisting of an electro-optical converter and an opto-electric converter, a comparison unit and a radio transmitter. The current sensor is able to obtain signals of instaneous phase current values, and the null-indicator is able to register their positive or negative sign. The output of the null-indicator is connected to the input of electro-optical converter and the first input of the comparison unit, the output of the opto-electric converter is connected to the second input of the comparison unit, and the output of the comparison unit is connected to the input of the radio transmitter. The re-receiving module is common for transmitting modules of all phases of the protected zone and comprises a power supply unit, a radio receiver and an electro-optical converter. Operation of the device is based on the phase-comparison relaying principle where the keying value is the fact of zero-crossing by the primary current phase. The invention allows to simplify the protection device against short circuits in dead zones and ensure reliable operation of an outdoor switchgear.