SU439876A1 - Differential protection relay - Google Patents

Description

1 J

There are known differential protection relays containing a transreactor, to the output of which a rectifying bridge is connected, a resonant circuit tuned to the mains frequency, and a relay element connected in series, a time delay element and an output element.

In order to increase the degree of detuning from the magnetizing current surges in the proposed relay, a resonant circuit is connected between the rectifying bridge and the input of the relay element.

The drawing is a diagram of the described relay.

In the normal mode, the current in the primary winding of the transreactor 1 is small, so the current at the input of the relay element 2 is also small and the relay element, and therefore the time delay element 3 and the output organ 4 do not work. Since the inrush current magnetization pauses in it at a frequency of 50 Hz, the first harmonic of significant magnitude is emitted in the filter formed by capacitor 5, choke 6 and resistor 7. The output of the relay element 2 arrives

constant current component. Higher harmonics are attenuated. The input current of the relay element during part of the period has a negative sign. In this case, a pause occurs at its input and the time delay element having a setpoint over a period of industrial frequency does not work.

The relay can be used to protect low power transformers and

high voltage electric motors.

Subject invention

A differential protection relay containing a transreactor, to the output of which a rectifying bridge is connected, a resonant circuit tuned to the mains frequency, and a series-connected relay element, a time delay element and an output organ, characterized in that, in order to increase the degree of detuning from magnetization current surges , a resonant circuit is connected between the rectifier bridge and the input of the relay element.

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