SU649086A2 - Differential phase relay - Google Patents

Description

The drawing shows a structural diagram of the proposed differential-phase relay.

Differential-phase relay contains input transformers 1 connected to current transformers (CT) installed at the terminals of the protected transformer. The input transformers are connected by a conversion circuit 2 with a comparison circuit 3. The output of the comparison circuit is connected to a reacting organ 4, the brake input of which is connected to the braking unit 5 at inrush currents. The relay contains three such schemes according to the number of phases of the transformer to be protected. Filters 6 currents of one of the symmetric components of the asymmetrical mode are connected to current transformers of the respective sides. The choice of the type of filters depends on the wiring diagram of current transformers installed at the terminals of the protected object. When connecting current transformers according to the star-delta scheme, only negative-sequence current filters can be used, and when connecting current transformers according to the star-star scheme (it is possible to install current transformers on the low voltage side in the branches of the power transformer triangle), it is reasonable The use of zero sequence current filters.

The outputs of the filters 6 are connected to the operating inputs of the differential current element 7, the brake input of which is connected to the highs of the detuning unit 8 from magnetizing current surges, the inputs of the latter are connected to the output of the corresponding brake units. One of the blocking inputs of the body 7 is connected to the blocking 9 when the power transformer is over-excited, the second one is connected to the lockout output 10 at overcurrents, the inputs of which are connected to the respective arms of the corresponding comparison circuits 3. The output of the differential current body is the relay output.

The relay works as follows.

When the coil circuit in the protected transformer and the presence of flowing load current to the body 7 receives the current due to the current coil circuit. If the magnitude of this current exceeds the actuation current of organ 7 (0.06 -0.12). 1n, the latter is triggered and gives a signal to turn off the transformer. If the geometrical difference between the flowing and flowing currents of the transformer of one of the phases exceeds the current of the operation of the phase circuit, the response body 4 of this phase is triggered, which gives a signal to turn off the transformer. In case of short-circuit overcurrents, signals from comparison circuit 3 trigger a lock 10, which

It blocks the work of a differential current organ 7, due to which there is no need to rebuild it from modes beyond short shorts with large current transformer faults. In this mode, only phase circuits work. rye have high selectivity and speed. When the magnetizing current is injected, the detuning of the phase circuits is achieved by braking the reacting body 4 with a signal from the braking unit 5. The detuning of the differential current element 7 is carried out by a brake signal from the detuning block 8 from the shots, which produces a signal depending on the output signals of all the phase braking units. When a quasi-stationary, overvoltage exceeding 1.25UH occurs, blocking 9 delivers a differential signal to the differential current body 7 that blocks the relay when the power transformer is over-energized. As a lock 9, a known voltage level device can be used, the threshold organ of which blocks the operation of the differential current organ 7 at a voltage value causing a dangerous increase in the magnetizing current.

In the proposed differential-phase: no. M relay, the response current when the coil winding x is reduced to (0.06-0.12) 1,

0. Therefore, its high sensitivity is sufficient for detecting the closure of one winding of a power transformer (sensitivity factor of 2-3) and all types of internal short circuits.

A prototype of the proposed differential-phase relay was manufactured and tested under production conditions on a ZkhOTs-417 MVA transformer of an enlarged unit of the Krasnora hydroelectric station. The relay had a sensitivity of 0.08 IH - It showed

good detuning from short circuits. With internal short-circuits and with a maximum aperiodic term, the relay was 27 ms. The detuning of the relay from the inrush current was tested in laboratory

5 conditions on the dynamic model.

The proposed differential-phase relay provides protection against all internal short circuits and coils in the windings of the transformer.

Claims (1)

1. USSR author's certificate number 473254, cl. H 02 H 3/28, 1973.