SU758349A1 - Maximum ac relay - Google Patents

Description

The invention relates to relay protection and can be used to protect against short circuits and abnormal operating conditions of electrical installations with a voltage of 6-10 kV. five

A device for relay protection [1] is known, having a measuring current organ, a threshold organ and an executive organ.

The closest technical 10

Entity is a current protection relay <

consisting of a current level detector, a logical element And, one.

entrance! which is connected directly to the level detector, and the second one — through the setpoint driver, which includes the generator as a synchronizing signal, which uses the output signal of the current level detector, and a memory device.

However, the known device can perform only a cutoff function, and has a low reliability. Its sensitivity is limited by the possibility of false alarms from transient currents accompanying the start and self-starting of electric motors. The current level detector is triggered only when the current exceeds a specified value of 30

in the positive half of the period, which reduces the speed of protection.

The purpose of the invention is to expand the functionality by changing the setting depending on the magnitude of the current.

The goal is achieved by the fact that the relay, which contains a series-connected current level detector, a driver for the tripping signal and an exposer, the driver for the tripping signal contains a logic element ⁽ 'I', the first input of which is connected directly to the current level detector , a block for automatic change of the set-up consisting of a series-connected pulse drive and a thyristor switch, connected between the output of the current level detector and p regulates the input of the setpoint.

The level detector can be designed as a reed switch connected to a current transducer. Shaper setpoint can be made in the form of an adjustable delay element.

758349

The drawing shows the functional diagram of the relay.

The relay contains a current level detector ί connected to a tripping signal generator 2, which consists of; logic element And 3 and generator 7 setpoint. Block 5 automatic-. "* The setpoint change is connected between the current level detector 1 and the setpoint driver 4 and consists of a pulse accumulator b and a thyristor switch '7. Current level detector 1

'may be performed on the reed switch, and the driver 4 settings on an adjustable delay element. The delay time is determined by the calculated frequency ratio of the fault current with respect to the setpoint of the detector 15 level of operation 1 level • The relay operates as follows.

In case of a short

short-circuits when the current reaches the trip level, detector 1 closes its contacts. The signal from the detector 1 is fed to the driver - 2 tripping signal. In the forma- Le 2 of the tripping signal, the signal is sent to the logical element I 3 and to the shaper 4 of the setpoint, which, after the expiration of the preset time set to 6.5 ms, gives a short pulse of 0.5 ms duration. The signal from the shaper 4 setpoint is fed to the second input of the logical element AND 3. There is a coincidence in time ....... pulses arriving at the two inputs of the logical element I, 3, since the time of the closed state of the reed switch is longer than the selected delay time with short closure. The output of the logic element And 3 appears 'signal', which is fed to the disconnecting switch coil.

At the same time, the signal from detector 1 enters the accumulator b of pulses of the block 5 of the automatic setpoint change. But from the output of the accumulator 6 pulses to the input of the thyristor key 7, no signal comes in. Like the accumulator 6 'pulses until the appearance of a shut-off pulse at the output

.. 'Logic Element And 3 has time to take no more than one signal from the reed switch

'in self-starting mode, the maximum value of the total current is below the short circuit current in absolute value, therefore, less and. the time of the closed state of the contacts of the detector 1.-lhh. "·,’ h

The signal of the detector 1 is supplied to the driver 2 tripping signal. Imyuls from shaper 4 of the setpoint arrives at the logical element 3 and after the signal disappears from herko ’“ H1, ”according to the signal coincidence / in time did not occur at the output of shaper 2 of the tripping signal, there is no pulse.

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At the same time, signals from the reed switch caused by the presence. aperiodic component of the current, continue to flow into the block 5 automatic changes setpoint. After the transition process, which lasts, as a rule, for a period of two, is over, detector 1 'stops producing signals. This indicates the normal mode of the engine. The device returns to its original state.

If the network has any violations of the normal mode and

“After a period of five periods, the reed switch still closes its contacts (this indicates that the accumulator received b pulses of ten clock pulses), the accumulator b pulses, and generates a signal to the thyristor key'7. The latter shunts a part of the resistance of the time-charge chain in the shaper 4 of the setpoint. As a result, the delay time is reduced to 2.8 ms. Therefore, now on both inputs of the logic element AND 3 the pulses from the detector and driver 4 of the setpoint coincide in time and at the output of the logic element. That And 3 the breaking impulse is formed,

The device has in comparison with the known advanced functionality: thanks to the introduction of -. It is possible to perform protection of instantaneous action against short circuits, as well as maximum-current with time delay on one single, horn current element. The appearance of transient currents accompanying the start and the starting of electric motors does not cause false triggering of the device.

Claims (3)

Claim 1. A maximum AC relay containing a series-connected current level detector and a tripping signal driver, made on the AND gate, the first input of which is connected directly to the current level detector, and the second through the set point driver, which is that, in order to extend the functionality by changing the setpoint depending on the current value, an automatic setpoint change unit was introduced, consisting of a sequence '. connected to the pulse drive and the thyristor switch, connected between the output of the current level detector and the control input of the setpoint driver. • 2. Relay on π. 1, that is, it is a level detector. Run in the form of a reed switch connected to the transmitter current. . 65 five 753349 6 3. The relay according to claim 1, characterized in that the setpoint driver is made in the form of an adjustable delay element.