SU1480004A2 - Device for differential protection of electrical installation - Google Patents

Abstract

The invention relates to electrical engineering and is intended for the relay protection of power transformers, electric motors, busbars and other objects from short circuits. The purpose of the invention is to increase the sensitivity at low short-circuit currents in the zone of action of protection. The goal is achieved by the fact that at low damage currents in the protection zone there is no signal from the output of the brake signal generation unit and the prohibition element transmits a signal about the response of the second comparator block, which is more sensitive, to the reacting organ. 3 il.

Description

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The invention relates to electrical engineering and is intended for the relay protection of power transformers, electric motors, busbars and other objects from short circuits.

The purpose of the invention is to increase the sensitivity at low short-circuit currents in the zone of action of protection.

FIG. 1 shows a functional diagram of the device; figure 2 - the same, a variant of the scheme; in fig. 3 - brake characteristics.

The device of the protected object 1 contains current transformers 2 and 3, to which the forming unit of the working 4 and brake 5 signals are connected, the second comparison unit 6, the threshold unit 7, the stable aperiodic link 8, the BAN element 9,

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first comparison unit 10, reacting authority 11.

The input of the threshold unit 7 can be connected to the output of a max-selector 12 currents of protection arms.

The device works as follows.

In the normal load mode, the output of the operating signal generation unit 4 is smaller than the output signal of the brake signal generation unit 5, which causes the first 10 and second 6 comparison units, and consequently, the response body 11, to fail.

During a short circuit outside the protection zone, the first unit 10 of the comparison does not work, since it is rebuilt from the maximum external short-circuit current. The second unit 6 of the comparison is rebuilt from the minimum current of external damage and in this mode

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may work. However, the signal at the input of the threshold unit 7 is greater than the setpoint of its operation, and the threshold body 7, which is triggered, triggers the prohibition element 9, resulting in a signal from the output of the second unit

6 comparison does not pass to the input of the reacting body 11 and the device does not work.

In case of a short circuit in the protection zone, in the case when the short circuit current is greater than the actuation current of the threshold organ 7, the first 10 and second 6 blocks of the comparison and the reacting body 11 are triggered. maximum current external damage to its braking characteristic (see figure 3, characteristic 13).

The second unit of comparison 6 is made more sensitive (its braking characteristic, see FIG. 3, characteristic 14) and works, and since the signal at the input of the threshold unit

7 less than its current response

then the threshold unit 7 does not work, thereby giving a permissive impulse to the element BAN 9, which leads to the response of the reacting authority 11

If necessary, detuning from a surge of magnetizing current of the second

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Comparison unit 6 can be made to be buried in the form of the input current.

The sensitivity gain using the proposed device is shown in FIG. 3 shaded area.

Thus, the device has an increased sensitivity to small short-circuit currents with reliable detuning from external damage currents.

Claims (1)

Claims of the Device for differential protection of electrical installations according to author. No. 1026228, characterized in that, in order to increase sensitivity at low short-circuit currents in the protection zone, a second comparator unit and a BAN element, a threshold unit, are additionally introduced into it, the first input of the second comparator unit being connected to the output of the formation unit the working signal, the second input - to the output of the brake signal shaping unit, to which the input of the threshold unit is also connected, the output of which is connected to the blocking input of the BAN element whose output is connected to the entrance of the reacting authority. Otll. Lra lp / IIcl 1 In 2 UfT7ff / 7. 2 B fig.Z a Ir 0.52 / Jij