SU1453506A2 - Relay for differential protection of buses - Google Patents

Abstract

The invention relates to electrical engineering, namely, relay protection and busbars. The purpose of the invention is to increase the selectivity in the case of an external short circuit with a predominance of aperiodicity in a current of damage. With this, the device additionally introduces a second time delay element for return and a second OR element, and the logic circuitry is changed so that, with uneven saturation of current transformer cores, the aperiodic busbar connections in the differential current retain the protection time lock flow transient in the differential current. 2 Il. (L

Description

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FIELD: electrical engineering;

Electrical systems, can be used to protect tires and busbars and is an improvement of the invention according to the author. St. No. 625283.

The aim of the invention is to increase the reliability of

, by increasing the selectivity in an external short circuit with a predominantly aperiodic component of the fault current.

FIG. 1 shows a schematic block diagram of the proposed relay; in fig. 2 - diagrams of work in the external short circuit mode.

The relay contains intermediate current transformers 1-3, connected to downstream bridges 4-6. The first, second, third, and fourths are connected to the outlets of the administrative bridges; resistors 7-10, diode 11 and capacitor 12. Shaper 13 rectangular

The coils of intermediate transformers 2 and 3 of the current pass through the currents of the protection arms, therefore, there is a rectified voltage on the first resistor 7 of the capacitor 12. However, it is not enough to trigger the additional driver 18. Diode 11 is predominantly driven by a capacitor 12 black.

10 is a resistor 7. The signals at the outputs of the second element OR 19 and the second element of the 20 time delay are equal to O.

With an external short-circuit removed with a maximum aperiodic component

15 in the current of damage, the currents of the protection arms i and ij (Fig. 2) are distorted to varying degrees due to the different operating conditions of the busbar current transformers. When this arose

20 em of the unbalance differential current which flows through the primary insulation of the intermediate transformer t 1 and the formation of the bodies of the body 13 is triggered. In this case, the current ratio K

The pulses through successively connected 25 are relatively small. The additional 14 low-pass filter, the first element 15 is a time delay and the first element OR 16 is connected to the executive unit 17. The secondary former 18 triggers in the first period after the occurrence of a short circuit due to the influence of the aperiodic composition of current currents i and i, and in the second

shaper 18 triggers in the first period after the occurrence of a short circuit due to the influence of the aperiodic component of currents i and i, and in the second, shaper shaper 18 returns to its original position after 30 seconds.

The second element OR 19 and the additional element .20 time delay are connected to the prohibitory input of the prohibition element 21, the output of which through the first time delay element 22 to return is connected to the second input of the first element OR 16, allowing the input of the prohibition element 21 and the input The second return time element 23 is connected to the output of the imaging unit 13. The output of the second return time delay element 23 is connected to the second input of the second element OR 19.

The device works as follows.

In the normal load mode, a small unbalance current flows through the primary winding of the intermediate current transformer 1, therefore, at the outputs of the shaper 13, the low-pass filter 14, the first time element 15, the second time element 23 for returning the BAN 21 element, the first exposure element 22 time to return 22 and the first element I.PI 16 there is a signal O, Executive body 17 does not work. According to the primary.

the coils of the intermediate transformers 2 and 3 of the current flow currents of the protection arms, therefore there is a rectified voltage on the first resistor 7 and the capacitor 12. However, it is not enough to trigger the additional driver 18. Diode 11 prevents the discharge of capacitor 12 through

0 resistor 7. The signals at the outputs of the second element OR 19 and the second element 20 of the time lag are equal to O.

When the external short-circuit is removed with the maximum aperiodic component

5 in the current of damage, the currents of the protection shoulders i and ij (FIG. 2) are distorted to varying degrees due to the different operating conditions of the busbar current transformers. In this case, a differential current of unbalance 1D arises, which flows through the primary winding of the intermediate current transformer 1 and the operation of the generator 13 is triggered. In this case, the ratio of the short-circuit current

relatively small. Additional

shaper 18 is activated in the first period after the occurrence of a short circuit due to the influence of the aperiodic component of currents i and i, and in the second period it returns to its original position

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life due to a decrease in currents i and i. The constant discharge time of the condensate bubble is accepted within the range of 20-30 ms. In the first period after the occurrence of the short-circuit differential, the unbalance differential current Gd arises after the additional forcing of 18 for 2–3 ms. due to this, the signal at the output of the imaging unit 13 appears later than the signal at the output of the second time delay element 20 having a delay of 1 ms, and the signal at the output of the prohibition element 21 remains equal to O. Additional shaper 18 remains in the activated state for about 20 ms, and then returns to its original state. The signal from the output of the imaging unit 13 is expanded by 25 ms by the second element 23 of the delay time to return, and a constant signal is generated at the output of the latter. This signal is fed to the input of the second element OR 19, the output of which also produces a constant signal. This signal through the second element 20 of the time lag goes to the prohibiting entry of the element BANGE 21 and maintains the blocking of the protection device.

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In case of short-circuit in the protected zone, the current 1d is equal to the sum of the currents i and i, therefore, it occurs simultaneously with their occurrence. The formers 13 and 18 are triggered at the same time, which leads to the appearance of signal 1 at the output of the BANGE 21, since the signal at its prohibitory input appears with a 1 ms delay created by the second time delay element 21. The signal from the output of the element BANGE 21 is expanded by the first element 22 of the time delay for the return and through the first element OR 16 enters the input of the executive body 17.

Increasing the detuning from unbalance currents with a predominance of the aperiodic component in the current of damage with remote external faults allows to increase the selectivity of tire protection and reduce its excess overdraft

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Claims (1)

Invention Formula Relay differential protection tires auth. St. No. 625283, characterized in that, in order to increase the reliability of operation by increasing the selectivity in an external short circuit with a predominance of the aperiodic component of the fault current, the second return time delay element and the second OR element included between the additional driver and the additional element are additionally introduced The time delay and the second return time element are included between the input of the low pass filter and the second input of the second OR element. FI.1 2