SU1457049A1 - Device for current protection of transformer/autotransformer against external shorting - Google Patents

Abstract

This invention relates to electrical engineering, in particular, to relay protection. The purpose of the invention: - increase the sensitivity of protection in case of short circuits on the disconnected output of a transformer (autotransformer) in a non-full-phase mode of operation of the three-phase line connected to it. The device contains a power transformer 1 connected to a power source 2 by wires of phases 3, 4, 5 of the power line, current transformers 7, 8, 9. The secondary windings of current transformers 7, 8, 9 are connected to each other and grounded, and the other ends of these The windings are connected respectively to the same terminals of the current relays 10, 11, 12. When the circuit of phase 3 of the transmission line connected to the output of the power transformer 1 closes, another current or current is generated to the other phase or to ground. The secondary current of the current transformer 7 triggers the current relay 10, which closes its contacts in the logical part of the protection. This triggers the executive part of the protection. 2 Il. i (L

Description

1

The invention relates to electrical engineering and can be used to protect a transformer (autotransformer) from external short circuits.

SRI.

The purpose of the invention is to increase the sensitivity of protection in case of short circuits on the disconnected output of a transformer (auto-transformer) in a non-full-phase mode of operation of the three-phase line connected to it.

Figure 1 shows the functional diagram of the power transmission and current protection circuits; figure 2 - diagram of the logical part of the protection.

 power and current protection circuits contains a power transformer 1 connected to the source

2 power wires 3-5 phases of the transmission line and the wire phase

3 is disconnected from the power source by the switching device 6, the phase current sensors of the current transformers 7–9, connected by the primary windings to the center of the power transformer at the place of their connection to the wires of the power transmission lines 3-5. The secondary windings of current transformers 7-9 are connected at one end to each other and grounded, and the second ends of these windings are connected respectively to one terminals of current relays 10-12, the second terminals of which are connected to each other and connected to the common point of connection of one ends of the secondary windings.

The logical part of the protection (figure 2) consists of the closing contact 13 of the current relay 10, which is connected to the source 14 by the first output and no protection to the second output, to the first output of the closing contact

15 current relay 1.1., The second output of contact 15 of the relay 11 is connected to the first terminal of the closing contact 16 of the current relay 12j the second output of the contact

16 relay 12 is connected to the input of the executive part of the protection 17.

Current protection works as follows.

In the normal non-phase-load mode of transmission in the primary winding of current transformers 8 and 9 (FIG. 1) currents of wires of phases 4 and 5 of the power line flow, ia in the primary winding of the transformer, and there is no current in the terminal 7. The currents of the secondary windings of the transformers 8 and 9 of the current cause the operation of the current of the relays 11 and 12, which close their contacts 15 and 16 in the logical part. Thus, a chain of action protection in case of a short lock is prepared.

When the circuit of phase 3 of the transmission line connected to the output of the power transformer 1 closes, a current arises on the other phase or on the ground in the primary winding of the current transformer 7. The secondary current of the current transformer 7 triggers the operation of the current relay 10, which closes its contacts 13 in the logical part of the protection (figure 2). Thus, by closing the contacts 13 with the contacts 15 and 16 pre-closed, the actuator is energized and the protection is activated. . .

Claims (1)

Invention Formula A device for current protection of a transformer (autotransformer) against external short circuits, containing three current relays, windings, which are connected to the outputs of the transformer (autotransformer) phase current sensors, shorting contacts of the current relay are included in the logical part of the protection, in order to increase the sensitivity of protection in case of short circuits on the disconnected output of a transformer (autotransformer) in a non-full-phase mode of operation of the three-phase line connected to it, the closing contacts of the relay are current and in the circuit of the logical part of the protection are connected in series.