SU1681363A2 - Device for stand-by protection of transformer - Google Patents

Abstract

The device relates to the power industry and is designed to perform a transformer of 141 tons of a simplified substation without a constant operational power supply. The purpose of the invention is to increase the reliability of protection. This goal is achieved by the fact that the back-up protection action for disconnecting the separator can be accomplished even in the absence of charge in the storage capacitors, since the control of the disconnect switch-off gate is carried out through intermediate current transformers 28 and 32. 1 Il.

Description

The invention relates to electric power industry and can be applied to protect a transformer of a backup substation (with a separator and a short-circuit on the higher voltage side).

The aim of the invention is to improve the reliability of the device.

The drawing shows a diagram of the device.

The protected transformer 1 contains a separator 2 and a short circuiter 3 on the higher voltage side, switches 4-6 on the middle, lower voltage side and the head substation, current sensors 7-9 on the high side of the transformer. In the circuit of the short circuit 3, a current transformer 10 is installed, loaded on the current relay 11c with the opening contacts. The circuits of current transformers include serially connected coils of short-circuit connectors 12, 13, the primary windings of the time relay 14, 15, the primary windings

intermediate transformers 16-19 (16, 17 - saturating intermediate transformer) and basic protection 20 of the transformer with contacts 21, 22. A capacitor 23, auxiliary contact 24, contacts 25,26, a rectifier 27 are installed. The saturated intermediate transformer has two first windings 16, 17 and the secondary winding 28. A shut-off electromagnet 29, a rectifier 30, a resistor 31 are installed. The second intermediate transformer also has two primary windings 18, 19 and a secondary winding 32 loaded with a resistor 31. The windings are included in the disconnecting circuit 2 of the separator Erez rectifiers 27, 30. The circuit interrupting isolator 2 includes an electromagnet 29 connected in series and disconnecting the storage capacitor 23, a block 24 for short contacts 3, normally closed relay contacts 26 11 current. The burden relay has two primary windings 14, 15 and three

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contact: the first one controls the opening of the switches 4, 5 (not shown), the second 25 and the third 33 controls the opening of the separator 2.

The closure time of the first contact is selected to be coordinated with the response times of the protections of the medium and low voltage connections. The response time of the second contact is taken to the selectivity level longer than the sum of the closing times of the short circuit 3 and turning off the switch 6 of the head substation, the closing time of the third contact of the time relay is longer than the second contact time to the step Selectivity of the turning off time switch 6 of the head substation.

The device worked as follows.

If the transformer 1 is damaged, its protection 20 triggers and with its contacts 21, 22 the shunt coils 12, 13 of the short-circuit connector 3, Short circuit 3 is turned on, causing a short circuit on the higher voltage side of the transformer 1. Switch 6 of the circuit breaks. the head substation and in the empty pause the separator 2 is disconnected. If the short circuit breaker failed for some reason, then the fault current continues to flow through the current transformers 7-9 and the windings 14, 15 of the saturating transfo Rmator time relay. The first time relay contact closes and the switches 4, 5 are disconnected. After the second time delay has been set, the second time relay contact 25 is closed, connected in parallel with the short-circuit block terminal 24 3. If the latter does not turn on, the normally-closed current relay 26 remains closed and creates a circuit to disconnect the separator 2. The separator knife moves away from the contacts. Since the separator is not designed for switching off the short-circuit current, its destruction is possible. However, this causes a phase-to-phase short circuit on the higher voltage side of transformer 1. This short circuit is accompanied by the protection of the head substation, the switch 6 trips,

If the storage capacitor 23 is discharged (the substation is turned on for damage after repair or

the circuit breaker in the auxiliary transformer circuit has been disconnected), then the separator does not trip. A fault current continues to flow through transformer 1. WITH

the third time delay closes the time relay contact 33 and creates a circuit (secondary windings 28, 32 intermediate transformers, separator disconnect coil 29, contact 26). If the transformer has a small power (2-10 MVD) or a short circuit occurs through a transient resistance, then the secondary current of the current transformers 7-9 may not be enough to operate the separator 2 turning off electromagnet 2. Therefore, the secondary winding 28 of the saturated transformer is connected in series with the secondary winding 32 of the intermediate transformer. transformer. The saturating transformer is chosen so that the amplitude of its secondary current is approximately twice the current amplitude of the second intermediate transformer (secondary winding 32). Such a connection of the windings makes it possible to ensure reliable disconnection of the separator, since the presence of a short current pulse helps to overcome the mechanical inertia of the electromagnetic disconnecting device.

Claims (1)

0 claims Device backup protection transformer auth. St. Ms 684667, characterized in that, in order to increase the reliability of the device, two intermediate current transformers, one of which is saturating, the primary windings of which are connected in series with the short-circuit coils, are additionally introduced 0 the secondary winding of the intermediate current transformer is loaded on a resistor and connected to the input terminals of the first rectifier, the secondary winding of the intermediate saturated transformer 5 is connected to the input terminals of the second rectifier, parallel to the serially connected coil of the separator disconnecting electromagnet and the disconnecting contact of the current relay on the circuit of the series connected additional closing relay of the time relay and connected according to the output terminals of the first and second rectifiers. 12, - 18 L / lgch / 5 tfx- / 7, - # 20