RU1793510C - Device for redundancy of failure of current protection of step-down transformer - Google Patents

Abstract

The invention relates to electrical engineering - KyoMdel - simplification of the device. The goal is achieved by backing up the power supply circuit of the condense; the main power supply unit of the power supply unit 2 from the current sensor 1. With independent control of the voltage drop from the short circuit at the substation and the set time countdown on it from its own transformer protection and the necessary delay of energy storage sufficient for the operability of the actuator 8 both during operation of the step-down transformer 12 and when it is turned on. 1 ill.

Description

The invention relates to electrical engineering, to a device for redundant current protection of a step-down transformer in the absence of the possibility of long-term redundancy.

A device is known for redundant protection of a transformer with a separator and a short-circuit on the higher voltage side, which uses a special circuit for charging a capacitor from a short-circuit current or from its operation, followed by disconnecting the separator from the energy of the capacitor in case of failure to turn on the short-circuit.

The device is subject to the operation of relay protection devices. transformer, serviceability of power supply of current circuits and availability of operational circuits of commutation: transformer switching devices.

Consequently, redundancy is ensured only when the short circuit is most likely to be defective and the possibility of damage to the substation equipment if other protection elements of the soldering step-down substation are violated.

A device for additional overcurrent protection with voltage blocking is known, which operates with a delay time provided that the current increases and the voltage decreases to reserve the main transformer protections to trip when they fail to operate in the event of a short circuit on the transformer or on the mains supply.

The disadvantage of this device is the lack of separate power supplies for current circuits and operational circuits, which causes a failure in its action in the event of a malfunction of the common power circuits. The backup power supply of the backup protection requires considerable costs for its implementation, therefore, such protection cannot be used, which causes significant damage to the main equipment of the substation in case of failure of the backup transformer protection due to the failure of common circuits with the main protection of step-down transformers and the inability to provide long-distance redundancy.

The purpose of the invention is to simplify the device.

A device for backing up a failure of the current protection of a step-down transformer contains a current sensor 1, to the output of which a capacitor unit 2 of the power supply and a current relay 3 are connected, the output of the latter is connected through an AND 4 element

delays to the control input of the actuator 6, a voltage sensor 7, to the output of which are connected in series voltage relays 8,

Element 9 Prohibition and reset time relay 10, the output of the latter is connected to the second input of AND element 4, the control input of the element Prohibition 9 is connected to the output of the start element 11, The drawing shows a step-down transformer 12, switch 13 and signal element Fault 14. The device is working in the following way .

With a short circuit on the transformer 12, current is supplied from the current sensor 1 to a capacitor supply unit 2, the capacitors of which are charged. The operation of the short-circuit outflow of the current relay 3 does not directly close the discharge control circuit of the capacitor block to the actuator 6 in the trip circuit of the switch 13, since the And 4 element does not work during the time delay of the 10 element, which is controlled separately from the voltage relay 8 ;

5 voltage connected to the transformer 7. Simultaneously with the occurrence of a short-circuit current, the voltage decreases, causing, with a selected delay, the closure of the And 4 element in the discharge circuit of the capacitor block

0 2 to the executive body b trip switch 13 of the transformer 1.

For the selected delay time of element 10, it is possible to tune from the time of the protection of the transformer 5 and the charge of the capacitor block 2 from the current sensor 1 is achieved. Since the circuit operates by delay only in the capacitor charge circuit and current control without energy consumption, the time relay

0, return 10, therefore, the power of current sensor 1 is not required commensurate with the power of switch 13, it can be significantly less, which allows using overhead current transformers or magnetic current sensors instead of conventional high-voltage current transformers. This greatly reduces the cost of implementing the device for backup failure of the current protection of the transformer and ensures its independence of operation both in the measurement and operational circuits, since the backup device does not have common circuit elements with its own transformer protections.

5 The use of only common voltage control circuits does not reduce the reliability of the backup device, since when they fail, a signal circuit (14) arises and measures are taken to restore the power supply and operability of ap:

substation voltage monitoring equipment for proper operation of the own and redundant step-down protection transformers.

To ensure the operability of the backup device when the transformer 12 is turned on by the circuit breaker 13, in the event of a short-circuit, in the event of failure of its protection from the command to turn on the start-up element 11 through the element Prohibition 9, the time element 10 is removed, the contacts of which are closed with a delay together with the contacts of the current relay 3 through the element And 4 create a discharge circuit of the capacitor unit to the actuator 6 to turn off the circuit breaker 13 after enough energy is accumulated for such a backup protection action. For detuning from the non-simultaneous operation of the current relay 3 and the And 4 element, a delay element 5 was used, which also detects the effect of the backup protection against transients and inrush currents of magnetization when the transformer 12 is turned on.

0

Since the circuit elements of the device for redundant current protection of step-down transformers and the devices of the usual main and backup transformer protection are completely independent from each other both in the switching circuit and in the territorial position, therefore, the short-range backup device ensures its usefulness.

As a result of using an independent circuit of the delay action of the voltage blocking, it is necessary to operate the device to reserve the failure of the current protection of step-down transformers with the minimum cost of its execution due to the accumulation of the required energy from a low-current source and the expense of turning off the transformer in case of failure of its protection when Short circuit on it, regardless of their condition.

Claims (1)

The claims Device for back-up failure protection of a step-down transformer, comprising a current sensor intended for installation on the supply side, to the output of which a current relay input and an input of a capacitor power supply are connected, the output of which is connected to a power input, an actuator, a voltage sensor for connection to the busbars of the lower voltage, to the output of which is connected, the input of the voltage relay, the time relay for the return, the start element, the output of which is intended for connection to the switching circuit of the switch of the step-down transformer, since the fact that, in order to simplify, they are additionally introduced in series the included AND elements and the delay element, the FORBID element, for this the output of the current relay is connected to the first input of the And element, to the second input of which the output of the return time relay is connected, the input of which connected to the output of the voltage relay through the element BAN. the control input of which is connected to the output of the start element, the output of the delay element is connected to the control input of the actuator.