RU2573595C1 - Remote protection device for multiterminal power line - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: remote protection device for multiterminal power line comprises resistance measuring element, which output is connected to input of time-delaying element coupled to input of actuating element, which output serves as the device output. The device comprises additionally communication channel between substations at the line ends, signals transmitter transmitting through the communication channel, signals receiver receiving signals from the communication channel, two summators, at that the second input of the second summator is inverting, and current-voltage converter. Input of signals transmitter is coupled to current transformer at the opposite line end and output is coupled to input of the communication channel, which output is coupled to input of signals receiver connected by its output to the second output of the first summator, which first input is coupled to the line current transformer at the site of protection device installation, to which input of current-voltage converter is also connected and which output is coupled to the second output of the second summator, which first input is coupled to voltage transformer of busbar system at the site of protection device installation; output of the first summator is connected to current input of resistance measuring element and output of the second summator is coupled to voltage input of resistance measuring element.

EFFECT: improved sensitivity of the remote protection device.

1 dwg

Description

The present invention relates to the field of relay protection of elements of electrical systems and can be used as a backup stage of the distance protection of a power line with a branch, designed to act in case of short circuits behind the branch transformer.

Known current protection of power lines with branches [Chernobrovov N.V., Semenov V.A. Relay protection of energy systems. - M .: Energoatomizdat, 1998, p. 251], installed on one side of the line and reacting to currents in the place of installation of protection. These protections include a current relay, a time relay, and an actuator.

The disadvantage of current protection is the low sensitivity during short circuits behind branch transformers.

The more sensitive distance protection of power lines with branches is known and adopted as a prototype [Chernobrovov N.V., Semenov V.A. Relay protection of energy systems. - M: Energoatomizdat, 1998, p. 365], installed on one side of the line and responding to voltage and current in the place of installation of protection. This protection device consists of a measuring resistance element, the current input of which is connected to the current transformer at the place of installation of protection, and the voltage input is connected to the voltage transformer of the bus system at the place of installation of protection. The output of the resistance measuring organ is connected to the input of the time delaying organ, the output of which is connected to the input of the executive organ. The output of the executive body is the output of the device as a whole. In the event of a short circuit behind the transformer, the time-delayed device acts to trip the line circuit breaker, reserving the transformer protection.

The disadvantage of this protection device is the lack of sensitivity in some cases to short circuits behind the branch transformer. This is determined, first of all, by the fact that the measurement of resistance during a short circuit behind the branch transformer is significantly affected by the feed currents from the system of the opposite end of the line and the power flow along the line. In addition, this device must be detached from the resistance determined by the power flow along the line, which, as a rule, is much less than the load resistance of the branch transformer.

The technical problem to which the claimed invention is directed is to increase the efficiency of backup protection of power lines with branches.

The technical result of the invention is to increase the sensitivity of distance protection to short circuits behind the branch transformer and improve its detuning from load conditions.

The technical result is achieved by the fact that in the device for remote protection of a power line with a branch, on which two current transformers and a voltage transformer are installed, containing a measuring resistance element, the output of which is connected to the input of the time delay organ, the output of the time delay organ is connected to the input of the executive organ, and the output of the executive body is the output of the device, additionally introduced: the communication channel between the substations at the ends of the line, the signal transmission device on the channel a communication device, a signal receiving device from a communication channel, two adders, the second input of the second adder being inverting, and a current to voltage converter, wherein the input of the signal transmission device is connected to a current transformer of the opposite end of the line, and the output of the signal transmission device is connected to the input of the communication channel , the output of the communication channel is connected to the input of the signal receiving device, the output of which is connected to the second input of the first adder, the first input of the first adder is connected to the line current transformer in the place of new protection, to which the input of the current-to-voltage converter is also connected, the output of the current-to-voltage converter is connected to the second input of the second adder, the first input of which is connected to the voltage transformer of the bus system at the installation site, the output of the first adder is connected to the current input of the resistance measuring organ, and the output of the second adder is connected to the voltage input of the measuring resistance element.

In FIG. 1 shows a diagram of an electrical network and a structural diagram of the proposed device.

In FIG. 1 shows the following elements of the electrical network: 1 - protected line; 2 - branch from the line with branch transformer; 3 - power system adjacent to the substation in the place of installation of protection; 4 - power system adjacent to the opposite end of the line; 5 - line switch in the place of installation of protection; 6 - switch of the opposite end of the line; 7 - line current transformer in the place of installation of protection; 8 - current transformer of the opposite end of the line; 9 - voltage transformer of the spike system in the place of installation of protection.

The device comprises a communication channel 10 between the substations of both ends of the line, a signal transmission device 11, a signal receiving device 12, a first adder 13, a second adder 14, the second input of the second adder 14 being inverting, the current to voltage converter 15, the resistance measuring element 16, the organ time delay 17 and the executive body 18.

The input of the signal transmission device 11 is connected to a current transformer of the opposite end of line 8, and the output of the signal transmission device 11 is connected to the input of the communication channel 10. The output of the communication channel 10 is connected to the input of the signal receiving device 12, the output of which is connected to the second input of the first adder 13. K the line current transformer at the installation of protection 7 is connected to the first input of the first adder 13 and the input of the current to voltage converter 15. The output of the current to voltage converter 15 is connected to the second input of the second adder 14, the first input is The output of the first adder 13 is connected to the current input of the measuring resistance element 16, and the output of the second adder 14 is connected to the voltage input of the measuring resistance element 16. The output of the resistance measuring element 16 is connected to the input of the holding element time 17. The output of the body time delay connected to the input of the executive body 18, the output of which is the output of the device as a whole.

The protection device operates as follows.

At the first input of the first adder 13, current is supplied from the line current transformer at the place of installation of protection 7. At the second input of the same adder 13, through the signal receiving device 12, the communication channel 10 and the signal transmission device 11, current is supplied from the current transformer of the opposite end of the line 8. Therefore a current equal to the sum of currents at the ends of the protected line 1 is supplied to the current input of the measuring resistance element 16 from the output of the adder 13:

,

,

- ток на токовом входе измерительного органа сопротивления 16;Where $${\dot{I}}_{3\mathrm{BUT}U}$$

- current at the current input of the measuring organ of resistance 16;

- ток от трансформатора тока линии в месте установки защиты 7; $${\dot{I}}_{\mathrm{one}}$$

- current from the line current transformer in the place of installation of protection 7;

- ток от трансформатора тока противоположного конца линии 8. $${\dot{I}}_2$$

- current from the current transformer of the opposite end of line 8.

на сопротивлении части защищаемой линии 1. Это напряжение подается на второй вход второго сумматора 14, а на его первый вход подводится напряжение от трансформатора напряжения системы шин в месте установки защиты 9. Поэтому к входу напряжения измерительного органа сопротивления 16 подводится напряжение, равное:At the input of the current transformer to voltage 15, current is supplied from the line current transformer at the place of installation of protection 7. The transmission coefficient of the current converter to voltage 15 is taken to be equal to the resistance of the protected line 1 from the place of installation of protection to branch 2. Therefore, the voltage at the output of converter 15 will be equal to the voltage drop from current in the place of installation of protection $${\dot{I}}_{\mathrm{one}}$$

on the resistance of the part of the protected line 1. This voltage is supplied to the second input of the second adder 14, and voltage is supplied to the first input from the voltage transformer of the bus system in the place of installation of protection 9. Therefore, the voltage equal to:

,

,

where U _ZAShT - voltage at the second input of the measuring organ of resistance 16;

- напряжение на шинах в месте установки защиты; $${\dot{U}}_W$$

- voltage on the tires in the place of installation of protection;

- сопротивление части защищаемой линии 1 от места установки защиты до места ответвления 2. $${\underset{\_}{Z}}_{L\mathrm{one}}$$

- the resistance of the part of the protected line 1 from the place of installation of protection to the point of branch 2.

The measuring resistance element 16 of the proposed distance protection device responds to a resistance value equal to:

,

,

- замер сопротивления на зажимах защиты.Where $${\underset{\_}{Z}}_{3\mathrm{BUT}U}$$

- measurement of resistance at the protection terminals.

The measuring resistance element 16 compares the resistance measurement with the response characteristic and gives a signal to the input of the time delay 17 if the resistance measurement is in the protection response area. After a time equal to the response time, the time delay 17 sends a signal to the input of the executive body 18, the output of which is the output of the device. From the output of the executive body 18, a signal is sent that the protection has been activated with the action pa, opening the line circuit breaker at the place of installation of protection 5.

In case of a short circuit behind branch transformer 2, the measurement of the proposed protection device is equal to the resistance from the point of branch to the place of short circuit.

In the load mode, the sum of the currents at the ends of the protected line 1 is equal to the load current of the branch 2. Therefore, the resistance measurement in the load mode is equal to the load resistance of the branch 2.

With external short circuits outside the protected line 1, the sum of the currents at the ends of the line also turns out to be equal to the branch current 2. Therefore, the resistance measurement in these modes is also equal to the load resistance of branch 2.

To ensure the sensitivity of protection to damage behind the branch transformer 2, the response of the protection should cover only the sum of the resistances: the line resistance from the branch to the transformer and the resistance of branch transformer 2.

To ensure failure in the load mode and with external short circuits, the response of the protection is only detached from the load resistance of branch transformer 2.

To ensure selectivity in case of damage beyond branch transformer 2, the response time of the time delay organ 17 of the protection device is selected to be longer than the backup protection time of the branch transformer 2.

The technical result of the application of the proposed device is to ensure the sensitivity of the protection is significantly higher than the existing one, because in case of a short circuit on branch 2, the proposed device appears to be connected to a network with one-way power supply, where there is no roughening protection, the effect of recharge from the opposite system 4 and power flow along the protected line 1.

In addition, to ensure failure in load conditions, it is sufficient to ensure detuning only the branch transformer 2 from the load resistance, and not from the power flow along the protected line 1, which significantly improves the detuning from load conditions.

Claims (1)

A device for remote protection of a power line with a branch, on which two current transformers and a voltage transformer are installed, containing a resistance measuring organ, the output of which is connected to the input of the time delay organ, the output of the time delay organ is connected to the input of the executive organ, and the output of the executive organ is the output of the device , characterized in that the communication channel between the substations at the ends of the line, the signal transmission device on the communication channel, a signal receiving device from a communication channel, two adders, the second input of the second adder being inverting, and a current to voltage converter, wherein the input of the signal transmission device is connected to a current transformer of the opposite end of the line, and the output of the signal transmission device is connected to the input of the communication channel, output the communication channel is connected to the input of the signal receiving device, the output of which is connected to the second input of the first adder, the first input of the first adder is connected to the line current transformer in the place of installation you, to which the input of the current-to-voltage converter is also connected, the output of the current-to-voltage converter is connected to the second input of the second adder, the first input of which is connected to the voltage transformer of the bus system at the installation site, the output of the first adder is connected to the current input of the resistance measuring organ, and the output of the second adder is connected to the voltage input of the measuring resistance element.