JP2000023348A - Current differential relay system for protecting transmission line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To operate a relay system, even if a voltage cannot be detected at a load end by utilizing the abnormal detection signal of a voltage relay as a switcher drive fail-safe signal and at the same time utilizing a main signal and the fail-safe signal as the trip signal for driving the switcher at the load end. SOLUTION: A detection current I1 of a current transformer CT1 and the detection voltage of a transformer PT are inputted to a protective device 1 at a power supply end, and a detection current I2 of a current transformer CT2 is inputted to a protective device 2 of the power supply end. A transmission circuit 3 is laid between the protective devices 1 and 2. Then, not only a main signal but also a fail-safe signal, that is the failure detection signal of a shortage voltage relay are sent to a load end. As a result, even if the current transformer is not installed at the load end, a switcher CB2 can be made to trip based on a shortage voltage based on the voltage at the power supply end.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission line protection current differential relay system capable of omitting voltage detection of a load end device of a transmission line.

[0002]

2. Description of the Related Art A current differential relay system for protecting a transmission line includes a current differential relay (automatic device number 87), an undervoltage relay (automatic device number 27), and a signal transmission path as main components. It is used for section protection.

[0003] Current differential relays are provided at both ends (power supply end and load end) of a transmission line, and detect a failure inside the transmission line by ratio differential calculation.

[0004] Further, undervoltage relays are provided at both ends (power supply end, load end) of the transmission line, respectively, and detect an abnormal voltage at both ends of the transmission line for fail-safe (prevention of malfunction).

Accordingly, when viewed as a whole of the current differential relay system, the power supply terminal outputs a trip signal under the operation AND condition of the current differential relay and the undervoltage relay at the power supply terminal, and the load terminal outputs the trip signal. The trip signal is output under the operation AND condition of the undervoltage relay at the load end.

[0006]

However, at the load end of the transmission line, a voltage input PT (instrument transformer) may not be installed in some cases. Therefore, an undervoltage relay cannot be provided. There is a problem that the relay system in the form cannot be used, and the reliability of the system is reduced.

Accordingly, an object of the present invention is to realize a current differential relay system that can operate even in a transmission line having a power supply end and a load end even when voltage cannot be detected at the load end.

[0008]

Means for Solving the Problems (1) In the current differential relay system for transmission line protection of the present invention, a protection device including a current differential relay element, a voltage relay element and a transmission terminal device is installed at a power supply end. A protection device with a transmission terminal device is installed at the load end, a transmission line is laid between the protection device at the power supply end and the protection device at the load end, and the protection device at the power supply end is a current differential relay. Is used as the switch drive main signal M at the power supply end, the voltage relay abnormality detection signal is used as the switch drive failsafe signal FS, and the main signal M and the failsafe signal FS are transmitted through a transmission line. The load-end protection device uses the transmitted main signal and fail-safe signal as a trip signal for driving the switch at the load end. (Claim 1).

In the current differential relay system for protecting a transmission line according to the present invention, since the voltage at the load terminal and the voltage at the power supply terminal are generally substantially equal, even if the voltage abnormality at the load terminal is detected based on the voltage at the power supply terminal. On the assumption that the relay calculation error is negligibly small.

Therefore, the load-end protection device operates even if it does not have a voltage relay at its own end by using the sent main signal and fail-safe signal as a trip signal for driving the switch at the load end. It becomes possible.

It is needless to say that the detection target of the "current differential relay element" is determined according to the current phase to be protected. For example, in the case of ground fault protection, the zero-phase current is targeted, and in the case of short-circuit protection, the current of each phase is targeted. Similarly, the “voltage relay element” covers zero-phase voltage for ground fault protection and the voltage of each phase for short-circuit protection.

(2) When a transmission failure is detected at the power supply end or the load end, it is preferable to lock the drive of the switch (claim 2). This is to prevent malfunction due to transmission failure.

[0013]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a system diagram of a transmission line to which the present invention is applied. The power transmission line is provided between a substation serving as a power supply terminal and a substation serving as a load terminal. The power supply terminal includes a current transformer CT1 (hereinafter referred to as "current transformer") and a transformer (hereinafter referred to as "current transformer"). PT), and a current transformer CT2 is provided at the load end. CB1 and CB2 are switches installed at a power supply end and a load end, respectively.

The detection current I1 of the current transformer CT1 and the transformer PT
Is input to the protection device 1 at the power supply end, and the detection current I2 of the current transformer CT2 is input to the protection device 2 at the power supply end. A data transmission line 3 using an optical fiber is laid between the protection device 1 and the protection device 2.

FIG. 2 is a configuration diagram of common hardware of the protection device 1 or 2. The detection current of the current transformer CT and the detection voltage of the transformer PT are converted into digital signals by an A / D converter and sent to a data bus. The data bus includes a CPU that performs a relay operation, a transmission terminal device 5,
An input / output device I / O is connected and the transmission terminal device 5
Is connected to the transmission line 3, and the input / output device I / O is connected to the switch CB1 or the switch CB2.

FIG. 3 is a functional block diagram for explaining the operation of the protection device 1 at the power supply end. Current I detected by current transformer CT1
1 is input to the ratio differential relay 6, and the detected current I2 at the load end is also input to the ratio differential relay 6 through the transmission terminal device 5, where the ratio differential operation is performed.

The detected voltage V of the transformer PT is input to an undervoltage relay 7, where an undervoltage operation is performed.

The detection current I1 of the current transformer CT1 and the detection current I2 of the load terminal are input to the difference current detection circuit 4,
If the difference current is detected longer than a predetermined time (for example, 10 seconds), it is determined that the phases of the current detection at the power supply terminal and the current detection at the load terminal are out of phase, and the trip lock is performed through the OR circuit 10. Send a signal. On the other hand, when the transmission terminal device 5 detects a transmission failure, it also sends a trip lock signal through the OR circuit 10.

The abnormality detection output of the ratio differential relay 6 is AND
The main signal M is output from the AND circuit 8 on condition that there is no trip lock signal. Further, an abnormality detection signal of the undervoltage relay 7 is output as a fail-safe signal FS.

Both signals are supplied to an input / output device I / O through an AND circuit 9, from which a trip signal of the switch CB1 is output.

On the other hand, the main signal M and the fail-safe signal FS are input to the transmission terminal device 5, where they are converted into a predetermined signal format and transmitted to the protection device 2 at the load end through the transmission line 3. As described above, a feature of the present invention is that not only the main signal M but also the fail-safe signal FS which is an abnormality detection signal of the undervoltage relay 7 is sent to the load terminal.

FIG. 4 is a functional block diagram for explaining the operation of the protection device 2 at the load end. Current I detected by current transformer CT2
2 is input to the transmission terminal 5a, from which the transmission line 3
To the protection device 1 at the power supply end. The main signal M and the fail-safe signal FS sent from the protection device 1 at the power supply end through the transmission line 3 are connected to the AND circuit 11.
Is input to The output of the AND circuit 11 and the inverse of the transmission failure detection signal F of the transmission terminal device 5a are AND
The trip signal of the switch CB2 is input to the circuit 12 and output from the AND circuit 12 through the input / output device I / O.

With the circuit configuration as described above, an abnormality detection signal of the undervoltage relay 7 is sent as a fail-safe signal FS from the protection device 1 at the power supply end to the protection device 2 at the load end. Therefore, the trip operation of the switch CB2 can be performed based on the undervoltage based on the voltage of the power supply terminal without installing a transformer at the load terminal.

[0025]

As described above, according to the current differential relay system for transmission line protection of the present invention, in a transmission line having a power supply end and a load end, even if voltage cannot be detected at the load end, a malfunction may occur. No current differential relay system can be realized.

[Brief description of the drawings]

FIG. 1 is a system diagram of a transmission line to which the present invention is applied.

FIG. 2 is a configuration diagram of hardware of a protection device.

FIG. 3 is a functional block diagram illustrating an operation of the power supply end protection device 1.

FIG. 4 is a functional block diagram illustrating an operation of the protection device 2 at the load end.

[Explanation of symbols]

 CB switch CPU Central processing unit CT Current transformer for instrument I / O input / output device PT Transformer for instrument 1, Protection device 3 Transmission line 5, 5a Transmission terminal device 6 Ratio differential relay 7 Undervoltage relay

Claims (2)

[Claims] 1. A current differential relay system for protecting a transmission line for protecting a section between a power supply terminal having a transformer and a current transformer and a load terminal having a current transformer, wherein the power supply terminal has a current difference. A protection device equipped with an active relay element, a voltage relay element and a transmission terminal device is installed.A protection device equipped with a transmission terminal device is installed at the load end, and between the protection device at the power supply end and the protection device at the load end. The transmission line is laid, and the protection device at the power supply terminal uses the abnormality detection signal by the current differential relay as the main signal for driving the switch at the power supply terminal, and uses the abnormality detection signal of the voltage relay as the fail-safe signal for the switch drive. At the same time, the main signal and the fail-safe signal are transmitted to the protection device at the load terminal through the transmission line, and the protection device at the load terminal converts the transmitted main signal and the fail-safe signal into a switch at the load terminal. Transmission line protection current differential relay system characterized by utilizing as a trip signal dynamic. 2. The current differential relay system for protecting a transmission line according to claim 1, wherein when a transmission failure is detected at a power supply end or a load end, the switch drive is locked.