JPH11205996A - Breaker control and protective relay device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a breaker trip exactly and rapidly by preventing generation of impossible cut-off due to a large amount of DC components included in the accident current of a power system. SOLUTION: A protective relay device 14 takes in its own terminal current 12a and mated terminal current 15a periodically, and outputs computed results through a protective relay calculating module 21. When an accident occurs at a transmission line 10, a trip signal 21a (=1) is outputted. The current data 12a of its own terminal side is taken in a DC component detection module 22, and if the DC component 22a is a specified value K or higher, a signal 23a=1 is outputted to a logic circuit 24 from a logic circuit 23, so that the output of a trip signal 14a is locked. By a decrease in the DC component 22a to a specified value K or lower, the signal 23a=0 is obtained, and the trip signal 14a is outputted to a breaker 11. As a result, the breaker 11 is tripped at the initial zero cross point of the current 12a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective relay device for protecting a power system, and more particularly, to a protective relay system when an AC system includes a DC component.

[0002]

2. Description of the Related Art In an AC power system for power transmission and distribution, a protective relay device takes in various state quantities of a power system and calculates them to determine a system state. For example, when a ground fault of a transmission line is detected, a trip to a circuit breaker is performed. A command is output, and the circuit breaker is tripped at the zero crossing point of the fault current.

In recent years, with an increase in the power system, the DC component tends to increase together with the fault current. FIG. 4 shows a time chart of the fault current waveform and the trip output.
As in the In the case of (a), small transition by DC component, if the DC component time constant τ is about 50～100Ms, the fault current time T ₀ for outputting a trip command contains mostly DC component Because there was no, the circuit breaker could be tripped without any problem at the zero crossing point after the command. On the other hand, as in the case of (b), the DC component time constant τ of the fault current becomes 1 due to the increase of the DC component.
Becomes about 00～200Ms, the fault current of the trip command when T ₀ contains many DC component, because it takes several to several tens of cycles to reach the zero-crossing point, the arc is generated in the circuit breaker contacts in the meantime The problem that damage or inability to shut off occurs.

As a countermeasure against this, Japanese Patent Application Laid-Open No. 55-17955 discloses
In the number, the offset has a positive level and a negative level setting,
A method that detects when the DC deviation of the fault current waveform goes from positive to less than the negative level or from negative to more than the positive level, determines that a zero-cross point exists in the fault current, and then outputs a trip command. Has been proposed.

[0005]

However, in the above-mentioned prior art, the output of the trip command of the circuit breaker involves determination of a zero-crossing point which is originally unnecessary, so that the circuit configuration becomes complicated. Also, despite the fact that the fault current has no zero crossing point or almost no DC component and is in a trippable state, the zero crossing point is not detected because it does not exceed the upper / lower level of the offset, There is a possibility that the output of the trip command will be delayed by that amount and the accident will increase.

SUMMARY OF THE INVENTION In view of the problems of the prior art, an object of the present invention is to provide a circuit breaker capable of immediately tripping a circuit breaker at the first zero crossing point due to DC component attenuation when a fault component includes DC component. It is an object of the present invention to provide a control method of a switch and a protection relay device for the control method.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention detects a current from each transmission line of an AC power system and periodically performs a predetermined protection relay operation. In the control method for tripping the circuit breaker connected to the transmission line when it is determined that the DC current is detected from the fault current, the trip to the circuit breaker is performed until the DC value attenuates to a predetermined value that can be cut off. It is characterized by locking the command.

The predetermined value is set so that the lock can be released before the fault current having a DC deviation reaches the zero-cross point.

Further, the relay protection device of the present invention provides a predetermined protection relay by periodically taking in a state quantity of a system including a current of the transmission line from an AC power system connecting the transmission line via a circuit breaker. A device for performing a calculation and outputting a trip command to the circuit breaker when a failure is determined based on a calculation result, comprising: a DC detection means for detecting a DC component from the current; and outputting the trip command when the DC component exceeds a certain value. And a circuit breaker trip command lock means for releasing the lock when the DC component is below a certain value is provided. The DC detection means can be constituted by a low-pass filter.

[0010]

An embodiment of the present invention will be described below in detail with reference to the drawings. Note that the same reference numerals are given to the same elements throughout the drawings.

FIG. 2 shows a schematic configuration of a power system protection relay system to which the present invention is applied. The transmission line 10 is connected to the AC power system to be protected via the breaker 11 at the end (the breaker at the other end is not shown). Protection relay 14
Is calculated by taking in the CT current 12a at its own end,
When a failure of 0 is detected, a protection command 14a for tripping the circuit breaker 11 is output. The protection relay device 14 of the present embodiment includes:
Digital current difference with excellent selection performance, in which information 15a (current 13a in this case) of the other end of the transmission line 10 is introduced from the protection relay device 15 as well as the electrical condition of the installation point at its own end and comprehensively determined. It is configured as a dynamic protection relay.

FIG. 1 shows a configuration diagram of a digital protection relay device according to one embodiment. The protection relay device 14 takes in the current 12a at its own end and the current 15a at the other end, performs a predetermined protection relay calculation process, and outputs a trip signal 21a when the transmission line 10 is abnormal. A module 21 is provided.

Further, a direct current component detecting module 22 for detecting a direct current component from the current 12a, and a direct current component detection signal 23a which becomes 1 when the direct current component quantity 22a is equal to or more than a specified value K and becomes 0 when the direct current component quantity 22a is less than K. Logic circuit 23 and signal 23
A trip command lock circuit 25 comprising a logic circuit 24 for locking the trip command 14a to the circuit breaker 11 when a = 1 is provided. The logic circuit 23 treats the DC component state quantity 22a as an absolute value, and can deal with both positive and negative DC deviations of the current 12a.

Here, the prescribed value K is slightly larger than 0 and is set to a DC level at which occurrence of an arc in the circuit breaker due to a trip does not pose a problem. The DC component state quantity 22a is the specified value K.
If less than the signal 23a = 0, the trip signal 21
As a result, the trip command 14a is output to the circuit breaker 11.

FIG. 3 shows an outline of a DC component detection module. The DC component detection module 22 includes addition filters 32, 3
3 and a low-pass filter that passes only the DC component. The low-pass filter for detecting a DC component is described in, for example, "Digital Relay (Electric Joint Research, Vol. 41, No. 4, published in 1986, 41-42).
Page) ".

FIG. 5 shows a time chart of circuit breaker control by the protection relay device of the present embodiment. An example will be described in which the fault current has a DC deviation as shown in FIG. Protection relay computation module 21 when determining the establishment of trip condition from a fault current, outputting a trip signal 21a at the timing of T _0. On the other hand, the DC component detection module 22 detects a DC component from the fault current, and outputs a DC component detection signal 23a = 1 while the value is equal to or larger than the threshold value K.
The output of 4a is locked.

The DC component detection by T ₁ in which the DC component is less than the attenuation by K of fault current, signal 23a is zero. As a result,
The lock is released, the trip command 14a is output, and the tripping of the circuit breaker 11 is realized at the zero cross point T _z1 immediately after that. If the fault current does not include a DC component, T
_At the timing of ₀ , the conventional high-speed trip is performed.

According to the present embodiment, the trip command of the circuit breaker is locked while the fault current includes a large amount of DC component, and the lock is released immediately before the DC component is attenuated and the circuit is ready to be cut off. The circuit breaker is not tripped due to the occurrence of an arc, and the circuit breaker is immediately tripped at the first zero crossing point due to the DC attenuation. In addition, since a general-purpose low-pass filter can be added to the conventional protection relay device to easily configure the protection relay device, application to an existing relay device is also easy.

[0019]

According to the present invention, the trip command of the circuit breaker is locked until the DC component in the fault current of the system is attenuated to a predetermined value (greater than 0) that can be cut off. Can prevent the occurrence of an arc, and can avoid damage to the circuit breaker. Further, a reliable protective relay device that can be reliably removed at the first zero-cross point due to the attenuation of the DC component can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a protection relay device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a protection relay system for a power system to which the present invention is applied.

FIG. 3 is a block diagram showing a configuration of a DC component detection module according to one embodiment.

FIG. 4 is a time chart for explaining a relationship between a conventional fault current and a trip output.

FIG. 5 is a time chart illustrating a control operation of the circuit breaker according to one embodiment of the present invention.

[Explanation of symbols]

10 ... transmission line, 11 ... breaker, 12, 13 ... CT, 1
4, 15 protection relay device, 21 protection relay operation module, 22 DC component detection module, 23, 24 logic circuit, 25 trip signal lock circuit, 32, 33
Additive filter.

Claims (4)

[Claims] 1. A method for detecting a current from each transmission line of an AC power system, periodically performing a predetermined protection relay operation, and disconnecting the transmission line when the operation result indicates that the current is a fault current. A control method for tripping a circuit breaker, wherein a DC component is detected from the fault current, and a trip command to the circuit breaker is locked until the DC value attenuates to a predetermined value that can be cut off. Method. 2. The control method for a circuit breaker according to claim 1, wherein the predetermined value is set so that the lock can be released before a fault current having a DC deviation reaches a zero-cross point. . 3. A predetermined protection relay operation is performed by periodically taking a state quantity of a system including a current of the transmission line from an AC power system connecting the transmission line via a circuit breaker, and performing a predetermined protection relay operation, and determining a failure based on the operation result. A protection relay that outputs a trip command to the circuit breaker at the time, DC detection means for detecting a DC component from the current, and locks the output of the trip command when the DC component exceeds a certain value; A protection relay device comprising a circuit breaker trip command locking means for releasing the lock when the minute is equal to or less than a predetermined value. 4. The protection relay device according to claim 3, wherein the DC detection unit includes a low-pass filter.