JPH0452048B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a protective relay device that controls the opening of a circuit breaker based on the differential principle based on the current at each terminal of a power transmission line, and also performs reclosing. The present invention relates to a protective relay device that is capable of detecting a cutoff phase with high precision during reclosing.

[Background of the invention]

Conventionally, in the re-closing method of power transmission line protection devices, in order to detect and confirm the cut-off phase, a method has been used to detect unconditional power flow or no-voltage conditions on the line. A method is adopted in which the signals are transmitted to each end of the power transmission line protection section using some kind of transmission means, and the cutoff phase detection conditions at each end are detected and confirmed. This method is particularly advantageous in multi-terminal systems where the phase cutoff cannot be reliably detected based on the power flow conditions at each end, and is often used in current differential protection relay systems for multi-terminal systems. .

An example is shown in FIG. In order to simplify the explanation, the example in FIG. 1 shows an example in which a two-terminal power transmission line is applied. The signals are transmitted to each other through the path T2, and each end performs confirmation detection of a shutoff phase such as re-closing. Although the reclosing circuit is not shown in Figure 1, the general idea behind this is that, as is already well known, most accidents on power transmission lines are recoverable; After opening the circuit breaker, wait for an appropriate amount of time and then try closing the circuit breaker again. This reclosing operation is not carried out unconditionally, but is subject to conditions such as the absence of line current, the line's no-voltage time, or the connection of two or more phases of the transmission line. This will be implemented only when this is true. Regarding the connection of power transmission lines, for example, confirm that there is a connection of two or more phases in total for two lines. Specifically, the open/close states of the pallet switches 52-1b to 52-3b of the circuit breakers at each terminal are collected using the transmission device D-2, and it is confirmed that the pallet switches of the circuit breakers of the same phase at each terminal are both open. It is determined that this phase is blocked. One of the conditions for allowing reclosing is that the terminals are interconnected in two or more phases. Further, the current signals of each phase are introduced into the protective relays RY1 to RY3 through the current transformer CT, and mutually transmitted through the transmission device D-1 and the transmission line T1, thereby detecting internal and external faults. These systems are used to protect a three-terminal system, as shown in the example of FIG. 2, or a multi-terminal system.

It should be noted that malfunction or malfunction of these cutoff phase detection functions may lead to erroneous addition of a different system at the time of re-closing, so there is a strong desire for higher reliability.

To explain this high reliability in more detail, the pallet switch 52 of the circuit breaker of the mating terminal
-1b to 52-3b open/closed status is transmission device D-2
Since the signal is obtained via a transmission channel, there is a risk that the signal may be received differently from the original signal due to transmission abnormalities. For example, suppose that an accident occurs in the a-phase and a command to open the a-phase circuit breaker is issued by the protective relay at each terminal, but the circuit breaker at the other end is not opened.
In this case, if the contact signal is received indicating that the circuit breaker has opened even though it was not originally opened, the reclose circuit waits for the no-voltage time to elapse and issues a reclose command, and as a result, the accident continues. The circuit will be reclosed, resulting in an extremely large impact on the power system. Not limited to this case, various problems can be expected due to the contact signal not being sent correctly.

[Purpose of the invention]

In view of the above, it is an object of the present invention to provide a protective relay device that can be expected to perform a highly reliable reclosing operation.

[Summary of the invention]

In other words, Fig. 3 shows a current differential protection relay that can realize ratio differential characteristics with scalar sum suppression (Fig. 1).
RY) for one phase (example of A terminal for three-terminal system in Figure 2).
I _A and the other end current I _B obtained through the transmission device,
Introducing I _C from input terminals 1 to 3, as the operating amount,
The vector sum of the currents at each end |ΣI| is derived by the vector synthesis circuit 4 as shown in |ΣI|=|I _A +I _B +I _C |...(1), and the scalar sum of the currents at each end is calculated as the suppression amount. Σ｜I｜
is derived by the scalar sum synthesis circuit 5 as shown in Σ|I|=|I _A |+|I _B |+|I _C |...(2), and |ΣI|−kΣ|I|I _S ... The operation determination circuit 6 makes a determination based on the operation determination formula (3), and outputs the result from the output terminal 7. still,
In equation (3), k represents a suppression coefficient and _IS represents a sensitivity constant.

_Now , focusing on the scalar sum current Σ | _{I C} is zero, and Σ|I|=0...(4). However, as shown in Fig. 5, when the A-terminal circuit breaker is off and there is connection at the B and C terminals, I _B = -I _C and Σ|I|≠0 ...(5). The present invention focuses on the above scalar sum condition, and when all ends are blocked, Σ|I|=0
This condition is used together with the circuit breaker shutoff signal sent from the other party to improve the reliability of confirmation and detection of the all-end shutoff condition used for re-closing conditions, etc. A mismatch between the conditions and the transmitted circuit breaker cutoff signal is detected to easily detect circuit abnormalities.

[Embodiments of the invention]

FIG. 6 shows a specific example according to the present invention. however,
In this figure, only the a-phase device installed at the A terminal is described; in reality, this A-terminal device includes three phases including other b and c phase circuits with the same configuration as the circuit in Figure 6. is set up. Also, A is connected to the B and C terminals.
A device with the same configuration as the terminal device is installed, but
In order to understand the present invention, it is sufficient to understand the operation of the A terminal and the a phase, so the description is omitted. The part consisting of circuits 4, 5, and 6 is the protective relay RY shown in Fig. 3, and the circuits 8, D-
2, 10, 11, 14, 15, and 12 constitute a part of the reclosing circuit.

First, the protective relay RY consisting of circuits 4, 5, and 6 has the same configuration as the circuit in Figure 3,
The circuit for the a phase is shown. The function of this circuit has already been explained in FIG. 3, so a description thereof will be omitted. Next, the reclosing circuit side circuit (circuit 8, D-2, 10, 11, 14, 1
5 and 12), only the circuit portion for checking the disconnection status of each terminal of the a-phase, for example, is described here as part of the original function of the reclosing circuit. First of all, D-2 is a signal transmission device, and the open/closed state of the B terminal breaker detected at the B terminal of the power transmission line is obtained via a signal transmission path to the terminal B of D-2. Similarly, the open/close state of the C terminal breaker detected at the C terminal of the power transmission line is obtained at the terminal C via a signal transmission path.

The signals obtained at terminals B and C are, for example, guaranteed to be 1 when the circuit breaker is opened and 0 when the circuit breaker is closed. On the other hand, the level determination circuit 8 inputs the output of the scalar sum deriving circuit 5 of the ratio differential protection relay RY, and is guaranteed to give an output of 1 when the scalar sum is lower than a predetermined value. Here, the predetermined value is a level set for the purpose of confirming that the scalar sum is approximately zero, and therefore, the state where output 1 is given means that each terminal connected to this phase This means that the detected current is almost zero. In this state, it can be inferred that all the circuit breakers at each terminal of this phase are open.

In the present invention, the AND circuit 10 determines whether the output of the level determination circuit 8 and the output of the terminal B of the signal transmission device D-2 match, and the output of the level determination circuit 8 and the output of the terminal C of the signal transmission device D-2 are determined by the AND circuit 10. By determining the coincidence with the AND circuit 11, it is possible to improve the reliability when obtaining the open/closed state of the other end circuit breaker via the signal transmission device D-2. In other words, reliability can be improved by adopting different method duplication in which the open/close states of the mating terminal circuit breakers are obtained using different methods and the results are matched.

Although the opening/closing state of the a-phase circuit breaker at terminal A can be obtained directly from the contacts of the pallet switch, a duplex method with the output of the level determination circuit 8 can be adopted as appropriate. The contact 52-1b of the palette switch and the outputs of the AND circuits 10 and 11 are matched by the AND circuit 12, and based on this output, it is determined that all terminals of the a-phase have been cut off. This judgment is similarly carried out for the b and c phases, and it is confirmed that two or more circuits are connected, which is one of the conditions for allowing re-closing. Note that an abnormality in the signal transmission circuit or the like can also be detected using the outputs obtained at the terminals 16 and 17 of the mismatch detection circuits 14 and 15.

〔Effect of the invention〕

According to the present invention, the reliability of cutoff phase detection can be improved with a simple circuit configuration, and erroneous re-closing can be prevented.
The abnormality can be easily detected.

[Brief explanation of the drawing]

Figure 1 is a system diagram of a conventional cutoff phase detection circuit;
The figure is a system diagram of a three-terminal power transmission line, Figure 3 is a block diagram of a current differential protection system with scalar sum suppression, Figure 4 is a system diagram when all ends are cut off at the same time, and Figure 5 is a system diagram of a current differential protection system with scalar sum suppression. FIG. 6 is a block diagram showing a specific embodiment of the cutoff phase detection method according to the present invention. 1, 2, 3...Input terminal, 4...Vector sum synthesis circuit, 5...Scalar sum synthesis circuit, 6...Operation determination circuit, 7, 12, 13, 16, 17...Output terminal, 8... Level determination circuit, 9...Transmission device, 1
0, 11... AND circuit, 14, 15... Mismatch detection circuit.

Claims (1)

[Claims] 1. A system that inputs the detected current of each terminal of a power transmission line, detects an accident on the power transmission line based on the current differential principle, opens the circuit breaker of the terminal, and then recloses the circuit breaker. In the protective relay device, the operating amount is the vector sum of the currents at each terminal of the transmission line, and
A current differential protection relay that detects a fault on a transmission line based on the current differential principle in which the scalar sum of each terminal current is the suppression amount and issues a break command to the circuit breaker of the terminal; A reclosing circuit that issues a reclosing command to the circuit breaker at the terminal after a shutdown command, a signal transmission means that transmits the open/closed state of the circuit breaker at the other terminal of the power transmission line to its own terminal, and information obtained from the signal transmission means A determination circuit that determines that the open/closed state of the circuit breaker at the other terminal indicates an open state and that the scalar sum of the current differential protection relay is approximately zero, and a determination circuit that determines that the open/closed state of the circuit breaker at the own terminal is determined from the output of the determination circuit and the open/closed state of the circuit breaker at the own terminal. A protective relay device consisting of a detection circuit that detects that the circuit breakers of all transmission line terminals of this phase are opened, and a re-closing circuit that includes a re-closing circuit.