JPS6012849B2 - Computerized protection relay device for power system - Google Patents

Description

[Detailed description of the invention] The present invention relates to a computerized protection relay device for power systems.

With the development of electronics technology, electronic computers have been introduced into control systems in many industrial fields.

Figure 1 shows an example of the conceptual configuration of a generally considered computerized protection relay when a computer is used in the power system protection system.
The current is input to the computer input/output circuit PI/0 via the voltage transformer PT and the current transformer T.

In the example shown in the figure, PI/0 also includes an AD converter, and PT,
A digital quantity proportional to the output value of the CT is generated for each sample, and when the output of the judgment result of the computer CPU should trip the circuit breaker CB, it converts the signal into a predetermined trip signal. . CPU
is a unit that performs judgment and timing control, and consists of logic elements, comparison elements, memory elements, calculation elements, timing control elements, etc. Based on the flow program shown in FIG. 2, which is stored in the memory element in advance, It is configured such that signals such as data storage contents, storage locations, etc. are appropriately applied to each element along with a predetermined timing control signal, and the signals can be processed according to a fixed procedure. If you follow the flow shown in Figure 2 above, by devising the contents, you can create either a single input or multiple input relay. It is known that this can be applied to all IJ Rays.

However, there are many difficulties in applying this directly to protection relay systems for power systems.

This is because, unlike general control systems, protection relay systems need to detect extremely rare system faults at extremely high speed and with high reliability. For example, in order to ensure operational reliability, in conventional protection relay systems using dedicated hardware, the idea is to issue a corresponding trip command based on at least two or more principles of accident determination results in order to detect one type of accident. Although much research has been done on this idea, if this idea is directly applied to a computer-based protection IJ system, it will require a large number of computers, making it impractical.

In other words, as is well known, the conventional protective relay system using analog-only equipment has separate accident detection relays and main protection (accident section selection) relays, and protection is performed by the AND output of the relays. When converted into a device, two computers are required. Further, when each phase is protected, three phases are required, so a total of six computers are required. Furthermore, a method that provides protection for each short circuit and ground fault requires a total of four computers. In order to reduce this number,
A system configuration as shown in FIG. 3 (a system in which an accident detection relay and a main protection relay for the same protection object are housed in the same computer) has been proposed. More specifically, taking the protection of each phase as an example, three computers 1, 2, and 3 are used, and computer 1 has a built-in program FDA for failure detection of phase A and MA for main failure detection of phase A. Similarly, calculator 2
, 3 have similar programs FDB and M for phase B and phase C, respectively.
E, FDc, and Mc are built in, and a single computer calculates the double ratio using software, and outputs the judgment results based on the respective programs LIF, LIM, L2M, L3F, -
M is taken out through the AND gate. In addition, in a method in which protection is provided for short circuits and ground faults, FD and M for short circuits and FD and M for ground faults are stored in one computer. Although this method can reduce the number of computers to 1/2, there is a problem in terms of operational reliability, as described below.

This will be explained with reference to FIG. 7, assuming that the program FD^ is a task ■ and the program M^ is a task ■ in the computer 1 of FIG. 3. First, let P be the probability that the computer will become inoperable due to a computer failure, and let Q be the probability that the computer will malfunction, then the malfunction rate of the computer as a whole is (P + Q
), and when this malfunction occurs, the probability Qi that task (2) will give an output on the malfunction side and the probability (P) that task (2) will give an output on the non-operation side are each assumed to be 1/2 of (P+Q). Similarly, the probabilities P and Q for task @ are 1 of (P + Q).
/2. In Figure 7, (i) is a case where both tasks ■ and @ are inoperative, (ii) and (iii) are cases where one is inactive and the other is malfunctioning, and (iii) is a case where both are malfunctioning. Yes, each case (i~GW
The probability of occurrence of each is 1/4 of the fraudulent operation rate (P + Q).

In other words, in the system configuration shown in FIG. 3, an output on the malfunction side is obtained from the AND circuit 4 one out of every four times when the computer 1 malfunctions. In this way, the system configuration shown in FIG. 3 allows the number of computers to be reduced, but it cannot be said to be good in terms of reliability.

The present invention has been made in view of these circumstances, and it is an object of the present invention to provide a computerized protection relay device that overcomes the above-mentioned drawbacks by devising a method of arranging an accident detection program.

FIG. 4 shows a typical embodiment of the present invention, which is an example of application to a case where a fault in each phase of a three-phase one line is detected using three computers.

In the figure, computers 11, 12, and 13 each store a main accident detection program M and a failure detection program FDi of different phases.

For example, in the case of the computer 11, it has a built-in program for detecting failures in the A phase and a program for detecting main faults in the C phase. It operates to output to the outside through lines LIIF and LIIM. The computers 12 and 13 also output their respective judgment results through two signal lines in exactly the same manner. The external circuit has 3 AND gates 14,
15 and 16 are placed, and the AND gate 14 outputs the AND of LIIF and LIIM, so it can output "1" when a fault is detected in the a phase, and similarly, 15 is the b-phase, and 16 is the c
A “1” output can be generated when a phase fault is detected. If these outputs are introduced into a disconnection command generating section (not shown), a disconnection command can be issued to the corresponding circuit breaker based on these outputs. The feature of the method shown in FIG. 4 is that the target phases of the main accident detection program and the failure detection program stored in each computer are arranged differently. This method can reduce the probability of malfunction. For example, FIG. 4 AND circuit 1
Focusing on 4, the malfunction rate of FD^ and M^ is 3,000,000, respectively, but since each is stored in a different computer, the probability of obtaining a malfunction output in 14 is 2. With this invention, it is possible to achieve the same malfunction rate by 1/20% compared to the case where the same method used in the dedicated hardware of '11 was applied directly to the system configuration method of the computerized protection relay.
The required number of units is 2.

(For one line with three phases, six units are required when following the concept of the conventional system, but according to the present invention, only three units are required). ■ Compared to the software-based duplication method as shown in Fig. 3, the malfunction rate can be improved by about 2 degrees on the same hardware scale.

It has become possible to bring about significant improvements in terms of reliability and system economy.

FIG. 5 shows the operational flow in the embodiment of FIG. 4.

This figure is expressed using FIG. 2, and the eleventh means or step in this figure corresponds to the first means or step in FIG. The eleventh means to be noted is that sampling means and AD conversion means for system information regarding the a phase and the system information regarding the c phase should be included. Similarly, the 21st means or step corresponds to the second means or step in FIG. 2, and also includes a preprocessing function as well as the acquisition of data related to both the a-phase and c-phase data. . The 31st means or step is a c-phase main fault detection calculation section, and the output of this section is outputted to the outside via the signal line LIIM. The 32nd means or step indicates an a-phase failure detection calculation unit,
The output of this portion is output to the outside via the signal line LIIF. That is, the part shown in FIG. 5 and 7 is the computer 1 in FIG.
This corresponds to the task performed by 1. In exactly the same way, the parts indicated by 8 and 9 correspond to the tasks performed by the computers 12 and 13 in FIG. 4, respectively.

It will therefore be clear that the objects of the present invention can be achieved by providing the means shown at 10 in FIG. In the above description, the system information is limited to voltage and current, but it goes without saying that it may be any general electrical quantity such as impedance, phase, frequency, etc.

FIG. 6 shows an operation time chart in the embodiment of FIG. 4.

As explained above, according to the present invention, only 1/2 the number of computers is required compared to the case where the concept of secondary hardware is followed, and moreover, the software
Compared to the weighting method, the malfunction rate can be improved by about 2 times.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a conventional computerized protection relay, Figure 2 is its operation flow, and Figure 3 is a conventional system configuration method.
Fig. 4 is a system configuration diagram in one embodiment of the present invention, Fig. 5 is its operation flow, Fig. 6 is its operation time chart, and Fig. 7 shows errors and failures of each task when a computer has multiple tasks. It is an explanatory diagram of operation rate. 11, 12, 13... Computer, FD^, FDB, FDc
...Fault detection program for A, B, C phases, M^
'MB, Mc... Main fault detection program for A, B, C phases, 14, 15, 16... Asodo gate. ※1 evil momme 2 evil hate 3 mother Shigeru 4 mother Shigeru 5 prisoner *68 Shigeru 7 spots

Claims (1)

[Claims] 1. In a computerized protective relay device that uses multiple computers to detect faults in a three-phase power system and issue shutdown commands,
There are three computers, and each computer accommodates a main accident detection calculation program and a failure detection calculation program of different phases, and each computer performs the main accident detection calculation and failure detection calculation and outputs the respective results. A computer protection relay device for an electric power system, characterized in that a fault determination output for each phase is obtained by logically multiplying determination results for the same phase among the determination results made by each computer.