JP2002051447A - Digital type protection relay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To assure a short period of time for updating a program by removing a memory in order to update the program which has been once stored in an existing digital type protection relay. SOLUTION: The digital type protection relay comprises an input circuit 2, including an analog/digital converter for converting an input current/voltage of a power system into a digital value after sampling hold of a value with the prescribed sampling frequency, an arithmetic processing circuit 3 for executing the prescribed arithmetic processings to the digital signal outputted from this input circuit 2 using an operation decision program; and a memory device 4 for storing various programs, including the operation decision program and an output circuit 5 for receiving the arithmetic processings result from the arithmetic processing circuit 3 and then outputting the result to external circuits. Therefore, the memory device 4 can store, in addition to the operation judging program, a monitor program for deciding the true or false state of the operation program, with sum check and the operation judgment is stopped, when the monitor program detects a fault in the operation decision program.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital protection relay for detecting an accident in a power system, and more particularly to a digital protection relay provided with a monitoring program for monitoring an operation determination program.

[0002]

2. Description of the Related Art A conventional digital protection relay is a fourteenth type.
As shown in the figure, an input circuit 2 converts an input current and a voltage to a predetermined level, and then converts the input current and voltage to a digital value and outputs the digital value.
An arithmetic processing circuit 3 for inputting the digital signal and performing predetermined arithmetic processing; a memory 11 for storing an operation determination program 4-1; and an output circuit 5 for receiving the determination of the arithmetic processing circuit 3 and outputting to the outside A serial input / output circuit (hereinafter referred to as an SIO circuit) 6 for serially transmitting and receiving data to and from the outside of the relay, and a serial interface 7 for connecting the SIO circuit 6 to an external terminal device 8 outside the relay. And was composed of

In the conventional digital protection relay, since the program area cannot be divided and partially written, in order to rewrite the program once written, the memory device 11 storing the operation determination program must be removed. Did not.

[0004]

As described above, in the conventional digital protection relay, the program once written cannot be easily rewritten, and the memory must be removed when changing the program. Since it did not exist, it took time to rewrite the program, which was inconvenient.

According to the present invention, a monitoring program for monitoring programs is provided in addition to the operation determining program, and a memory for storing these programs is divided into separate program areas so that a part thereof can be rewritten. It is an object of the present invention to provide a digital protection relay capable of easily rewriting a program without removing the protection relay.

[0006]

In order to achieve the above object, an invention according to claim 1 is an input converter for converting an input current / voltage into a size suitable for processing by a protective relay and a predetermined voltage. An input circuit including an analog-to-digital converter that converts an analog value sampled and held at a sampling frequency into a digital value, and a digital signal output from the input circuit is converted into a predetermined value using an operation determination program necessary for determining the operation of the relay. A digital protection relay comprising: an arithmetic processing circuit for performing arithmetic processing; a memory device for storing various programs including the operation determination program; and an output circuit for receiving an arithmetic processing result of the arithmetic processing circuit and outputting the result to the outside. In the memory device, in addition to the operation determination program, a monitoring program for monitoring the operation determination program Stores the grams, if this monitoring program detects the abnormality of the operation determination program, in which so as to stop the operation determination.

According to a second aspect of the present invention, there is provided a serial input / output circuit for serially transmitting and receiving data to and from the outside of a relay,
A serial interface for connecting the output circuit to an external terminal device outside the relay is provided, and when the operation determination program receives data transmitted from the external terminal device, the operation determination program is rewritten instead of stopping the operation determination. It is like that.

According to a third aspect of the present invention, a program format indicating the name of the operation determination program as a rewrite history of the operation determination program, a unique value indicating the operation determination program, and a rewrite date and time are stored in the operation determination program. It is intended to be saved.

According to a fourth aspect of the present invention, when the operation determination program is rewritten from the external terminal device, a program format of an existing operation determination program is input from the external terminal device, and the input data is operated in advance. The operation determination program is rewritten only when the program format matches the program format written in the determination program.

According to a fifth aspect of the present invention, when rewriting the operation determination program from the external terminal device, the rewriting of the operation determination program is permitted by inputting a document number related to the operation determination program,
The document number once input is read from the external terminal device.

According to a sixth aspect of the present invention, when the operation determination program is rewritten from the external terminal device, an existing operation determination program is transferred to the external terminal device before the rewritten program is transferred from the external terminal device. The program is transferred to a storage medium, the existing program is compared with the transferred program, and the operation determination program is rewritten only when there is no difference in the result.

According to a seventh aspect of the present invention, when the external terminal device rewrites the operation determination program, the external terminal device performs a virus check before transferring the rewritten program from the external terminal device, The virus check result is transmitted from the terminal device to the operation determination program, the operation determination program determines whether the virus check result is normal or abnormal, and rewrites the operation determination program only when the result is normal. It was done.

The invention according to claim 8 is a means for receiving rewriting data of an operation determination program from an external terminal device connected to a relay, and determining whether writing of data in the operation determination program is permitted. By turning off the power of the digital protection relay, the operation determination program reads the hardware lock signal, determines whether or not data rewriting is permitted, and operates only when rewriting is permitted. The judgment program is rewritten.

According to a ninth aspect of the present invention, the rewriting data of the operation determination program is received from an external terminal device connected to the relay, and the state of the setting switch of the digital protection relay is read. It is determined whether or not the operation is to be performed, and the operation determination program is rewritten only when rewriting is permitted.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) (Claim 1)
FIG. 1 is a block diagram of a digital protection relay according to the first embodiment of the present invention. In the figure, 1
Is a digital protection relay. The code after 2 is
The hardware of the protection relay 1 is shown divided into blocks for each function. Reference numeral 2 denotes an input converter for converting input current and voltage to a size suitable for processing by the protection relay, and a digital converter for converting the sampled and held analog value into a digital value. This is an input circuit including an analog-to-digital converter that converts the value into a value.

Reference numeral 3 denotes an arithmetic processing circuit for performing predetermined arithmetic processing required for determining the operation of the relay using the operation determination program 4-1 on the digital signal output from the input circuit 2. Reference numeral 5 denotes an output circuit which receives the result of the arithmetic processing by the arithmetic processing circuit 3 and outputs the result to the outside.

The operation determining program 4-1 usually includes several types of unit relays or composite relays (for example, an overcurrent relay,
The operation determination program for each of the overvoltage relay, the distance relay, and the current differential relay) is included, and is stored in an independent memory that can be individually separated. Further, a monitoring program 4-2 for monitoring the operation determining program 4-1 is also stored in a memory such as a ROM which is independent from other programs.

This monitoring program 4-2 is disclosed in
According to the “checksum” known in JP-A-141264,
Determines whether the program is true or false. That is, the monitoring program adds the unique checksum value A added at the time of writing the operation determination program for the first time to the data of the operation determination program stored in the address of the memory area for all areas. If the value (the calculated sum value B) matches (A = B), it is determined to be normal, and if it does not match (A ≠ B), it is determined to be abnormal. In the present invention, the entire memory storing the above-described operation determination program 4-1 and the entire memory storing the monitoring program 4-2 are referred to as a memory device 4.

FIG. 2 is a flowchart for explaining the present embodiment. In FIG. 2, in step S1, it is determined whether or not a sum value has been added for all areas of the data relating to the operation determination program stored at the address of the memory area. If all the sum values have not been added in step S1 (NO), data is added and the address is updated in step S3.

If all the sum values have been added in step S1 (YES), the sum value B calculated or added in step S2 and the sum value added when the program is first written first (checksum value A). ) Match. If both sum values match in step S2 (YES), the process proceeds to step S4 to continue the operation processing of the operation determination program, which is a normal operation.

If the sum values do not match (NO),
In step S5, the arithmetic processing is stopped, and in step S1
Return to The reason why the sum values do not match is that the data in the area storing the program is destroyed due to an element error in the memory (ROM), or the area of the checksum (also referred to as a unique sum value) becomes abnormal. It is possible that If the protection operation is performed in such a state, a malfunction or a malfunction may occur, and the operation is stopped because there is no reliability.

As described above, according to the present embodiment, the abnormality of the operation determination program 4-1 can be detected by the monitoring program 4-2, and the reliability of the memory device 4 can be improved and the digital protection can be improved. The reliability of the relay can be improved.

(Second Embodiment) FIG. 3 is a block diagram showing a digital protection relay according to a second embodiment of the present invention. In the figure, FIG.
The same parts as those described above are denoted by the same reference numerals, and redundant description will be omitted. In the present embodiment, the arithmetic processing circuit 3 is configured to output the arithmetic result to the outside by the output circuit 5 and to transmit and receive data to and from the external terminal device 8 via the SIO circuit 6 and the serial interface 7.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG. First, in step S1, it is determined whether or not a sum value has been added for all areas of the data relating to the operation determination program stored at the address of the memory area. If all the sum values have not been added in step S1 (NO), step S1 is executed.
In step 3, the data is added and the address is updated.

If all have been added in step S1, (YE
S), in the next step S6, it is determined whether or not a command to rewrite the program from the external terminal device 8 by the operator or the like is received. If a program rewrite command is received in step S6, a sum value unique to the operation determination program 4-1 is deleted in step S7.

If the unique sum value is deleted, in the next step S2, the added or calculated sum value B is compared with the unique sum value (check sum value A) added when the program is first written. If they do not agree
(NO), the operation determination program is rewritten in step S8.

If the program rewrite command is not received in step S6 (NO), the process passes step S7 and shifts to the next step S2, where the sum, that is, the calculated sum value B and the program are stored first. If the unique sum value (check sum value A) added at the time of first writing matches (YES), the operation processing of the operation determination program, which is a normal operation, is continued in step S4.

As described above, according to the present embodiment, when a program rewriting command is received from the outside, the program for maintaining the quality can be maintained without removing the memory storing the operation determination program for the digital protection relay. Can be rewritten, and the efficiency of design / test time can be improved as well as the time required for rewriting the program.

(Third Embodiment) (Corresponding to Claim 3) In the case of this embodiment, since the block diagram of the hardware is the same as that of FIG. 3 of the second embodiment, the description of the hardware block configuration will be described. Are omitted, and the operation will be described with reference to the flowchart of FIG.

First, in step S1, it is determined whether or not a sum value has been added to all areas of the data relating to the operation determination program stored at the address of the memory area. If all the sum values have not been added in step S1 (NO), data is added and the address is updated in step S3.

In step S1, if all have been added (YE
S), In step S6, it is determined whether or not a command to rewrite the program has been received from the external terminal device 8 by the operator. If a program rewrite command has been received (YES), the sum value inherent in the operation determination program is deleted in the next step S7.

When the sum value is erased, the sum value B calculated in the next step S2 does not coincide with the unique sum value (check sum value A) added when the program is first written for the first time. NO), proceeding to step S9,
Here, the format, the sum value, and the date and time of the program to be updated are rewritten and stored in the memory, and then the operation determination program is rewritten in step S8.

If the program rewrite command has not been received in step S6 (NO), the sum value B added or calculated in the next step S2 and the program are first stored in the same manner as in the above-described embodiment. Then, it is determined whether or not the unique sum value (check sum value A) added at the time of writing to the memory matches, and if the sum value matches, the arithmetic processing as a normal operation is continued (step S4).

According to the present embodiment, the program can be rewritten while maintaining the quality without removing the memory storing the operation determination program of the digital protection relay, and the time required for rewriting the program can be reduced. Naturally, the efficiency of design / test time can be improved, the change history of the program can be reliably managed, and maintenance is facilitated.

(Fourth Embodiment) (Corresponding to Claim 4) Also in the case of this embodiment, since the block diagram of the hardware is the same as that of FIG. 3 of the second embodiment, the hardware block The description will be omitted, and the operation will be described with reference to the flowchart of FIG.

FIG. 6 is a flowchart in the embodiment of the present invention. First, in step S1, it is determined whether or not a sum value has been added for all areas of the data relating to the operation determination program stored at the address of the memory area. If all the sum values have not been added in step S1 (NO), data is added and the address is updated in step S3. Only when the operator receives a command to rewrite the program from the external terminal device 8 in step S6 from the external terminal device 8 and the program matches the existing program format (step S10) under the condition that all the additions are made in step S1. Delete the sum value inherent in the operation determination program (step S
7) Yes.

When the sum value is deleted in step S7,
Naturally, the sum value B calculated in the next step S2 does not match the unique sum value (check sum value A) added when the program is first written first (NO). In this case, the operation determination program is rewritten. (Step S
8).

If the received program does not match the format of the original program in step S10, and if the sum value matches in step S2, the arithmetic processing which is a normal operation is continued (step S4).

According to the present embodiment, the program can be rewritten while maintaining the quality without removing the memory storing the operation determination program of the digital protection relay, and the time required for rewriting the program can be reduced. Naturally, the efficiency of design / test time can be improved. Also, when writing the operation determination program, the program can be written after confirming that the program format previously written in the area of the operation determination program matches the program format input from the external terminal device. In addition, it is possible to prevent human errors such as writing an unintended program by mistake.

(Fifth Embodiment) (corresponding to claim 5) Also in the case of this embodiment, since the block diagram of the hardware is the same as that of FIG. 3 of the second embodiment, the hardware block The description will be omitted, and the operation will be described with reference to the flowchart in FIG.

FIG. 7 is a flowchart according to the embodiment of the present invention. In step S1, it is determined whether or not a sum value has been added for all areas of the data relating to the operation determination program stored at the address of the memory area. If all the sum values have not been added in step S1 (NO), data is added and the address is updated in step S3.

If all have been added in step S1, (YE
S), the external terminal device 8 by the operator in step S6
It is determined whether or not a command for rewriting the program has been received from (YES). If it has been received (YES), it is determined in step S11 whether or not a document related to the operation determination program has been received.

If it has been received (YES), in step S7 the sum value inherent in the operation determination program is erased, and the sum value calculated in step S2 matches the checksum value written in the program area. It is determined whether or not to do.

Since the sum value is erased, the sum value B calculated in the next step S2 does not coincide with the unique sum value (check sum value A) added when the program is first written (NO). After the document number is stored in the memory in step S17, the operation determination program is rewritten (step S8). If the sum values match, the arithmetic processing, which is a normal operation, is continued (step S
4) Yes.

According to the present embodiment, the program can be rewritten while maintaining the quality without removing the memory B storing the operation determination program of the digital protection relay, and the time required for rewriting the program can be reduced. In addition, the efficiency of design / test time can be improved.

Further, since the document number relating to the program of the operation determination program is known, it can be used at the time of design / test, and the required document number can be surely grasped at the time of on-site work.

(Sixth Embodiment) (corresponding to claim 6) In the case of this embodiment, the block diagram of the hardware is the same as that of FIG. 3 of the second embodiment. The description will be omitted, and the operation will be described with reference to the flowchart in FIG.

FIG. 8 is a flowchart of the present embodiment. In step S1, it is determined whether or not a sum value has been added for all areas of the data relating to the operation determination program stored at the address of the memory area.
If all the sum values have not been added in step S1 (NO), data is added and the address is updated in step S3.

When a program rewriting command is received from the external terminal device 8 by the operator in step S6, the existing operation determination program is stored in the storage medium of the external terminal device 8 in step S12. When the operation check program and the compare check are executed and the operation is completed normally, the sum value inherent to the operation judgment program is deleted in the next step S7.

When the unique sum value is deleted, the sum value B calculated in the next step S2 does not match the unique sum value (check sum value A) added when the program is first written for the first time. So (NO), the next step S8
Rewrites the operation determination program. If the sum values match, the arithmetic processing, which is a normal operation, is continued (step S
4) Yes.

According to the present embodiment, the program can be rewritten while maintaining the quality without removing the memory storing the operation determination program of the digital protection relay, and the time required for rewriting the program can be reduced. Naturally, the efficiency of design / test time can be improved. Also, by transferring the operation determination program written in the memory to the storage medium of the external terminal device and comparing the transferred program with the program written in the memory, it can be confirmed that the transferred program has been correctly transferred. You can check.

Therefore, it is possible to save the existing program in the storage medium before rewriting the operation determination program, and to restore the original program even after rewriting the operation determination program. It is possible to repair.

(Seventh Embodiment) (Corresponding to claim 7) Also in the case of this embodiment, since the block diagram of the hardware is the same as that of FIG. 3 of the second embodiment, the hardware block The description will be omitted, and the operation will be described with reference to the flowchart in FIG.

FIG. 9 is a flowchart in the embodiment of the present invention. First, in step S1, it is determined whether or not a sum value has been added for all areas of the data relating to the operation determination program stored at the address of the memory area. If all the sum values have not been added in step S1 (NO), data is added and the address is updated in step S3.

In step S6, when the operator receives a command for rewriting the program from the external terminal device 8 by the operator,
In step S14, a virus check is performed on the program to be updated, and if it is determined that there is no computer virus (YES), the sum value inherent in the operation determination program is deleted in step S7.

If the unique sum value is erased, the sum value B calculated in step S2 and the unique sum value (check sum value A) added when the program is first written first do not match. (NO), since they do not match, the operation determination program is rewritten in step S8.
When the sum values match in step S2, the arithmetic processing which is a normal operation is continued (step S4).

According to the present embodiment, the program can be rewritten while maintaining the quality without removing the memory storing the operation determination program of the digital protection relay, and the time required for rewriting the program can be reduced. Naturally, the efficiency of design / test time can be improved. In addition, before writing the operation determination program, it is possible to check in advance whether a computer virus is present or not, so that writing a program with a virus does not adversely affect the digital protection relay.

(Eighth Embodiment) (corresponding to claim 8) FIG. 10 is a block diagram of a digital protection relay 1 according to an eighth embodiment of the present invention. The same portions are denoted by the same reference numerals, and duplicate description will be omitted. Reference numeral 9 denotes a hardware lock unit that determines whether data writing is permitted.

Next, the operation of this embodiment will be described with reference to FIG. First, in step S1, it is determined whether or not a sum value has been added for all areas of the data relating to the operation determination program stored at the address of the memory area. If all the sum values have not been added in step S1 (NO), data is added and the address is updated in step S3.

In step S6, a command for rewriting the program is received from the external terminal device 8 by the operator (YES).
Then, in step S15, the power of the digital protection relay is turned off, and the operation determination program recognizes the state of the hardware lock, and determines whether or not the program rewrite is permitted. When it is determined that the rewriting is permitted, the sum value inherent in the operation determination program is erased in the next step S7.

If the sum value is erased, naturally the next step S
2 and the unique sum value (checksum value A) added when the program is first written for the first time
Does not match (NO), the operation determination program is rewritten (step S8). If the program rewrite command is not received in step S6, or if the state of the hardware lock signal is not rewritable in step S15, the sum value added in step S2 and the sum value written in the program area are changed. It is determined whether or not they match, and when the sum values match, the arithmetic processing which is a normal operation is continued (step S4).

According to this embodiment, the program can be rewritten while maintaining the quality without removing the memory storing the operation determination program of the digital protection relay, and the time required for rewriting the program can be reduced. Naturally, the efficiency of design / test time can be improved.

Further, since a hardware lock is not provided in a normal operation state, there is no need to rewrite a program unnecessarily, and a safe digital protection relay can be provided.

(Ninth Embodiment) (corresponding to claim 9) FIG. 12 is a block diagram of a digital protection relay 1 according to a ninth embodiment of the present invention. Are denoted by the same reference numerals, and redundant description is omitted. In the figure, reference numeral 10 denotes a setting switch for inputting various setting values used when the arithmetic processing circuit 3 performs a relay operation based on an operation determination program.

FIG. 13 is a flowchart of this embodiment. In FIG. 13, in step S1, it is determined whether or not a sum value has been added for all areas of the data relating to the operation determination program stored at the address of the memory area. If all the sum values have not been added in step S1 (NO), data is added and the address is updated in step S3.

If all the additions have been made in step S1, a command for rewriting the program is received from the external terminal device 8 by the operator in step S6, and the state of the setting switch 10 is recognized in step S16 to determine that rewriting is permitted. (YES), step S7 operation determination program 4
The sum value inherent to -1 is deleted.

If the unique sum value is deleted, the sum value B calculated in the next step S2 does not match the unique sum value (check sum value A) added when the program is first written for the first time. NO), the operation determination program is rewritten in step S8. If the instruction to rewrite the program is not received and the two sum values match, the arithmetic processing as a normal operation is continued (step S4).

According to the present embodiment, the program can be rewritten while maintaining the quality without removing the memory B storing the operation determination program of the digital protection relay, and the time required for rewriting the program can be reduced. Naturally, the efficiency of design / test time can be improved.

The difference from the eighth embodiment is that a setting switch provided in advance inside the digital protection relay is used for a program rewrite permission signal without installing a hardware lock for permitting program rewrite. There is no need to turn off the power of the digital protection relay, and the time required for rewriting the program can be shortened while maintaining the quality.

[0070]

According to the present invention, the memory device is provided with a monitoring program for monitoring the operation determination program in addition to the operation determination program, and the program can be rewritten without removing the memory for storing these programs. By using the memory B that can be used, when an abnormality is found in the operation determination program due to some kind of abnormality, the abnormality can be promptly detected and the arithmetic processing can be stopped, so that a malfunction can be prevented. A digital protection relay can be provided.

Further, by receiving the program rewriting command from the terminal device outside the digital protection relay by the operation determination program, it is possible to remove the memory without removing the memory.
The operation determination program written in the memory B can be rewritten, and the time required for changing the program can be saved.

In addition, not only a program to be changed from an external terminal device is sent unconditionally, but also a mechanism that does not permit writing unless a predetermined condition is input, a hardware lock means, a setting switch, and the like are provided. Accordingly, it is possible to prevent erroneous operation of a human system when rewriting the operation determination program. In addition, since the virus check can be automatically performed before rewriting the program, the reliability of the writing operation determination program can be improved.

Further, the user can input the document number of the operation judgment program, and can manage the change history of the program inside the digital protection relay.
It can be useful for maintenance.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a digital protection relay according to a first embodiment of the present invention.

FIG. 2 is a flowchart according to the first embodiment of the present invention.

FIG. 3 shows second, third, fourth, fifth, sixth and seventh embodiments of the present invention.
FIG. 2 is a block diagram of a digital protection relay in each of the embodiments.

FIG. 4 is a flowchart according to a second embodiment of the present invention.

FIG. 5 is a flowchart according to a third embodiment of the present invention.

FIG. 6 is a flowchart according to a fourth embodiment of the present invention.

FIG. 7 is a flowchart according to a fifth embodiment of the present invention.

FIG. 8 is a flowchart according to a sixth embodiment of the present invention.

FIG. 9 is a flowchart according to a seventh embodiment of the present invention.

FIG. 10 is a block diagram showing a digital protection relay according to an eighth embodiment of the present invention.

FIG. 11 is a flowchart according to an eighth embodiment of the present invention.

FIG. 12 is a block diagram showing a digital protection relay according to a ninth embodiment of the present invention.

FIG. 13 is a flowchart according to a ninth embodiment of the present invention.

FIG. 14 is a block diagram of a conventional digital protection relay.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Digital protection relay, 2 ... Input circuit, 3 ... Operation processing circuit, 4 ... Memory device, 4-1 ... Operation determination program, 4-2 ... Monitoring program, 5 ... Output circuit, 6 ... SI
O circuit, 7: serial interface, 8: external terminal device, 9: hardware lock means, 10: setting switch, 11: memory device, S1: sum value calculation end determination step, S2: sum value comparison determination step, S3 ... Sum value calculation processing step, S4 ... calculation continuation processing step, S5 ...
Calculation stop processing step, S6 ... command reception determination step,
S7: Sum value erasing processing step, S8: Program rewriting processing step, S9: Rewriting information storage processing step, S10: Program format collation determining step, S11
... document number reception judgment step, S12 ... existing program storage processing step, S13 ... program collation judgment step, S14 ... computer virus existence judgment step, S15 ... hardware lock judgment step, S
16: setting switch state determination step; S17: document number storage processing step.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Naoyoshi Yamanaka 2-24-24 Harumi-cho, Fuchu-shi, Tokyo Toshiba System Technology Co., Ltd. (72) Inventor Tomoyuki Kawasaki 1-Toshiba-cho, Fuchu-shi, Tokyo F-term in Toshiba Fuchu Office (reference) 5B001 AA14 AB06 AC01 AE01 5B076 BB06 CA01 CA08 EB03 5G042 GG03 GG08

Claims (9)

[Claims] An input converter for converting an input current / voltage into a size suitable for processing by a protection relay and an analog / digital converter for converting an analog value sampled and held at a predetermined sampling frequency into a digital value. An input circuit, an arithmetic processing circuit that performs a predetermined arithmetic process using a digital signal output from the input circuit using an operation determination program necessary for determining the operation of the relay, and stores various programs including the operation determination program. A memory device for storing the result of the arithmetic processing by the arithmetic processing circuit;
In a digital protection relay comprising an output circuit for outputting to the outside, the memory device stores the operation determination program separately in a plurality of memory areas and stores a monitoring program for monitoring the operation determination program. The monitoring program includes a checksum added when the operation determination program is written for the first time, and an added value (a calculated sum value) for all areas of the data relating to the operation determination program stored at the address of the memory area. ), The arithmetic processing is continued, and if they do not match, it is determined that there is an abnormality, and the operation determination is aborted. 2. A digital protection relay according to claim 1, wherein a serial input / output circuit for serially transmitting and receiving data between said arithmetic processing circuit and an external terminal device, and said serial input / output circuit. A serial interface for connecting a circuit to the external terminal device is provided, and when data transmitted from the external terminal device is received by the arithmetic processing circuit, instead of stopping the operation determination by the operation determination program, an operation determination program is executed. Digital protection relay characterized by rewriting. 3. The digital protection relay according to claim 2, wherein when the operation determination program is rewritten from the external terminal device, a program format indicating a name of the operation determination program as a rewrite history and an operation determination program are indicated. A digital protection relay, wherein a unique value and a rewriting date and time are stored on an operation determination program. 4. The digital protection relay according to claim 2, wherein when the operation determination program is rewritten from the external terminal device, a program format of an existing operation determination program is input from the external terminal device and the input data is input. A digital protection relay characterized in that the operation determination program is rewritten only when the program type matches a program format previously written in the operation determination program. 5. The digital protection relay according to claim 2, wherein when rewriting the operation determination program from the external terminal device, rewriting of the operation determination program is permitted by inputting a document number associated with the operation determination program. A digital protection relay, wherein a document number once input is read from a terminal device outside the relay. 6. The digital protection relay according to claim 2, wherein when rewriting the operation determination program from the external terminal device, before transferring the rewritten program from the external terminal device, the existing operation determination program is rewritten to the external terminal device. A digital protection relay, wherein the digital protection relay is transferred to a storage medium of a terminal device, compares an existing program with the transferred program, and rewrites an operation determination program only when there is no difference in the result. 7. The digital protection relay according to claim 2, wherein when rewriting the operation determination program from the external terminal device, the external terminal device checks for viruses before transferring the rewritten program from the external terminal device. And transmits the virus check result from the external terminal device to the operation determination program. The operation determination program determines whether the virus check result is normal or abnormal, and determines operation only when the result is normal. Digital type protection relay characterized by rewriting the program. 8. The digital protection relay according to claim 2, further comprising hardware lock means for judging whether data writing is permitted for the operation determination program, and rewriting data of the operation determination program from an external terminal device. When the hardware lock signal is in a data rewrite permission state, and rewrites the operation determination program only when the data rewrite is permitted. . 9. The digital protection relay according to claim 2, wherein rewriting data of an operation determination program is received from the external terminal device, and a state of a setting switch of the digital protection relay is read to permit data rewriting. A digital protection relay, characterized in that a judgment is made as to whether or not the operation has been performed, and the operation judgment program is rewritten only when the operation is permitted.