JP2013251970A - Current differential protective relay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current differential protective relay in which band consumption can be suppressed when transmitting each terminal data by using a variable length transmission data.SOLUTION: The current differential protective relay includes an A/D conversion unit 8 performing A/D conversion by sampling the quantity of electricity of its own terminal, a communication unit 11 for outputting the quantity of electricity data from the A/D conversion unit 8 and receiving the quantity of electricity data converted into digital data from each mating terminal via a transmission line 5, and an operation unit 9 performing protective operation from the quantity of electricity data of its own terminal and the quantity of electricity data of mating terminal. The operation unit 9 determines the range of sampling data which each mating terminal must transmit, on the basis of the difference between a maximum transmission delay time of a mating terminal having a largest transmission delay time when viewed from the terminal performing differential operation, and a transmission delay time of a mating terminal which exchanges data with the terminal performing differential operation. The communication unit 11 transmits the range information of the sampling data thus determined to each mating terminal.

Description

  Embodiments described herein relate generally to a current differential protection relay that exchanges data between terminals of a power transmission line by opposing transmission.

  The current differential protection relay that protects the transmission line is arranged at each terminal of the transmission line that is the protection section, and the current data sampled at a predetermined cycle at each of its own terminal and other terminals is mutually exchanged via the transmission line. By transmitting each other, it is a device that performs a differential operation between its own terminal and the received other terminal and determines whether or not there is an accident on the power transmission line.

  The differential operation calculates the difference current from the vector sum of the current data (each terminal data) sampled at each terminal, calculates the amplitude value that is the magnitude of the difference current, and compares it with the set judgment value. Judgment. In order to calculate the amplitude value, sampling data for a plurality of past times are required in addition to the latest sampling data.

  For example, as a representative amplitude value calculation, by adding six absolute values of sampling data at an electrical angle of 30 ° (interval of 1.67 ms when the system frequency is 50 Hz and 1.38 ms interval when the system frequency is 60 Hz), There is a method for calculating an amplitude value.

  In this method, each terminal data received in the past by the current differential protection relay is stored in a memory a plurality of times and used for differential calculation. If an error occurs in transmission and each terminal data used for the calculation cannot be obtained, the differential function cannot be performed, so the protection function is locked. After that, even if the transmission error is recovered, the past terminal data used for differential calculation is lost for several transmission cycles until the necessary number of consecutive terminal data is collected. The lock continues.

  Further, there is a method in which all counterpart terminals transmit all terminal data necessary for differential calculation within one transmission cycle in order to shorten the time during which the protection function is locked when a transmission error is recovered.

  In this method, in a configuration with three or more terminals, sampling data transmitted from a terminal having the longest transmission delay time (maximum transmission delay terminal) among two or more counterpart terminals to be received and sampling at the same time The sampling data of the self terminal and other terminals that have been used are used for differential calculation.

  For this reason, when fixed-length data is used for transmission data as in the prior art, the number of sampling data included in the transmission data is fixed, so that each terminal is the same as that of each terminal used in differential operation as shown in FIG. In addition to the number of data K, it is necessary to always transmit past sampling data for the maximum transmission delay time m that can occur.

  However, in normal times when no transmission error occurs, a plurality of past sampling data that is not used is transmitted. Among these sampling data, the past sampling data from the range used for the calculation is not used for the calculation even after receiving the data, and there is a problem that the band is consumed.

  On the other hand, due to recent technical progress, a current differential protection relay capable of transmitting and receiving variable-length data using Ethernet (registered trademark) in a transmission line has been proposed.

JP 2009-165235 A

  An object of an embodiment of the present invention is to provide a current differential protection relay capable of suppressing band consumption when transmitting each terminal data using variable-length transmission data.

  In order to achieve the above-mentioned object, the embodiment of the present invention is installed at each terminal of a power transmission line of a power system composed of three or more terminals, and from each terminal via a transmission path capable of transmitting and receiving variable length data. In a current differential protection relay that performs a predetermined output from the obtained information, an A / D converter that performs analog / digital conversion by sampling the amount of electricity at its own terminal, and an amount of electricity output from the A / D converter A communication unit that outputs data and receives electrical quantity data converted into digital data from the opposing counterpart terminals via the transmission line; and the electrical quantity data of the local terminal and the electrical power of the opposing counterpart terminals A calculation unit that performs a protection calculation from the amount data, and the calculation unit has a maximum transmission delay time (TDmax) with a counterpart terminal having the longest transmission delay time when viewed from a terminal that performs differential calculation, A range determination unit that determines a range of sampling data to be transmitted by each counterpart terminal based on a difference (TDmax−TDself) between a transmission delay time (TDself) between the terminal that performs dynamic calculation and the counterpart terminal that exchanges data; And the communication unit transmits range information of the sampling data determined by the range determination unit to each counterpart terminal.

Schematic which shows the whole structure which applied the current differential protection relay which concerns on the 1st Embodiment of this invention to the electric power system. The block diagram which shows the detailed structure of the calculating part of the current differential protection relay which concerns on 1st Embodiment. The figure which shows the transmission timing of the sampling data by 3 terminals. The flowchart which shows the procedure of the data transmission method by 1st Embodiment. The figure which shows the structure of the transmission data containing the some sampling data used by 1st Embodiment. 9 is a flowchart showing a procedure of a data transmission method according to the second embodiment. The block diagram which shows the detailed structure of the calculating part of the current differential protection relay which concerns on 3rd Embodiment. The figure which shows the batch compression method of each terminal data in 3rd Embodiment. The figure which shows the individual compression method of each terminal data in 3rd Embodiment. The flowchart which shows the procedure of the data transmission method by 4th Embodiment. The figure which shows the structure of the transmission data containing several sampling data of a prior art example.

  Embodiments of the present invention will be specifically described below with reference to the drawings.

[First Embodiment]
(overall structure)
FIG. 1 is a schematic diagram showing an overall configuration in which a current differential protection relay according to a first embodiment of the present invention is applied to a power system.

  In FIG. 1, a current transformer 2 and a circuit breaker 3 are installed for each terminal on the transmission line 1 to be protected, and each current transformer 2 and each circuit breaker 3 protect the power transmission line 1. Current differential protection relays 4a, 4b and 4c are connected to each other.

  The current differential protection relays 4a, 4b, and 4c input an electric quantity and state quantity of the power system, convert them into digital quantities, and perform predetermined protection control calculations using the digital quantities. The current differential protection relays 4a, 4b, and 4c perform protection control of the power transmission line 1 by controlling the circuit breakers 3 connected thereto according to the calculation results. The current differential protection relays 4a, 4b, and 4c are provided with a transmission line 5 using Ethernet (registered trademark) for transmitting and receiving data between them.

  Further, a device that performs differential operation is a current differential protection relay 4a (terminal A), a current differential protection relay 4b (terminal B) that transmits data at each end to the terminal A, and a current differential protection relay 4c (terminal C). ) Is the mating terminal. The terminal C is a maximum transmission delay terminal that takes the longest time for data transmission to the terminal A. Normally, the current differential protection relays 4a, 4b, and 4c installed at each terminal mutually perform differential calculation and transmission of each terminal data.

  Normally, the power transmission line 1 to be protected is a three-phase alternating current, but in FIG.

(Configuration of current differential protection relay 4a)
Since the current differential protection relays 4a, 4b, and 4c all have the same configuration, the current differential protection relay 4a will be described below as an example.

  The current differential protection relay 4a includes an input conversion unit 6 that converts a current flowing through the transmission line 1 into a voltage signal of a predetermined magnitude, an analog filter unit 7 that removes harmonic components that cause errors, and analog data as digital data. An analog / digital (A / D) conversion unit 8 for converting to a digital signal, a calculation unit 9 for performing a differential calculation, an output unit 10 for performing a predetermined output based on the calculation result, and a digital signal via a transmission line 5 The communication unit 11 transmits current data of the power transmission line 1 and the sampling synchronization control unit 12 synchronizes sampling based on the calculation result.

(Calculation unit 9)
FIG. 2 shows a detailed configuration of the calculation unit 9. The calculation unit 9 includes a relay calculation unit 21 that performs differential calculation, a transmission delay time calculation unit 23 that calculates a transmission delay time for each terminal, and a range determination unit 25 that determines the range of sampling data to be transmitted by each terminal. ing.

(Differential operation method with current differential protection relay 4a)
A method for controlling the circuit breaker 3 by performing a differential operation with the current differential protection relay 4a configured as described above will be described.

  First, the current differential protection relay 4 a installed at the terminal A introduces a current flowing through the power transmission line 1 via the current transformer 2. The introduced current is converted into a voltage signal of a predetermined magnitude by the input conversion unit 6, and after removing the harmonic component that becomes a folding error by sampling in the analog filter unit 7, sampling is performed at a predetermined cycle, The analog / digital converter 8 converts the digital data.

  Thereafter, the current data of the transmission line 1 converted into digital data is transmitted from the communication unit 11 to the current differential protection relays 4b and 4c via the transmission path 5.

  Next, the current differential protection relay 4b installed at the terminal B converts the current data of the transmission line 1 converted into digital data from the communication unit 11 via the transmission path 5 into the current differential protection relays 4a and 4c. Transmit to.

  Furthermore, the current differential protection relay 4c installed at the terminal C passes the current data of the transmission line 1 converted into digital data from the communication unit 11 via the transmission line 5 to the current differential protection relays 4a and 4b. To transmit.

  In the current differential protection relay 4a, the relay of the arithmetic unit 9 is used for the current data at its own terminal A and the current data transmitted from the current differential protection relay 4b (terminal B) and the current differential protection relay 4c (terminal C). A differential calculation is performed by the calculation unit 21, a predetermined output is output from the output unit 10 based on the calculation result, and the circuit breaker 3 of each terminal is controlled according to the output.

  At this time, if an error occurs in the data transmission, the current differential protection relay 4a cannot obtain the data of the counterpart terminal used for the calculation and cannot perform the differential calculation, so that the protection function is locked. After that, even if the transmission error is recovered, the past end data used for differential calculation is lost for several transmission cycles until the necessary number of consecutive terminal data is collected. The lock continues.

(Sampling data transmission timing by 3 terminals)
FIG. 3 shows a transmission timing diagram of sampling data by the three terminals A, B, and C.

  In the figure, the terminal C is the maximum transmission delay terminal as viewed from the terminal A, the transmission delay time (sampling period number) between the terminal A and the terminal B is TDab, and the transmission delay time (sampling period number) between the terminal A and the terminal C. ) TDac. In addition, ● represents sampling data that can be used when the terminal A performs computation, and ◯ represents sampling data that has not reached the A terminal when the terminal A performs computation.

  Since the past sampling data is also used in the differential operation, the sampling data range (range indicated by K in FIG. 3) required for the differential operation is determined from the sampling timing of the latest sampling data received from the maximum transmission delay terminal C. The range is the range up to the past (the range indicated by X in FIG. 3) by the number of each end data used in the calculation.

  When each terminal transmits all the sampling data necessary for differential calculation within one transmission period in order to shorten the time for which the protection function lock is continued when the transmission error is recovered, the number of end data K used for the calculation In addition, it is necessary to transmit sampling data up to the past by the difference in transmission delay time from the maximum transmission delay terminal C at a time.

  That is, when the terminal B transmits sampling data to the terminal A in FIG. 3, the transmission delay time (TDab) between the terminal A and the terminal B in addition to the data number K of the terminal B used for the differential calculation by the terminal A. ) And the maximum transmission delay time (TDac) between the terminal A and the maximum transmission delay terminal C, it is necessary to include all the sampling data (range shown in FIG. 3Y) up to the past by the difference (TDac−TDab).

(Data transmission method according to this embodiment)
For this reason, in this embodiment, transmission data is made into variable length, and the calculating part 9 increases / decreases the number of sampling data contained in transmission data as needed.

  FIG. 4 is a flowchart showing the procedure of the data transmission method according to the present embodiment.

  First, the transmission delay time calculation unit 23 of the calculation unit 9 calculates the transmission delay time for each terminal (step S11). For example, in the example shown in FIG. 3, the transmission delay time (sampling period number) between the terminal A and the terminal B is TDab, and the transmission delay time (sampling period number) between the terminal A and the terminal C is TDac.

  Next, the transmission delay time calculation unit 23 calculates the maximum transmission delay time (maximum transmission delay time) from the transmission delay time (step S12). In the above example, since the terminal C is the maximum transmission delay terminal when viewed from the terminal A, the maximum transmission delay time is TDac.

  Further, the range determination unit 25 determines the range of sampling data to be transmitted by each terminal based on the transmission delay time for sending data and the maximum transmission delay time (step S13).

  In the above example, the range of sampling data to be transmitted by the counterpart terminal B includes the number K of sampling data per terminal necessary for differential calculation, the transmission delay time (TDab) between the terminal A and the terminal B, and the terminal From the difference (TDac−TDab) between A and the maximum transmission delay time (TDac) between the maximum transmission delay terminal C, K + (TDac−TDab).

  The number of sampling data to be transmitted by the maximum transmission delay terminal C is the number of sampling data K per terminal necessary for differential calculation, the transmission delay time (TDac) between the terminal A and the terminal C, and the terminal A And the maximum transmission delay time (TDac) between the maximum transmission delay terminal C and the difference (TDac−TDac).

  In this example, since the terminal A knows all the transmission delay times with the counterpart terminals, the current differential protection relay 4a calculates the range of sampling data to be transmitted to each counterpart terminal.

  Subsequently, the range information of the sampling data to be transmitted by each terminal is transmitted to the communication unit 11, and is transmitted from the communication unit 11 to the other current differential protection relays 4b and 4c by data transmission (step S14).

  Next, the current differential protection relays 4b and 4c receive the sampling data range information to be transmitted to the terminal A (step S15).

  The current differential protection relays 4b and 4c transmit the transmission data in the designated sampling data range to the terminal A based on the received sampling data range information (step S16).

  FIG. 5 shows the structure of transmission data including a plurality of sampling data used in this embodiment. This transmission data has a variable length, and has a structure in which the fixed portion (K) is combined with the variable portion (TDd). The variable part (TDd) is the difference between the transmission delay time (TDmax) of the maximum transmission delay terminal and the transmission delay time (TDself) of the terminal itself that transmits the transmission data.

  By making the transmission data variable in this way, each counterpart terminal can omit the sampling data that is not used for the operation and transmit only the necessary sampling data. For this reason, the number of sampling data to be transmitted is reduced, and the transmission data size can be reduced.

(effect)
Conventionally, since the number of sampling data included in the transmission data is fixed, the past sampling data must be constantly transmitted for the maximum delay time that can occur.

  However, according to the present embodiment, the transmission data is variable length, and the number of sampling data per terminal necessary for differential calculation and the number of sampling data required are calculated from the transmission delay time difference between the counterpart terminal and the maximum transmission delay terminal. By transmitting to each counterpart terminal, the number of past sampling data included in the transmission data can be reduced when each counterpart terminal transmits sampling data required in one transmission cycle.

  Therefore, it is possible to reduce the amount of bandwidth used for data transmission, and it is possible to reduce the time for which the protection function lock continues when a transmission error is recovered.

[Second Embodiment]
In the first embodiment, the terminal A notifies the range of sampling data to be transmitted to each counterpart terminal. However, the terminal A may notify each counterpart terminal of the maximum transmission delay time by data transmission. In the second embodiment, an example in which the maximum transmission delay time is notified by data transmission will be described.

  FIG. 6 is a flowchart showing the procedure of the data transmission method according to the second embodiment.

  In this embodiment, the transmission delay time calculation unit 23 of the calculation unit 9 calculates the transmission delay time for each terminal (step S11), and then the transmission delay time calculation unit 23 becomes the maximum from the transmission delay time. The point of calculating the transmission delay time (maximum transmission delay time) (step S12) is the same as in the first embodiment.

  Next, in the present embodiment, the obtained maximum transmission delay time is sent to the communication unit 11, and is transmitted from the communication unit 11 to the other current differential protection relays 4b and 4c by data transmission (step S17).

  Next, the current differential protection relays 4b and 4c receive the maximum transmission delay time (step S18). The current differential protection relays 4b and 4c calculate the range of sampling data to be transmitted to the terminal A that performs the differential operation from the difference between the maximum transmission delay time and the transmission delay time between the terminal A and the terminal A that the terminal itself knows. Then, the transmission data is transmitted to the terminal A within this range (step S20).

  According to this embodiment, similarly to the first embodiment, it is possible to reduce the amount of bandwidth used by data transmission, and it is possible to shorten the time for which the protection function lock continues when a transmission error is recovered.

[Third Embodiment]
(Data transmission method using data compression)
When a plurality of sampling data is transmitted, the amount of transmission data increases, and a larger band is required for transmission. In this case, it is possible to suppress an increase in the amount of transmission data by performing data compression on the transmission data. However, when a fixed-length frame is used as in the conventional example, the amount of data to be transmitted needs to be a multiple of the frame length. For this reason, when data having a fraction less than one frame length is generated by compression, padding is performed, and data is transmitted after a length of one frame.

  However, since data added by padding is not used for calculation, data compression efficiency is reduced when padding occurs. For this reason, in the present embodiment, a method for transmitting data without reducing the data compression efficiency will be described.

(Constitution)
FIG. 7 is a block diagram showing a detailed configuration of the calculation unit of the current differential protection relay according to the third embodiment.

  The current differential protection relay according to the present embodiment has the same configuration as that of the first embodiment except that a calculation unit 9 ′ is used instead of the calculation unit 9. The calculation unit 9 ′ is configured in the same manner as the calculation unit 9 of the first embodiment except that the compression unit 27 is provided after the range determination unit 25. In addition, the same code | symbol is attached | subjected to the component same as 1st Embodiment, and description is abbreviate | omitted.

(Data compression method according to this embodiment)
Data compression by the compression unit 27 may be performed on a plurality of sampling data as shown in FIG. 8 or may be performed on a sampling data basis as shown in FIG. When compression is performed for each sampling data as shown in FIG. 9, it is preferable to add control data such as size information for each compressed data so that the boundary of the data can be understood.

  As a data compression method, for example, a Deflate algorithm used in ZIP compression, differential compression for each end data in an arbitrary calculation cycle, or a method combining them can be used.

  If sampling data cannot be acquired due to a transmission error, only the entire compressed data or sampling data missing due to the transmission error is decompressed and the decoded data is used. By these operations, the differential calculation can be performed only with the sampling data transmitted in one transmission cycle.

(effect)
According to this embodiment, when transmitting a plurality of sampling data required in one transmission cycle, transmission is performed by compressing data to one or more sampling data included in the transmission data with the transmission data as a variable length. The amount of data can be reduced and the bandwidth used for transmission can be reduced.

  For this reason, it is possible to reduce the time during which the protection function lock continues when the transmission error is recovered.

  Further, according to the present embodiment, for example, in a transmission method with a variable transmission data length such as Ethernet (registered trademark), data addition due to padding does not occur, so that more efficient transmission of compressed data is possible. become.

[Fourth Embodiment]
(Selection of transmission method)
In the first to third embodiments, each terminal always transmits sampling data that is transmitted in one transmission cycle with a variable length. However, in this embodiment, the example is limited to a case where a transmission failure occurs. explain.

  FIG. 10 is a flowchart illustrating a procedure of a data transmission method according to the fourth embodiment.

  First, when the relay calculation unit 21 of the calculation unit 9 determines a transmission failure (step S21) and detects a transmission failure (Yes in step S21), as described in the first to third embodiments, After the operation of calculating the transmission delay time by the transmission delay time calculation unit 23, the sampling data transmitted by each terminal in one transmission cycle is transmitted with a variable length to perform differential calculation (step S22).

  On the other hand, when a transmission failure is not detected (No in step S21), the differential calculation is performed using only the latest sampling data as usual (step S23).

  Data compression can also be performed on the latest sampling data. In this case, the decompressed data can be used every time data is received and the restored data can be used.

(effect)
According to the present embodiment, efficient transmission can be performed as a whole by transmitting sampling data transmitted by each terminal in one transmission cycle only when a transmission failure occurs.

[Other embodiments]
(1) In each of the above embodiments, the terminal that performs the differential operation is the terminal A and the terminal C is the maximum transmission delay terminal. However, the present invention is not limited to this, and the terminal that performs the differential operation is the terminal B or C. The maximum transmission delay terminal can be the terminal A or B.

(2) In each of the above-described embodiments, the example of the three terminals of the terminal A to the terminal C has been described. However, more terminals than the three terminals may be provided.

(3) In each of the above embodiments, the number of sampling data used for the differential calculation is six, but it may be other than six.

(4) Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Power transmission line 2 ... Current transformer 3 ... Circuit breakers 4a, 4b, 4c ... Current differential protection relay 5 ... Transmission path 6 ... Input conversion part 7 ... Analog filter part 8 ... Analog / digital (A / D) conversion part 9, 9 '... operation unit 10 ... output unit 11 ... communication unit 12 ... sampling synchronization control unit 21 ... relay operation unit 23 ... transmission delay time calculation unit 25 ... range determination unit 27 ... compression unit

Claims (6)

In a current differential protection relay that is installed at each terminal of a power transmission line of a power system composed of three or more terminals and performs a predetermined output from information obtained from each terminal via a transmission path capable of transmitting and receiving variable length data ,
An A / D converter that samples the amount of electricity at its own terminal and performs analog / digital conversion;
A communication unit that outputs the electrical quantity data output from the A / D conversion unit and receives electrical quantity data converted into digital data from each opposing terminal via the transmission line;
A calculation unit that performs a protection calculation from the electric quantity data of the own terminal and the electric quantity data of the opposing counterpart terminals,
The arithmetic unit has a maximum transmission delay time (TDmax) with a counterpart terminal having the longest transmission delay time when viewed from a terminal that performs differential computation, and a transmission delay time between a terminal that performs differential computation and a counterpart terminal that exchanges data. A sampling unit that determines a range of sampling data to be transmitted by each counterpart terminal based on a difference (TDmax−TDself) with respect to (TDself), and the communication unit determines the sampling determined by the range determination unit A current differential protection relay that transmits data range information to each counterpart terminal.   2. When sampling range information of the sampling data is received, sampling data in a range specified by the range information is transmitted in one transmission cycle with variable-length transmission data to a terminal that has transmitted the range information. The current differential protection relay described.   Instead of transmitting the range information of the sampling data to be transmitted by each counterpart terminal, the communication unit sets the transmission delay time of the maximum transmission delay terminal having the largest transmission delay time among the counterpart terminals performing data transmission to the own terminal. The current differential protection relay according to claim 1 for transmission.   When the transmission delay time of the maximum transmission delay terminal is received, the range of sampling data to be transmitted is calculated from the difference from its own transmission delay time, and the sampling of the calculated range is performed for the terminal that performs the differential operation The current differential protection relay according to claim 3, wherein the data is transmitted in one transmission cycle by variable length transmission data.   The current differential protection relay according to claim 1, wherein the calculation unit further includes a compression unit that compresses a part or the whole of the variable length transmission data after the range determination unit.   The current differential protection relay according to claim 5, wherein differential operation is performed only with transmission data of one transmission period by receiving and decoding the compressed variable-length transmission data.

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