JP2009017680A - Protective relay system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent-reliability protective relay system that can attain high-sensitivity and high-precision protection calculation, by reducing effects of errors due to an optical sensor and an optical cable. <P>SOLUTION: An error reduction calculation part 42 of a detection determination part 4 is composed of an input part 42A of each phase, a resultant current calculating circuit 42B, a memory circuit 42C, and a true-value calculating circuit 42D. The resulting current calculating circuit 42B calculates a vector sum of each current amount of each phase by conflating each current amount of each phase inputted by the input part 42A of each phase so as to output it to the memory circuit 42C as an error amount of the current amounts, and the memory circuit 42C stores this. The true-value calculating circuit 42D calculates each true value of the current amount of each phase, by subtracting each error amount stored by the memory circuit 42C from each current amount of each phase so as to transmit it to a protection calculation determining part 43 that executes relay calculations. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a protection relay system that protects an electric power system by detecting a current amount of the electric power system and makes a protection calculation determination, and more particularly, to a protection relay system that uses an optical sensor and an optical cable when detecting the electric current amount of the electric power system. .

  In general, a protection relay system is known as a system for protecting an electric power system. In the protection relay system, stable operation of the power system is maintained by controlling a circuit breaker or the like when the amount of electricity exceeds a predetermined range due to an accident in the power system. Among such systems, the current differential protection type protection relay system is widely used for main protection of important trunk lines because it is excellent in determining an accident section.

  By the way, an electric quantity is usually input to the protection relay system via a wound-type transformer or current transformer, and a protection relay system including an optical sensor has been proposed as a wound-type current transformer. . That is, an optical sensor is used to detect the current amount of the power system, and a detection determination unit is connected to the optical sensor via an optical cable, and a protection calculation is performed from the current amount detected by the optical sensor at the detection determination unit. It is the structure which guides the determination result. Since the optical sensor has the characteristics of high accuracy and wide dynamic range, the protection relay system using the optical sensor is being developed and researched as being capable of realizing highly sensitive and highly accurate protection computation.

For example, the differential protection relay system described in Patent Document 1 includes a differential relay that performs current differential protection using currents at both ends of a transmission line in which overhead lines and power cable lines are mixed, and both ends of a power cable line section. It is composed of a differential relay that detects a fault in the power cable line section by obtaining a differential current from the amount of current, and cascades the output of the optical sensor at both ends of the power cable line as a fault detection in the power cable line section They are connected to obtain a differential current.
JP 2004-304915 A

  However, the following problems have been pointed out in the protection relay system using the optical sensor and the optical cable. That is, external influences such as vibration and magnetic field are applied to the optical sensor and the optical cable. Therefore, these effects are reflected in the amount of electricity corresponding to the optical signal transmitted by the optical sensor and the optical cable, and when input to the detection determination unit of the protection relay system, the error due to the external influence is reflected. Is included in the amount of current.

  When the error amount of the current amount input to the protection relay system is large, there is a problem that the sensitivity and accuracy of the protection calculation performed by the detection determination unit is reduced. For this reason, it is important to accurately obtain the true value of the current amount of the power system from which the error is removed. In this way, in a protection relay system that uses an optical sensor and optical cable, the optical sensor and optical cable are affected by external effects such as vibration and magnetic field and contain errors. Therefore, it has been a problem to increase the sensitivity and accuracy of the protection calculation.

  The present invention has been proposed in order to solve the above problems, and with a simple configuration, it is possible to reduce the influence of errors caused by the optical sensor and the optical cable, and to realize highly sensitive and highly accurate protection calculation. An object of the present invention is to provide a protective relay system with excellent reliability.

  In order to solve the above-described problems, the present invention is provided with an optical sensor for detecting a current amount of a power system, and the current amount of the power system detected by the optical sensor is input to the optical sensor via an optical cable. The power system protection relay system to which the current amount input unit is connected has the following characteristics.

  That is, the current amount of each phase input by the current amount input unit is combined to obtain a vector sum of the current amounts of the respective phases, and an error amount calculation unit that outputs an error amount in the current amount, and the error amount calculation unit An error amount storage unit for storing the output error amount, and a true value for obtaining a true value for the current amount by subtracting the error amount stored in the error amount storage unit from the current amount input by the current amount input unit. A value calculation unit and a protection calculation determination unit that performs relay calculation with a true value at the current amount obtained by the true value calculation unit and outputs a protection calculation determination are provided.

  In the protection relay system of the present invention as described above, the current amount input unit inputs the current amount of the power system detected by the optical sensor via the optical cable, and sends this to the error calculation unit. The error calculation unit synthesizes the current amounts of the respective phases to obtain a vector sum of the current amounts of the respective phases. The vector sum of the current amounts of the respective phases is always 0 if the power system is normal and the current amounts of the respective phases consist only of true values, that is, the current amount does not include an error.

  That is, as long as the power system is normal, if the vector sum of the current amounts of each phase is not 0, this value is nothing but the error amount of the current amount of each phase. It is possible to represent the amount of error. In this way, the error amount calculation unit can determine the error amount of the current amount, and the error amount storage unit stores this.

  The true value calculating means takes the current amount input by the current amount input unit and the error amount stored in the error amount storage unit, and subtracts the latter from the former to accurately obtain the true value of the current amount. Can do. Since the protection calculation determination unit performs the relay calculation based on the true value of the current amount obtained by the true value calculation means, it is possible to perform a protection calculation determination output with high sensitivity and high accuracy.

  According to the protection relay system of the present invention, when the current amount by the optical sensor and the optical cable is transmitted, the error amount is obtained by synthesizing the input current amounts of the respective phases, and the error amount is removed by removing this from the current amount. Since the influence can be reduced, highly sensitive and highly accurate protection calculation judgment can be performed, and the power system can be reliably protected.

  A representative embodiment of a protection relay system according to the present invention will be specifically described with reference to the drawings. In addition, in the following embodiment, the same code | symbol is attached | subjected regarding the same member. Each figure is shown as a configuration for one phase for convenience of explanation, but there are individual inputs for three phases.

(1) First Embodiment [Configuration]
The first embodiment will be described with reference to FIGS. FIG. 1 is a configuration diagram of the first embodiment, and FIG.

  As shown in FIG. 1, an optical sensor 2 for detecting a current amount is installed in the power system 1, and an optical cable 3 is connected to the optical sensor 2. The optical sensor 2 is an element that converts the detected current amount into an optical signal and outputs the optical signal, and the optical cable 3 is a transmission path that transmits the optical signal output from the optical sensor 2.

  The optical cable 3 is connected to the detection determination unit 4. The detection determination unit 4 includes a signal processing unit 41, an error reduction calculation unit 42, and a protection calculation determination unit 43. Among these, the signal processing unit 41 includes a photoelectric converter that converts an optical signal transmitted by the optical cable 3 into an electric signal. The error reduction calculation unit 42 is a main part of the present embodiment and has the configuration shown in FIG.

  That is, the error reduction calculation unit 42 includes each phase input unit 42A, a combined current calculation circuit 42B, a memory circuit 42C, and a true value calculation circuit 42D. Each phase input unit 42A is a part that inputs the current amounts Ia, Ib, and Ic of each phase in the power system detected by the optical sensor 2 via the optical cable 3 from the signal processing unit 41 as electrical signals.

  The combined current calculation circuit 42B is a circuit that determines the vector sum of the phase current amounts Ia, Ib, and Ic by combining the current amounts of the respective phases input by the respective phase input units 42A. If the power system 1 is normal and the current amounts Ia, Ib, and Ic of each phase are the true values Ita, Itb, and Itc of the current amounts that do not include the error current Iε, the vector summed current 3Io is Always 0. Therefore, the value of the combined current 3Io that is not other than 0 indicates an error included in the combined current 3Io of the current amounts Ia, Ib, and Ic.

  Since each phase is similarly affected from the outside, Io, which is 1/3 of the combined current 3Io, becomes an error current Iε included in the current amount of each phase. The combined current calculation circuit 42B outputs the error current Iε to the memory circuit 42C as an error Io in each phase current amount Ia, Ib, Ic. The memory circuit 42C is a circuit for storing the error Io output from the combined current calculation circuit 42B for a predetermined time.

  The true value calculation circuit 42D takes in the current amounts Ia, Ib, Ic of the respective phases input by the respective phase input units 42A and the error amount Io in the current amounts of the respective phases stored in the memory circuit 42C, and the current amounts of the respective phases. An error Io is subtracted from Ia, Ib, and Ic to obtain true values Ita, Itb, and Itc in the current amounts of the respective phases. The protection calculation determination unit 43 is a part that performs relay calculation using the true values Ita, Itb, and Itc at the current amount obtained by the true value calculation circuit 42D, and outputs a protection calculation determination.

[Function and effect]
The operational effects of the first embodiment as described above are as follows. As already described, since the optical sensor 2 and the optical cable 3 receive vibrations and magnetic fields from the outside, the current amounts Ia, Ib, and Ic of each phase input to the detection determination unit 4 include the same error current Iε. It will be. That is, as shown in the following formulas (1) to (3), the current amounts Ia, Ib, and Ic of each phase are the true values Ita, Itb, Itc and the error current Iε of the current amounts of the three phases. The sum of

Ia = Ita + Iε (1)
Ib = Itb + Iε (2)
Ib = Itc + Iε (3)

  Such current amounts Ia, Ib, and Ic are input to each phase input unit 42A of the error reduction calculation unit 42. In order for the protection calculation determination unit 43 to perform relay calculation with high sensitivity and high accuracy, it is necessary to input only the true values of the current amounts Ita, Itb, Itc, and errors from the current amounts Ia, Ib, Ic of the respective phases. The current Iε must be removed.

Therefore, the combined current calculation circuit 42B combines the current amounts Ia, Ib, and Ic of the respective phases to obtain the vector sum 3Io. That is, equation (4) is obtained.
Ia + Ib + Ic = 3Io (4)

Substituting the right side of the above formulas (1) to (3) into the left side of the formula (4),
Ia + Ib + Ic = Ita + Itb + Itc + 3Iε (5)
It becomes. That is, the vector sum 3Io of the current amounts Ia, Ib, and Ic of each phase is the sum of the true current values Ita, Itb, and Itc and three times the error current Iε.

If the power system 1 is not in the event of an accident, the sum of the true current values Ita, Itb, Itc is always 0 (see equation (6)), so this equation (6) is substituted into the right side of equation (5). Thus, the following equation (7) is established, and it can be seen that the combined current 3Io can be expressed by the error current Iε.
Ita + Itb + Itc = 0 (6)
3Io = 3Iε (7)

  That is, I0, which is 1/3 of the combined current 3Io, is equal to the error current Iε affecting the current amounts Ia, Ib, and Ic of each phase. Accordingly, I0 is an error included in the current amounts Ia, Ib, and Ic of each phase. In place of the error current Iε in the right side of the above formulas (1) to (3), an error amount I0 is inserted and transferred to the left side to obtain the following formulas (8) to (10).

Ita = Ia−I0 (8)
Itb = Ib−I0 (9)
Itc = Ic−I0 (10)

  These equations (8) to (10) are obtained from the current amounts Ia, Ib, and Ic of each phase input to the error reduction calculation unit 42, and an error I0 that is 1/3 of the combined current 3Io of each phase. This means that the true values Ita, Itb and Itc of the current amount necessary for the relay calculation can be obtained. In this way, the true value calculation circuit 42D of the present embodiment can determine the true values Ita, Itb, Itc of the current amount and provide them to the protection calculation determination unit 43. The protection calculation determination unit 43 that has obtained the true values Ita, Itb, Itc of the accurate current amounts can perform the relay calculation with high sensitivity and high accuracy.

  In the event of an accident in the power system 1, the combined current 3Io does not become 0. Therefore, during actual operation, I0 that is 1/3 of the combined current 3Io before the accident is stored in the memory circuit 42C for a predetermined time, The true values Ita, Itb and Itc are obtained by using the stored I0 for calculation.

  The first embodiment eliminates the error I0 (1/3 of the combined current 3Io) due to the external influence (vibration, magnetic field, etc.) received by the optical sensor 2 and the optical cable 3 as described above. It is possible to input the true values Ita, Itb, Itc in the current amount of the system 1 to the protection calculation determination unit 43. Thereby, the protection calculation determination part 43 can implement a relay calculation with high sensitivity and high precision, and can contribute to the improvement of the reliability of a protection relay system.

(2) Second Embodiment [Configuration]
Next, a second embodiment will be described with reference to FIG. The basic configuration of the second embodiment is the same as that of the first embodiment shown in FIG. 1, and the internal configuration of the error reduction calculation unit 42 shown in FIG. 3 is characterized.

  That is, in the error reduction calculation unit 42 of the second embodiment, a delta calculation circuit 42E is provided. The delta calculation circuit 42E is a circuit that performs vector calculation on the current amounts of the respective phases input by the respective phase input units 42A for every two different phases. The protection calculation determination unit 43 is configured to perform a relay calculation with the amount of current calculated by the delta calculation circuit 42E as a vector.

[Function and effect]
In the second embodiment described above, until the currents Ia, Ib, and Ic1 for each of the three phases containing the error current Iε are input to the error reduction calculation unit 42, they are the same as in the first embodiment. In the second embodiment, the error current Iε is derived by vector calculation of the delta calculation circuit 42E. That is, by performing vector calculations as shown in the equations (11) to (13) in the delta circuit calculation 42E, the error current Iε can be removed before input to the protection calculation determination unit 43 that performs the relay calculation. The true values Iab, Ibc, and Ica of the AB phase, BC phase, and CA phase can be obtained.

Ia−Ib = Ita + Iε−Itb−Iε = Ita−Itb = Iab (11)
Ib−Ic = Itb + Iε−Itc−Iε = Itb−Itc = Ibc (12)
Ic−Ia = Itc + Iε−Ita−Iε = Itc−Ita = Ica (13)

  Note that the current input to the protection calculation determination unit 43 is equivalent to a delta current, but the sensitivity at the time of a one-wire ground fault also changes from when the true values Ita, Itb, Itc of each phase current are input. It can be seen from the following formulas (14) and (15) that there is no error. Therefore, it is possible to detect with the same sensitivity even in the case of a one-line ground fault.

When the symmetrical current at the time of 1-line ground fault in the case of each phase current input is I1 (normal phase) = I2 (reverse phase) = I0 (zero phase),
Ita = I1 + I2 + I0 = 3I1 (14)
^{Iab = Ita-Itb = (1} -a 2) I1 + (1-a) I2
= (1-a ² + 1−a) I1 = 3I1 (15)
However, a and a ² are a = −1 / 2 + j√3 / 2, a ² = −1 / 2−j√3 / 2, and a ² + a + 1 = 0

  According to the second embodiment, the memory circuit 42C is not required in the error reduction calculation unit 42. Therefore, in addition to the operational effects of the first embodiment, the circuit configuration can be simplified. is there.

(3) Third Embodiment [Configuration]
Next, a third embodiment will be described with reference to FIG. As shown in FIG. 4, the third embodiment is characterized in that it includes an optical sensor 21 and an optical cable 31 that are not connected to the power system 1. The optical sensor 21 that is not connected to the power system 1 is installed in the same manner as the optical sensor 2 that obtains the current amount of the power system 1.

  The optical cable 31 connected to the optical sensor 21 is installed in the same manner as the optical cable 3 that transmits the optical signal of the optical sensor 2 connected to the power system 1. For this reason, the optical sensors 2 and 21 and the optical cables 3 and 31 are similarly affected by external influences such as vibration and magnetic field, and the error included in the current amount due to the external influences is the same. It becomes size.

  As shown in FIG. 4, the detection determination unit 4 is provided with a second signal processing unit 44 in addition to the signal processing unit 41 that connects the optical sensor 2 and the optical cable 3. Further, the error reduction calculation unit 42 is provided with a current amount input unit 42F and a true value calculation circuit 42G. Of these, the current amount input unit 42 </ b> F inputs the current amount from the two signal processing units 41 and 44. Further, the true value calculation circuit 42G obtains true values Ita, Itb and Itc in the current amount of the power system 1 from the difference between the two kinds of current amounts input by the current amount input unit 42F.

[Function and effect]
Since the optical sensor 21 is not connected to the power system 1, the amount of current detected by the optical sensor 21 is always 0, and the amount of current corresponding to the optical signal obtained from the optical signal processing unit 44 is only the error current Iε. . Therefore, in the third embodiment, the current amount obtained from the second signal processing unit 44 is input to the true value calculation circuit 42G as an error, and is calculated with the current amount obtained from the optical sensor 2. It is possible to obtain Ita, Itb, and Itc that are true values.

The basic formula can be handled as in the formulas (16) to (18), and the protection calculation determination unit 43 can perform a relay calculation with high sensitivity and high accuracy.
Ita = Ia−Iε (16)
Itb = Ib−Iε (17)
Itc = Ic−Iε (18)

  According to the third embodiment as described above, the combined current calculation circuit 42B and the memory circuit 42C can be omitted and the circuit configuration can be further reduced as compared with the error reduction calculation unit 42 in the first embodiment. It can be simplified.

(4) Other Embodiments The present invention is not limited to the above-described embodiments, and the configuration and arrangement of each member can be changed as appropriate. For example, as a modification of the first embodiment, two optical sensors 2 and 22 are connected in cascade, and the differential amount of the current flowing through the power system 1 is taken into the signal processing unit 41 of the detection determination unit 4. (See FIG. 5). According to such an embodiment, the same operational effects as those of the first embodiment can be obtained.

1 is a configuration diagram of a first embodiment according to the present invention. The principal part block diagram in 1st Embodiment. The principal part block diagram in 2nd Embodiment which concerns on this invention. The block diagram of 3rd Embodiment which concerns on this invention. The block diagram of other embodiment which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electric power system 2, 22 ... Optical sensor 21 ... Unconnected optical sensor 3 ... Optical cable 31 ... Non-connected optical cable 4 ... Detection determination part 41, 44 ... Signal processing part 42 ... Error reduction calculating part 42A ... Each phase input part 42B ... Composite current calculation circuit 42C ... Memory circuits 42D, 42G ... True value calculation circuit 42E ... Delta calculation circuit 42F ... Current amount input unit 43 ... Protection calculation determination unit

Claims (3)

An optical sensor for detecting a current amount of a power system is installed, and the optical sensor is connected to a current amount input unit for inputting a current amount of the power system detected by the optical sensor via an optical cable. In the relay system,
An error amount calculation unit that combines the current amounts of the respective phases input by the current amount input unit to obtain a vector sum of the current amounts of the respective phases, and outputs an error amount in the current amount;
An error storage unit that stores the error output from the error calculation unit;
A true value calculating means for subtracting the error stored in the error storage from the current input by the current input unit to obtain a true value in the current;
A protection relay system comprising a protection calculation determination unit that performs a relay calculation with a true value at the current amount obtained by the true value calculation means and outputs a protection calculation determination. An optical sensor for detecting a current amount of a power system is installed, and the optical sensor is connected to a current amount input unit for inputting a current amount of the power system detected by the optical sensor via an optical cable. In the relay system,
With respect to the current amount input by the current amount input unit, a delta calculation unit that performs vector calculation for every two different phases;
A protection relay system, comprising: a protection calculation determination unit that performs relay calculation using the amount of current calculated by the delta calculation unit as a vector and outputs a protection calculation determination. An optical sensor for detecting a current amount of a power system is installed, and the optical sensor is connected to a current amount input unit for inputting a current amount of the power system detected by the optical sensor via an optical cable. In the relay system,
The non-connected optical sensor and optical cable that are not connected to the power system are installed so as to receive the same influence from the outside independently of the optical sensor and the optical cable,
The current amount input unit is configured to input a current amount corresponding to an optical signal from the non-connected optical sensor and optical cable not connected to the power system,
A true value calculating means for obtaining a true value in the current amount from a difference between two kinds of current amounts input by the current amount input unit;
A protection relay system comprising a protection calculation determination unit that performs a relay calculation with a true value at the current amount obtained by the true value calculation means and outputs a protection calculation determination.

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