JP5078133B2 - Protection relay and accident point locating device for power transmission and distribution system and transient component elimination method thereof - Google Patents

Description

  The present invention provides a transient component removing method for removing a DC component that is transiently attenuated from a physical quantity detected when an accident such as a short circuit or a ground fault occurs in a power transmission / distribution system, and this transient component removing method. The present invention relates to applied protection relays and accident location systems.

  The power receiving and distribution equipment that constitutes the power transmission and distribution system is provided with a protective relay that outputs a disconnection command to the circuit breaker to eliminate the cause of the accident when a short circuit or ground fault occurs in the transmission and distribution system It has been. Since the waveform of the current detected at the time of occurrence of the accident includes a DC component that attenuates transiently, if relay calculation is performed using this waveform as it is, an error occurs in the relay characteristics. In order to prevent this, conventionally, an analog bandpass filter has been used as means for removing a transient component from a physical quantity such as a current measured at the time of an accident in a power transmission and distribution system. However, the analog band-pass filter has a problem that a change in characteristics due to temperature, an aging of the element, and the like occur.

  In order to deal with such technical problems, Patent Documents 1 and 2 disclose techniques for removing transient components using three consecutive sampling data using digital techniques. Patent Document 3 discloses a technique using four sampling data separated by a half cycle of commercial frequency, one cycle, and one cycle and a half.

  Patent Document 1 discloses a sampling device that samples an input AC waveform including a DC component at time intervals Δt, and sampling values Pn-2, Pn-1, and Pn at successive sampling times tn-2, tn-1, and tn. And an arithmetic unit that calculates ((Pn) -2 (Pn-1) + (Pn-2)) / (2cos (ωΔt) -2) as input, and outputs the output of the arithmetic unit at time tn-1 There is disclosed a technique for obtaining an instantaneous value of a fundamental wave component obtained by removing a DC component from an AC waveform.

  Patent Document 2 discloses a method for removing a damped DC component included in a signal immediately after an accident when performing a calculation of a protection relay of a power system, and sampling and sampling data of an input signal at equal intervals. After digital conversion, obtain the value (Vj) -2 (Vj + 1) + (Vj + 2) of the relational expression between three consecutive data Vj, Vj + 1, Vj + 2 and convert these values Is applied to the multiplier matrix mij to extract the AC component V′i (i = 0, 1, 2,...) From which the attenuated DC component has been removed.

Patent Document 3 discloses a method for removing a damped DC component included in a signal immediately after an accident when calculating a protection relay of an electric power system. The input signal is sampled n times per cycle at equal intervals, and sampling is performed. Digitally convert the data, Xj = (Vj-Vi + n / 2)-(Vj-Vj + n) (Vj-Vj + n) / [(Vj-Vj + n) + (Vj + n / 2-Vj + 3n / 2)], and a technique for calculating an AC component Xj from which the attenuated DC component is removed from the difference between the half cycle and one cycle of the fundamental wave is disclosed.
Japanese Patent Publication No.54-30311 JP-A-8-163768 JP-A-8-163767

  In the method using three consecutive sampling data Pn, Pn-1, and Pn-2 disclosed in Patent Documents 1 and 2, the difference value (ΔPa) between the two consecutive sampling data Pn and Pn−1, Further, a calculation is performed for obtaining a difference value (ΔPb) between Pn-1 and Pn-2 and further obtaining a difference value (ΔP) between the difference values ΔPa and ΔPb. However, when the sampling frequency is high, the difference values ΔPa and ΔPb are almost equal, and as a result, the difference value ΔP is also close to zero, which is normal due to minute noise and quantization error during digital conversion. There was a technical problem that the value could not be calculated. In Patent Documents 1 and 2, since only an attenuated DC component is assumed as a noise component, there is a technical problem that a normal value cannot be calculated with a complex waveform other than the attenuated DC component generated at the time of an accident.

  Such a technical problem is the same in Patent Document 3, and furthermore, in Patent Document 3, four limited data at times j, j / 2, j + n, and j + 3n / 2 are used in the formula. When noise is superimposed, it becomes an error factor, and the four data exist in the range of one and a half cycles of the commercial frequency. However, it is desirable that the calculation period is short when used for a protection relay.

  In addition, when the accident point is determined off-line based on the physical quantity detected at the time of the accident, the above-mentioned conventional technology cannot selectively remove only the attenuated DC component. It was difficult to position correctly.

  The object of the present invention is to solve all the above-mentioned problems of the prior art, and can cope with the increase in sampling speed, is robust against noise and quantization error, and reduces the time range of data to be used. Another object of the present invention is to provide a protective relay and an accident point locating device for a transmission / distribution system and a method for removing a transient component thereof.

  To achieve the above object, the present invention provides a transient component removal method for removing a transient DC component from a physical quantity measured at the time of an accident in a power transmission / distribution system, and a system based on the physical quantity from which the transient component has been removed. The protection relay and accident point locating device that protects the vehicle are characterized by the following measures.

(1) The protection relay of the present invention includes a means for sampling a measured physical quantity, a means for calculating a moving average value of sampling data for each predetermined moving average section, and subtracting the moving average value from the physical quantity to obtain an AC component. means for extracting performs relay operation based on the AC component, seen including a relay operation means for outputting a cut-off command to the breaker, the sampling means, N + 1 times the commercial frequency of physical quantity which is measured (N is The moving average section includes N + 1 sampling data, and the means for extracting the AC component subtracts the moving average value of the section from the sampling data at the midpoint of the moving average section. A component is extracted, and the N is an even number .

(2) The accident point locating device of the present invention comprises means for sampling the measured physical quantity, means for calculating the moving average value of the sampling data for each predetermined moving average section, and subtracting the moving average value from the physical quantity for alternating current. see contains means for extracting component and a fault point locating means for locating the fault point based on the AC component, sampling means samples the measured physical quantity in N + 1 times the commercial frequency (N is an integer) The moving average section includes N + 1 sampling data, and the means for extracting the alternating current component extracts the alternating current component by subtracting the moving average value of the section from the sampling data at the intermediate point of the moving average section, The N is an even number .

(3) The transient component removal method of the present invention samples the measured physical quantity and stores the sampling data, and the average of N + 1 sampling data from the i-th to i + N + 1-th First-time average value calculation procedure for obtaining a value, next-time average value calculation procedure for obtaining an average value of N + 1 sampling data from i + 1 to i + N + 2 The initial value calculation procedure is repeated while updating i, and the initial average value calculation procedure calculates the average value by dividing the total of N + 1 sampling data by the number of samples N + 1, After that, the average value calculation procedure is to calculate the value obtained by dividing the difference between the i-th sampling data and i + N + 2nd sampling data by N + 1, and N + 1 from i-th to i + N + 1-th The average value is obtained by subtracting from the average value of the sampling data.

  According to the present invention, the following effects are achieved.

  (1) Since moving average values are obtained for physical quantities that are detected by the power transmission / distribution system and contain transient DC components and noise components, transient DC components and noise components are efficiently calculated from physical quantities. Can be removed well.

  (2) Since the physical quantity is sampled at N + 1 times the commercial frequency, noise components depending on the commercial cycle can be efficiently removed.

  (3) Find the average value of N + 1 sampling data (N is an even number) in the moving average section, and extract the AC component by subtracting the moving average value of the section from the sampling data at the midpoint of the moving average section As a result, the transient DC component can be accurately removed from the physical quantity.

  (4) Since the moving average value is obtained approximately using the moving average value of the previous section except for the first time, the amount of calculation can be reduced.

  (5) In the protection relay, the moving average value is obtained for physical quantities that are detected by the power transmission and distribution system and contain transient DC components and noise components. And robust protection against quantization errors.

  (6) In the accident location system, the moving average value is obtained for physical quantities that are detected by the power transmission and distribution system and contain transient DC components and noise components. Makes it possible to locate accident points robust to noise and quantization errors.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the main part of an accident point locating device to which the present invention is applied. The physical point (current) measured at the time of an accident on a transmission and distribution line is used as input data to locate the accident point. Output location information.

  The analog filter 11 removes the sampling frequency aliasing noise from the physical quantity measured at the time of the accident. The sample and hold circuit 12 holds the physical quantity from which aliasing noise has been removed for a predetermined time in order to sample at equal time intervals. In this embodiment, the sampling frequency is set to N + 1 times the commercial frequency (N is an even number). The AD converter 13 quantizes the held physical quantity and stores it in the storage unit 14 as sampling data. As will be described in detail later with reference to a flowchart, the DC removal filter 15 extracts transient components, that is, attenuated DC components, from the stored sampling data and extracts AC components. The accident point locating unit 16 locates the accident point using the AC component from which the transient component has been removed, and outputs the position information.

  FIG. 2 is a block diagram showing the configuration of the main part of the DC removal filter 15, and a moving average calculation unit 15 a that sequentially obtains N + 1 moving average values of sampling data stored in the storage unit 14. And a transient component removing unit 15b that extracts an AC component from which the transient attenuated DC component is removed based on the sampling data and the moving average value.

  The moving average calculation unit 15 a includes an initial average value calculation unit 151 that calculates an average value of N + 1 pieces of sampling data from i-th to i + N + 1-th stored in the storage unit 14, and a storage unit 14. Next, the average value calculation unit 152 from the next time, which approximately obtains the average value of the sampling data of the next moving average interval stored in the N + 1 sampling data from the (i + 1) th to the (i + N + 2) th, is stored. Including.

  The initial average value calculation unit 151 obtains an average value by dividing the sum of N + 1 sampling data by the number of samples N + 1 in the moving average section. The average value calculation unit 152 from the next time onward calculates a value obtained by dividing the difference between the i-th sampling data and the i + N + 2th sampling data by the number of samples N + 1 in the moving average interval. An average value is approximately obtained by subtracting from the average value of the immediately preceding moving average section calculated in 151, that is, the average value of N + 1 sampling data from the i-th to i + N + 1-th.

  The repetition unit 153 repeats the average value calculation by the average value calculation unit 152 after the next time while updating the i, and not only the average value of the sampling data from the (i + 1) th to the (i + N + 2) th but also the i + The average value of the sampling data from the second to i + N + 3, the average value of the sampling data from i + 3 to i + N + 4, and so on are approximately calculated.

  Next, the procedure for removing the attenuated DC component in the DC removal filter 15 will be described with reference to the flowchart of FIG.

In step S1, a variable i for specifying the storage position of the leading data when N + 1 pieces of sampling data stored in the storage unit 14 are read out and the average value is obtained is initialized (for example, i = 1). The In step S2, N + 1 consecutive sampling data from the i-th to i + N + 1-th stored in the storage unit 14 are read, and the sampling data V (1) and V (2) are read out, respectively. , V (3)... V (N), V (N + 1) are stored in the initial average value calculation unit 151. In step S3, the initial average value calculation unit 151 applies the N + 1 sampling data to the following equation (1) to execute the “first calculation”, and calculates the average of the current (i-th) moving average interval. A value, that is, a DC component Xdc1 is obtained.

In step S4, the DC component Xdc1 and the sampling data V (N / 2 + 1) at the midpoint of the current moving average section are applied to the following equation (2) in the transient component removing unit 15b, and the DC component The current AC component U (N / 2 + i) from which Xdc1 has been removed is calculated. In step S5, the AC component U (N / 2 + i) is output. At this time, in this embodiment, N is an even number, and the sampling data V (N / 2 + 1) at the midpoint of the moving average section includes the average value of the DC component. By subtracting Xdc1 from V (N / 2 + 1), it becomes possible to extract the AC component from which the DC component has been accurately removed.

In step S6, the next value (i + N + 2th data) is read from the storage unit 14 and stored as sampling data V (N + 2) in the average value calculation unit 152 after the next time. In step S7, the next and subsequent average value calculation unit 152 applies the DC component Xdc1 and the sampling data V (1) and V (N + 2) to the following expression (3) to execute “calculation after the next time”. , The next (i + 1) th moving average interval, that is, N + 1 consecutive sampling data V (2), V (3), V (4) from i + 1 to i + N + 2 ... DC component Xdc2 of V (N + 2) is obtained.

  Thus, in this embodiment, when the average value Xdc1 of the i-th moving average section is obtained based on the i-th to i + N + 1-th sampling data, the next i + 1-th to i + N + 2 The average value Xdc2 of the moving average interval up to the second is newly calculated without calculating the sum of N + 1 sampling data V (2), V (3), V (4) ... V (N + 2). The difference [V (N + 2) -V (1)] between the sampling data V (N + 2) added to the moving average section and the data V (1) outside the moving average section was divided by the sampling number N + 1. The value [V (N + 2) −V (1)] / (N + 1) is approximately calculated by subtracting from the previous average value Xdc1.

In step S8, the DC component Xdc2 and the center value V (N / 2 + i + 1) of the current sampling period are applied to the following equation (4) in the transient component removing unit 15b, and the DC component Xdc2 is The removed AC component U (N / 2 + i + 1) for this time is calculated. In step S9, the AC component U (N / 2 + i + 1) is output.

  In step S10, the variable i is incremented. In step S11, data shift is executed, and the current sampling data V (2), V (3), V (4)... V (N + 2) are respectively V (1), V (2), V (3 ) ... V (N), shifted to V (N + 1). Furthermore, the DC component Xdc2 is shifted to Xdc1.

  Thereafter, the process returns to step S6, and the calculation is repeated from the next time and the alternating current components are sequentially output in the same manner as described above.

  FIG. 4 shows an accidental current V, an attenuation transient component X1 included in the accidental current V, an attenuation transient component estimated value X2 according to this embodiment, an AC component U1, and an attenuation transient component estimation from the accidental current V. It is a figure showing the relationship with the AC component estimated value U2 obtained by subtracting the value X2, and it can be observed that the estimated value X2 of the DC component is almost equal to the true value after a half cycle of the commercial frequency.

  In the above-described embodiment, the present invention has been described by taking the application to an accident point locating device as an example. However, the present invention is not limited to this, and is based on physical quantities measured in a power transmission and distribution system. It can also be applied to protection relays in power transmission and distribution systems that open circuit breakers.

  FIG. 5 is a block diagram showing a configuration of a main part of the protection relay according to the present invention, and the same reference numerals as those described above represent the same or equivalent parts. In this embodiment, the relay calculation means 17 that performs relay calculation based on the physical quantity and outputs a cutoff command to the circuit breaker performs relay calculation based on the physical quantity from which the transient DC component is removed by the DC removal filter 15. It is characterized in that it is done.

It is the block diagram which showed the structure of the principal part of the accident point location apparatus to which this invention is applied. It is the block diagram which showed the structure of the principal part of a direct current | flow removal filter. It is the flowchart which showed the operation | movement of the direct current | flow removal filter. FIG. 6 is a waveform diagram of DC component estimation and removal simulation in the present invention. It is the block diagram which showed the structure of the principal part of the protection relay to which this invention is applied.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Accident point location device, 2 ... Protection relay, 11 ... Analog filter, 12 ... Sample hold circuit, 13 ... AD converter, 14 ... Memory | storage part, 15 ... DC removal filter, 16 ... Accident point location part, 15a ... Movement Average calculating unit, 15b ... transient component removing unit, 17 ... relay calculating unit, 151 ... first average value calculating unit, 152 ... average value calculating unit from next time, 153 ... repeating unit

Claims (6)

In the power transmission / distribution system protection relay that opens the circuit breaker based on the physical quantity measured in the power transmission / distribution system,
Means for sampling the measured physical quantity;
Means for calculating a moving average value of sampling data for each predetermined moving average section;
Means for subtracting the moving average value from the physical quantity to extract an AC component;
Performs relay operation based on the AC component, seen including a relay operation means for outputting a cut-off command to the circuit breaker,
The sampling means samples the measured physical quantity at N + 1 times the commercial frequency (N is an integer),
The moving average section includes N + 1 sampling data,
The protection relay characterized in that the means for extracting the AC component extracts the AC component by subtracting the moving average value of the section from the sampling data of the intermediate point of the moving average section, and the N is an even number . The means for calculating the moving average value is:
an initial average value calculating means for calculating an average value of N + 1 sampling data items from i-th to i + N + 1-th;
Mean value calculating means for calculating the average value of N + 1 sampling data from i + 1 to i + N + 2
Means for repeating the average value calculation by the average value calculating means after the next time while updating i,
The initial average value calculating means obtains an average value by dividing the sum total of N + 1 sampling data by the number of samples N + 1,
The average value calculation means from the next time, the value obtained by dividing the difference between the i-th sampling data and the i + N + 2th sampling data by N + 1, and the N + from the i-th to i + N + 1-th 2. The protection relay for a power transmission and distribution system according to claim 1, wherein an average value is obtained by subtracting from an average value of one sampling data. In the fault location system for power transmission and distribution systems that locates fault points based on physical quantities measured at the time of an accident in the power transmission and distribution system,
Means for sampling the measured physical quantity;
Means for calculating a moving average value of sampling data for each predetermined moving average section;
Means for subtracting the moving average value from the physical quantity to extract an AC component;
Look including a fault point locating means for locating a fault point on the AC component,
The sampling means samples the measured physical quantity at N + 1 times the commercial frequency (N is an integer),
The moving average section includes N + 1 sampling data,
The means for extracting the alternating current component extracts the alternating current component by subtracting the moving average value of the section from the sampling data of the intermediate point of the moving average section, and the N is an even number. Accident location system. The means for calculating the moving average value is:
an initial average value calculating means for calculating an average value of N + 1 sampling data items from i-th to i + N + 1-th;
Mean value calculating means for calculating the average value of N + 1 sampling data from i + 1 to i + N + 2
Means for repeating the average value calculation by the average value calculating means after the next time while updating i,
The initial average value calculating means obtains an average value by dividing the sum total of N + 1 sampling data by the number of samples N + 1,
The average value calculation means from the next time, the value obtained by dividing the difference between the i-th sampling data and the i + N + 2th sampling data by N + 1, and the N + from the i-th to i + N + 1-th 4. The fault location system for a power transmission and distribution system according to claim 3 , wherein an average value is obtained by subtracting from an average value of one sampling data. In the transient component elimination method that removes transient components from physical quantities measured at the time of an accident in the power transmission and distribution system,
Sampling the measured physical quantity;
A procedure for calculating a moving average value of sampling data for each predetermined moving average section;
Look including a procedure for extracting the AC component by subtracting the moving average value from the physical quantity,
The sampling procedure samples the measured physical quantity at N + 1 times the commercial frequency (N is an integer),
The moving average section includes N + 1 sampling data,
Power transmission and distribution lines procedure for extracting the AC component extracts the alternating current component by subtracting the moving average value of the interval from the sampling data of the intermediate point of the moving average section, wherein said N is an even number Of removing transient components. The procedure for calculating the moving average value is as follows:
an initial average value calculating procedure for calculating an average value of N + 1 sampling data from i-th to i + N + 1-th;
The average value calculation procedure from the next time to calculate the average value of N + 1 sampling data from i + 1 to i + N + 2
A procedure of repeating the average value calculation by the average value calculating means after the next time while updating i.
In the initial average value calculation procedure, the total value of N + 1 sampling data is divided by the number of samples N + 1 to obtain an average value,
The average value calculation procedure after the next time is obtained by dividing the difference between the i-th sampling data and the i + N + 2th sampling data by N + 1, and the N + from the i-th to i + N + 1-th 6. The method for removing a transient component of a power transmission and distribution system according to claim 5 , wherein the average value is obtained by subtracting from the average value of one piece of sampling data.

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