JPH0687627B2 - Protective relay - Google Patents

Description

The present invention relates to a protective relay device for electric power equipment.

[Conventional technology]

FIG. 3 is a block diagram showing a conventional protective relay device shown in, for example, NEC technique, vol.35, No. 1, which is intended for transmission lines as protected power equipment. In the figure, (1) is a transmission line connecting the A and B substations, (2) is an A / D converter, (3) is a microprocessor, (4A) and (4B) are photoelectric converters,
(5) is an information transmission unit, (6) is a modulation / demodulation unit, (7) is a carrier terminal device, (8) is a wireless device, (9) is a full duplex line,
(10) is an I / O unit, (11) is a circuit breaker, and (12) is a sampling synchronization unit.

Next, the operation will be described. The A / D converter (2) converts the electric current of the power transmission line (1) into a digital value after sample-holding, and inputs the digital value to the microprocessor (3). The A / D converter (2) The digital value output by the photoelectric conversion unit (4A), photoelectric conversion unit (4B),
The information is transmitted to the B substation via the information transmission unit (5), the modulation / demodulation unit (6), the carrier terminal device (7), the wireless device (8) and the full duplex line (9). .

On the other hand, the digital value of the current sampled in the substation is similarly transmitted to the A substation via the full duplex line (9), and in response to this, the A substation transmits the digital value to the wireless device (8). ), A carrier terminal device (7), a modulator / demodulator (6),
The data is input to the microprocessor (3) via the information transmission section (5), the photoelectric conversion section (4B) and the photoelectric conversion section (4A).

Then, in the microprocessor (3), is the sum of the current value sampled at the A substation and the current value sampled at the B substation by the processing step S41 shown in FIG. 4 close to 0 within a predetermined range? If it is not close to 0, a trip command is sent out in processing step S42, and this trip command is sent to the I / O unit (10).
Transmitted to the circuit breaker (11) via
The B substation also operates in the same way.

Here, the determination method in the microprocessor (3) is based on Kirchhoff's law, and when there is no accident in the transmission line (1), there is no outflow current except at the A substation side terminal and the B substation side terminal. This is because the sum of the current value at the B substation and the current value at the B substation becomes zero. Therefore, the current value of the A substation and the current value of the B substation used for this determination must be at the same time, and for this reason, the sampling synchronization unit (12) is provided, which allows the A substation to operate. And sampling at B substation are controlled at the same time.

Next, this sampling synchronization control will be described. A
One of the substation side and the B substation side is a master station for sampling synchronization and the other is a slave station, and a synchronization signal is transmitted between the master station and the slave station at a time period T longer than the sampling synchronization.
The time from the transmission of this synchronization signal at the master station to the reception of the synchronization signal from the slave station is TM, the time from the transmission of the synchronization signal at the slave station to the reception of the synchronization signal from the master station is TS, By transmitting the TM value measured by the master station to the slave station, the slave station adjusts the synchronization signal transmission timing of the slave station so that the TM value sent from the master station becomes equal to the TS value measured by the slave station. Therefore, the synchronization signal will be sent out simultaneously at Substation A and Substation B,
By sampling at a constant cycle h based on this timing, the A substation and the B substation are sampled at the same time.

The control of the synchronization signal by the sampling synchronization unit (12) will be described with reference to the processing flow as shown in FIGS. 5 (a) and 5 (b). That is, in the main station, the synchronization signal is transmitted and the processing step S52 is performed in the processing step S51 every synchronization signal transmission cycle T.
The TM value counter is reset by means of the TM value counter, the TM value counter is incremented by the processing step S53 in each time period I which is sufficiently shorter than the TM, and the TM value by the processing step S54 is received when a synchronization signal is received from the slave station. The counter contents are frozen and transmitted. On the other hand, in the slave station, the periodic signal is transmitted in the processing step S55 and the TS value counter is reset in the processing step S56 for each synchronization signal transmission cycle T, and the TS value counter is processed in the processing step S57 for each time period I sufficiently shorter than TS. The TS value counter is incremented, and further processing step S58 at the time of receiving a synchronization signal from the main station
The contents of the TS value counter are frozen according to step S59, the TS value is compared with the value TM according to step S59, and the synchronization signal transmission timing is corrected. When the correction is performed, the synchronization signal transmission period T of the slave station temporarily changes slightly.

It should be noted that both the master station and the slave stations operate on the basis of a clock that can be self-propelled with sufficient accuracy for practical use during a time equal to the synchronization signal transmission cycle T. In addition, even if the master station and the slave stations sample at the same time, there is transmission time between stations, so after receiving the sampling value from the partner station, the sampling value and calculation at the corresponding same time in the own station will be performed. It will be possible.

[Problems to be solved by the invention]

As described above, the conventional protective relay device that performs digital calculation performs sampling of the electric quantity at the same time with a plurality of terminals,
Since the calculation was performed based on the digital conversion value,
A control circuit was required to synchronize sampling.

The present invention has been made to solve the above problems, and an object thereof is to obtain a protective relay device that can eliminate a control circuit that constitutes a sampling synchronization unit.

[Means for solving problems]

A protective relay device according to the present invention is a protective relay device that samples electric quantities at a plurality of electric quantity detection terminals at a fixed time cycle and protects electric power equipment based on the digital conversion value, at the same time. A means for calculating the quantity of electricity at each terminal is provided, and the means for calculating the quantity of electricity corresponds to an arbitrary time t in the section (O, Nh) from the digital value x (nh) at N points obtained by sampling at a constant time period h. Electricity x (t)
To Where qm is; when N is even, ; N is an odd number, n is an integer value from 1 to N, and is calculated by the following operation.

[Action]

In the protective relay device according to the present invention, the electricity quantity at any time can be calculated by the electricity quantity calculating means from the digital value of the electricity quantity sampled in the constant time period, and the circuit necessary for sampling synchronization between the terminals can be omitted.

〔Example〕

FIG. 1 shows an embodiment according to the present invention. The same parts as those in FIG. 3 are indicated by the same reference numerals, and the difference is that the present invention does not have a sampling synchronization part. FIG. 2 shows a program flow of processing performed by the microprocessor (3) according to the present invention, which is a processing step S21 for obtaining a time difference between sampling at the A substation and sampling at the B substation. Starting factor determination processing step S22, processing step S23 of calculating the current value at the A substation at the same time as the sampling time at the B substation based on the formula described below, and determining whether the sum of the current values is close to 0 It has a processing step S24 for performing and a processing step S25 for issuing a trip command.

Next, the operation will be described. Hereinafter, the operation on the A substation side will be mainly described, but the operation on the B substation side is similar. The A / D converter (2) converts a current, which is an electric quantity of the power transmission line (1), into a digital value after sample-holding, and inputs the digital value to the microprocessor (3). On the other hand, A / D
The digital value output from the conversion unit (2) is an opto-electric conversion unit (4A), an opto-electric conversion unit (4B), an information transmission unit (5), a modulation / demodulation unit (6), a carrier terminal device (7), a wireless device. (8) and the full-duplex line (9) are transmitted to the B substation, while the digital value of the current sampled in the B substation is also passed through the full-duplex line (9). Then, at the A substation, the digital value is received by the wireless device (8), carrier terminal device (7), modulator / demodulator (6), information transmitter (5), optical transmitter. The data is input to the microprocessor (3) via the electric conversion unit (4B) and the photoelectric conversion unit (4A).

In the present invention, however, the sampling synchronization unit does not exist, and the sampling at the A substation and the sampling at the B substation are performed at a constant time period h based on the free-running clock that is asynchronous with the partner substation.

The microprocessor (3) performs the processing shown in the flow of FIG. This process is performed at the time of A / D conversion completion at A substation and B
This is done when the current value is received from the substation. First, in processing step S21, the time difference between the sampling at the A substation and the sampling at the B substation is obtained. For example, the counter value, which is incremented at each time cycle sufficiently shorter than the sampling cycle h, is taken in when the A / D conversion is completed at the A substation and when the current value is received from the B substation. It can be calculated by considering the transmission time for transmitting the current value from the substation to the A substation. The transmission time from the B substation to the A substation is a fixed time as long as the transmission line is invariable. For example, it can be calculated theoretically or measured once and always use that value. Can handle.

Next, in process step S22, when the current value is received from the B substation, the process branches to process step S23, otherwise, the process is terminated and the next process start condition is satisfied.

In process step S23, the current value at the A substation at the same time when the current value received from the B substation is sampled is calculated by the following equation.

Now, a value at an arbitrary point on the time axis is obtained from discrete time sampling of a sample x (t) by a sampling theorem (sampling theorem).

For example, as is well known from "Theory of Information" (pages 56 to 95, selection book for basic physics 15, Shokabo Publishing, Hiroshi Sato), the function x (t) of time t has a cycle T = Nh. If there is no frequency component of 1 / 2h or more, then
Arbitrary time t in the (O, Nh) section based on the digital value x (nh) of N points obtained by sampling at a constant time period h
X (t) is decomposed into the form of the sum of the harmonic component having the direct current component and the fundamental frequency, that is, the form of the direct current component and the sum of the sine wave and the cosine wave of several frequencies, and its Fourier expansion is Can be expressed as

Where qm is; when N is even, ; N is an odd number, n is an integer value from 1 to N, q is a variable relating to frequency, h is a sampling time period, x (nh) is a sampling value of current at the A substation at time nh, and x (t) is from the B substation It is the current value at the A substation at the same time t when the incoming current value was sampled.

However, the starting point of the time is the first sampling time of the current at the substation A used in the calculation of the formula, which is 1h.

The time t indicates the sampling time at the B substation relative to the sampling time at the A substation, and can be determined based on the value calculated in the processing step S21.

Next, the sum of the current value sampled at the B substation at the processing step S24 and the current value at the A substation at the same time calculated at the processing step S23 is 0 within a predetermined range.
If it is not close to 0, a trip command is issued in processing step S25. This trip command is transmitted to the circuit breaker (11) via the I / O unit (10) and opens the circuit breaker (11).

In the above equation, the sampled amount x (t) is the time period N.
• Applies to any t in the (O, Nh) interval when h is periodic. Therefore, for example, when applying an alternating current of 50 Hz for every h = 1/600 seconds, the current is 1 /
Since it is periodic in 50 seconds, N = (1/50) / (1/600) = 1
You can set it to 2. However, the above expression holds when it can be practically considered that the sampled amount x (t) does not have a frequency component of 1/2 h Hz or more.

Further, as described at the beginning of the description of the operation of the present invention, the above operation is similarly performed on the B substation side.

In the above embodiment, a transmission line as power equipment, a current as an amount of electricity, a case where a determination method based on the current side of Kirchhoff as a calculation for protection is applied is shown.
INDUSTRIAL APPLICABILITY The present invention is generally applicable to a protective relay device that performs an operation based on a sampling value of an electric quantity that can be regarded as periodic in time.

Further, depending on the selection of the sampling time period h and the number of data N targeted by the above equation, the values that can be taken by the sine function and the cosine function in the equation may be limited, so the calculation of the equation can be speeded up. . For example, assuming that the number of data is N = 12 for the power system with the fundamental frequency of fHz, the equation for calculating Aq and Bq in the equation is the sampling time period h = 1 / (12f). Then, the determinant A on the next page can be written.

That is, every time the sampling data x (nh) is obtained And calculate If x and n (nh) are stored in the memory, Aq and Bq can be calculated only by addition and subtraction as calculation every time sampling data is obtained except for multiplication by 1/6. This is advantageous in that it can be executed at a high speed in that multiplications that require a long calculation time can be reduced as compared with executing the equation as it is.

In the above embodiment, the current value obtained in step S23 of FIG. 2 can be obtained for the specific frequency component as follows. Electricity (t) of specific frequency component of each terminal at the same time Is associated with the value q = r of the specific frequency component here, Can be calculated.

Further, regarding the fundamental frequency component, the current value (t) of the fundamental frequency component at the A substation and the current value (of the fundamental frequency component at the B substation at the same time when the current value received from the B substation was sampled t) can be expressed as follows.

here, Where h is the sampling time period, x (nh) is the current sampling value at the A substation at time nh, and y (nh-u) is the current sampling value at the B substation at time (nh-u). , U is the sampling time difference between A substation and B substation, N is the number of predetermined even number of data, (t) is the basic frequency at A substation at the same time t when the current value received from B substation is sampled The current value of the component, (t) is the current value of the fundamental frequency component at the B substation at the same time t when the current value received from the B substation was sampled, and n is an integer value from 1 to N.

The starting point of the time is 1 h as the first sampling time of the current at the substation A used for the calculation of the equation.

Also, the values that the sine function and the cosine function in the equation can take can be limited depending on the selection of the sampling time period h and the number of data N to be the subject of the equation, so the calculation of the equation can be speeded up. For example, assuming that the number of data N = 12 for the power system of the fundamental frequency of fHz, the formula for calculating A ₁ and B ₁ in the formula in the sampling time period h = 1 / (12f) is Then, we can write as follows.

A ₁ = 1/6 {C ・ X (1h) + S ・ X (2h) -S ・ X (4h)
-C ・ X (5h) -X (6h) -C ・ X (7h) -S ・ X (8
h) + S ・ X (10h) + C ・ X (11h) + X (12h)} B ₁ = 1/6 {S ・ X (1h) + C ・ X (2h) + X (3h) + C
・ X (4h) + S ・ X (5h) -S ・ X (7h) -C ・ X (8
h) −X (9h) −C · X (10h) −S · X (11h)} That is, each time sampling data x (nh) is obtained, And calculate If x and n (n) are stored in the memory, A ₁ and B ₁ can be calculated only by addition and subtraction as calculation every time sampling data is obtained except multiplication by 1/6. This is advantageous in that it can be executed at a high speed in that multiplications that require a long calculation time can be reduced as compared with executing the equation as it is.

In general, a protection relay device of a power system often employs a protection method focusing only on the fundamental frequency component of the amount of electricity. For example, in the case of the transmission line protection method based on the Kirchhoff current law described above, the Kirchhoff current law is in principle established for each frequency component even if currents of multiple frequency components are superposed at the time of a system fault. However, it is possible to perform protection based on Kirchhoff's current law by using only the frequency of the power supply, that is, the fundamental frequency component, as the frequency that surely exists.

Further, even when the protection calculation is performed by paying attention to a plurality of specific frequency components, the present invention can eliminate the need for sampling synchronization.

Therefore, if only the amount of electricity of the specific frequency component is calculated, the calculation speed becomes faster and the response speed of the relay device becomes faster,
The protection operation can be performed early.

〔The invention's effect〕

As described above, according to the present invention, the amount of electricity at any time can be calculated from the digital value of the amount of electricity sampled in the constant time period h, and it is not necessary to synchronize the sampling, so that the device is inexpensive. In addition, there is an effect that it can be miniaturized.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a program flow diagram executed by a microprocessor in an embodiment of the present invention, and FIG. 3 is a block diagram showing a conventional protective relay device. Fig. 4 is a program flow chart that was performed by a microprocessor in a conventional protective relay device.
FIGS. 5 (a) and 5 (b) are process flow charts performed in the sampling synchronization unit in the conventional protective relay device. In the figure, (1) is a power transmission line, (2) is an A / D converter, (3) is a microprocessor (electric quantity calculation means), and S21 is a time difference between sampling at the A substation and sampling at the B substation. To obtain the process start factor determination processing step, S23 is a processing step for calculating the current value at the A substation at the same time as the sampling time at the B substation, and S24 is the sum of the current values to 0. S25 is a processing step of determining whether or not they are close, and S25 is a processing step of issuing a trip command. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] 1. A protective relay device for protecting electric power equipment on the basis of electric quantities of a plurality of electric quantity detection terminals at the same time, comprising electric quantity calculation means for calculating the electric quantities of respective terminals at the same time, This electricity quantity calculating means is operated at a constant time period h
Based on the digital value x (nh) at N points obtained by sampling the respective electric quantities at the plural electric quantity detection terminals at the same time at each electric quantity detection terminal for an arbitrary time t in the (O, Nh) section. The electric quantity x (t) at Where qm is; when N is even, ; N is an odd number, n is an integer value from 1 to N, q is a variable relating to frequency, h is a sampling time period, x (nh) is a sampling value of current at the A substation at time nh, and x (t) is from the B substation A protective relay device characterized in that the incoming current value is calculated by the calculation of the current value at the A substation at the same time t when the current value was sampled. 2. The electric quantity calculating means associates the electric quantity (t) of the specific frequency component of each terminal at the same time with the value q = r of the specific frequency component. here, The protective relay device according to claim 1, wherein the protective relay device is calculated by the following calculation.