JPH0251309A - Digital protective relay - Google Patents

Abstract

PURPOSE:To achieve a counter time limit characteristic having small error over a wide frequency band by employing a function represented by Z conversion for digital filter processing then calculating the amplitudes of current and voltage based on the digitally processed data and judging the operation based on an operation judging formula represented by an integration formula. CONSTITUTION:The sampling period is set to 1/4n of commercial period (where, n is a natural number) then input current and voltage (v) are fed to a digital filter for performing Z conversion of 1/2(1-Z<-2n>). The square values of the amplitudes of output current Im=1/2(im-im-2n) and output voltage Vm=1/2(vm-vm-2n) (where, m is a sampling time series) are operated through amplitude squaring method I<2>=I -ImIm-2n, V<2>=V -VmVm-2n, thus judging the necessity of operation based on an operation judging formula shown by the integration formula II. Consequently, a counter time limit characteristic having square approximation characteristic can be achieved over a wide frequency band through combination of a frequency characteristic based on digital processing and a frequency characteristic based on amplitude squaring operation.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to digital protective relays.

(Conventional technology) Conventionally, a counter-time overcurrent relay with digital voltage suppression is
It uses the algorithm described below.

In the inductive disk type reverse time-limited overcurrent relay with voltage suppression,
When the drive current flows, torque is generated.

The torque equation can be approximated as shown in equation (1).

In equation (1), the second term on the right side is dominant, and the third term
This term is an adjustment term to prevent inertia and jump from occurring due to the braking magnet in the second term. θ is the rotation angle.

It determines the stroke of the disk and determines the operation time.

Further, the contact point of the first disc can further rotate by θ1 after the circuit is closed, and the first disc can further rotate if there is a torque that overcomes the spring restraint of the fixed contact. This distance (rotation) affects the release time. In addition, when the current becomes zero, after the contact is opened, it returns to the return point at a constant angular velocity due to the spring suppression of 8 degrees and the permanent magnet braking torque.

In addition, in equation (1), ■ is the input current - "IIET is the current setting value, and Kd and K are constants. Also, the operation of the induction disk type must be strictly simulated based on equation (1). The inertia term on the right-hand side of equation (1) is ignored because it is difficult to It is.

From the above, the algorithm for determining the operation of the digital inverse time relay is expressed by the integral equation (2).

The rotational distance of the disk is ``ゞ - the distance determined by the position, and in order to simulate the motion characteristics, the integrand term on the left side is h
It is divided into several regions, for example, four regions, and furthermore, in order to simulate the return characteristic (return to the return point), a region below the minimum sensitivity current is provided. The release time characteristic is delicately related to the characteristics of the contact spring, etc., and complete simulation requires complicated formulas and processing, so generally the entire area is approximated by one function.

FIG. 7 is a flowchart showing the processing contents,
FIG. 8 is an inverse time characteristic diagram. Note that the details of the processing will be described later. Since the present invention can be understood in the same way as the explanation of FIGS. 1 and 6, the explanation will be omitted here.

(Problem to be Solved by the Invention) As shown in equation (2) above, a linear equation for input current 1/I, ..., and input voltage V is used to determine the operation of conventional anti-time relays. Therefore, it has been difficult to obtain inverse timing characteristics of wide frequency characteristics.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a digital protective relay having inverse timing characteristics with small errors over a wide frequency band including commercial frequencies.

[Structure of the invention]

(Means for solving problems) In the present invention, AC signals of current and voltage are input.

In a digital protective relay that performs a protective operation by sampling the AC signal at a constant cycle and performing an amplitude value calculation using the distal data obtained by analog/digital conversion, the sampling cycle is set to 1/1 of the commercial cycle. 4n (however, n is a natural number), and the input amount i m
Iopsinca+t, v=Vopsinωt, and the square value of the width value is the amplitude square method I""Im-n"'-・1m
-2n.

v2-v2-v-v is calculated, and it is configured to determine whether a motion is necessary or not based on a motion determination formula expressed as m-n m m-2n by the integral formula of equation (3).

(Function) First, the frequency characteristics obtained by digital processing are as shown in Figure 4, while the frequency characteristics obtained by amplitude square law calculation are as shown in Figure 4.
As shown in the figure, these composite characteristics become wide frequency characteristics as shown in FIG.

Furthermore, the operation determination formula is as shown in formula (3).

A quadratic equation for input current I/l5zt is used.

Therefore, an inverse timing characteristic of a square-law approximation characteristic can be obtained over a wide frequency band.

(Example) Examples will be described below with reference to the drawings.

FIG. 1 is a flowchart of an embodiment showing the steps of digital filter processing, amplitude value calculation processing, and inverse time characteristic calculation processing applied to a digital protective relay according to the present invention.
It is a chart.

In order to simplify the explanation, the explanation will be given starting from the block diagram of the digital protective relay shown in FIG.

In Fig. 2, 20 is an input converter, which is an input electric quantity x1~
Convert each Xn to an appropriate voltage.

This output is passed through an analog filter 21 to remove frequency error components. The output of this analog filter is sent to the input selection circuit (multiplexer) via the sample and hold circuit 22.
The input to MPX 23 and the output selected here is A.
/! 'b is converted into a digital quantity by the conversion circuit 24 and C
It is input to PU 25. The CPU 25 stores programs in the ROM 27, data from the RAM 28, and the setting section 26.
Perform calculations based on signals from. If a trip output is required as a result of the calculation, the trip output is performed via the interface circuit 29.

Next, the processing contents shown in FIG. 1 will be explained.

First, 101 is digital data input processing.

The sample value obtained by sampling the input AC signal is converted into an r digital signal.

Digital data due to this $Bs 5z-1s'm
-2...s□, sm-1+ vm-2...(
m is a time series) is read and processed. In this case, the sampling period is 1/4n (n is a natural number) of the commercial period (reciprocal of frequency).

The post-embedding data % 1 mlυ1rn is determined and input to the first-order amplitude value calculation operation 1030 (K is a constant).

In amplitude value calculation operation 103, amplitude values I and V are calculated by the square method expressed by equation (5).

Next, the integral calculation value is Sm, the time lever equivalent (time setting) is TL, and K. 1 Judgment process 10 when is a constant
In step 5, it is determined whether S, Tl penalty ≧KoTL. Judgment process 10
5, if Sm-1≧KoTL is not determined, determination process 11
3 and the current setting value! 1lIT as X(I/
Isit) = I2/I2sgr-Kxv2
When X(I/Is+ct)≧2oo is determined (Koo is a constant). If the determination result is N in the 0 determination process 113, the process is carried out to process 114 and Srn = Sm-
1-co calculation (Goit,
If ≧O, a non-operation process 124 is performed. Judgment process 12
2, if Sm≧0, then in process 123 3m=a I
J and performs the inoperation process.

If in the determination process 113,
Ko, is determined (Koj is a constant).

If the determination result in determination process 115 is N, process 11
6 and set Sm=Sm-1+01.

An inoperation process 124 is performed. If the determination result in determination processing 115 is Y, determination processing 117 is performed.

Determine X (I/I s gT)≧Ko2 (Ko2
is a constant). If the determination result in determination process 1170 is N, the process is carried out to process 118 where Sm-8,1+G2 is determined (G2 is a function of X).

An inoperation process 124 is performed. Judgment Department IJ! If the determination result is Y in step 117, it is introduced into determination processing 119, and X(I
/I 81T ) ≧ Determine Ko3 (Kos is a constant)
. If the judgment result of judgment JA filling 119 is N, process 120
is introduced into Sm -8m-10G3, and a non-operation process 124 is performed. If the judgment result is Y in the judgment process 119, it is introduced into the process 121 and Srn=Sm-104
(G4 is a function of X), and a non-operation process 124 is performed.

In addition, in the 1 determination process 105, 5r11-1≧KoTL
If so, it is introduced into the determination process 106 and X(I/I.T)
≧nimo. If the determination result of the 0 determination process 106 is N, it is reset in process 108 and introduced into process 109. If the determination result of determination process 106 is Y, it is set in process 107 and introduced into process 109. In process 109, Sm=5. It is set as Tl-40GW (G is a function of X) and is introduced into the % determination process 110. Judgment process 1
In step 10, it is determined whether deception≧Ko(TL+TV) (TV is set for a time equivalent to the release time). The judgment result of the judgment process 110 is N.
If so, operation processing 112 is performed. If the determination result of determination process 110 is Y, in process 111 Sm=0(TL+
TV) and then performs operation processing 112.

Next, I will explain how it works. Digital data obtained from digital input processing 101 is subjected to digital filter processing 10.
In step 2, filtering according to equation (4) is performed, and its frequency characteristics are as shown in FIG.

In the amplitude value calculation calculation process 103, the calculation of equation (5) is performed, and its frequency characteristics are as shown in FIG. Therefore, the overall characteristic is a wide frequency characteristic as shown in FIG.

Note that the gist of the present invention is not the digital filter processing itself, so a detailed explanation will be omitted.

Next, in 1 judgment process 105, it is determined whether the relay is to be activated or not activated by the integral calculation value Sm-1 up to the previous sampling time.
The determination is made based on whether 5m-1≧koTL holds true or not. Therefore, when it is determined that the condition does not hold, the relay at the time of the previous sampling is not activated.

Next, the process proceeds to determination processing 113, where input 11X (I/I
5it) is greater than or less than 2 to the square of the set value K, and oo o.

When the value is less than 1, the process proceeds to step 114, and the input current is calculated from the integral value S, 1 up to the previous sampling. The value obtained by subtracting the function G0=Kao・(X(I/Isr+t)D) based on the return lever position (where Kao is a constant) is set as the integral value 5rrI.If the value is negative in the judgment process 122, When the value is reached, the integral value Sm is set to 0 in process 123. Then, process 12
At step 4, the relay is rendered inoperative and the process moves to the next sampling. Note that if the determination result is Y in determination processing 113, the process advances to determination processing 115, where it is determined that X(I/l5zt)≧01. Here, input amount X (I/lllIC?
) is the setting value K. When it is less than 1 (Ko 1 > Ko o ), the process proceeds to step 116, and the integral value s up to the previous sampling is calculated.
1. Input current■Return 4-Function based on position, G,=
)1・(X(I/l5zt)-1), (However, KG
(l is a constant) is set as the integral value Sm, and the process proceeds to relay inoperation processing 124. If the determination result is Y in the determination process 115, the process proceeds to determination process 117, where X(work/work, 8
T) ≧ heart 2 is determined.

Here, the input amount X (I/Isr+T) is the set value K. □ If it is less than (Ko2>Kol), proceed to process 118 and input the current to the integral value S up to the previous sampling! and a function based on the input voltage V and the return lever position, G2=Ko2・(X
(I/Is!+T) K112) r (Ka2*
The value obtained by adding KH2 (KH2 is a constant) is set as the integral value Sm, and the process proceeds to relay inoperation processing 124. Similarly, determination processing 117
If the determination result is Y, the process proceeds to determination process 119, where
I/l5zt)≧K.

A judgment will be made. Here, the input amount I/Isza is the set value K. If it is less than 5 (Ko5>Ko2), process 12
0, and the integral value Sm-1 up to the previous sampling is a function based on the input current I, the input voltage V, and the return lever position.

G5""G5・(X(IABrr) -15) r
(K63 + KH3 is a constant) is the integral value Sn
1, the process advances to relay inoperation processing 124. Similarly, if the judgment result of judgment process 119 is Y, the process proceeds to process 121, where the integral value Sm-1 up to the previous sampling is given a function based on the input current and the return lever position, G4 "" K04
(X (I/” BET) -KH4).

(441KH4 is a constant) is set as the integral value S□ and the process proceeds to relay inoperation processing 124.

Further, in the judgment by the 1 judgment process 105, for the integral calculation value Sm-1 up to the previous sampling, Sm-, ≧KoT
If it is determined that L is established, that is, if it is determined that relay operation is to be performed, the process advances to determination processing 106, and X
A determination is made that (I/I 81CT )≧Koo.

Here, the input amount X (■/l8IT) is the square of the setting value Ko
It is determined whether it is greater than or less than 1, and if it is less than 1, the integral value at the current sampling is not added in step 108. If it is greater than 'Koo', the integral value at the current sampling is added in step 107. Next, in process 109, the integral value Sm-1 up to the previous sampling is given a function based on the input current and the return lever position, GW=Kow・(X(■/Work58T)-1),
(where K is a constant), the integral value Sfn
As a result, the process proceeds to determination processing 110.

In the determination process 110, the integral value Sm and the time lenoch position T
Based on L and the release time TV, it is determined whether Sni≧0 (TL+TV) holds true or not using the function Ko (TL+TV). If the result is true, proceed to process 111.

5rn1111 Ko (TL+T, , ), and if not established, the current integral calculation value 5rfl is left as is and the process proceeds to step 112, where the relay is activated.

When the above-described processing is expressed on the input current-operating time characteristic, it becomes an inverse time-limiting characteristic correlated with the functions 00 to G4 as shown in FIG.

According to the above embodiment, the wide frequency characteristic shown in FIG. 5 can be realized, and at the same time, since the square value of the nine input lids used to realize the wide frequency characteristic is directly used, a reaction signal having the wide frequency characteristic as described above is used. It is possible to realize a time limit characteristic and, at the same time, to realize an inverse time limit characteristic of square approximation.

In the above embodiment, it has been explained that the number of digital filters or this approximation function is used, but the invention is not limited to this, and it may be a function that is divided by 1, for example, 2, or this approximation function. Therefore, the amplitude values of current and voltage are calculated using this digitally processed data, and the operation is determined using an operation determination formula consisting of an integral formula. It is possible to provide a digital retention relay having reverse time-limited overcurrent characteristics with suppression.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the processing contents of the digital protection relay according to the present invention, FIG. 2 is a block diagram of the digital protection relay, and FIG. 3 shows that the amplitude value calculation may be an approximate function. [Effects of the Invention] As explained above, according to the present invention, the sampling period of input AC is set to 1/4n (n is a natural number), and the frequency characteristics are determined by two conversions and amplitude square method calculations as digital filter processing. 6 is a composite dyne frequency characteristic diagram, FIG. 6 is a reverse time overcurrent characteristic diagram with voltage suppression according to the present invention, FIG. 7 is a flowchart showing the processing contents of a conventional reverse time overcurrent relay with voltage suppression, and FIG. 8 is a conventional reverse time overcurrent relay with voltage suppression. FIG. 3 is a characteristic diagram of a reverse time-limiting overcurrent relay with voltage suppression. 20... Input converter, 21... Filter, 22...
・Sample hold circuit, 23... multiplexer,
24...A/D conversion circuit, 25...CPU, 26.
...Settling section. 27...ROM, 28...RAM, 29...
I10 Patent Applicant Toshiba Corporation Patent Attorney Norio Ishii Figure 2 Figure 3 Ditch Figure 7

Claims (1)

[Claims] A protective operation is performed by inputting an alternating current and voltage signal, sampling the alternating current signal at a constant cycle, and performing an amplitude value calculation operation using digital data obtained by analog/digital conversion. In a digital protective relay, the sampling period is set to 1/4n (where n is a natural number) of the commercial period (reciprocal of the frequency), and the digital data is subjected to Z-transformation as digital filter processing to obtain K・[(1+kZ＾−＾) 2^n)/(1-k)] (where K and k are constants |k|<1), or is performed using this approximation function, and the amplitude value calculation processing is performed after digital processing. Data are Im and Vm (m is sampling time series), amplitude value is I
, V, at least I^2=I^2_m_-_
n-I_m・I_m_-_2_n and V^2=V^2_
When calculating the following formula using the calculated values I^2 and V^2 using the formula m_-_n-V_m・V_m_-_2_n, there are ▲mathematical formulas, chemical formulas, tables, etc.▼However, F( I^2) is a function H of I^2 (V^2) is a function K_S_O of V^2, C is a constant constant T, K_S_O, and C are calculated by performing two or more operations with different relationships using digital processing. A digital protective relay with voltage suppression and inverse time-limited overcurrent characteristics that determines its operation.