JPS61221516A - Digital protective relay - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a digital protective relay device.

[Conventional technology]

An example of a conventional digital protective relay device is the 1975 IEEJ National Conference Preliminary Collection (P1149-P1150).

As shown in "Simulation Results of 884 Product Calculation Digital Protection System", all of them had the configuration shown in FIG. 4. Fig. 4 shows an example of a digital protective relay device for overcurrent protection, where 1 is an auxiliary transformer, 2 is an analog filter (FIL), 3 is a sample and hold circuit (S, H,),
4 is an analog/digital converter (A/D), and 12 is a software signal processing section. The signal processing section 1
2 is the first digital filter 5 and the current value calculation process (
Electricity calculation processing unit)6. Operation/non-operation determination processing part B
It is made up of. 9 is a digital output circuit (Dlo
), 10 is an output auxiliary relay coil, and 11 is the output auxiliary relay contact.

Next, the operation will be explained. The harmonics of the current insulated by the auxiliary transformer 1 are attenuated by the analog filter 2, and the voltage value corresponding to the current value is held at every fixed electrical angle by the sample-and-hold circuit 3, resulting in analog-to-digital conversion. The voltage value held by the sample and hold circuit 3 is converted into a 12-bit digital quantity by the digital filter 4, and is input to the first digital filter 5.

This first digital filter 5 and the above-mentioned analog filter 2 obtain the necessary filter characteristics as a protective relay device, and then the current value calculation processing section 6 calculates the current value such that, for example, l2=( I(i))2+(I(t-T))2
......(1) I(t)...Latest current value I(t-T)--I(t) and previous current value T--
. . . The square of the peak value of the stain flow is calculated in a time period equivalent to 90, and its output is input to the operation/non-operation determination processing section 8.

In the operation/non-operation determination processing section 8, for example, I2>K
If I2>K is established, a logic 1 is output to the digital output circuit 9, and the output auxiliary relay coil 10 is excited by the output of the digital output circuit 9.
Its contact 11 is closed.

[Problem that the invention seeks to solve]

Conventional digital protective relay devices are configured as described above, so in order to eliminate the effects of harmonics, it is necessary to use the analog filter 2 or the first digital filter 5, and the harmonics There have been problems in that the higher the attenuation of the analog filter 2, the more complex the analog filter 2 becomes, and the speed at which its protection operates becomes slower.

This invention was made to solve the above-mentioned problems, and provides a digital protective relay device that can sufficiently eliminate the effects of harmonics even when the analog filter is simple and has a sufficiently high operating speed. The purpose is to

[Means for solving problems]

The protective relay device according to the present invention has a first digital filter that has a different attenuation characteristic from the first digital filter between the current value calculation processing section (electrical quantity calculation processing section) and the operation/non-operation determination processing section in the conventional device. 2 digital filters are arranged.

[Effect]

The second digital filter of the present invention has the function of being able to remove harmonics that cannot be removed by the first digital filter when sampling at a constant electrical angle.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, numerals 1 to 6 and 8 to 12 indicate the same parts as the conventional digital protective relay device for overcurrent protection shown in FIG. 4 described above. A second digital filter 7 is provided between the current value calculation processing section (electrical quantity calculation processing section) 6 and the operation/non-operation determination processing section 8, and has a different attenuation characteristic from the first digital filter 5. I have to. That is, the first digital filter 5 uses a method that takes the difference from the previous data by 90 in electrical angle, and the second digital filter 7 takes the difference from the previous data by 45 in electrical angle. The operation and effect of the embodiment will be explained.

In the embodiment shown in FIG. 1, the sampling period is set to 45 degrees in electrical angle, and the first digital filter 5 uses a method of calculating the difference from the previous data by 90 degrees in electrical angle. Watarugo L・・・・・・(2)x
y(t)...Digital filter output x(t
) e...Digital filter input x(t-T
)...Input T before x(t) by 906...
・The time period is set to 90", and the second digital filter takes the difference from the previous data by 45" in electrical angle.
That is, yy(t)...Digital filter output y(i)...Digital filter input y(
t-”)...Input T 45 degrees before y(t)...
...The time limit is equivalent to 90°. At this time, when fo is the fundamental frequency, each of the first and second digital filters 5,
7 is the frequency gain characteristic of the first digital filter 5.
2, and the second digital filter is shown in FIG. 3.

The first digital filter 5 uses a DC component.

Only 4f, , 8f, . . . can be removed.

Next, the calculation result when harmonics are included in I(t), which is the input to the above-mentioned equation (1), will be illustrated.

If I(t) includes the third harmonic, I(t)=
11ainωot”15sin3ω.tωo=2πf.

As, I2= (11aina)Qt+15sin3a+ot
)'+(Illinω.(i-T)+15sin3ωo
(t-T))2 = II + i5-21113eos 4ω. t
−・−(4) If I(t) includes the 5th harmonic, I(t) = 115lna+Ot + 15ai
As n 5ωOt, I” = (I, sinωot+15sin5ωOt
)” + (II ginωo(t-T)+15ain
5ω. (t-T) )2 = Il +i, + 21115eO@4ωot
m m (5).

As can be seen from equations (4) and (5), the third, 51I
The wave will appear as the fourth harmonic in the output of the calculation of equation (1).

Therefore, as shown in the present invention, if the output of the current value calculation processing section 6 which performs the process shown by equation (1) is passed through the second digital filter 7 which performs the process shown by equation (3), There is no fourth harmonic in the output of , and the output of the second digital filter T for equation (4) is 112+1,2. ...(6) The second digital filter TO output for equation (5) is: ■, 2+l, 2 ...-I・(7
).

That is, due to the effect of the second digital filter, for example, for the third harmonic, conventionally
Instead of having to consider an error of 1, it becomes K if we only need to consider 1 as an error. To illustrate this with a numerical example,! □=1, l,=0.3 (i.e., I
In the case where there are 3 (l) third harmonics in (t), the conventional method is ! According to the present invention, it was necessary to consider an error of 30%, but the error becomes 4.4+%.

It can thus be seen that the second digital filter 7 has the effect of significantly suppressing the influence of harmonics that could not be removed by the analog filter 2 and the first digital filter 5.

In order to suppress the influence of harmonics to the same degree as in the present invention using the analog filter 2, it is necessary to increase the attenuation of the gain in the harmonic region, and as a result, the operation speed is lower than that in the present invention. Furthermore, since the analog filter 2 is a complex filter, the adjustment becomes complicated and the characteristics tend to change due to changes in temperature and humidity over time, so the present invention is not applicable from the viewpoint of characteristics and cost. It is more advantageous to do so.

In addition, the same performance as in the present invention is overridden in the first digital filter 5 due to constraints on the sampling period caused by various calculation algorithms in the current value calculation processing section 6.
Furthermore, it is practically difficult to implement a large number of relay functions with a single processor, considering processing time constraints and the like.

It should be noted that the present invention was carried out with the main aim of improving the performance and reducing the cost of installing protective relays, but since the present invention relates to "measuring the amount of electricity etc.", various measuring devices, It is clear that similar effects can be achieved when applied to a control device.

〔Effect of the invention〕

As described above, according to the present invention, harmonic components that cannot be removed by the analog filter and the first digital filter are removed by the second digital filter, so there is no need to complicate the structure of the analog filter. ,
Therefore, it is possible to obtain a digital protective relay device which has a sufficiently high operating speed, sufficiently improved harmonic characteristics, excellent resistance to environmental changes and changes over time, is easy to adjust, and is inexpensive.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the digital protective relay device of the present invention, and FIGS. A frequency gain characteristic diagram of the second digital filter, FIG. 4 is a block diagram of a conventional digital protective relay device. In the figure, 1 is an auxiliary transformer, 2 is an analog filter,
3 is a sample hold circuit, 4 is an analog-to-digital conversion circuit, 5 is a first digital filter, 6 is a current value calculation processing section (electricity calculation processing section), 7 is a second digital filter, and 8 is an operation/invalidity circuit. 9 is a digital output circuit, 10 is an output auxiliary relay coil, 11 is an output auxiliary relay contact, and 12 is a signal processing section. In the figures, the same reference numerals indicate the same or equivalent parts. Original person for patent: Mitsubishi Electric Corporation (2 others) -- Procedural amendment (voluntary) 18.6% 7.2 days

Claims (1)

[Claims] an analog filter that attenuates harmonic components from the analog signal output from the transformer; a sample-and-hold circuit that samples and holds the analog signal from the analog filter at fixed electrical angle intervals; and an analog circuit that converts the sample-and-held signal into digital form.・Digital converter and
a first digital filter that attenuates harmonic components from a digital signal output from the analog-to-digital converter; and an electricity quantity calculation processing unit that calculates an electricity quantity by inputting the digital output of the first digital filter; Operate based on the output signal from the electricity quantity calculation processing section.
In a digital protective relay device comprising an operation/non-operation determination processing unit that determines non-operation, and a relay that operates based on an output from the operation/non-operation determination processing unit, the electric quantity calculation processing unit and the operation A digital protective relay device, characterized in that a second digital filter having a different attenuation characteristic from the first digital filter is provided between the inoperation determination processing section and the inoperation determination processing section.