JPS5842691B2 - Houkou Kayden Sochi - Google Patents

Description

[Detailed description of the invention] The present invention relates to a directional relay device for power, etc.

Generally, determining the direction of power flowing through power transmission lines and the like is an important problem in protecting and controlling the power system.

Conventional 1. It was common practice to determine direction using analog amounts of voltage and current, but as power transmission voltage and capacity have increased and distances have increased, it has become possible to digitize and centrally process information between multiple power stations, making protection and control possible. It is effective for high speed 1 and high reliability.

Therefore, in the present invention, an alternating current voltage signal and an alternating current signal having arbitrary phase angles are sampled and converted into digital values obtained by analog-to-digital conversion, and the voltage signal or current signal is converted into a digital value. By comparing the sample number that falls between the points where the polarity of the sign bit of each sampling changes with the signal obtained by differentiating either of them, the directionality of the power, etc. can be determined. Focusing on high speed and digital calculation,
The purpose is to provide a method that can determine the direction of power, etc. in a grid with high sensitivity.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram for explaining the present invention in detail, in which reference numeral 8 indicates a power system line, and 7 and 7' are instruments provided on this line section 8, respectively, for detecting voltage signals and current signals. These are detectors for transformers PT, current transformers CT, etc.

Reference numerals 1 and 1' designate sampling circuits for respectively sampling the voltage signal and current signal detected by the detectors 7 and 7'.

Reference numerals 2 and 2' designate analog-to-digital converters connected after the sampling circuits 1 and 1'.

Reference numeral 3 denotes a differentiator circuit connected, for example, after the analog-to-digital converter 2, and is provided to obtain an output that is approximately 90 degrees ahead of the voltage signal.

4 is a first logic circuit connected to the output terminals of the analog-to-digital converter 2' and the differentiating circuit 3, and the set number of samples Sk and the point where the sign bit of the current signal ■ is positive; A comparison is made with the number of samples Sa falling between the points where the sign bit of the differentiated voltage signal V' becomes negative.

5 is a second logic circuit connected to the output terminals of the analog-to-digital converters 2' and 2, and it is a logic circuit that is connected to the output terminals of the analog-to-digital converters 2' and 2, and is configured to calculate the set number of samples Sk', the point where the sign bit of the current signal I becomes positive, and the voltage. A comparison is made with the number of samples Sa' between the point where the sign bit of the signal V becomes positive.

6 is an OR circuit, which connects the first and second logic circuits 4,
If any of the comparison judgment conditions 5 is satisfied, an output is generated.

Next, the principle of determining the direction in the power system according to the present invention will be explained with reference to the configuration diagram shown in FIG. 1 and the waveform diagram shown in FIG. 2.

*Direction determination in a power system is to determine within what degree the phase angle of a current is with respect to a reference quantity of electricity, such as voltage.

For example, when detecting the direction of a short-circuit accident on a power transmission line, the positive phase of the line,
Since most of the reverse phase impedance is actance, the phase angle of the short circuit current lags behind the voltage by about 70° to 800°.

Therefore, the phase characteristics of the directional relay described in the embodiment of the present invention are such that the current delay can be completely detected using the voltage as a reference, as shown in FIG. 3d, which will be described later.

As shown in FIG. 2a, the alternating voltage signal v = V s
AC current signal i, =I, having an arbitrary phase difference with inωt
sin(ωt×θ1) or 12=Isin(ωt−θ2
) (where V is the maximum value of the voltage signal V, ω is the angular frequency, t
is the time, ■ is the maximum value of the current signal i, θ1 is the lead angle, θ2
is the delay angle), and the line 8 as shown in FIG.
is detected by current transformer 7' and potential transformer 7.

The sampling circuits 1 and 1' perform sampling as shown in FIG.
A first analog-to-digital converter 2 and a second analog-to-digital converter 2' connected to the next stage of the analog-to-digital converter 1' convert it into a digital quantity.

The voltage signal v = Vsinωt is differentiated by a differentiating circuit 3 connected to the output terminal of the digital converter 2, and v' = ω.
A digital value corresponding to Vcosωt and a current signal converted into a digital value by the analog-to-digital converter 2' are input to the logic circuit 4.

As shown in FIG. 2, the sampling value v of the voltage corresponding to time t1 is assumed to be arbitrary sampling times t1 and t2.
1=Vsin ωt1, the sampling value of the voltage corresponding to time t2 is V2=Vsin (ωt1+φ), and φ is the sampling interval, then the differentiating circuit 3 performs the following calculation.

stnφ If you perform this kind of calculation, only jan”□ will have a phase □□□φ−
An advanced waveform of 1 can be obtained.

Mathematically, differentiating V=Vsinωt is to obtain v'=ω■αaωt with a 90° phase advance, but in the present invention, in practice, even if the 90' phase is not strictly advanced,
Approximate differential values can be used without any problem.

FIG. 3a is for explaining the operation of the first logic circuit 4. In FIG.

Figure 3 a converted to the source waveform before it was converted into a digital value
Referring to , the polarity of the sign bit changes, for example, between the point Si where the sign bit of the current signal i changes from negative to positive and the point Si where the sign bit of the differentiated voltage signal V' changes from positive to negative. Let Sn<
Compare and judge using the conditional inequality of Sk.

To further discuss the comparison and judgment in the first logic circuit 4, the digital data of the current converted by one analog-to-digital converter 2' is, for example, a logic "I".
There is a sign bit in the word that indicates negative with I and positive with logic 11O1'.

The sign bit is represented by 8 bits, 12 bits, etc., and is the most significant bit of digital data. FIG. 4 shows an example of data represented entirely by 8 bits.

That is, as shown in Figure 4a, when the most significant bit is logic O, it indicates positive data, and as shown in Figure 4, when the most significant bit is logic ``1'', it indicates negative data. show.

In addition, the first logic circuit 4 detects the change point of the sign bit, starts the counting operation of a predetermined counter by the trigger pulse generated at this point, and converts the voltage converted by the other analog-to-digital converter 2. The counting operation is performed by the above-mentioned counter until the change point of the sign bit of the data obtained by advancing the phase of the digital data by 90 degrees by the differentiating circuit 3 to calculate the counted value.

This count value corresponds to the number of samples Sa that falls between the point Si where the sign bit of the current signal i changes from negative to positive and the point Si where the sign bit of the differentiated voltage signal changes from positive to negative.

Therefore, it is only necessary to compare and determine the digital value corresponding to the number of samples Sa and the digital value corresponding to the number of samples Sk to the setting based on the phase angle converted from the predetermined directionality.

The number of samples Sa determines θ1 in FIG. 3d.

θ1 determines the limit of operation even if the current i is ahead of the voltage V in phase.

Generally, in a short-circuit relay for a power transmission line, the current i does not lead the voltage V in phase, but the number of samples Sk is set so that the current i is about 3'0 degrees considering the margin of the operating range.

The first logic circuit 4 outputs an output to the OR circuit 6 when the current i is within the range of 900 lags from the lead of θ1 with respect to the voltage V, as shown in FIG. 3C.

Note that FIG. 3C shows FIGS. 3a and 3b using the same coordinates.

Furthermore, it is more practical to consider that the first logic circuit 4 is processed by software rather than that it includes a hardware counter.

The details of the comparison and judgment in the second logic circuit 5 are also described above and can be considered in the same way as in the case of the first logic circuit 4.In the second logic circuit 5, the sign bit From the point where the polarity of changes, for example, the point Si' where the sign bit of the voltage signal V changes from negative to positive, and the point S' where the sign bit of the current signal i becomes positive, the number of samples S at and the predetermined directionality. The set sample number Sk' based on the converted phase angle is compared and determined using the conditional inequality Sn'<sk'.

This determination is made by the second logic circuit 5 outputting to the OR circuit 6 when the current signal i is in the range of the delay angle θ2 determined by the set number of samples Sk' from being in phase with the voltage signal V.

In the OR circuit 6 where the output of the first logic circuit 4 and the output of the second logic circuit 5 are common inputs, when either of the conditions Sa<Sk and Sa'<Sk' is satisfied, Output and operate.

That is, as described above, the first logic circuit 4 outputs the current signal i to the OR circuit 6 when it is within the range of 90' delay from the lead of θ1 with respect to the voltage signal V. The circuit 4 determines the range of 900+θ1 shown in FIG. 3d, and ultimately determines θ1.

In addition, the second logic circuit 5 has a delay angle θ determined by the set number of samples Sk' when the current signal i is in phase with the voltage signal V.
Since θ2 is output to the OR circuit 6 when it is within the range of 2, θ2 is determined in FIG. 3d.

Since the outputs of logic circuits 4 and 5 are passed through OR circuit 6,
It is possible to obtain a directional relay that operates when the current signal i is in the range from a lead of θ1 to a lag of θ2 with respect to the voltage signal V.

In this way, in the present invention, as explained in FIGS. 3a and 3b, the number of data existing at the change point from the change point of the plus or minus sign bit of the data is set in advance, regardless of the magnitude of the input digital signal. By comparing this number with the number, it is possible to provide a predetermined electrical direction discrimination function for a certain reference amount of electricity.

Now, the direction can also be detected by using the voltage signal V as a reference without providing the differentiating circuit 3, detecting the lead or lag of the current signal i with respect to the voltage signal V, and determining the lead angle θ1 or the lag angle θ2. .

However, in this case, the following problem occurs.

That is, both the polarity of the voltage signal and the current signal may change during the sampling interval φ.

When both the polarity of the voltage signal and the current signal change, there are cases in which the voltage signal changes first and cases in which the current signal changes first.

In these cases, if you add a judgment function to the system and give this judgment function a function to judge whether the polarity of the voltage signal changes first, it will not be possible to judge if the polarity of the current signal changes first. become.

To prevent this, it is possible to set the count to O when the polarity of both sign bits changes, but in this case, it is necessary to determine 1≦Sn≦Sk, and θ1 is determined. Therefore, it is necessary to discriminate between 1≦Sn and Sn≦Sk, which requires twice the number of discrimination circuits, which is uneconomical.

On the other hand, if the differentiating circuit 3 is provided, in order to detect the lead angle θ1 of the current signal i with respect to the voltage signal V, the current signal i
It is only necessary to judge Sa and Sk from the time when the polarity of the sign bit changes until the differentiated voltage signal V' changes, and the circuit configuration is simple and economically advantageous.

Next, a case will be described in which the above principle of the present invention is applied to an actual directional relay.

Number of samples n = 12 (φ = 15°
), the current signal i with respect to the voltage signal V has an advance angle θ1 of 300 and a lag angle θ2=120, as shown in FIG. 3d.
If you want to obtain a directional relay with an operating range in the range of °, by setting the set values as 5k = 9, 5lc = 9, the current signal i will satisfy the conditional inequality of Sn × Sk as shown in Figure 3a. The maximum advance is defined as 5n=8.

In other words, 15° x 8 = 120°, when the current signal i is 60° behind the voltage signal V with v/ which is 90° in phase (v/ is ideally led by 90° in this case). is the limit of operation.

Therefore, the operating limit is reached when i leads V by 300 at 900-60°=30°.

Also, as shown in Figure 3, S A/ (s k
From the conditional expression /, the maximum delay Sn' is defined as 8.

That is, when Sn'=8, it becomes 15°X8=120° and V
On the other hand, i has an operating range up to a 120° delayed phase.

As mentioned above, the half period T/2 has 12 samples, so each sample is 15°, and the phase angles are in the range of θ1=30° and θ2=120° as shown in FIG. 3d.

In the above embodiments, the voltage signal V is differentiated, but when determining the direction based on two quantities, current and voltage, it is sufficient to use either one as a reference. Therefore, even if the voltage signal V is differentiated, the current signal i is differentiated. Since similar characteristics can be obtained by changing 8ktSk' for determination, the current signal i may be differentiated.

Furthermore, when tracking changes in the polarity of the sign bit, in the above embodiment, the point of change in polarity of the sign bit of the voltage signal is used as a reference, but the polarity changes every half cycle of the differential waveform of the current signal or either of the two. It is possible to determine the direction of electric power, etc. using any of the points as a reference.

In other words, considering the case in which the differentiating circuit 3 is provided only after the analog-to-digital converter 2' in the one shown in FIG. 5, and the differential circuit 3
The output of is input to the first logic circuit 4.

Furthermore, the output of the analog-to-digital converter 2 is input to a first logic circuit 4 and a second logic circuit 5, and the outputs of these first logic circuit 4 and second logic circuit 5 are input to an OR circuit 6. is input.

Figures 5a and 5b show the operating characteristics in this case.
i' is the differentiated current signal i.

As shown in FIG.
θ1 is determined by the number of samples that fall between points Si′ where the polarity of the sign bit changes from negative to positive.

In addition, in FIG. 5a, Si2 is the differentiated current signal i
′ indicates the point where the polarity of the sign bit of S changes from negative to positive,
i indicates the point at which the magnitude of the current signal i' changes from positive to negative.

Therefore, depending on the number of samples that fall between the point Sm where the polarity of the sign bit of the voltage signal V changes from positive to negative and the point Sm where the polarity of the sign bit of the current signal i' changes from positive to negative, θ
2 is decided.

Therefore, the differentiating circuit 3 is replaced by the analog-to-digital converter 2.
' If it is installed after the second stage, as shown in Figure 5,
The first logic circuit 5 determines the range of 90°+θ2, and the first logic circuit 4 determines θ1.

It turns out. As described above, in the present invention, a signal obtained by sampling and converting an alternating current voltage signal and an alternating current signal having an arbitrary phase angle into a digital value, and a signal obtained by differentiating either the voltage signal or the current signal. Since we compared and determined the point at which the polarity of the sign bit of each sampling changes with the number of samples that fall between the two and the predetermined number of samples, we can determine the range of the phase angle by simply setting the predetermined number of samples appropriately. The directionality of power, etc. can be determined at high speed and with high sensitivity.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram for explaining the present invention in detail, FIG. 2 a, b, and c are diagrams for explaining the principle of the present invention, and FIG. Waveform diagram for explanation of
FIG. 3d is an ideal characteristic diagram of a directional relay device for explaining the present invention, FIG. 4 is a diagram showing an example of a sign bit, FIG. 5a is another waveform diagram for explaining the present invention, FIG. 5 is another ideal characteristic diagram of the directional relay device for explaining the present invention. 1.1'...Sampling circuit, 2,2'...
...Analog-digital converter, 3...
Differential circuit, 4゜5...Logic circuit, 6...
・OR circuit.

Claims (1)

[Claims] 1 A sampling circuit that synchronously samples an alternating current voltage signal and an alternating current signal having an arbitrary phase angle with respect to the alternating voltage signal, and a sampling circuit that is connected to the output terminal of the sampling circuit and converts the sampling value of the voltage signal into an analog a first analog-to-digital converter for digital exchange; a second analog-to-digital converter connected to the output end of the sampling circuit for converting the sampled value of the current signal from analog to digital; and the analog-to-digital converter a differentiation circuit connected to a subsequent stage and differentiating either the digitized voltage signal or the current signal; and a differentiation circuit connected to the output terminals of the first analog-digital converter and the second analog-digital converter, and A differentiated digital signal and an undifferentiated digital signal are supplied to a differentiating circuit, and the polarity of the sign bit of this undifferentiated digital signal changes from negative to positive (or from positive to negative), and then the differentiated digital signal becomes positive. a first logic circuit that compares and determines the number of samples that enter during a change from negative to positive (or from negative to positive) and a set number of samples based on a phase angle converted from a predetermined directionality; A digital signal is connected to the converter and the output terminal of the second analog-to-digital converter, and is supplied with a digital signal that is not differentiated by the differentiating circuit. and a set number of samples based on a phase angle converted from a predetermined directionality, and an OR circuit connected to output terminals of the first logic circuit and the second logic circuit. A directional relay device characterized by: