JPH0993788A - Ratio differential relay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make small a fault current in an external fault at the distant end to prevent malfunction of a relay by providing a second arithmetic element which accumulates the combined amount of electricity under the conditions of the output of a first arithmetic element which operates when the combined amount of electricity exceeds the predetermined value and outputs a protection command when the accumulated amount of the electricity has exceeded the predetermined value. SOLUTION: A drive input is issued to an anti time-limit judging means 23 from a logical AND circuit 22 and thereby amount of operation |Id| is obtained in the anti time-limit judging means 23, while amount of suppression multiplied by k1 in the ratio calculating means 16 is obtained in an adding circuit 18 as the combined amount of electricity. Although accumulation of combined amount of electricity is performed, since this fault is an external fault, a fault is removed by the other relay before the accumulated value exceeds the predetermined value and malfunction of relay can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ratio differential relay used for protecting rotating machines such as generators and other equipment.

[0002]

2. Description of the Related Art FIG. 11 shows a generator protection circuit. In FIG. 11, G is a generator, TR is a transformer, CB is a circuit breaker, and power is supplied to the grid through the circuit breaker CB. Indicates. CT1 and CT2 are current transformers for meters, and are configured so that the currents from these CT1 and CT2 are introduced into the ratio differential relay 87 provided across the generator.

FIG. 12 is a functional block diagram of a ratio differential relay having a variable ratio characteristic having the operation region shown in FIG. 13A, which corresponds to the ratio differential relay 87 of FIG.
The currents I _CT1 and I _CT2 introduced from CT1 and CT2 are converted into digital quantities I ₁ and I ₂ through an analog / digital converter A / D, and are soft-processed in a calculation unit CPU.

Reference numeral 11 denotes an operation amount creating section, which is a vector sum Id = I ₁ + I with the input digital amounts I ₁ and I _2.
2 (Id: referred to as movement amount) is created. Further, the amplitude value calculation unit 12 obtains the amplitude value | Id | of this operation amount Id.

In the amplitude value calculators 13 and 14, the amplitude values | I ₁ | and | I ₂ | of the respective digital quantities I ₁ and I ₂ inputted.
Then, the amplitude values respectively obtained here are introduced into the suppression amount creating unit 15, and the suppression amount creating unit 15 adds the scalar sum | Ir | = | I ₁ | + | I ₂ | (of the digital quantities I ₁ and I ₂ Ir: referred to as the suppression amount) is created.

Further, the suppression amount Ir is multiplied by k1 and k2 in the ratio calculation units 16 and 17, respectively (k1 and k2 are constants). In the adder circuit 18, the calculation results of the amplitude value calculation unit 12 and the ratio calculation unit 16 are added (| Id | −k1 · | Ir |), and when the combined electricity amount becomes a certain value or more in the DF1 determination unit 20. DF
The 1 determination unit 20 outputs. The above is summarized as equation (1), which is a characteristic diagram of DF1.

Further, the combined electricity quantity from the output of the adder circuit 19 is introduced into the DF2 judging section 21, and when the DF2 judging section 21 exceeds a certain value, the DF2 judging section 21 outputs it. The above is summarized as formula (2), which is the DF1 determination unit 20 and D of FIG.
The logical product of the two outputs of the F2 determination unit 21 is output as the protection command 31.

[0008]

## EQU1 ## | Id | -k1. | Ir | .gtoreq.k3 (k3 is a constant) ... (1) | Id | -k2. | Ir | .gtoreq.k4 (k4 is a constant) ... (2)

When an external accident occurs at the near end of the generator like F1 in FIG. 11, a large accident current is generated. If a transient DC component is superimposed on this fault current, the magnetic flux of the CT iron core may increase and cause saturation.

When the same CT saturation occurs in both CT1 and CT2, the difference between the secondary current waveforms of CT1 and CT2 is small, and the resulting differential current (operation amount) is the CT saturation region shown in FIG. 13 (b). Therefore, the relay does not enter the operation range of the relay and the relay does not operate. As described above, the conventional ratio differential relay has a variable ratio characteristic to prevent malfunction of the relay.

[0011]

[Problems to be Solved by the Invention]
CT saturation at the far end accident will be described with reference to FIG. When an accident occurs at the far end of the generator like F2 in FIG. 11, the accident current passing through CT1 and CT2 is small, and the superimposed transient DC component also has a value proportional to this.

However, if this continues for a long time, the magnetic flux of the CT iron core due to the transient DC component accumulates with time and causes saturation. As a result, CT saturation will occur some time after the accident occurs. The situation of CT saturation changes depending on the characteristics of CT, the magnitude of the fault current, the magnitude of the transient DC component, etc. However, if the CT characteristics of CT1 and CT2 are different, the time until CT saturation will be different, so the A time delay occurs and a differential current (operation amount) Id is generated.

Further, since the suppression amount Ir is small at the far end,
In some cases, the CT saturation region may enter the operation range of the relay as shown in FIG. 14 (b), which causes a malfunction of the relay. In this way, in the variable ratio characteristic of the conventional ratio differential relay, when the external accident at the far end continues for a long time,
The ratio differential relay could malfunction.

Although it is conceivable to reduce the operating ratio of the ratio differential relay in order to avoid this malfunction, it is difficult to reduce the ratio sensitivity above a certain level in order to protect the rotating machine.

The present invention has been made to solve the above-mentioned problems, and when the fault current is small due to an external far-end accident of the ratio differential relay and a transient DC component is generated for a long time, the ratio differential relay is generated. It is an object of the present invention to provide a ratio differential relay that does not malfunction even if the CT applied to is saturated.

[0016]

A ratio differential relay according to claim 1 of the present invention samples two or more alternating currents at a constant time interval and takes them in as an analog / digital converted digital quantity, and An arithmetic unit that performs an arithmetic operation based on the digital amount of the alternating current, and a vector sum and a scalar sum are calculated by the arithmetic unit based on the digital amount of the alternating current, and the vector sum is the operating amount and the scalar sum is suppressed. As a ratio differential relay having first calculation elements 20 and 21 for outputting a protection command when the combined electric quantity obtained from the relationship between the operation quantity and the suppression quantity becomes a predetermined value or more, the combined electric quantity When the output of the first computing element 20 or 21 that operates when is equal to or more than a predetermined value is added, the combined electric quantity is integrated, and when the value of the integrated electric quantity integrated here is equal to or larger than a predetermined value. With a second computing element 23 for outputting a protection command.

Therefore, when the fault current is small due to an external accident at the far end, and the transient DC component is generated for a long time to cause saturation of the CT applied to the ratio differential relay,
Both of the judgments with the calculation elements 20 and 21 of are output and may fall inside the variable ratio characteristic.

However, in this case, the activation input is issued to the anti-time limit determination section which is the second arithmetic element. Therefore, the operation amount | Id | and the control amount | Ir | multiplied by k1 by the ratio calculation unit are obtained as a combined electricity amount by the anti-time limit determination unit through the addition circuit, but this integration is predetermined because of an external accident. The accident is eliminated by another relay before the value exceeds the value of, and the relay does not malfunction.

In the case of an internal accident, the first computing elements 20, 21
Both of the determinations are output, the variable ratio characteristic is entered, and the activation input is issued to the counter time limit determination unit. In this case, since it is an internal accident, the accident is not eliminated by another relay, and the operation amount | Id | and the suppression amount | Ir | multiplied by k1 in the ratio calculation unit 16 are added in the counter circuit. The combined electric quantity obtained through 18 is integrated, and when this integrated value is equal to or greater than a predetermined value, relay operation is performed.

According to a second aspect of the present invention, in addition to the first aspect, a third arithmetic element to be output when the operation amount exceeds a predetermined value is added. Therefore, in the event of an external accident, there is no malfunction due to the time-delayed operation by the second computing element, and in the case of an internal accident, the accident is eliminated by the instantaneous operation by the third element.

According to a third aspect of the present invention, in addition to the first aspect, a fourth arithmetic element output is added, which is output when the combined electric quantity obtained from the relationship between the operation amount and the suppression amount exceeds a predetermined value. It was done. Therefore, in the event of an external accident, the second
The calculation element of operates in a timed manner by inputting the synthetic electric quantity,
Accident is removed by another relay and it does not malfunction. But,
In the event of an internal accident, the first and fourth computing elements operate and the relay operates.

Further, in claim 4 of the present invention, the condition in which the combined electric quantity obtained from the relationship between the operation amount and the suppression amount is equal to or more than a predetermined value in place of the second computing element in claim 1 is provided. Is added with a fifth operation element that outputs the integrated value when the integrated value exceeds a predetermined value.
Therefore, the relay operation is performed on condition that the operation amount is equal to or greater than the predetermined value and the internal accident is clear in the operation of the first arithmetic element, but the first arithmetic element does not operate in the external accident. , Will not malfunction.

[0023]

1 is a functional block diagram of an embodiment of a ratio differential relay according to claim 1 of the present invention.
In FIG. 1, the same parts as those in FIG. The characteristic part of the configuration shown in FIG. 1 is that the anti-time limit determination unit 23 is provided to obtain the activation input from the AND circuit 22.

Therefore, when there is a start input, the counter time limit determination unit
In 23, the operation amount | Id | and the suppression amount | Ir | multiplied by k1 in the ratio calculation unit 16 are obtained as the combined electric amount through the adder circuit 18, and the integrated amount of the combined electric amount is expressed by the equation (3). It is determined whether or not it is equal to or more than a predetermined value.

When the expression (3) is satisfied, the protection command 24 is output. Further, when there is no activation input introduced through the AND circuit 22, the integration of the combined electric quantity obtained through the pre-addition circuit 18 is cleared.

[Equation 2] ∫ (| Id | −k1 · | Ir |) dt ≧ k5 (k5 is a constant) (3)

Next, the operation will be described. First, when the fault current is small due to an external accident at the far end, and the transient DC component is generated for a long time to cause saturation of the CT applied to the ratio differential relay, the DF1 determination unit 20 of the functional block diagram is shown. 2 and the DF2 determination unit 21 output both,
It may fall within the operating range of the variable ratio characteristic of (a).

In this case, a start input is issued from the AND circuit 22 to the anti-time limit determination unit 23, and the anti-time limit determination unit 23 operates the operation amount | Id | and the ratio calculation unit 16 multiplies the suppression amount by k1. Ir
| Is obtained as a combined quantity of electricity through the adder circuit 18. Then, the integrated amount of electricity is integrated, but in this case, since it is an external accident, the accident is removed by another relay before the integrated value exceeds a predetermined value, and the relay does not malfunction.

On the other hand, at the time of an internal accident, both the judgments of the DF1 judging section 20 and the DF2 judging section 21 of the functional block diagram of FIG. 1 are output and enter the protection area of the variable ratio characteristic of FIG. 2 (a). However, the activation input is not issued from the AND circuit 22 to the anti-time limit determination unit 23, and the accident is not eliminated by another relay.

The amount of suppression | Ir | multiplied by k1 in the arithmetic unit 16 is integrated by the combined amount of electricity obtained through the adder circuit 18. When this integrated amount exceeds a predetermined value, relay operation is performed. Further, the present invention is not limited to the above-described embodiment, and the operation amount | Id | and the suppression amount | Ir multiplied by k2 by the ratio calculation unit 17
It is also possible to obtain the combined amount of electricity from | and the addition circuit 19 and to introduce the obtained combined amount of electricity into the counter time limit determination unit 23.

According to the present embodiment, both the DF1 judging section and the DF2 judging section satisfy the operation judgment formula due to the influence of CT saturation due to the fault current outside the protection range, and even if the operation range shown in FIG. 2 is reached, It is possible to provide a ratio differential relay that does not output a protection command by the anti-time limit determination unit and does not malfunction due to the effect of CT saturation due to a fault current outside the protection range.

FIG. 3 is a block diagram showing a modification of FIG.
In this modification, the ratio calculation unit 32 and the addition circuit 33 are separately provided, and the operation amount | Id | and the suppression amount | Ir | multiplied by k8 in the ratio calculation unit 32 are calculated from the combined electric amount obtained through the addition circuit 33. The equation (4) may be determined in the counter time limit determination unit 23.

[Equation 3] ∫ (| Id | −k8 · | Ir |) dt ≧ k5 (k5 is a constant) (4)

FIG. 4 is a block diagram of an embodiment of a ratio differential relay according to claim 2 of the present invention. In this embodiment, the HOC judging section 25 is provided at the output stage of the amplitude value calculating section 12 of FIG.

Then, the judgment output of the DF1 judgment unit 20 and the DF
2 The output of the judgment output of the judgment unit 21 is ANDed through the AND circuit 22 and the output of the HOC judgment unit 25.
The logical product is performed through 26, and the output of the logical product circuit 26 and the output of the anti-time limit determination unit 23 are logically summed through the logical sum circuit 27, and the output is output as a protection command.

In the HOC determination unit 25, the operation amount is (5)
Determine if the formula is satisfied. Therefore, the operation amount is HOC
When it is less than the set value of the determination unit 25, it has the anti-time limit operation area FIG. 5 (a) as in FIG. 1, and when it is more than the set value, it is the instantaneous operation area. This is shown in the characteristic diagram of FIG.

[Expression 4] | Id | ≧ k6 (k6 is a constant) …………… (5)

In short, in the ratio differential relay of this embodiment,
In the case of an internal accident in which a considerably large operation amount Id occurs in the operating range, the judgment output of the DF1 judging section 20 and the judgment output of the DF2 judging section 21 are AND circuits because the accident is in the operating range of the ratio differential relay. There will be an ANDed output through 22.

Further, a considerably large movement amount | Id | is introduced into the HOC judgment unit 25 through the amplitude value calculation unit 12, and the movement amount | Id | satisfies the equation (5) in the HOC judgment unit 25.
When the HOC determination section 25 also outputs, the AND of the output of the AND circuit 22 and the output of the HOC determination section 25 is further output through the AND circuit 26.

In this case, the output of the logical product circuit 26 is output through the logical sum circuit 27 regardless of the output of the anti-time limit determination section 23, and the logical sum output is output, and the protection command is output. According to the present embodiment,
It becomes possible to detect an internal accident at high speed in the large current region at the time of an internal accident with respect to the ratio differential relay of FIG.

FIG. 6 is a block diagram of an embodiment of a ratio differential relay according to claim 3 of the present invention. In the present embodiment, the HOC determination unit 29 is provided, and the combined electric quantity that has passed through the adder circuit 18 is fetched as an input of the anti-time limit determination unit 23, and the HOC determination unit is also used.
It is also configured to be input as 29 inputs.

As is apparent from FIG. 6, the HOC determination unit 29
In, the motion judgment of Eq. (6) is performed.

[Expression 5] | Id | -k1 · | Ir | ≧ k6 (k6 is a constant) ……… (6)

Therefore, the operation is as follows:
And the determination output of the DF2 determining unit 21 are AND circuits.
The output that is logically ANDed through 22 and the output of the HOC determination unit 29 are logically ANDed through an AND circuit 26, and further the AND circuit
The output of 26 and the output of the anti-time limit determination section 23 are ORed through the OR circuit 27 and the output is output as a protection command.

In this embodiment, in the ratio differential relay, the operation amount | Id | and the suppression amount | Ir | multiplied by k1 in the ratio calculation unit 16 are obtained through the adder circuit 18 in the operating range. The quantity (| Id | -k1 · | Ir |) becomes large in the case of an internal accident, and because it is an accident within the operating range of the ratio differential relay, the judgment output of the DF1 judgment unit 20 and D
The judgment output of the F2 judging unit 21 is logically output through the logical product circuit 22.

Further, a considerably large amount of the above-mentioned combined electric quantity is introduced into the HOC judging section 29 through the amplitude value calculating section 12, and the HOC judging section 29 satisfies the formula (6) by the combined electric quantity, and the HOC judging section 29 is satisfied. Is also output. Therefore, the logical product of the output of the logical product circuit 22 and the output of the HOC determination unit 29 is further output through the logical product circuit 26.

In this case, the output of the logical product circuit 26 is output through the logical sum circuit 27, and the protection command is issued regardless of the output of the anti-time limit determination unit 23 (FIG. 7). According to the present embodiment, before the HOC determination unit 29 operates, the counter time limit determination unit 23
The anti-time limit operation is performed, and in a large current area at the time of an internal accident, the internal accident is detected at high speed and a protection command is output.

Further, the present invention is not limited to the above embodiment, and the combined electric quantity is obtained from the operation quantity | Id | and the suppression quantity | Ir |
The combined electric quantity obtained here is used as the counter time limit determination unit 23 and the HOC.
You may make it introduce | transduce into the determination part 24. Then, the counter time limit determination unit 23 determines the expression (7).

[Equation 6] ∫ (| Id | −k2 · | Ir |) dt ≧ k5 (k5 is a constant) …… (7)

FIG. 8 is a modification of FIG. 6, in which the input of the HOC determination unit 29 is changed. That is, FIG.
As shown in FIG. 3, the ratio calculation unit 34 and the addition circuit 35 are separately provided, and the operation amount | Ir | and the suppression amount | Ir | multiplied by k8 in the ratio calculation unit 34 are obtained as the combined electricity amount through the addition circuit 35. Based on this combined quantity of electricity, the HOC determination unit 29 (8)
The expression is determined.

[Expression 7] | Id | -k8 · | Ir | ≧ k5 (k5 is a constant) ……… (8)

FIG. 9 is a block diagram of an embodiment of a ratio differential relay according to claim 4 of the present invention. In FIG. 9, the same parts as those in FIG. In this embodiment, the input of the anti-time limit determination section 30 is replaced with the motion amount. That is, the input of the anti-time limit determination unit 30 is based on the motion amount | Id |.

Therefore, the determination output of the DF1 determination section 20 and the determination output of the DF2 determination section 21 are logically ANDed through the AND circuit 22, and this output is introduced as a start input to the anti-time limit determination section 30.

When there is a start-up input, the anti-time limit determination section 30 determines whether or not the cumulative value of the operation amount | Id | is greater than or equal to a predetermined value by the equation (9). Then, when the expression (9) is satisfied, a protection command is output. When there is no start input introduced through the AND circuit 22, the equation (10) and the integration of the operation amount | Id | are cleared.

[0049]

[Equation 8] ∫ | Id | dt ≧ k5 (k5 is a constant) ……… (9) ∫ ｜ Id ｜ dt = 0 …………………… (10)

According to the present embodiment, both the DF1 and DF2 satisfy the motion judgment formula due to the influence of CT saturation due to the protection range external fault current, and even if the motion range is reached, the anti-time limit judgment unit 30 causes The protection command is not output, and malfunction does not occur due to the effect of CT saturation due to the fault current outside the protection range.

[0051]

As described above, according to the present invention, when the fault current is small due to the external far end accident of the ratio differential relay and the transient DC component is generated for a long time, the present invention is applied to the ratio differential relay. It is possible to provide a ratio differential relay that does not malfunction even if the CT that is saturated is saturated.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a ratio differential relay according to claim 1 of the present invention.

FIG. 2 is a characteristic diagram of the ratio differential relay shown in FIG.

FIG. 3 is a modification of FIG.

FIG. 4 is a configuration diagram of an embodiment of a ratio differential relay according to claim 2 of the present invention.

5 is a characteristic diagram of the ratio differential relay shown in FIG. 4;

FIG. 6 is a configuration diagram of an embodiment of a ratio differential relay according to claim 3 of the present invention.

7 is a characteristic diagram of the ratio differential relay of FIG.

FIG. 8 is a modification of FIG.

FIG. 9 is a configuration diagram of an embodiment of a ratio differential relay according to claim 4 of the present invention.

FIG. 10 is a characteristic diagram of the ratio differential relay shown in FIG. 9.

FIG. 11 is an application example of a ratio differential relay.

FIG. 12 is a functional block diagram for explaining a conventional ratio differential relay.

FIG. 13 is a characteristic diagram of a conventional ratio differential relay.

FIG. 14 is a characteristic diagram for explaining problems of the conventional ratio differential relay.

FIG. 15 is a diagram for explaining the generation of a motion amount due to a far end accident outside the protection range.

[Explanation of symbols]

 11 Motion amount creation unit 12, 13, 14 Amplitude value calculation unit 15 Suppression amount creation unit 16, 17, 32, 34 Coefficient calculation unit 18, 19, 33, 35 Adder circuit 20 DF1 determination unit 21 DF2 determination unit 22, 26 Logic Product circuit 23, 30 Reverse limit time determination unit 25, 29 HOC determination unit 27 OR circuit 87 Ratio differential relay

Front page continuation (72) Inventor Tetsuya Sobue 1-24-2 Harumi-cho, Fuchu-shi, Tokyo Inside Toshiba System Technology Co., Ltd.

Claims (4)

[Claims] 1. An arithmetic unit for sampling two or more alternating currents at a constant time interval, taking in as an analog / digital converted digital amount, and performing an arithmetic operation based on the digital amount of the alternating current; Part calculates a vector sum and a scalar sum based on the digital value of the alternating current, and the vector sum is an operation amount, and the scalar sum is a suppression amount, and a combined electric amount obtained from the relationship between the operation amount and the suppression amount is predetermined. In a ratio differential relay having a first arithmetic element that outputs a protection command when the value becomes equal to or more than a value, the first arithmetic element output that operates when the combined electricity amount becomes a predetermined value or more is used as a condition. , Integrating the combined electricity quantity,
A ratio differential relay characterized by comprising a second arithmetic element for outputting a protection command when the value of the integrated electric quantity accumulated here becomes a predetermined value or more. 2. A logic which adds a third arithmetic element to be output when the operation amount exceeds a predetermined value and operates when both the first arithmetic element output and the third arithmetic element output are derived. The ratio differential relay according to claim 1, further comprising means for setting a logical sum output of the product output and the second operation element output as a protection command. 3. A fourth arithmetic element for outputting when the combined electric quantity obtained from the relationship between the operation amount and the suppression amount becomes a predetermined value or more, and the first arithmetic element output and the fourth arithmetic element are added. A logical product output that operates when both the output and
2. The ratio differential relay according to claim 1, further comprising means for making a logical sum output with the output of the arithmetic element as a protection command. 4. In place of the second calculation element, the operation amount is integrated on condition that the combined electricity amount obtained from the relationship between the operation amount and the suppression amount is equal to or more than a predetermined value, and the integrated value is set to a predetermined value. The ratio differential relay according to claim 1, further comprising a fifth arithmetic element that outputs a value equal to or greater than a value.