JP3558309B2 - Ratio differential relay - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a ratio differential relay used for protecting a rotating machine such as a generator and other devices.
[0002]
[Prior art]
FIG. 11 shows a protection circuit for the generator. In FIG. 11, G indicates a generator, TR indicates a transformer, and CB indicates a circuit breaker, and shows a state in which power is supplied to the system via the circuit breaker CB. CT1 and CT2 are instrument current transformers, and are configured to introduce currents from these CT1 and CT2 to a ratio differential relay 87 provided across a generator.
[0003]
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, and 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 subjected to software processing in the arithmetic unit CPU.
[0004]
Reference numeral 11 denotes an operation amount creating unit which creates a vector sum Id = I ₁ + I ₂ (Id: referred to as an operation amount) with the input digital amounts I ₁ and I ₂ . Further, the amplitude value calculating section 12 obtains the amplitude value | Id | of the movement amount Id.
[0005]
The amplitude value calculators 13 and 14 determine the amplitude values | I ₁ | and | I ₂ | of the input digital quantities I ₁ and I ₂ , and introduce the determined amplitude values into the suppression amount generator 15. Then, the suppression amount creating unit 15 creates a scalar sum | Ir | = | I ₁ | + | I ₂ | (Ir: referred to as suppression amount) of the digital amounts I ₁ and I ₂ .
[0006]
Further, the suppression amount Ir is multiplied by k1 and k2 (k1 and k2 are constants) by the ratio calculation units 16 and 17, respectively. The addition circuit 18 adds the calculation results of the amplitude value calculation unit 12 and the ratio calculation unit 16 (| Id | −k1 · | Ir |), and when the combined electric quantity becomes a certain value or more in the DF1 determination unit 20. Then, the DF1 determination unit 20 outputs. Summarizing the above, the equation (1) is obtained, which is a characteristic diagram of the DF1.
[0007]
Further, the combined electric quantity from the output of the adder circuit 19 is introduced to the DF2 judging section 21, and when the DF2 judging section 21 becomes a certain value or more, the DF2 judging section 21 outputs. The above is summarized as equation (2), and the logical product of the two outputs of the DF1 determination unit 20 and DF2 determination unit 21 in FIG.
[0008]
(Equation 1)
| Id | −k1 · | Ir | ≧ k3 (k3 is a constant) (1)
| Id | −k2 · | Ir | ≧ k4 (k4 is a constant) (2)
[0009]
When an external accident occurs near the end of the generator as in F1 of FIG. 11, a large accident current occurs. When a transient DC component is superimposed on this fault current, the magnetic flux of the iron core of the CT increases and saturation may occur.
[0010]
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) exists in the CT saturation region shown in FIG. As a result, the relay does not enter the operation range 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 time of a far-end accident such as F2 in FIG. 11 will be described with reference to FIG. When an accident occurs at the far end of the generator as indicated by F2 in FIG. 11, the accident current passing through CT1 and CT2 is small, and the superimposed transient DC component also takes a value proportional to this.
[0012]
However, if this continues for a long time, the magnetic flux of the CT iron core due to the transient DC component accumulates over time, causing saturation. As a result, CT saturation occurs after a certain time from the point of occurrence of the accident. The state of CT saturation changes depending on the characteristics of the CT, the magnitude of the fault current, the magnitude of the transient DC component, and the like. However, when the CT characteristics of CT1 and CT2 are different, the time until CT saturation is different. A time delay occurs and a differential current (operation amount) Id is generated.
[0013]
In addition, since the suppression amount Ir is small at the far end, the CT saturation region may enter the operation region of the relay as shown in FIG. 14B, causing a problem that the relay malfunctions. As described above, according to the variable ratio characteristics of the conventional ratio differential relay, when the external accident at the far end continues for a long time, the ratio differential relay may malfunction.
[0014]
In order to avoid this malfunction, it is conceivable to lower the operation ratio of the ratio differential relay. However, it is difficult to lower the ratio sensitivity to a certain level or more for protection of the rotating machine.
[0015]
The present invention has been made to solve the above-mentioned problem, and is applied to a ratio differential relay when the fault current is small and a transient DC component occurs for a long time in an external far end accident of the ratio differential relay. It is an object of the present invention to provide a ratio differential relay which does not malfunction even if the CT in which saturation occurs occurs.
[0016]
[Means for Solving the Problems]
A ratio differential relay according to claim 1 of the present invention samples two or more AC currents at fixed time intervals, takes in the analog / digital converted digital amount, and based on the AC amount digital amount. calculates the amplitude value of their vector sum and scalar sum, the synthesis electric quantity calculation element which calculates the amplitude values and combining the electrical quantity obtained from the scalar sum outputs of the vector sum, from the synthesized electrical quantity computation means The first calculation element which is output when the combined electric quantity of the first element becomes equal to or more than a predetermined value (K ₁ ), and the same combined electric quantity as described above are integrated under the condition of the output of the first arithmetic element. A second operation element for outputting when the value of the combined electric quantity becomes equal to or more than a predetermined value (K ₂ ), and means for setting an output of the second operation element to a protection command output .
[0017]
Therefore, when the fault current is small due to an external fault at the far end, and a transient DC component is generated for a long time and the CT applied to the ratio differential relay is saturated, the first arithmetic elements 20 and 21 May be output and may fall within the variable ratio characteristic.
[0018]
However, in this case, a start input is issued to the reciprocal time determination unit that is the second calculation element. Then, the operation amount | Id | and the control amount | Ir | multiplied by k1 in the ratio calculation unit are obtained as a combined electric amount through the addition circuit in the time limit determination unit. The accident is eliminated by another relay before the value becomes equal to or more than the value of, and the relay does not malfunction.
[0019]
Also, in the event of an internal accident, both judgments with the first arithmetic elements 20 and 21 are output, and the operation enters the variable ratio characteristic and an activation input is issued to the time limit judgment unit. In this case, since the accident is an internal accident, the accident is not eliminated by another relay, and the operation amount | Id | in the time limit judgment unit and the suppression amount | Ir | multiplied by k1 in the ratio calculation unit 16 are added to the addition circuit. The integration of the combined amount of electricity obtained through 18 is performed, and the integration becomes a predetermined value or more, and the relay operation is performed.
[0020]
According to a second aspect of the present invention, in the first aspect, a third operation element that is output when an amplitude value of the vector sum becomes equal to or more than a predetermined value (K ₃ ) is added, and the first operation element is added. Means are provided for setting a logical sum output of an AND output that operates when both the output and the third operation element are derived and the output of the second operation element as a protection command output.
[0021]
Further, in claim 3, claim 1 of the present invention, the synthesis electric quantity from the synthesized electrical quantity calculating means adds a fourth computing element for output when a predetermined value (K ₄₎ above, wherein a logical product output that operates when the output and the operation element outputs of the fourth of the first computing element is derived both, comprises means for the protection Directive outputs the logical sum output of the second calculation element output Was.
[0022]
Further, in claim 4, claim 1 of the present invention, the second in place of the computing element, on condition the first operation element output, integrates the amplitude of the vector sum, this integrated value is predetermined A fifth operation element for outputting when the value becomes equal to or more than the value (K ₅ ) is provided, and means for using the output of the fifth operation element as a protection command output is provided.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 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 configuration in FIG. 1 is characterized in that a time limit judging unit 23 is provided to obtain a start-up input from the AND circuit 22.
[0024]
Accordingly, when there is a start input, in the time limit determination unit 23, the operation amount | Id | and the suppression amount | Ir | multiplied by k1 in the ratio calculation unit 16 are obtained as a combined electric amount through the adder circuit 18. Then, it is determined whether or not the integration is equal to or more than a predetermined value as shown in Expression (3).
[0025]
(3) If the expression is satisfied, the protection command 24 is output. When there is no start 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)
[0026]
Next, the operation will be described.
First, when a fault current is small due to an external fault at the far end and a transient DC component is generated for a long time and the CT applied to the ratio differential relay is saturated, the DF1 determination unit 20 in the functional block diagram is used. 2 and the DF2 determination unit 21 are both output, and may fall within the operation range of the variable ratio characteristic shown in FIG.
[0027]
In this case, an activation input is issued from the AND circuit 22 to the time limit determination unit 23, and the action amount | Id | in the time limit determination unit 23 and the suppression amount | Ir | It is obtained as a combined electric quantity through the adding circuit 18. Then, the integration of the combined electric quantity is performed. In this case, since the accident is an external accident, the accident is eliminated by another relay before the integration becomes a predetermined value or more, and the relay does not malfunction.
[0028]
On the other hand, at the time of an internal accident, both the judgments of the DF1 judgment unit 20 and the DF2 judgment unit 21 in the functional block diagram of FIG. 1 are output, and the inside of the protection area of the variable ratio characteristic shown in FIG. However, an activation input is issued from the AND circuit 22 to the time limit determination unit 23, and the accident is not eliminated by another relay.
[0029]
The amount of suppression | Ir | multiplied by k1 in the operation unit 16 is integrated through the addition circuit 18 to integrate the combined electric amount, and this integration becomes equal to or more than a predetermined value, and the relay operation is performed. Further, the present invention is not limited to the above-described embodiment, and a combined electric quantity is obtained via the adder circuit 19 from the operation quantity | Id | and the suppression quantity | Ir | The obtained combined amount of electricity may be introduced to the time limit determination unit 23.
[0030]
According to the present embodiment, both the DF1 determination unit and the DF2 determination unit satisfy the operation determination expression 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. It is possible to provide a ratio differential relay that does not output a protection command and does not malfunction due to the influence of CT saturation due to a fault current outside the protection range.
[0031]
FIG. 3 is a configuration diagram showing a modified example 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. Expression (4) may be determined in the time limit determination unit 23.
(Equation 3)
∫ (| Id | −k8 · | Ir |) dt ≧ k5 (k5 is a constant) (4)
[0032]
FIG. 4 is a configuration diagram of one embodiment of the ratio differential relay according to claim 2 of the present invention. In this embodiment, an HOC determination unit 25 is provided at the output stage of the amplitude value calculation unit 12 in FIG.
[0033]
Then, an output obtained by ANDing the judgment output of the DF1 judgment unit 20 and the judgment output of the DF2 judgment unit 21 through the AND circuit 22 and the output of the HOC judgment unit 25 are ANDed through the AND circuit 26. It is characterized in that the output of the AND circuit 26 and the output of the time limit judging section 23 are logically ORed through the OR circuit 27 and the output is output as a protection command.
[0034]
The HOC determination unit 25 determines whether the amount of operation satisfies the expression (5). Therefore, when the amount of operation is less than the set value of the HOC determination unit 25, the time limit operation area is shown in FIG. 5A as in FIG. 1, and when it is more than the set value, it becomes the instantaneous operation area. This is shown in the characteristic diagram of FIG.
(Equation 4)
| Id | ≧ k6 (k6 is a constant) (5)
[0035]
In short, in the ratio differential relay according to the present embodiment, in the case of an internal fault in which a considerably large operation amount Id occurs in the operation range, the fault is in the operation range of the ratio differential relay, so that the determination output of the DF1 determination unit 20 and DF2 There is an output obtained by performing a logical product of the determination output of the determination unit 21 and the logical product circuit 22.
[0036]
Also, a considerably large operation amount | Id | is introduced into the HOC determination unit 25 through the amplitude value calculation unit 12, and the HOC determination unit 25 satisfies the expression (5) with the operation amount | Id |, and the HOC determination unit 25 also outputs If there is, the logical product of the output of the logical product circuit 22 and the output of the HOC determination unit 25 through the logical product circuit 26 is further output.
[0037]
In this case, the output of the logical product circuit 26 passes through the logical sum circuit 27 and, regardless of the output of the time limit determination unit 23, the logical sum is output and the protection command is output. According to the present embodiment, the internal fault can be detected at high speed in the large current range at the time of the internal fault with respect to the ratio differential relay of FIG.
[0038]
FIG. 6 is a configuration diagram of one embodiment of the 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 addition circuit 18 is captured as an input to the time limit determination unit 23 and is also captured as an input to the HOC determination unit 29.
[0039]
As is apparent from FIG. 6, the HOC determination unit 29 performs the operation determination of the expression (6).
(Equation 5)
| Id | −k1 · | Ir | ≧ k6 (k6 is a constant) (6)
[0040]
Therefore, as an operation, the logical product of the output of the DF1 determining unit 20 and the logical output of the DF2 determining unit 21 through the logical product circuit 22 and the output of the HOC determining unit 29 are logical producted through the logical product circuit 26. Further, an output obtained by performing an OR operation on the output of the AND circuit 26 and the output of the infinite time determination unit 23 through the OR circuit 27 is output as a protection command.
[0041]
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 within the operation range. Id | −k1 · | Ir |) is large in the case of an internal accident, and is an accident within the operating range of the ratio differential relay, so that the judgment output of the DF1 judgment unit 20 and the judgment output of the DF2 judgment unit 21 are: There is an output that is ANDed through the AND circuit 22.
[0042]
In addition, the considerably large combined electric quantity is introduced into the HOC determining section 29 through the amplitude value calculating section 12, and the HOC determining section 29 satisfies the expression (6) and outputs the HOC determining section 29 with the combined electric quantity. It becomes. Therefore, the AND of the output of the AND circuit 22 and the output of the HOC determination unit 29 is further output through the AND circuit 26.
[0043]
In this case, the output of the AND circuit 26 passes through the OR circuit 27. In this case, regardless of the output of the time limit judging section 23, the output of the logical sum is output and a protection command is issued (FIG. 7). According to the present embodiment, before the HOC determination unit 29 operates, the time limit operation is performed by the time limit determination unit 23, and the internal fault is detected at high speed in a large current region at the time of the internal fault, and a protection command is output.
[0044]
Further, the present invention is not limited to the above-described embodiment. A combined electric quantity is obtained via the adder circuit 19 from the operation quantity | Id | and the suppression quantity | Ir | The combined electric quantity obtained may be introduced into the time limit judgment unit 23 and the HOC judgment unit 24. Then, the time limit determination unit 23 determines Expression (7).
(Equation 6)
∫ (| Id | −k2 · | Ir |) dt ≧ k5 (k5 is a constant) (7)
[0045]
FIG. 8 is a modified example of FIG. 6, in which the input of the HOC determination unit 29 is changed. That is, as shown in FIG. 8, a ratio calculation unit 34 and an addition circuit 35 are separately provided, and the operation amount | Ir | and the suppression amount | Ir | The HOC determination unit 29 determines the expression (8) based on the combined amount of electricity.
(Equation 7)
| Id | −k8 · | Ir | ≧ k5 (k5 is a constant) (8)
[0046]
FIG. 9 is a block diagram of an embodiment of the ratio differential relay according to claim 4 of the present invention. In FIG. 9, the same parts as those in FIG. In the present embodiment, the input of the time limit determination unit 30 is replaced with the operation amount. That is, the input of the time limit determination unit 30 is based on the operation amount | Id |.
[0047]
Therefore, the judgment output of the DF1 judgment unit 20 and the judgment output of the DF2 judgment unit 21 are ANDed through the AND circuit 22, and this output is introduced as a start input to the infinite time judgment unit 30.
[0048]
When there is a start input, the time limit determination unit 30 determines whether or not the integration of the operation amount | Id | is equal to or larger than a predetermined value by using Expression (9). Then, when the equation (9) is satisfied, a protection command is output. When there is no start input introduced through the AND circuit 22, the integration of the equation (10) and the operation amount | Id | is cleared.
[0049]
(Equation 8)
∫ | Id | dt ≧ k5 (k5 is a constant) (9)
∫ | Id | dt = 0 ………………… (10)
[0050]
According to the present embodiment, both DF1 and DF2 satisfy the operation determination formula due to the influence of CT saturation caused by the fault current outside the protection range. Output does not occur, and no malfunction occurs due to the influence of CT saturation due to a fault current outside the protection range.
[0051]
【The invention's effect】
As described above, according to the present invention, when the fault current is small and the transient DC component occurs for a long time in the external far end accident of the ratio differential relay, the CT applied to the ratio differential relay is saturated. Thus, it is possible to provide a ratio differential relay that does not malfunction even if the above-mentioned situation occurs.
[Brief description of the 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
FIG. 2 is a characteristic diagram of the ratio differential relay of FIG. 1.
FIG. 3
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.
FIG. 5 is a characteristic diagram of the ratio differential relay of FIG. 4;
FIG. 6 is a configuration diagram of an embodiment of a ratio differential relay according to claim 3 of the present invention.
FIG. 7 is a characteristic diagram of the ratio differential relay of FIG. 6;
FIG. 8 is a modified example of FIG. 6;
FIG. 9 is a configuration diagram of one 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 of FIG. 9;
FIG. 11 shows 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 a problem of the conventional ratio differential relay.
FIG. 15 is a diagram for explaining occurrence of an operation amount due to a far-end accident outside the protection range.
[Explanation of symbols]
Reference Signs List 11 Operation amount creation units 12, 13, 14 Amplitude value calculation unit 15 Suppression amount creation units 16, 17, 32, 34 Coefficient calculation units 18, 19, 33, 35 Addition circuit 20 DF1 determination unit 21 DF2 determination unit 22, 26 Logic Product circuits 23, 30 Reverse time limit determination unit 25, 29 HOC determination unit 27 OR circuit 87 Ratio differential relay

Claims (4)

Two or more of the alternating current was sampled at regular time intervals, capture a digital quantity which is an analog / digital converter, calculates the amplitude values and the scalar sum of the vector sum on the basis of the digital quantity of the alternating current , is a synthetic electrical quantity computation element calculates and outputs the amplitude value and the synthesis the quantity of electricity obtained from the scalar sum of the vector sum, the synthesis electric quantity from the synthesized electrical quantity computation means exceeds a predetermined value and (K ₁₎ or The combined electric quantity similar to the above is integrated under the condition of the first arithmetic element output when the first arithmetic element is output and the output of the first arithmetic element, and the value of the integrated electric quantity integrated is equal to or greater than a predetermined value (K ₂ ). And a second operation element that outputs when the output of the second operation element is obtained, wherein the output of the second operation element is used as a protection command output . In proportion differential relay according to claim 1, the amplitude value of the vector sum is added a third operation element outputs when a predetermined value (K ₃₎ above, wherein said first computing element output A ratio differential relay comprising means for setting a logical sum output of the logical product output operated when both the third arithmetic element is derived and the output of the second arithmetic element to a protection command output. . In proportion differential relay according to claim 1, wherein the synthesis electric quantity from the synthesis electric quantity calculating means adds a fourth computing element for output when a predetermined value (K ₄₎ above, wherein the first operational wherein the output element and said fourth computing element output is provided with a logical output which operates when derived together, the means to protect command output a logical sum output of the second calculation element output And the ratio differential relay. 2. The ratio differential relay according to claim 1, wherein the amplitude value of the vector sum is integrated under the condition of the output of the first arithmetic element instead of the second arithmetic element, and the integrated value is equal to a predetermined value (K ₅ ) A ratio differential relay, comprising: a fifth operation element that outputs when the above condition is satisfied, and a unit that uses the output of the fifth operation element as a protection command output .

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