JP2000224755A - Current differential protection relay - Google Patents

Abstract

(57) [Problem] In a current differential protection relay, an external accident occurs in a state where a large amount of residual magnetic flux remains, and does not malfunction when an accident current occurs in a relatively small area due to CT saturation. To do. SOLUTION: Means for reading required terminal data from a data memory in which detected data is stored, means 11 for creating an operation amount based on each read data, and each terminal in the data memory Means for creating an amplitude value proportional to each electric quantity using a data sequence; means for creating a suppression amount based on each of the amplitude values;
A means 13 for detecting a maximum value from among the suppression amounts during sampling; a means 14 for calculating a current sensitivity of a large current range characteristic according to the magnitude of the suppression amount; A determination means 17 having a small current range characteristic 15 and a large current range characteristic 16 for determining operation using values is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective relay for protecting a power system, and more particularly to a current differential protective relay for protecting a power transmission line based on a current differential principle.

[0002]

2. Description of the Related Art As a transmission line protection method, each terminal current value of a power system is sampled at the same time and at a constant period, and an external accident in a protection section of the transmission line is identified by using the sampled detection data. The current differential method is frequently used.

Hereinafter, the principle of current differential protection will be described with reference to FIG. This method uses a current transformer C at each end A, B and C terminals.
The absolute value | iA + iB + iC | of the vector sum of the currents iA, iB and iC obtained through T1 is defined as the operation amount, and the respective scalar sums of the currents iA, iB and iC | iA | + | i
B | + | iC | is multiplied by a constant R, and the operation is determined based on whether or not the difference between the operation amount and the suppression amount is equal to or greater than a fixed value K, and an accident inside or outside the terminals A, B, and C is performed. It is for identifying whether or not. This can be expressed by the following equation when expressed by an operation equation.

| IA + iB + iC | −R (| iA | + | iB | + | iC |) ≧ K (1)

[0004] To apply a current differential relay, for example, FIG.
As shown in FIG.
The current transformer CT1 is likely to saturate and flow out of the terminal. And at that time the inflow current i at the A and B terminals
If the current transformer CT1 at the A and B terminals does not saturate due to A and iB, the error due to the saturation of the current transformer CT1 generated at the C terminal is directly used as the differential current.

There is a possibility that a malfunction may occur depending on the degree of saturation. However, the malfunction can be prevented by making the second item of the equation (1) relatively large. However, FIG.
As shown in FIG. 1, when an internal accident occurs at the point F on the 1L and 2L sides of the parallel two-line transmission line, the 2L side of the C terminal becomes an outflow terminal, and even if there is no error in the current transformer CT1, the left side of the equation (1) 1
There is a possibility that the ratio between the operation amount of the item and the suppression amount of the second item approaches, and the ability to recognize an external accident decreases.

In this case, if the suppression amount of the second item in the equation (1) is increased, a malfunction occurs even though the accident is an internal accident. Therefore, even if an operation amount is generated by an external accident or a suppression amount is generated by an internal accident, a method of switching characteristics according to the magnitude of a current is usually applied in order to identify an accident outside the protection section with high sensitivity. That is, the characteristics are as shown in the following expression.

| IA + iB + iC | -R1 × (| iA | + | iB | + | iC |) ≧ K01 …………… Small current range …………… (2) | iA + iB + iC | −R2 × (| iA | + | iB | + | iC |) ≧ K02 large current region (3) where R1 <R2, K01> K02

The above equation (2) reduces the amount of suppression in a region where the current is relatively small to increase the sensitivity, and the equation (3) avoids the effects of various errors such as CT saturation in a region where the current is large. For this reason, the suppression amount is set relatively large to make the sensitivity low.

[0008]

In the case of CT saturation at the time of an external accident shown in FIG. 10, after a CT is saturated by a DC component included in an accident current due to an internal accident in a protection section, a state where a large amount of residual magnetic flux remains. When an external accident occurs in the protection section, the current transformer CT1 of the C terminal is more likely to be saturated than in the case where only an external accident occurs, so that CT saturation occurs even in a region where the accident current is relatively small. .

In the event of an external accident, the CT
FIG. 12 shows the temporal relationship between the amount of operation and the amount of suppression when
Shown in CT from point A under normal load condition
Until the influence of the waveform distortion due to the saturation appears, it is represented by a change between AB.

[0010] The change when the amount of operation increases after the waveform distortion appears relatively conspicuously is shown between BCs. CT
When the saturation continues and the vehicle mainly enters a region indicated by a hatched portion in FIG. 12, the vehicle enters a region where both the large current region and the small current region operate, so that the relay does not need to operate despite an external accident.

As described above, when CT saturation occurs with a smaller fault current in an external fault in a state where residual magnetic flux remains after a fault inside the protection section, an operation amount occurs in a small current range characteristic area. In the event of an external accident in the protection section, a malfunction may occur.

The present invention has been made in view of the above circumstances, and there is no fear of malfunction when a large amount of residual magnetic flux remains and an accident current is generated in a relatively small area due to CT saturation due to an external accident. It is an object of the present invention to provide a current differential protection relay.

[0013]

The current differential protection relay according to claim 1 of the present invention samples the terminal current values of the power system at the same time and at a constant period, and these sampled values are obtained. In a current differential protection relay that performs a protection operation using detection data, a means for reading required terminal data from a data memory in which the detection data is stored, and an operation amount based on the read data. Means for creating an amplitude value proportional to each electric quantity using each terminal data string in the data memory; means for creating a suppression amount based on each amplitude value; and Means for detecting the maximum value from among the suppressed amounts during the past n samplings, means for calculating the current sensitivity of the large current region characteristic according to the magnitude of the suppressed amount, and the operation amount and the suppressed amount The maximum value of It consisted determining means having an operating determining small-current region characteristics and a large current region characteristics are.

The current differential protection relay according to claim 1 of the present invention reads necessary terminal data from a data memory in which detection data is stored, and based on the read data. In addition to creating an operation amount, an amplitude value proportional to each electric quantity is created using each terminal data string in the data memory, and a suppression amount is created based on each amplitude value. Further, the maximum value is detected from the stored suppression amounts during the past n samplings, and the current sensitivity of the large current range characteristic is calculated in accordance with the magnitude of the suppression amount. Prevent malfunction.

[0015] The current differential protection relay according to claim 2 of the present invention is arranged such that the current sensitivity of the large current range characteristic is changed stepwise in claim 1. Therefore, the provision of the means for changing the current sensitivity of the large current range characteristic stepwise according to the magnitude of the suppression amount prevents malfunction due to CT saturation at the time of an external accident.

According to a third aspect of the present invention, the current differential protection relay device according to the second aspect further comprises means for clamping the sensitivity value so that the sensitivity value does not fall below a predetermined value. Therefore, by gradually changing the current sensitivity of the large current range characteristic according to the magnitude of the suppression amount, the operation sensitivity does not fall below a certain value so that an internal accident accompanied by a 流出 outflow can be normally detected. Is performed as described above.

According to a fourth aspect of the present invention, in the current differential protection relay according to the third aspect, the sensitivity switching means for switching the sensitivity so that the sensitivity is not unnecessarily high when the internal accident is suppressed beyond the maximum suppression amount. Configured. Therefore, by gradually changing the current sensitivity of the large current range characteristic according to the magnitude of the suppression amount,
The operation sensitivity is clamped so as not to be lower than a certain value so that an internal accident accompanied by a 1/2 outflow can be normally detected, and depending on the operation state of the relay, switching is performed to kill the current sensitivity calculation of the large current range characteristic.

According to a fifth aspect of the present invention, in the current differential protection relay device according to the third aspect, the hysteresis characteristic is obtained by multiplying the current sensitivity of the large current range characteristic by a positive constant depending on a relay operation state. . Therefore, by means for changing the current sensitivity of the large current range characteristic stepwise according to the magnitude of the suppression amount, the operation sensitivity does not fall below a certain value so that an internal accident accompanied by a 流出 outflow can be normally detected. And a hysteresis characteristic is obtained by multiplying the current sensitivity of the large current range characteristic by a positive constant depending on the operation state of the relay.

The current differential protection relay device according to claim 6 of the present invention according to claim 2 is provided with a function of retaining and restoring the current sensitivity calculation result of the large current range characteristic as a test function. Was. Therefore, a function of holding and returning the current sensitivity calculation result of the large current range characteristic is provided as a test function.

[0020]

FIG. 1 is a functional block diagram showing the configuration of a current differential protection relay according to a first embodiment. In FIG. 1, reference numeral 10 denotes a current differential protection relay, which is an operation amount detection unit 11, a suppression amount detection unit 12, a maximum suppression amount detection 13, a current sensitivity calculation unit 14 for a large current region characteristic, and a small current region calculation unit 15. , A large current range calculating means 16 and a relay operation determining means 17.

FIG. 2 is a flowchart for explaining the operation. First, in step S21, the current data (iAm) and (iB
m) and (iCm) are read, and a differential current component (idm) is created in step S22. The differential current idm is calculated from the terminal currents iAm, iBm and iCm by the following equation (4).

In step S23, the data (iAm, iBm, i) obtained in steps S21 and S22 is obtained.
Cm, idm), the quantities IAm, IBm, ICm, Idm proportional to the magnitude of the AC electricity quantity are calculated. In step S24, the IA obtained in step S23
m, IBm, and ICm, the suppression amount IRm by the equation (5).
Is calculated.

(3) idm = iAm + iBm + iCm (4) IRm = IAm + IBm + ICm (5)

Further, IRm is stored in a predetermined data memory because it is necessary for n samplings after the time point m. In step S25, the data is stored in a predetermined data memory that stores the IRm obtained in step S24 and the values (IRm-1, IRm-2,..., IRm-n) of the IRm during the past n samplings. Read, IRm (IRm-1, IRm-2, ..., IRm-
The maximum value IRMAXm in n) is detected.

At step S26, it is detected from the (Idm, IRMAXm) obtained at steps S23 and S25 and the constants R1, K01 whether or not the equation (2) holds. If this is established, it is determined that the operation is performed, and the process proceeds to step S27. Note that m represents a sampling time series, and it is assumed that the AC amount is sampled every 30 °.

Therefore, the difference between the time series (m) and (m-1) is one sampling, which means that (m) is at the latest sampling time. Also, (mn)
N indicates an arbitrary value, and the difference between the time series (m) and (mn) means that n sampling is performed. Step S2
At 7, the constant K02 'of the large current range characteristic determination formula is calculated. First, a sensitivity switching coefficient k between the predetermined value K1 and the suppression amount (IRm) is calculated by the equation (6).

From the sensitivity switching coefficient k obtained by the equation (6) and the constant K02 of the large current area characteristic determination equation, the constant K02 'of the large current area characteristic determination equation for the suppression amount (IRm) obtained in step S24 is represented by ( Calculated by equation 7). In step S28, the constant K02 'obtained by the equation (7) is obtained from the equation (3) from the K02' obtained by the equation (7), (Idm, IRMAXm) obtained in steps S23 and S25, and the constant R2. It is detected whether or not the condition is satisfied. If this is established, it is determined that the operation is performed, and the process proceeds to the next step. If the expression (2) is not satisfied in step S26, it is determined that no operation is performed, and the process proceeds to the next process. Further, when the formula (3) is not satisfied in step S28, it is determined that the operation is not performed, and the process proceeds to the next process.

K = IRm / K1 (6) K02 '= K02 × k (7)

FIG. 3 shows the operation of the above-described flowchart on the ratio characteristic diagram. FIG. 3 shows the change from point A in the constant load state to the influence of waveform distortion due to CT saturation from the occurrence of an external accident to the effect of waveform distortion due to CT saturation, and the change when the waveform distortion appears relatively remarkably thereafter between BC. Represents the case where the point C is in the operation region of the large current region and the small current region.

The locus of waveform distortion due to CT saturation at the time of an external accident is represented between AB and BC. The change in the maximum suppression amount (IRMAXm) during the past n samplings obtained in step S25 used for relay determination is as follows. , The change between A and B is the same until the influence of the waveform distortion due to CT saturation appears, but the change when the waveform distortion appears relatively remarkably thereafter is BC ′.
Between.

At this time, by calculating the current sensitivity of the large current range characteristic according to the magnitude of the suppression amount in step S27, the ratio characteristic when the fault current is at the point C is as follows:
The characteristics indicated by hatching in FIG. 3 indicate that the fault current point C falls within the large current range and the small current range operating region, but the maximum fault current suppression amount C 'deviates from the large current range operating region and does not operate. The relay does not operate unnecessarily because it is an area.

As described above, according to the present embodiment, even when waveform distortion occurs due to CT saturation at the time of an external accident, K02 'is calculated from the magnitude of the suppression amount, and the current sensitivity of equation (3) is calculated. , It is possible to prevent unnecessary response of the current differential protection relay due to distortion in a small current range.

FIG. 4 is a block diagram showing the second embodiment, which is shown as a flowchart of the processing contents. In the present embodiment, the sensitivity switching coefficient k is a predetermined discrete value. That is, in FIG. 4, step S27-1 is replaced with step S27-1 in FIG.

Using this sensitivity switching coefficient k, K
By calculating 02 ', the current sensitivity of the large current range characteristic is changed stepwise. From K02 'thus changing stepwise, (Idm, IRMAXm) obtained in steps S23 and S25, and constant R2, it is detected in step S28 whether or not the equation (3) is satisfied. In addition, unnecessary response of the current differential protection relay due to generation of distortion in a small current region can be prevented.

FIG. 5 is a block diagram showing the third embodiment, which is shown as a flowchart of the processing contents in the same manner as described above.
In the present embodiment, the sensitivity switching coefficient k is set to a predetermined discrete value, and is set so as not to be less than a certain value (x ≦ k). That is, instead of step S27 in FIG.
In FIG. 5, step S27-2 is performed.

That is, the sensitivity switching coefficient k is clamped to (x ≦ k) so as not to be less than a certain value in consideration of an internal accident accompanied by １ ／ outflow with respect to the sensitivity switching coefficient k.
At 8, the detection of the above equation (3) makes it possible to prevent erroneous operation during an internal accident.

FIG. 6 is a block diagram showing the fourth embodiment, which is shown as a flowchart showing the processing contents in the same manner as described above. In the present embodiment, the sensitivity switching coefficient k is set to a predetermined discrete value, not to be less than a certain value (x ≦ k), and not to be unnecessarily high (k ≦ y). is there. That is, step S27-3 is replaced with step S27-3 in FIG.

That is, the sensitivity switching coefficient k is clamped at a predetermined lower limit so as not to be less than a fixed value, and the sensitivity is switched so that the characteristic is not unnecessarily high when the internal accident is suppressed more than the maximum suppression amount. A coefficient k is calculated, and step S28
By the detection of the above equation (3), it is possible to prevent a malfunction and an error in an internal accident and a malfunction in an external accident.

FIG. 7 is a block diagram showing the fifth embodiment, and is shown as a flowchart showing the processing contents in the same manner as described above. In the present embodiment, the sensitivity switching coefficient k is set within a predetermined range (x
≦ k ≦ y), and the current sensitivity is multiplied by a positive constant to provide a hysteresis characteristic.

That is, step S27-3 is provided in place of step S27 in FIG. 2, and steps S28-1 and S28-2 are provided in place of step S28. In step S28-1, the current sensitivity is positive. The current sensitivity is multiplied by a positive constant Z2 in step S28-2 while multiplying by the constant Z1.

In short, in consideration of an internal accident involving 1/2 outflow with respect to the sensitivity switching coefficient k, the sensitivity switching coefficient k is clamped so that it does not fall below a certain value (x ≦ k). By giving a hysteresis characteristic by multiplying by a constant, it is possible to prevent a malfunction and an error in an internal accident and a malfunction in an external accident.

FIG. 8 is a block diagram showing the sixth embodiment, which is shown as a flowchart of the processing contents in the same manner as described above.
In the present embodiment, while the relay device is under test, the current sensitivity in the large current region is held at an arbitrary value so that the positive characteristic and the dynamic characteristic can be measured. Step S29 and step S30 are provided for this purpose. In step S29, it is determined whether or not the relay device is being tested, and in step S30, an arbitrary set value is set.

In the above embodiment, the power system has been described as a three-terminal configuration, but the present invention can be applied to a two-terminal configuration or a four-terminal configuration or more. In this case, equation (8) is calculated as an amount corresponding to the differential current idm in step S21 and the suppression amount IRm in step S24, and the maximum value (IRMAX) of the suppression amount and (2), (3) ) Equation may be applied.
Note that N in () is the number of terminals. In this embodiment, the protection section is described as a transmission line. However, the present invention is not limited to this, and it is needless to say that the protection section can be applied to protection of a bus, a transformer, and the like.

## EQU00005 ## idm = i (1) m + i (2) m +... + I (N) m IRm = I (1) m + I (2) m +... + I (N) m ... (8)

[0042]

As described above, according to the present invention, each terminal current value of a power system is sampled at the same time and at a constant period, and a protection operation is performed using the sampled detection data. In the protection relay, the current sensitivity of the large current range characteristic is calculated from the amount of suppression and the malfunction of the current differential protection relay is prevented by changing the large current range characteristic stepwise. It is.

Thus, after the CT is saturated by the DC component included in the fault current due to the fault inside the protection section, the CT saturation occurs when the fault current is small due to the fault outside the protection section while a large amount of residual magnetic flux remains. Even if it occurs, unnecessary response of the current differential protection relay can be prevented,
Further, it is possible to provide a current differential protection relay device which can be applied without impairing the detection sensitivity at the time of a normal internal accident.

[Brief description of the drawings]

FIG. 1 is a functional block diagram for explaining processing contents of a current differential protection relay device according to the present invention.

FIG. 2 is a flowchart illustrating the operation of claim 1 of the present invention.

FIG. 3 is a diagram conceptually showing a process of calculating a current sensitivity of a large current region characteristic.

FIG. 4 is a flowchart for explaining the operation of claim 2 of the present invention.

FIG. 5 is a flowchart illustrating the operation of claim 3 of the present invention.

FIG. 6 is a flowchart illustrating the operation of claim 4 of the present invention.

FIG. 7 is a flowchart for explaining the operation of claim 5 of the present invention.

FIG. 8 is a flowchart illustrating the operation of claim 6 of the present invention.

FIG. 9 is a diagram illustrating a general principle of a current differential protection system.

FIG. 10 is a diagram illustrating a state in which current flows intensively to one terminal during an external accident.

FIG. 11 is a diagram illustrating a case where a terminal from which a current flows during an internal accident occurs.

FIG. 12 is a diagram conceptually showing the relationship between the amount of operation and the amount of suppression at the time of accident elimination at the time of CT saturation and when the influence of saturation remains.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 current transformer 10 current differential protection relay device 11 operation amount detection means 12 suppression amount detection means 13 maximum suppression amount detection means 14 current sensitivity calculation means for large current range characteristics 15 small current range calculation means 16 large current range calculation means 17 Relay operation judgment means

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Ota 1 Toshiba-cho, Fuchu-shi, Tokyo Inside the Toshiba Fuchu Plant, Inc. 72) Inventor Masatoshi Onodera 2-24-24 Harumicho, Fuchu-shi, Tokyo Toshiba System Technology Corporation F-term (reference) 5G047 AA03 AA05 BB01 CA03 CB03

Claims (6)

[Claims] 1. A current differential protection relay device for sampling each terminal current value of a power system at the same time and at a constant period and performing a protection operation using the sampled detection data, wherein the detection data is stored. Means for reading each terminal data required from the read data memory, means for creating an operation amount based on each read data,
Means for creating an amplitude value proportional to each electrical quantity using each terminal data string in the data memory; means for creating a suppression amount based on each of the amplitude values; Means for detecting the maximum value from among the suppression amounts, means for calculating the current sensitivity of the large current range characteristic according to the magnitude of the suppression amount, and using the maximum value of the operation amount and the suppression amount A current differential protection relay device comprising: a determination unit having a small current range characteristic for determining operation and a large current range characteristic. 2. The current differential protection relay device according to claim 1, further comprising means for changing the current sensitivity of the large current range characteristic in a stepwise manner. 3. The current differential protection relay device according to claim 2, further comprising means for clamping the sensitivity so that the sensitivity does not fall below a predetermined value. 4. The current differential protection relay according to claim 3, further comprising means for switching the sensitivity so that the sensitivity is not unnecessarily high when the internal accident is suppressed to a maximum amount or more. Protection relay. 5. The current differential protection relay according to claim 3, wherein a hysteresis characteristic is obtained by multiplying a current sensitivity of the large current range characteristic by a positive constant depending on a relay operation state. Current differential protection relay. 6. The current differential protection relay according to claim 2, further comprising a function of holding and returning a current sensitivity calculation result of the large current range characteristic as a test function. Relay device.