JP3302131B2 - Current compensation type undervoltage relay - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current compensation type undervoltage relay for detecting a fault in a transmission line.

[0002]

2. Description of the Related Art Japanese Patent No. 1339128 discloses a current compensation type undervoltage relay. This is, as shown in FIG. 10, centered on the origin O on the current I-voltage V plane, centered on the arc of radius K 'and the tip P of the compensation vector ZI,
It has a so-called motion-field-shaped operating range surrounded by arcs having a radius K 'and segments in contact with these arcs, and is suitable for detecting a transmission line accident as static characteristics.

[0003]

However, the principle of the determination is based on the instantaneous value, and sufficient filtering is required to prevent the influence of the waveform distortion of the voltage and current at the time of an accident due to recent severe system conditions. According to this principle, one half cycle
The instantaneous value of the point actually determines the operating limit and requires a waiting time until its effective determination timing. Any of these means a delay in operation. By using the inner product and outer product of the vector by the so-called product algorithm, it is possible to make a valid decision continuously instead of one point in a half cycle, that is, at each sampling time, but focused on the fundamental wave And still requires sufficient filtering. The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a current compensation type undervoltage relay capable of performing continuous determination and having a small response with a small filtering.

[0004]

A current compensation type undervoltage relay according to a first aspect of the present invention receives a voltage sample value and a current sample value as inputs, and performs the above operation based on inductance and resistance of a target section of a transmission line. A line voltage drop in a target section is calculated, and a half period or one period of a system frequency is set as a predetermined period, and a first value which is a sum of a square of the voltage sample value in the predetermined period and the voltage sample value Calculating means for calculating a second value that is a sum of the product of the line voltage drop and the line voltage drop in the predetermined period, and a third value that is a sum of the square of the line voltage drop in the predetermined period, When the first value is equal to or less than a predetermined value, or when the first value
When the value obtained by subtracting twice the second value from the sum of the second value and the third value is equal to or less than the predetermined value, or when the second value is positive and equal to or less than the third value, and Determining means for generating an output when a value obtained by subtracting a value obtained by dividing a square of a value of 2 by the third value from the first value is equal to or less than the predetermined value;

A current compensation type undervoltage relay according to a second aspect of the present invention receives a voltage sample value and a current sample value as inputs, and determines a line voltage drop in the target section based on the inductance and resistance of the target section of the transmission line. Is calculated, and a half cycle or one cycle of the system frequency is set as a predetermined period, and a first value which is a sum of the square of the voltage sample value in the predetermined period, the voltage sample value, the line voltage drop, A second value that is the sum of the product of
Calculating means for calculating a third value, which is a sum of the square of the line voltage drop in the predetermined period, when the first value is equal to or less than a predetermined value, or when the first value is equal to or less than a predetermined value. Time, or the first value is a predetermined value and the second value
When the third value is less than or equal to a value obtained by subtracting the third value from the sum of the times, or when the first value is less than or equal to the sum of the predetermined value and the second value, and when the first value is the second value. When the value is equal to or less than the sum of the value obtained by dividing the square of the value by the third value and the predetermined value, an output is generated in any of the following cases.

According to a third aspect of the present invention, there is provided a current compensation type undervoltage relay comprising an undervoltage element, an offset element, a parallel element, and an OR element, wherein the undervoltage element has a voltage vector of a predetermined value or less. The offset element generates an output when the magnitude of a third voltage vector obtained by compensating the voltage vector with a second voltage vector consisting of an impedance drop is equal to or less than a predetermined value. A vertical element, a horizontal element, and a logical AND element, wherein the vertical element is the voltage with respect to the second voltage vector obtained from the magnitudes of the voltage vector, the second voltage vector, and the third voltage vector. The output occurs when the foot of the perpendicular from the vector tip is within the range of the second voltage vector, and the lateral element produces an output when the length of the perpendicular is less than or equal to a predetermined value. The product element produces an output when both the vertical element and the horizontal element produce an output, and the OR element produces an output when any of the undervoltage element, the offset element or the parallel element produces an output. Was to occur.

According to a fourth aspect of the present invention, in the current compensation type undervoltage relay according to the third aspect, the vertical element outputs an output when each of the magnitudes of the voltage vector and the third voltage vector is less than a predetermined value. Was to occur.

According to a fifth aspect of the present invention, in the current compensation type undervoltage relay according to the third aspect, the vertical element is configured to compensate the voltage vector with a voltage vector that is １ ／ of the second voltage vector. An output is generated when the magnitude of the voltage vector of No. 4 is equal to or smaller than a predetermined value.

According to a sixth aspect of the present invention, in the current compensation type undervoltage relay according to the first aspect, the predetermined period is a half cycle of a system frequency, n / 2 cycles of one cycle or n cycles (where n is a positive value). Integer).

[0010]

The current-compensated undervoltage relay according to the first and second aspects of the present invention is characterized in that the current-compensated undervoltage relay is proportional to the effective value of the voltage that compensates for the line voltage drop within the range of the target section from the self-terminal voltage / current. Is determined, and when this effective value is less than or equal to a predetermined value, it is determined that a transmission line accident has occurred. Then, a point where the effective voltage value is minimized in the target section of the transmission line is derived and an accident in the target section is detected, so that continuous determination is possible. In addition, such a point is almost a fault point, and the voltage at the fault point usually drops sufficiently, so that even if there is a distortion in the self-terminal voltage / current, it is hardly affected by the distortion. When the fault point resistance is large and the fault point residual voltage is large, the transient fault decay time constant is shortened due to the large fault point resistance and rapidly attenuates, so that it is hardly affected by the transient vibration component. Therefore, the filtering can be simple as required for sampling, and a fast response can be obtained. In particular, claim 2 is a modification of the determination formula of claim 1.

The current compensation type undervoltage relay according to claim 3, claim 4, or claim 5 of the present invention is of a type in which the determination is made based only on the magnitude of the alternating current. The determination is made based on the magnitude of the second voltage represented by the impedance drop and the magnitude of the third voltage represented by the difference between the voltage and the second voltage. In this case, since the instantaneous value of the AC amount is not directly used and is based only on the magnitude, the amount on which the calculation is based is an averaged amount, and the pre-filter can be simplified. In particular, if the magnitude is calculated by a so-called rectification addition type algorithm, it means an average value, and has a filtering effect itself, so that no special pre-filter is required. In particular, claims 4 and 5 are modifications of a part of the judgment formula of claim 3.

According to a sixth aspect of the present invention, in the current compensation type undervoltage relay according to the first aspect, the predetermined period is n / 2 cycles or n cycles of a system frequency (where n is a positive integer).
By doing so, it is more generalized.

[0013]

An embodiment will be described below with reference to the drawings. FIG.
FIG. 1 is a block diagram of an embodiment for explaining a current compensation type undervoltage relay according to the present invention. In FIG. 1, reference numeral 1 denotes calculation means (calculation step) and reference numeral 2 denotes determination means (determination step). The calculating unit 1 as an input voltage sample values v _m and the current sample value i _m, and calculates and outputs A, B and D by (1).

(Equation 1) Note that R and L represent the resistance and inductance of the target section of the transmission line, respectively, the subscript m represents the sampling time according to a general notation, and Σ represents the sum of one half cycle or one cycle of the system frequency. i ′ _m is an amount corresponding to the differential value of the current, and can be realized by a known method, for example, Japanese Patent No. 1660533.

When the equation (2) holds, the judgment means 2 outputs the output O
Produces P.

(Equation 2) Here, K is a value proportional to the effective value of the voltage to be detected. The proportionality constant is the same as the proportionality constant in which A in the above equation (1) is proportional to the effective value of the voltage. Unless below confusion,
The common proportionality constant is omitted and simply referred to as an effective value. The characteristic obtained by the configuration of FIG.
This is a characteristic equivalent to that of the conventional method, and further generalized including this. The reason will be described below.

The voltage v (x) _m at any point on the transmission line is
Before the accident point, it is expressed by equation (3). x is a normalized distance, 0 ≦ x ≦ 1 is the target section, x = 0 is its own end, x = 1
Means the far end of the target section. The effective value of v (x) _m is V
(X), if the proportionality constant is omitted as described above,
(4), and x = 0 at the own end and x = 1 at the far end. Therefore, equation (6) means that the effective voltage value at the self end or the far end is smaller than the predetermined value K.
Assuming that the predetermined value K is a value obtained by multiplying the square of the radius K 'in FIG. 10 by the above-mentioned common proportionality constant, the equation (6) can be expressed by a circle centered on the origin O in FIG. This means that it is equivalent to a characteristic corresponding to a circle centered on P.

[0016]

[Number 3] _{v (x) m = v m} -x (Ri m + Li 'm) ......... (3) V (x) 2 = Σv (x) m 2 = A-2Bx + Dx 2 ...... (4) V (0) ² = A, V (1) ² = A−2B + D (5) A ≦ K OR A−2B + D ≦ K (6)

Next, when x that minimizes V (x) is obtained,
Equation (7) is obtained. Therefore, the minimum value of V (x) ² is given by equation (8). If 0 ≦ B ≦ D, then 0 ≦ x ≦ 1
Equation (9) is obtained, and equation (9) means that the minimum value of the effective voltage value in the target section is smaller than the predetermined value K, and corresponds to the characteristic of the line segment in FIG. It can be seen that the sum of these corresponds to the characteristics of FIG.

From d (A−2Bx + Dx ² ) / dx = 0, x = B / D (7) V (x) ² = A−B ² / D... (8) ) 0 ≦ B ≦ D AND AB ² / D ≦ K (9)

As described above, Σ represents a total over a half cycle or one cycle of the system frequency.
The reason is as follows. That is, even if the calculation is performed at any sampling time, an integer period should be used to obtain a constant value, especially one period in consideration of responsiveness, but a half period may be used if the calculation is performed after removing the DC component. It is the same that the proportional constant becomes constant only when the proportional constant is different, and the response is further enhanced.
Thus, in the target section of the transmission line, the determination is made based on the point at which the effective voltage value is minimized, so that the influence of distortion is small and minimal filtering is required. Further, since the determination is made based on the effective value, a continuous determination can be made.

FIG. 2 is a block diagram showing the configuration of another embodiment of the present invention. Reference numeral 2-1 denotes a determination means obtained by equivalently converting the determination means 2 of FIG. Others are the same as FIG.
The determination means 3 keeps the relationship of OR with Expression (6) as it is,
The former half of equation (9) is replaced with equation (10).

A ≦ K + B AND A ≦ K + B ² / D (10) The fact that this is equivalent to the determination means 2 will be described below.

In the range of B ≧ D, K + 2B−D ≧ K + B
Therefore, if A ≦ K + B holds, then A ≦ K + 2B−
D holds true, regardless of whether A ≦ K + B ² / D is true or false.
Since equation (6) holds, equation (10) is included in equation (6) within this range. In the range of B ≦ 0, K + B ≦ K. Therefore, if A ≦ K + B holds, A ≦ K also holds, which is also included in the equation (6). In the range of 0 ≦ B ≦ D, B / D
≦ 1, therefore since the ^{A ≦ K + B 2 / D} ≦ K + B, (1
If the first half of equation (0) holds, the second half also holds, and the whole equation (10) holds. It is understood that the above is equivalent to the determination means 2 in total.

FIG. 3 is a block diagram showing the configuration of another embodiment of the present invention. Reference numeral 2-2 denotes a determination unit having a determination expression of the following expression (11), which is equivalent to the determination unit 2-1 of FIG.

Equation 6: A−K ≦ max 2min (B ² / D, B), 2B−D, 0｝ (11) In equation (11), the value obtained by subtracting the predetermined value K from the first value A is , Means that an output is generated when it is smaller than the following judgment values.
This determination value is the smaller of B ² / D and B, 2B-D,
This is the maximum value among 0. The first term in {}, min (B
² / D, B) is greater than the other two terms, ie, B ² /
If the smaller of D and B is positive and greater than 2BD,
Equation (11) becomes equation (12), which is equivalent to equation (10).

A ≦ K + min (B ² / D, B) That is, A ≦ K + B ² / D AND A ≦ K + B (12)

If the second term 2BD is the maximum,
Equation (11) means A ≦ K + 2B−D, which is equivalent to the latter half of equation (6). When both the first and second terms are negative, 0 becomes the maximum, and equation (11) indicates that A ≦ K And is equivalent to the first half of equation (6). In consideration of the above, the determining means 2-2 is equivalent to the determining means 2-1. According to the present embodiment, a point where the effective voltage value is minimized in the target section of the transmission line is derived and an accident in the target section is detected, so that continuous determination is possible.

FIG. 4 is a block diagram showing an embodiment of the third aspect of the present invention. In this embodiment, the determination is made based only on the magnitude of the alternating current. In the figure, reference numeral 3 denotes an undervoltage element, and the magnitude | V | of the voltage vector V (hereinafter, simply referred to as the magnitude of the voltage | V |;
The output PV is generated in the following cases. In addition, below a certain value (|
In the present invention, V | ≦ K) and a value smaller than a certain value (| V | <K) need not be particularly distinguished from each other. 4 is an offset element, the magnitude of a voltage vector U = V-ZI, in which the voltage vector V is compensated by the impedance drop voltage vector ZI |
An output PU is produced when U | = | V-ZI | is less than or equal to a constant value K. Hereinafter, the voltage vector ZI is referred to as a second voltage vector, and the voltage vector U is also referred to as a third voltage vector.

Reference numeral 5 denotes a parallel element, which comprises a vertical element 50, a horizontal element 51, and a logical product element 6. The vertical element 50 has a magnitude of voltage | V
|, The magnitude of the second voltage | ZI | and the magnitude of the third voltage | U |, the foot of the perpendicular of the voltage vector V lowered with respect to the second voltage vector ZI is obtained. An output PH is produced when within the voltage range. The judgment formula is (13)
It is an expression. The details will be described later with reference to FIG.

The horizontal element 51 produces an output PW when the length W of the perpendicular is equal to or less than a constant value K. The determination equation is equation (14). The AND element 6 produces an output PZ as a parallel element when the output PH and the output PW both occur. OR element 7
Produces a final output OP when any of the outputs PV, PU or PZ occurs.

## EQU8 ## 0 <H = Ｚ | ZI | + (| V | ² − | U | ² ) / | ZI |｝ / 2 <| ZI |...... ) W ² = | V | ² −H ² <K ² (14)

FIG. 5 is an explanatory diagram for explaining the operation of FIG.
10 shows characteristics on an IV plane similar to FIG. As can be seen from the above description, the radius of the undervoltage element 3 and the offset element 4 are K, and the centers are the origin O and the tip of the second voltage vector ZI, respectively. The characteristic of the parallel element 5 is the rectangular ABCD illustrated as described below. The illustrated point G is a perpendicular leg lowered from the tip of the voltage vector V to the second voltage vector ZI, and H is the distance between OGs, W
Is the length of the perpendicular. Here, H is a value having a sign, and is positive when OG is in the same direction as the second voltage vector ZI. The following equation (15) holds for these values, and when H is calculated from this, equation (16) holds.

| V | ² = W ² + H ² , | U | ² = W ² + (| ZI | −H) ² (15) When H is obtained from the above equation, H = ｛| ZI | + (| V | ² − | U | ² ) / | ZI |｝ / 2 (16)

Therefore, the above-mentioned determination formula (13) of the vertical element 50 means that the perpendicular foot G is within the range of the second voltage vector ZI. The judgment formula (14) of the horizontal element 51 is self-evident, and when these hold together, the voltage vector V is in the range of the illustrated rectangle ABCD. Further, it is apparent that the final characteristic obtained by combining these by OR is a so-called motion-type characteristic similar to FIG. Although not particularly shown, the judgment formula (1
3) and (14) can be transformed into (13 ') and (14') by simple calculations. Such modifications are, of course, within the scope of the present invention.

|| V | ² − | U | ² | <| ZI | ² ... (13 ′) W ² = | U | ² − (| ZI | −H) ² <K ^2. ……(14')

As described above, in this embodiment, the determination is made only by the magnitude of the AC amount, and the instantaneous value is not directly used. Therefore, the continuous determination, that is, the determination can be made effectively at each sampling time.
In addition, it is hardly affected by distortion, and the intended purpose can be achieved. Various known algorithms can be used to calculate the magnitude. In any case, the amount of the distortion of the instantaneous value is reduced. However, especially when a so-called rectification addition algorithm is used, the magnitude can be calculated by the average value. And has a large filtering effect.

FIG. 6 is a block diagram of still another embodiment of the present invention. In FIG. 6, the same parts as those in FIG. 50-1 is the vertical element (17), (18)
When both equations hold, the output PH is generated by the AND element 8.

| V | ² <K ² + | ZI | ² (17) | U | ² <K ² + | ZI | ² (18)

FIG. 7 is a characteristic diagram for explaining the operation of FIG. In the embodiment of FIG. 4, the characteristics of the horizontal element 51 are directly set to AB and CD. A, B, C and D are undervoltage elements 3
And two horizontal and horizontal elements 51 having the characteristics of the offset element 4
Is a point of contact with two straight lines having the following characteristics. Equation (17) indicates that the magnitude | V | of the voltage is equal to or less than the distance between the origin O and the contact point C or D. That is, the voltage vector V is centered on the origin point O and is inside the circle passing through the contact points C and D. Means that Similarly, equation (18) means that the voltage vector V is inside the circle passing through the contact point A or B centered on the tip of the second voltage vector ZI.

Therefore, in the embodiment shown in FIG. 4, the parallel element 3 produces an output in the area of the rectangular ABCD, whereas in the embodiment shown in FIG. 6, the arc AB line BC and the arc CD line D-D A
Produces an output in the region of By the way, straight line AB and arc A-
B or the area where the straight line CD differs from the arc CD overlaps with the area where the undervoltage element 3 or the offset element 4 produces an output, and therefore may be either horizontal element.

FIG. 8 is a block diagram of still another embodiment of the present invention. The same parts as those in FIG. 50-2 is a vertical element, and when the equation (19) is satisfied, an output PH is generated.

| V−ZI / 2 | ² <K ² + | ZI / 2 | ² (19)

FIG. 9 is a characteristic diagram for explaining the operation of FIG. Only necessary parts are shown as in FIG.
The above determination formula (19) means the inside of a circle passing through the contacts A, B, C and D with the center of the tip of the voltage vector ZI / 2, which is １ ／ of the second voltage vector ZI, as the center. Therefore, this embodiment also has the same effect as that of FIG. Although the embodiment of FIG. 7 or FIG. 9 is not particularly advantageous over the embodiment of FIG. 4, it shows that the vertical elements are not limited to the linear characteristics as in FIG. According to the above embodiment, since the determination is made based only on the magnitude of the AC amount, it is possible to obtain a performance that is less affected by distortion and has a quick response.

[0034]

As described above, according to the present invention, it is possible to provide a current-compensation undervoltage relay which can make a continuous determination, has little filtering, and can obtain a quick response.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment illustrating a current compensation undervoltage relay according to the present invention.

FIG. 2 is a configuration diagram of another embodiment.

FIG. 3 is a configuration diagram of still another embodiment.

FIG. 4 is a configuration diagram of still another embodiment.

FIG. 5 is a characteristic diagram for explaining the operation of FIG. 4;

FIG. 6 is a configuration diagram of still another embodiment.

FIG. 7 is a characteristic diagram for explaining the operation of FIG. 6;

FIG. 8 is a configuration diagram of still another embodiment.

FIG. 9 is a characteristic diagram for explaining the operation of FIG. 8;

FIG. 10 is a characteristic diagram of a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Calculation means 2,2-1, 2-2 Judgment means 3 Undervoltage element 4 Offset element 5 Parallel element

Continuation of front page (56) References JP-A-63-92216 (JP, A) JP-A-63-92217 (JP, A) JP-A-5-91646 (JP, A) (58) Fields studied (Int .Cl. ⁷ , DB name) H02H 3/24

Claims (6)

(57) [Claims] 1. A voltage sample value and a current sample value are input, and a line voltage drop in a target section of a transmission line is calculated based on an inductance and a resistance of the target section, and a half cycle or one cycle of a system frequency is determined. And a second value consisting of the sum of the square of the voltage sample value in the predetermined period and the product of the voltage sample value and the line voltage drop in the predetermined period. Calculating means for calculating a third value which is a sum of the square of the line voltage drop in the predetermined period; and when the first value is equal to or less than a predetermined value, or when the first value and the third value When a value obtained by subtracting twice the second value from the sum of the second value and the second value is equal to or less than the predetermined value, or when the second value is positive and equal to or less than the third value and the square of the second value. Is divided by the third value from the first value. Determining means for generating an output when the subtracted value is equal to or less than the predetermined value. 2. A voltage sample value and a current sample value are inputted.
And the inductance and resistance of the target section of the transmission line
Calculate the line voltage drop of the target section based on the
The half period or one period of the number is set as the predetermined period, and
From the sum of the square of the voltage sample value in the predetermined period,
A first value, the voltage sample value and the line voltage drop
A second value that is the sum of the product of the above and the product during the predetermined period
And the sum of the square of the line voltage drop in the predetermined period
Calculating means for calculating a third value comprising:
When the value is equal to or less than a predetermined value, or when the first value is equal to or less than a predetermined value, or when the first value is equal to twice the predetermined value and twice the second value, the third value is subtracted. When the first value is equal to or less than the sum of the predetermined value and the second value and the first value is the square of the second value divided by the third value. A current compensating type undervoltage relay , comprising: a judging means for generating an output at any one of a time equal to or less than a sum of the value and the predetermined value. 3. An undervoltage element, an offset element, a parallel element, and an OR element. The undervoltage element generates an output when the magnitude of a voltage vector is equal to or less than a predetermined value, and the offset element includes an impedance drop. An output is generated when the magnitude of a third voltage vector obtained by compensating the voltage vector with the second voltage vector is equal to or less than a predetermined value, wherein the parallel element has a vertical element, a horizontal element, and a logical AND element, The vertical element is the second voltage that is perpendicular to the second voltage vector obtained from the magnitudes of the voltage vector, the second voltage vector, and the third voltage vector. An output is generated when the vector is within the range of the vector, the horizontal element generates an output when the length of the perpendicular is less than a predetermined value, and the AND element generates an output when both the vertical element and the horizontal element are output. A current-compensated undervoltage relay, wherein the OR element produces an output when any of the undervoltage element, the offset element or the parallel element produces an output. 4. A current compensation type undervoltage relay according to claim 3.
A current-compensated undervoltage relay, wherein a vertical element produces an output when each of the magnitudes of the voltage vector and the third voltage vector is less than a predetermined value. 5. A current compensation type undervoltage relay according to claim 3.
The vertical element is one half of the second voltage vector
The fourth voltage vector obtained by compensating the voltage vector with the voltage vector
Characterized in that an output is generated when the magnitude of the voltage vector is equal to or smaller than a predetermined value. 6. A current compensation type undervoltage relay according to claim 1.
The predetermined period is a half cycle of the system frequency or
Is a current-compensated undervoltage relay characterized by one cycle of n / 2 cycles or n cycles (where n is a positive integer).