JP2615598B2 - Distance relay - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a distance relay for protecting two parallel transmission lines in a power system.

(Prior art)

The distance relay that protects the transmission line of two parallel lines is based on the guarantee of zero-phase current in the adjacent line of a ground fault distance relay, for example, 3-2-2, Vol. 37, No. 1, "Electric Cooperative Research" issued by Electric Cooperative Research. 3-5.
The figure is an explanatory diagram shown therein. In FIG. 3, for example, a power source 10, which is a generator, has two parallel transmission lines a,
a 'are connected, and distance relays 12, 13 are provided on the end A side of each transmission line a, a', respectively. When a ground fault occurs in the transmission line a, the phase current I _a and the zero-phase current I ₀ of the own line are transmitted to the fault line a, and the phase current I _a ′ and the zero-phase current are transmitted to the healthy line a ′. I ₀ 'flows, accidents voltage V _a of the installation point of the distance relay 13 at the end a side of the case is given by the following equation (1).

Where, I _a : phase current Z ₁ : normal phase impedance of transmission line Z ₂ : reverse phase impedance of transmission line Z ₀ : zero phase impedance of transmission line Z _M : zero phase mutual impedance X: between end A and B The distance (0 ≦ X ≦ 1) between the installation point of the distance relay and the accident point when 1 is set.

That is, the ranging impedance XZ ₁ distance relay 13 is in the transmission line of two parallel lines is affected by its own line and zero sequence impedance of the line cross at ground fault. In other words, it is necessary to perform compensation by the zero-phase current I ₀ of the own line and the zero-phase current I ₀ ′ of the adjacent line.

However, in this manner to compensate by self zero-phase current I ₀ and zero-phase current I ₀ of the next line of the circuit ', the horizontal axis represents the distance to the fault point, and their relationship to the vertical axis as a distance measurement impedance as in the fourth diagram shows the impedance Z _R See the ranging impedance XZ ₁ clogging distance relay to the distance relay correctly fault point of the accident line, represents the distance to the fault point D, the distance of a sound line The relay (represented by its ranging impedance Z _R ′) is sensitive to an adjacent line fault from its own end to a point β which is the fault point in the ranging setting which is the ranging setting value α.
Then, the overreach operation is performed when the impedance Z _R ′ seen by the distance relay falls below the correct impedance.
As a method of preventing this, there is known a method of performing compensation only by the current of the own line without performing compensation by the current of the adjacent line, and in this case, the impedance Z _R , Z seen by each of the distance relays 12 and 13 is known. The relationship between _R 'and the distance to the fault point is as shown in FIG. 5, and the overreach operation of the distance relay on the healthy line is eliminated, but the distance relay on the faulty line performs the underreach operation.

[Problems to be solved by the invention]

As described above, if the compensation is performed by the zero-phase currents of the own line and the adjacent line so that the distance relay can correctly measure the distance, the distance relay on the healthy line side may perform an overreach operation and malfunction. Conversely, if compensation is performed only with the zero-phase current of the own line, the distance relay on the fault line will operate under-reach, and it may not operate properly for an accident near the distance measurement setting. There is a problem that it is extremely difficult to do.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a distance relay that accurately measures a fault point on an accident line side and correctly measures a distance without performing overreach operation on an accident on an adjacent line side.

[Means for solving the problem]

The distance relay according to the present invention is a means for determining whether each of the effective zero-phase current values of the own line and the adjacent line are both zero, and the effective zero-phase current value of the own line and the effective zero-phase current value of the adjacent line. Means for calculating an adjacent line compensation coefficient including the square of the ratio of .times..times..times..times..times..times..times..times..times..times..ti- mes..times..times..times..times..times. .

[Action]

The distance relay determines whether the zero-phase current effective values of the own line and the adjacent line are both zero. If both of the zero-phase current effective values are not zero, the adjacent line compensation coefficient including the square of the ratio of the zero-phase current effective value of the own line to the zero-phase current effective value of the adjacent line is calculated. Neighboring line compensation is performed based on the line compensation coefficient.

As a result, the distance relay on the healthy line side correctly measures the distance at the fault point and does not perform an overreach operation due to the faulty line.
In addition, the distance relay on the accident line side measures correctly without underreach operation.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings showing the embodiments. Prior to the description of the embodiment, the principle of the distance relay according to the present invention will be described with reference to FIG. In order for the distance relay (hereinafter referred to as a relay) of the fault line to correctly measure the distance to the fault point D, it is necessary to compensate the impedance seen by the relay by the phase current of the own line and the adjacent line as described above. the impedance Z _R See the relay accident line _{when, Z R = V a / I} RY = XZ 1 ... (2) However, I _RY: input current next relay, (2) the formula V _a ( When the equation 1) is substituted, the normal phase impedance up to the fault point D is correctly measured as shown in FIG.
Z _R ′ is However, I _RY ′: input current of the relay of the healthy line I _a ′: phase current of the healthy line Therefore Therefore, substituting this into equation (3) gives Becomes The impedance Z _R ′ seen by the distance relay shown in FIG. 4 is obtained from the equation (4).

In other words, the relay of the healthy line responds to the adjacent line accident from the self end to the point β which is the fault point at the distance measurement set value α, and the impedance Z _R ′ seen by the relay falls below a certain impedance, and the Perform overreach operation in an accident. Unless the adjacent line is compensated by the zero-phase current of the adjacent line in order to prevent such an overreach operation, the input current I _RY of the faulty line relay is And the impedance Z _R seen by the relay on the accident line is Becomes here Therefore, when these are substituted into the equation (6), And Z _R is as shown in FIG. Then, the impedance Z _R See the relay of its own line as FIG. 5 by the influence of the (7) of the second term on the right side has a under-reach operate longer than the correct impedance.

On the other hand, the impedance Z _R ′ seen by a relay on a healthy line
Is And as above Substituting into equation (8) According to the second term on the right side of the equation (9), Z _R ′ becomes as shown in FIG. 5, and it can be seen that the overreach operation of the faulty line is canceled without operating due to the fault of the adjacent line.

In the case where the adjacent line compensation is not performed, the fault point is usually determined in the protection section (0) in consideration of the current transformer, the output error of the transformer, and the relay measurement error which become the relay input as the relay setting.
１1) in order not to exceed nZ ₁ (n = 0.7 to 0.
Settled in 8).

That is, as x = n, the impedance seen by the relay is calculated from equation (7).

This Wakashi current transformer described above, transformer output error, consider the sum of such relays measurement error (e.g., _{10%) (Z R / Z} 1)
If> 0.9, two lines of the power system are opened to the adjacent line in this set state, and there is a possibility that malfunction will occur if the first round is switched. However, in the case of the present invention, it will be described later (1.
6) The impedance seen by the relay when x = n is expressed by the equation Since the second term of equation (11) is a negative value when n = 0 to _1, even if n = 0.7 to 0.8, Z _R / Z ₁ cannot exceed 0.9, and no problem of malfunction occurs. . For relay setting, there is no actual harm by setting Z _R / Z ₁ so that, for example, n = 0.8.

When the adjacent line compensation is performed, the impedance seen by the relay on the healthy line side is calculated by equation (4) and becomes Z _R 'in FIG. Here, the distance measurement set value α (α is usually
0.7 to 0.8), if the fault point in the impedance seen by the relay obtained by substituting α into the equation (4) is β, the impedance seen by the relay in the range of x = 0 to β is α , The relay will operate. This indicates that the relay on the healthy line has overreached due to an accident on the adjacent line, which is a malfunction and is not allowed.

 These are summarized as follows.

(I) Case of only compensation by zero-phase current of fault line
As shown in the figure, the impedance Z _R , that is, the accident line side becomes underreach, and the range of ranging is 70 to
If it is set to 80%, if the power system changes to one-line operation, it may malfunction due to an accident outside the protection range.

(II) When Compensating the Neighboring Line Together with the Zero-Phase Current of the Faulty Line As shown in FIG. 4, the impedance Z _R ′, that is, the relay on the healthy line side is used when the distance x to the fault point is small. Malfunction occurs due to overreach.

(III) In the present invention, as shown in FIG. 2, the impedance Z _R , that is, the relay of a healthy line is correctly measured. On the other hand, the impedance Z _R , that is, the relay on the faulty line side slightly overreaches, but there is no actual harm by reducing the distance measurement setting of the relay accordingly. Further, even when the power system is operated by one line, there is no fear of malfunction.

In consideration of the above, the relay of the present invention calculates the adjacent line compensation coefficient including the square of the ratio of the zero-phase current effective value of the own line and the zero-phase current effective value of the adjacent line, and calculates the adjacent line compensation coefficient. If both the effective zero-phase current values of the lines are not zero, the relays of the faulty line and the healthy line are correctly operated based on the adjacent line compensation coefficient.

FIG. 1 is a flow chart showing the operation of the distance relay according to the present invention. The effective value | I ₀ | of the zero-phase current I ₀ of the own line and the effective value | I ₀ ′ of the zero-phase current I ₀ ′ of the adjacent line are calculated from the currents input from the transmission lines of the two parallel lines. (S
1). It is determined whether the calculated zero-phase current effective values | I ₀ | and | I ₀ '| are zero (S2). Effective value of each zero-phase current | I ₀ | = | I ₀ ′
If | = 0 (practically, it is set to zero when the value is smaller than the predetermined value <margin>), the adjacent channel compensation coefficient K is set to zero (S3).
If both the zero-phase current effective values | I ₀ |, | I ₀ ′ | are not zero, the adjacent line compensation coefficient K is (S4).

Next, the operation of the adjacent line compensation coefficient K will be described with reference to the a-phase ground fault shown in FIG. Since the fault point voltage Va at the installation point of the relay 13 of the fault line is calculated as in the above equation (1), the input current I _RY of the relay 13 is compensated for the own line and the adjacent line, and The current I _RY is Becomes Here, the distance from the relay 12 of the healthy line to the fault point D in FIG. 3 is 2-X. Is Can be considered as

Therefore, the impedance Z _R seen by the relay of the accident line
Is And where Therefore, when these are substituted into the expression (15), Next, by the second term, and the impedance seen the distance relay of the vertical axis, as indicated by impedance Z _R See the relay of the accident line in a second diagram showing the relationship between the distance to the fault point on the horizontal axis becomes, Z _R of the straight line W indicating the impedance relay sees the own line when performing both the own line and the adjacent channel compensation is overreach operation slightly below. However, since the Z _R = Z ₁ when the X = 1,
In the case of an accident near the other end, the distance is correctly measured, and no overreach operation to the adjacent line is performed.

Here, the reason why a slight overreach is allowed in the healthy phase will be described.

First, the underreach when the adjacent line compensation is not performed will be described with reference to FIG. FIG. 5 shows that the distance to the fault point determined as a relay becomes smaller (under reach) because the impedance actually seen by the relay is larger than the impedance set value of the relay.

Normally, a current transformer that becomes a relay input as a relay setting,
In consideration of the output error of the transformer and the measurement error of the relay, the fault point is set to nZ1 (n = 0.7 to 0.8) so as not to exceed the protection section (0 to ₁ ).

That is, assuming that x = n, the impedance seen by the relay is given by the equation (7). Equation (10) above is calculated.

If this is a current transformer as described above, the transformer output error, the sum of the measurement error of the relay (for example, 10%) believe (Z _R / Z ₁₎
If> 0.9, a malfunction may occur if two lines of the power system are switched to one line due to the opening of an adjacent line in this settled state. However, according to the present invention, since the impedance seen by the relay is expressed by the equation (16), the impedance seen by the relay when x = n is: Since the second term on the right side has a negative value when n = 0 to _1, even if n = 0.7 to 0.8, Z _R / Z ₁ cannot exceed 0.9 and no malfunction occurs.

Therefore, on relay setting, for example, Z is set so that n = 0.8.
Not harm by settling the _R / Z _1.

Next, as for the relay of a healthy line, the own line is a healthy line and the adjacent line is an accidental line. And the impedance Z _R ′ seen by the relay on the healthy line is And where By substituting these into the equation (19), Z _R ′ = (2-X) Z ₁ (20), and the relay 12 of the healthy line will correctly measure the distance without performing overreach and underreach operations. Second
In the figure, it is indicated by Z _R '. Note that the straight line W in FIG. 2 shows the impedance seen by the relay of the own line when both the own line and the adjacent line are compensated.

In this embodiment, the adjacent line compensation coefficient K is As shown, Then, for a relay on a healthy line, the correct distance measurement will be performed similarly, but for a relay on an accidental line, the impedance Z _R seen by that relay is And the underreach is achieved by the second term on the right side. But X = 1 in Z _R = Z ₁ next can be carried out correctly ranging in the vicinity of the remote end, a substantially similar operation. However, in this case, it is necessary to determine whether the relay is a relay on the faulty line or a relay on the healthy line, which complicates the configuration slightly.

Here, when the embodiment is compared with the case where only the adjacent line compensation is performed by the zero-phase current of the faulty line in the explanation of the principle, when illustrated by the equation (21) for the embodiment, for example, X = 0 and Z _R =
At 0 and X = 1, Z _R = Z ₁ is obtained, and a curve similar to the curve indicated by Z _R shown in FIG. 2 is obtained. Although the relay of the accident line slightly overreaches, there is no actual harm by reducing the setting of the relay accordingly. Further, there is an advantage that there is no possibility of malfunction even if the power system operates in one line.

In the present embodiment, it is not determined whether the relay is on the healthy circuit side or the faulty circuit side, and the zero-phase current used for compensation is the one on the own circuit side or on the adjacent circuit side. When an accident occurs on the own line, the relay becomes the relay on the accident line, and the relay on the adjacent line becomes a relay on the healthy line. However, the adjacent line compensation coefficient K is Therefore, it is necessary to determine the line.

Incidentally, when I ₀ > I ₀ ′, I ₀ is the faulty line side, and I ₀ ′ is the healthy line side. When I ₀ <I ₀ ′, I ₀ ′ is the faulty line side,
I ₀ can be determined as a healthy line side.

〔effect〕

As described in detail above, the distance relay of the present invention calculates an adjacent line compensation coefficient including the square of the ratio of the respective zero-phase current effective values of the own line and the adjacent line, and uses this adjacent line compensation coefficient. By compensating for the neighboring line, the distance relay of the healthy line does not perform the overreach operation, correctly measures the fault point, and the distance relay of the fault line performs a slight overreach operation in the middle of the distance to the fault point. However, the distance is correctly measured near the other end. Therefore, the present invention can provide a highly reliable distance relay and greatly contributes to protection of two parallel circuits.

[Brief description of the drawings]

FIG. 1 is a flowchart showing the operation of the distance relay according to the present invention, FIG. 2 is an impedance characteristic view of the distance relay of the present invention, FIG. 3 is a schematic diagram of two parallel lines, and FIG. FIG. 5 is an impedance characteristic view of the distance relay when adjacent line compensation is performed, and FIG. 5 is an impedance characteristic view of the distance relay when only own line compensation is performed. 10 ... power supply, 12, 13 ... distance relay In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (3)

(57) [Claims] 1. Detecting the voltage and current of two parallel lines and calculating the impedance corresponding to the distance to the fault point by compensating for the zero-phase current of the own line and the adjacent line, and protecting based on the calculated impedance. In the operating distance relay, means for judging whether or not each of the effective zero-phase current values of the own line and the adjacent line are both zero, and a ratio between the effective zero-phase current value of the own line and the effective zero-phase current value of the adjacent line. Means for calculating an adjacent line compensation coefficient including the square of the above, and when both effective zero-phase current values of the own line and the adjacent line are not zero, the adjacent line is compensated based on the adjacent line compensation coefficient to perform a protection operation. A distance relay, characterized in that it is configured to: 2. The adjacent line compensation coefficient K is The distance relay according to claim ₁ , wherein Z _M : zero-phase mutual impedance Z ₁ : positive-phase impedance of the own line. 3. The adjacent line compensation coefficient K is The distance relay according to claim ₁ , wherein Z _M : zero-phase mutual impedance Z ₁ : positive-phase impedance of the own line.