JPS59188327A - Zero phase current detecting method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting zero-sequence current in a power system, particularly in a power transmission line.

Conventionally, when a fault occurs in a power system, the method of detecting it is generally to use a current transformer or zero-sequence current transformer to detect the zero-sequence current, but these devices cannot handle high voltages. The higher the dielectric strength becomes, and the larger the current capacity, the larger the size, so that they are installed only in the minimum number of places necessary for measuring instruments and protective relays.

However, if zero-sequence current can be easily detected even in the middle of a power transmission line, if a fault occurs on a power transmission line, it will be useful in determining the fault section, and it will be extremely effective in recovering from a power transmission line fault.

In order to meet the above-mentioned needs, the present inventor previously filed an application for the invention of a zero-sequence current detection method with the aim of easily detecting zero-sequence current in the middle of a power transmission line (Japanese Patent Application No.
No. 173689, published December 8, 1980 H). The gist is that [a long and thin iron core for forming a magnetic path is
The core is installed perpendicular to the power line of the phase alternating current power line and at intervals sufficient to withstand the voltage applied to the power line. The length of the iron core is set so that the sum of the electromotive force generated in
Set magnetic constants such as cross-sectional area, position, and number of coil turns,
A zero-sequence current detection method that detects a zero-sequence current by the composite electromotive force of a coil that is induced in proportion to the zero-sequence current generated in a power transmission line. However, since this method requires three coils to be provided for each phase of a three-phase AC power transmission line, it is difficult to determine each magnetic constant, especially the position-related parameters, and it is difficult to move one coil. and the other 2
There was a problem in that the positions of the two coils had to be moved individually, and adjustment work required time and skill.

The present invention provides improvements over the previous invention,
Enables equivalent zero-sequence current detection with two coils,
This greatly facilitates the adjustment work.

The present invention will be explained below.

Figures 1-1, 1-2, and 1-3 are explanatory diagrams showing the principle of the present invention, and each is an example of a standard transmission line tower with two circuits. The case of a line installation pole is shown.

In the diagram, A, B, and C are three-phase alternating current A-phase, B-phase, and C-phase electric wires,
G is an overhead ground wire, FIG. 1-1 is a front view seen in the length direction of the power transmission line, and FIG. 1-2 is a side view seen from the side. Dl and 'D2 are elongated iron cores wound with coils m and n, respectively, and maintain a sufficiently safe insulation interval than electric wires A, B, and C, and the height of coil m is close to the human phase, and then close to the B phase. Place the coil n at the farthest position from the C phase.
The height of the electric wire A is close to the C phase, then the B phase G, and the electric wire A is placed at a position where it is farthest from the human phase.
, B, C, and the overhead ground wire G, and its direction is in the direction of the overhead ground wire. coil m
, n are connected so as to obtain a composite value of the electromotive forces m and n generated in each coil, as shown in FIGS. 1-3. (In addition, the value is a vector quantity, and the scalar quantity E
To distinguish it from the above, do nodo was added. same as below. ) Now, when a three-phase alternating current flows through electric wires A, B, and C, magnetic lines of force a and b center around each electric wire due to the current.

C occurs, and the coil m is formed using the iron core DI and D2 as the magnetic path.

Since it passes through n, an electromagnetic induced electromotive force is generated in the coil. Now, let the electromotive force generated in coils m and n due to the human phase current be IEma, 1Ena, and the electromotive force generated in coil m due to the B phase current.
, the electromotive force generated in n is amb+ 1Enb, and the electromotive force generated in the coil due to the C phase current is mc+ Enc
Then, the combined electromotive force is human phase eA=ema+Ena.

B phase component eB=emb+enb.

The O electromotive force, which is C phase component e+), -emc+enc, increases as the electric wire current increases. In addition, the closer the distance between the coil and the wire is, the larger the value becomes, and the closer the angle between the magnetic axis, that is, the line that passes through the coil in the longitudinal direction of the iron core, and the line that connects the wire and the coil becomes a right angle, the larger the value becomes. , depending on the position of the coil relative to the wire. In addition, it varies depending on the length of the iron core, cross-sectional area, number of turns of the coil, etc., so by adjusting these, the overall The value of +eB+ec to the combined electromotive force is set to be zero or very small. By the way, since death is 10 eB + death (H-em + 100,
In other words, in order for death A ten death B ten death C = 0, death m - death n to hold, Em - En, l8m l + 1θ as shown in Figure 2.
It is sufficient that n l = 180°. Note that θm,
θm is the coil m when the phase with current is taken as a reference,
is the respective phase angle of the voltage induced in n.

However, if an accident occurs on the transmission line and imbalance occurs in each phase current, imbalance will also occur in tA, eB, fE, and c, and the resultant electromotive force proportional to the zero-sequence current of the transmission line will be as shown in Figure 1-3. The zero-sequence current can be detected at the output of the composite circuit.

Although FIGS. 1-3 show an example in which two coils are connected in series, they may also be connected in parallel for detection.

The above is a case without an overhead ground wire, but in general,
As shown in the figure, there is an overhead ground wire G and the A phase.

An induced current flows in the overhead ground wire due to induction from C phase and C phase.If there is no fault on the transmission line, the current value is generally small, but if there is a fault, the current value increases. , the current value increases due to the addition of ground fault current, and the induced electromotive force generated when the magnetic lines of force gl and g2 pass through the coils m and n is the composite value of the above A, B, and C. As a result, a composite output that is not proportional to the zero-sequence current of the power transmission line appears at the output of the composite circuit shown in FIG. 1-3, resulting in an error in zero-sequence current detection. The current flowing through the overhead ground wire is not constant due to changes in the grounding resistance of the tower due to weather, changes due to distance from the electric station at both ends of the transmission line, and other reasons, so the above error value also changes, and the zero-phase This makes current detection increasingly difficult.

In the present invention, the longitudinal direction of the coil and the iron core are directed toward the overhead ground wire, and the angle between the two is at right angles, so that the magnetic lines of force generated by the current in the overhead ground wire do not penetrate the coil. , it is possible to detect the zero-sequence current of the power transmission line without being affected by the current of the overhead ground wire.

In addition to the method in which the iron core is provided separately between each phase as described above, it is also possible to have an integral structure common to each phase as shown in FIG.

The above is a case of a standard two-line steel tower with a single line installed on a pole, but FIG. 3 shows a case where a two-line line is installed on a pole.

A, B, and C are wires A phase, C phase, and C phase of line 1, and R, S
, T represent the R phase, S phase, and T phase of the wire No. 2, respectively.

In general, in a standard two-line steel tower, the wire arrangement of line 1 and line 2 is symmetrical, so the iron core and coil m,
Place n on the center line of line 1 and line 2, and place it facing the direction of the overhead ground line G and at right angles to the electric wires A, B, C, R, S, T and the overhead ground line G, Furthermore, Phase A and C of Line 1.

Combined electromotive force induced in coils rn and n by the balanced current of C phase A phase component = , B phase component eB, C phase component tc as the height, length, cross-sectional area of iron core and coil m .

By adjusting the position and number of turns of n and making the total combined electromotive force e for the C phase 10eB +ec zero or very small, in the event of an accident on transmission line 1, an electromotive force proportional to the zero-sequence current will be generated. However, zero-sequence current detection is possible.

Considering the influence of Line 2 R phase, S phase, and T phase in this case,
Lines 1 and 2 are symmetrical as mentioned above, so 2
Combined electromotive force R phase component eR, S phase component es induced in coils m and n by the balanced currents of side lines R phase, S phase, -T phase
, the T phase component is the total combined electromotive force eRjukuS by line 2 of D
The total combined electromotive force caused by Line 1 is A +4:a
When +ec is zero or very small, it automatically becomes zero or very small and does not occur. That is, there is no mutual influence between line 1 and line 2, and even if there is an accident in line 1 or line 2, the zero-sequence current in line 1 or line 2 can be detected.

If the iron core and coils m and n are not on the center line of line 1 and line 2, make sure that the total combined electromotive force f=s +4B +#c for the above C phase of line 1 is zero or very small. Even if the iron core and coil are adjusted to is also large, causing a phenomenon as if a zero-sequence current is occurring, making it unsuitable for detecting a zero-sequence current.

Next, the magnitude of the current flowing through the overhead ground wire in the event of a transmission line accident varies depending on the distance from the electrical stations at both ends of the transmission line to the accident point, the value of the grounding resistance of the steel tower, etc.

By the way, the electromotive force induced in the coils m and n is not only induced from each phase current of the electric wire, but also from the current flowing through the overhead ground wire, so an electromotive force that is not proportional to the zero-phase current is generated.
This is inconvenient for zero-sequence current detection. In order to eliminate this drawback, the present invention aims to orient the longitudinal direction of the iron core in the direction of the overhead ground wire,
As mentioned above, the magnetic field lines generated by the current flowing through the overhead ground wire are prevented from penetrating the coil via the iron core, so that no induced electromotive force is generated in the coil.

Figures 1-1, 1-2, and 3 show the case of one overhead ground wire. In the case of two overhead ground wires, as shown in Figure 4, the overhead ground wires are generally arranged symmetrically at the top of the tower, so by placing the iron core 1 on the center line, the coil m
, n, the electromotive force caused by the current flowing through the overhead ground wire G1 and the electromotive force caused by the current flowing through the overhead ground wire G2 are opposite in direction and cancel each other out, so they are always zero regardless of the magnitude of the current flowing through the overhead ground wire. becomes.

In the case of three overhead ground wires, as shown in Figure 5, one overhead ground wire Go is generally placed at the center of the transmission line, and the other two ground wires G1 and G2 are placed symmetrically across this. Therefore, by installing the iron core and coils m and n on the center line of the power transmission line, coils m and n are connected to the overhead ground wire G for the same reason as above.
No induced electromotive force is generated due to the current flowing through o, ci, and G2.

The above explanation is based on the case of a standard two-line steel tower, but a case with a multi-line steel tower or a three-phase power line arrangement with a different structure is explained above.
It is also applicable to the case of line towers.

An example of application to a multi-line tower is shown in Figure 6. As an example of application to a single-line tower, Figure 7 shows a case where there is an overhead ground wire for power transmission lines arranged in a triangular arrangement, and Figure 7 shows a case where there is no overhead ground wire. In Figure 8,
In addition, the case where there is no overhead ground wire for horizontally arranged power transmission lines is
As shown in the figure. These effects are similar to those described for the example above.

Among these application examples, in the case of FIG. 7, the iron core and coil are arranged so that the longitudinal direction of the iron core is directed toward the overhead ground wire and is symmetrical from the center line of the tower. coil m, n
As shown in FIG. 1-3, these are connected in such a way that the composite value of the electromotive force E m + n generated in each coil is obtained as a vector gem-tn only in this case.

The combined electromotive force is Physiognomic bones tp, -ems-ena B phase component eB = emb-enb C phase part death C=emc-enc and is expressed in the form of a difference.

In the non-fault power transmission state, the total combined electromotive force p2A+eB+
In order to make the value of lEc zero, em -IEn-0 is sufficient, and from this the relationship between the magnitude and phase of the vector as shown in FIG. 2 is derived.

As described above, in the zero-sequence current detection method of the present invention, an elongated iron core for forming a magnetic path is placed perpendicularly to the power line of a three-phase AC power transmission line, and the distance between the two power lines is determined by Coil 2 is placed on the core at intervals sufficient to withstand the applied voltage.
The length of the iron core, the cross-sectional area of one position, and the position of the coil should be adjusted so that the composite of the electromotive force generated in the coil by electromagnetic induction from the power line becomes zero or very small when the current in each phase of the power line is equal. By setting magnetic constants such as the number of turns, and when a zero-sequence current is generated in the transmission line, the zero-sequence current is detected by the composite electromotive force of the coils that is induced in proportion to the zero-sequence current. Compared to the method according to the previous invention in which iron cores and coils are installed, the adjustment work is significantly improved.

[Brief explanation of the drawing]

Figure 1-1 is a front view explaining the principle of zero-sequence current detection according to the present invention, Figure 1-2 is a side view thereof, Figure 1-3 is an explanatory diagram showing an example of coil connection, and Figure 2 is A vector diagram explaining the phase relationship of the electromotive force of each coil when ideal adjustment is made. Figure 3 is a front view showing an example of installing two circuits on a pole. Figures 4 and 5 are diagrams showing an example of an overhead ground wire. An explanatory diagram showing the arrangement of the iron core and coil in the case of 2 and 3 strands, Fig. 6 is an explanatory diagram showing the arrangement of the iron core and coil in the case of a 4-circuit tower, and Fig. 7 shows an overhead ground wire in a 1-circuit triangular arrangement. FIGS. 8 and 9 are explanatory diagrams showing the arrangement of the iron core and coil when there is only one wire, and FIGS. 8 and 9 are explanatory diagrams showing the arrangement of the iron core and coil when there is no overhead ground wire of one line of symmetrical wiring, respectively. Dl, D2. D: Iron core m,, n, ml, nl, m2. n
2: Coils G, G1, G2. Go: Overhead ground wire A, B, C, R, S, T AI, A2, B1, B2Cl
, C2, R1, R2 51, 32, TI, T2: Wire patent applicant Nishimu Electronics Co., Ltd. Agent Masu Tegori (and 2 others) Figure 1-1 Figure 1-2 Figure 1 bo9 B \ \ th Figure 1-3 Figure 3 Old Oat! No. 4 No. 5 Figure G2 GI G2GOG + Figure 6
Figure 7 Figure 8 Figure 9

Claims (1)

[Claims] 1. An elongated iron core for forming a magnetic path is placed perpendicular to the power line of a three-phase AC power transmission line, and the distance from each power line is set at a distance sufficient to withstand the pressurized voltage of the power line. Two coils are installed on the core, and the length of the core is set so that the combination of the electromotive force generated in the coil by electromagnetic induction from the power line becomes zero or very small when the current in each phase of the power line is equal. , set magnetic constants such as the cross-sectional area, two positions, and the number of turns of the coil, and when a zero-sequence current occurs in the power transmission line, the zero-sequence current is detected by the composite electromotive force of the coil that is induced in proportion to this. A zero-sequence current detection method characterized by the following. 2. In the case of an even-numbered power transmission line in which the wire arrangement is symmetrical, the zero-sequence current detection method according to claim 1, characterized in that the iron core is arranged on the center line of the symmetrical wires. 3. In the case of a power transmission line with one overhead ground wire, the iron core should be arranged so that the longitudinal direction of extension points toward the overhead ground wire, so that the current flowing through the overhead ground wire can be induced into the coil. The zero-sequence current detection method according to claim 1 or 2, characterized in that generation of electromotive force is suppressed. 4. In the case of a power transmission line with two or more symmetrically arranged overhead ground wires, the longitudinal extension line of the iron core should be aligned with the symmetrical center line of the overhead ground wire, and the overhead ground wire should be The zero-sequence current detection method according to claim 1 or 2, characterized in that the generation of induced electromotive force in the coil due to the current flowing in the line is suppressed.