JPH0354404B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steel core aluminum stranded wire (hereinafter referred to as ACSR) which has greatly improved conduction loss during power transmission.

Looking at today's power transmission industry, the location requirements for power sources are becoming increasingly strict, and power transmission to demand areas is becoming longer and longer distances.

As a result, the current loss that occurs during power transmission cannot be ignored, and this is a problem not only from an economic standpoint but also from an energy conservation standpoint, and although various measures such as ultra-high voltage have been put into practice, it is still a problem. There are many issues.

The main causes of conduction loss in overhead transmission lines using ACSR are resistance loss due to the aluminum conductor itself, and iron loss due to electromagnetic effects due to the presence of the steel core. For the former, it would be better to increase the conductivity of the conductor, but when considering mechanical strength as well, the current EC grade aluminum is already at its limit, and even if strength is ignored and the purity is increased, the conductivity will still be high. At best, the rate can be increased by 1%. In order to relatively lower the resistance of the conductor, it would be better to increase the cross-sectional area of the conductor, but this would increase the outer diameter of the wire, increase the weight, and increase the wind pressure load, which would cause the steel tower to become heavier. A new problem arises in that the strength of the power must be increased. In addition, iron loss is a very troublesome problem due to the nature of ACSR, which uses a steel core as a tension member.

Under the above-mentioned circumstances, the present invention enables a change in the way of thinking and significantly reduces current loss, and can be applied as is by making conventional accessories, tools, or construction methods. It was created to provide ACSR.

The following is a sequential explanation based on examples.

The main points to be solved by the inventors are to first substantially reduce the resistance when the conductor is energized without changing the outer diameter of the wire, and thereby create a low-loss type that does not require reinforcement of the steel tower. We focused on obtaining ACSR. They discovered that this can be achieved by changing the shape of the conductor from a circular cross section to a fan-shaped cross section and increasing the space factor of aluminum.

That is, the space factor of aluminum when using a conventional wire with a circular cross section is about 75%, but when it is made into a fan-shaped conductor, it is possible to achieve a space factor of 85 to 95%. This increase in the space factor can be achieved without increasing the outer diameter of the wire, so there is no increase in wind pressure load, and the effective cross-sectional area when energized increases by the amount of the increase in the space factor. Resistance losses are reduced as a result.

However, focusing only on increasing the space factor,
It has also been found that if all the aluminum strands, including even the outermost strands, are made into fan-shaped conductors in order to further reduce resistance loss, various problems arise.

In other words, ACSR is composed entirely of sector-shaped conductors.
In this case, conventional accessories can no longer be used and specially designed accessories are required, and tools used for overhead lines cannot be used and must be specially made. It was also discovered that the overhead line construction method had to be changed to a special one, which would cause serious inconvenience. It has also been found that such problems can be completely solved by making the outermost layer strands have a circular cross section as before. Therefore, according to the present invention
The first feature of ACSR is that the outermost layer of wire has a circular cross section, and the aluminum wires in the other layers have fan-shaped cross sections.

The second feature is that the twisted layers of the aluminum stranded wires configured as described above are composed of an even number of layers with different twisting directions, and the radial width of the strands of fan-shaped cross section is X ₁ , The space factor is R ₁ , the diameter of the circular cross-section wire of the outermost layer is X ₂ , _the space factor in that case is R ₂ , and each is ( _{X 1 /} The present invention is configured so that the above-mentioned iron loss is dramatically reduced.

To explain this according to the drawings, FIG. 1 is a cross-sectional view of an ACSR according to the present invention having four twisted aluminum wire layers (an even number of layers such as two or six layers is sufficient). 1 is a steel core, 2 is a fan-shaped strand 3 is a circular strand, and the first to third layers have a fan-shaped cross section as shown in the figure, and the fourth layer, which is the outermost layer, has a circular cross section. I'm going to be beaten.

FIG. 2 is an explanatory diagram showing the dimensional relationship of the strands in each layer in FIG. 1. The first to third layers have a length of X ₁ in the radial direction, and the fourth layer has a length of X _2. This indicates that it has a certain length.

When a current is passed through an ACSR configured as shown in FIG. 1, a magnetic field is generated in each layer. Let H 1 be the magnetic field in the first layer, and H _{2 ,} H ₃ and H ₄ be the magnetic fields in the second, third and fourth layers, respectively.

In this case, the direction in which the ACSR is twisted is reversed for each layer, i.e., if the first layer is in the S direction, the second layer is in the Z direction, and the third layer is in the S direction again. A cancellation phenomenon occurs in the magnetic field, and if the magnetic field of the entire ACSR is H, then H=H ₁ −H ₂ +H ₃ −H ₄ (1).

The magnetic field strength Hi (i=1 to 4) of each layer is given by the following equation.

Hi=(K・π・Di・χi・Ii・αi)/(Di/2) =2πK・χi・Ii・αi …(2) K: Constant Di: Diameter of center of each aluminum layer (mm) χi: Radial width of each aluminum layer (mm) Ii: Current density of each aluminum layer (A/mm ² ) αi: Aluminum space factor of each aluminum layer Since the first to third layers all use the same sector-shaped conductor, Since the space factors are all the same and only the fourth layer differs, this can be expressed as R ₁ and
It is expressed as _R2 .

α ₁ = α ₂ = α ₃ = R ₁ α ₄ = R 2Similarly, if χi is expressed by X ₁ and _{X 2 ,} χ ₁ = χ ₂ = χ ₃ = X ₁ χ ₄ = X ₂ Current density of each layer can be considered to be the same, so I ₁ = I ₂ = I ₃ = I ₄ = I Substituting these into equations (1) and (2) and summarizing, _we get H = 2πK・I (R _{1 −R 1 X 1 + R 1 X 1 −R 2 _ R 2 _ _ _ _} The aluminum layer of the outermost layer and the inner layer are different,
Setting the ratio of the radial width of each wire to the reciprocal of its space factor, (X ₁ /X ₂ ) = (R ₂ /
R ₁ ) ...(5) It can be seen that the iron loss is minimized by configuring it as follows.

By combining this with the first feature of the present invention, it becomes possible to obtain a highly low-loss ACSR that can minimize resistance loss and iron loss.

In this way, the steel core aluminum stranded wire of the present invention
The outermost layer of the aluminum stranded wire layer on the outer periphery of the steel core is composed of wires with a circular cross section, and the other layers are composed of wires with a fan-shaped cross section, so that conventional accessories, tools, and construction methods can be applied, and aluminum can be used. The resistance loss of the conductor can be reduced (increase the cross-sectional area), and secondly, by making the aluminum stranded wire layer an even number of layers with different twist directions for each layer, the magnetic field of each layer can be canceled out, especially the outermost layer. The feature is that the diameters and space factors of the circular strands and the inner fan-shaped strands are configured to have the relationship shown in the above equation, thereby minimizing iron loss.

Therefore, strictly speaking, as mentioned above, it is necessary that (X ₁ /X ₂ ) = (R ₂ /R ₁ ), but when this idea is put into practice, It is no exaggeration to say that it is impossible to exactly match the formula.

In reality, there is no other way to realize the present invention by setting a value close to this theoretical value. I would like to define it as a range.
(In the field of electric wires, it is normal for nominal values and actual values to differ, so it is difficult to design unless this degree is allowed.) In other words, as far as the technical scope of the present invention is concerned, the above formula can be expressed as follows: Become.

0.9(R ₂ /R ₁ )≦(X ₁ /X ₂ )≦1.1(R ₂ /R ₁ )…(6) Needless to say, the theoretical ideal value is equation (5),
Although there is no critical significance in the range of formula (6), since it is impossible to realize formula (5) industrially, a range close to it is determined as a means of achieving almost the intended effect of the present invention. Therefore, we believe that we have no choice but to identify the range that can be realized at an industrial level.

Next, the present invention will be explained based on specific numerical values.

Regarding the ACSR according to the present invention, which has a four-layer structure
Consider using a fan-shaped cross-section conductor with R ₁ =0.88 and a circular cross-section conductor with R ₂ =0.75. From formula (4), 0.88X ₁ = 0.75X ₂ ...(7) Now, if the outer diameter of the wire is D and the outer diameter of the steel core is D ₀ , the width of the aluminum stranded wire portion is (D - D ₀ )/ It is 2. Therefore, (D-D ₀ )/2=3X ₁ +X ₂ (8) When calculating X ₁ and X ₂ from equations (7) and (8), the following results are obtained.

X ₁ =0.11981×(D−D ₀ ) X ₂ =0.14057×(D−D ₀ ) (9) It can be seen that when formula (9) is satisfied, the iron loss becomes zero.

Now, considering 810(1) ACSR, its nominal values are D ₀ = 9.6 mm and D = 38.4 mm, so from equation (9), X ₁ = 3.47 mm and X ₂ = 4.0 mm are found. With this configuration, iron loss becomes zero.

^When calculating ^the cross-sectional area A of aluminum of ACSR according to _the present invention where X _{1 and} ^{D 2} _{−2 _} ^{_ _ _ _}
Therefore, in the case of ACSR according to the present invention, the aluminum cross-sectional area increased by about 10.4%,
Assuming that the conductivity of the aluminum conductor and the twist rate of the ACSR are the same, the electrical resistance of the ACSR according to the present invention is reduced by about 10.4%.

As explained in detail above, the ACSR according to the present invention can be used by modifying conventional accessories, tools, overhead wire construction methods, etc., and can dramatically reduce loss during energization. Therefore, its effect on industry is enormous.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the ACSR according to the present invention, and FIG. 2 is an explanatory view showing the dimensional relationship thereof. 1: Steel core, 2: Fan-shaped cross-section aluminum wire, 3: Circular-section aluminum wire.

Claims (1)

[Claims] 1. An even number of layers of aluminum wire are twisted around the outer periphery of a steel core with different twisting directions for each layer, and each aluminum wire in each layer other than the outermost layer is configured to have a fan-shaped cross section. Let the width be X ₁ and the aluminum space factor of each layer be R ₁ ,
The outermost layer of wire is configured to have a circular cross section, and its diameter is
X ₂ and its aluminum space factor is R ₂ , and is configured so that 0.9 (R _{2 /} R ₁ ) ≦ ( _{X 1 /} Steel core aluminum stranded wire.