JPH0713926B2 - Self-cooling gas insulation transformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a transformer in which a large number of tubular windings are arranged in a multiple tubular configuration, and in particular, it is interposed between the tubular windings. The present invention relates to a self-cooling gas insulated transformer with improved interlayer insulation and vertical duct structure.

(Prior Art) FIG. 6 shows a winding structure of a conventional transformer of this type in a longitudinal section. That is, in the figure, 1 is an inner insulating cylinder, 2 is a large number of cylindrical windings formed by winding an insulation-coated wire conductor in a cylindrical shape, and these are arranged in a concentric multiple cylindrical shape. . Each cylindrical winding 2 has an interlayer insulator 3 interposed between every other layers, and a plurality of spacers are arranged at intervals in the circumferential direction between every other layer without the interlayer insulator 3. By doing so, the vertical duct 4 for cooling is secured. Further, since the winding traveling directions of the respective cylindrical windings 2 are alternately inverted, the interlayer connection by the crossovers 5 is alternately performed at the upper end and the lower end.

According to the above configuration, the insulating gas, which is the cooling medium, circulates by natural convection rising in the vertical duct 4 due to the temperature difference between the upper and lower parts to cool the winding. In such a gas-insulated transformer, unlike a mineral oil-insulated transformer or the like, a gas layer having a significantly lower thermal conductivity than that of oil-filling using mineral oil or the like is interposed in the interlayer insulating material, and the heat of the interlayer insulating material 3 is reduced. Since the conduction resistance is high, it is preferable for cooling to provide a vertical duct 4 for cooling on at least one surface of the winding layer, that is, the cylindrical winding 2. On the other hand, when insulation between the cylindrical windings 2 is provided, it is solid. Insulation is preferable because the required insulation distance can be shortened and the winding can be made compact. Therefore, it is generally a good idea to alternately arrange the vertical ducts 4 and the interlayer insulators 3 layer by layer as shown in FIG.

By the way, the flow rate of this gas is determined so that the circulation force (in the case of the self-cooling type, that is, the gas natural circulation cooling, it is determined by the thermal buoyancy due to the difference in gas temperature between the upper and lower sides) and the pressure loss of the gas flow passage in the winding are balanced.

Regarding the pressure loss h in the winding, the vertical duct 4 can be regarded as a rectangular duct having a width w (m) and a radial gap length, that is, a thickness d (m), as shown in FIG. The pressure loss h (mmAg) in the winding when the amount of gas flowing into the lower portion of the vertical duct 4 is Q (m ³ / s) can be generally approximated by the following formula (I).

Here, γ is the specific weight of the gas (kg / m ³ ), g is the gravitational acceleration (m / s ² ), ξ ₁ is the inlet loss coefficient of the vertical duct 4, ξ ₂ is the friction loss coefficient in the vertical duct 4, ξ ₄ is the exit loss coefficient of the vertical duct 4. Further, ΔQ is an increase in gas volume due to heat taken from the winding in the vertical duct 4, β (1 / ° C) is the coefficient of thermal expansion of the gas, and Δθ (is the gas temperature difference between the inlet and the outlet of the vertical duct 4. C)) is generally represented by the following formula (II).

ΔQ = β · Δθ · Q (II) Fig. 8 shows another conventional example of a self-cooling type gas insulation transformer. In Fig. 8, the same parts as those in Fig. 6 are designated by the same reference numerals. It is attached. In the winding structure shown in FIG. 8, the interlayer insulator 6 is made of an insulating material by sequentially changing the insulating thickness from t to t'according to the degree of insulation required between the cylindrical windings 2. The amount is reduced. Correspondingly, the thickness of the vertical duct 7 (radial gap length) is also tapered so that it gradually changes from d ₁ to d ₂ . As for the pressure loss h in the winding in this case, the vertical duct 7 has
Since it can be regarded as a duct having the shape shown in the figure, it can be approximated by the following equation (III).

Now, assuming that the average thickness of the vertical ducts 4 and 7 is the same in FIGS. 6 and 8, that is, d ₁ + d ₂ = 2d, the pressure loss h in the winding and the vertical duct in FIG. The relationship between the upper and lower thicknesses d ₂ and d _{1 of} 7 can be expressed by the following equation (IV) using the equations (II) and (III).

By the way, generally, the duct entrance and exit loss coefficients ξ ₁ , ξ ₃
Is about ξ ₁ = 0.5, ξ ₃ = 1.0, and the coefficient of thermal expansion β is 1
Since it is about / 273, the value of {} in this IV formula, that is, If the value of C is C, then h ∞ CQ ² ……… (V), where C is the gas temperature difference Δ between the inlet and outlet of the vertical duct.
It is determined by θ and the upper and lower thicknesses d ₂ and d _{1 of the} vertical duct, and thus C can be said to be a constant representing the magnitude of pressure loss.

For example, for temperature differences Δθ = 20 ° C and Δθ = 100 ° C,
When the relationship between the constant C and the vertical ratio d ₂ / d ₁ of the duct thickness is calculated, characteristic lines A (Δθ = 20 ° C.) and B (Δθ =) in FIG. 4 are obtained.
100 ° C). As you can see from Figure 4,
In the case where the average thickness of the vertical duct is constant, d ₂ compared with d ₁
When is smaller, the pressure loss h in the winding increases at an accelerating rate,
In a cooling medium having a large coefficient of thermal expansion such as gas, the tendency becomes more remarkable as the gas temperature difference Δθ increases. When using a refrigerant with a small coefficient of thermal expansion such as insulating oil
As pointed out in Japanese Patent Publication No. 14885, it is possible to improve the cooling of the winding by improving the heat transfer coefficient of the upper portion of the winding by making the vertical duct tapered as shown in FIG. In the insulation transformer, especially in the self-cooling type, the coefficient of thermal expansion of the gas as the cooling medium is large, and a certain temperature difference Δθ is required to secure the gas circulation force. In addition, the pressure loss in the winding is increased, and therefore the gas circulation flow rate is reduced, resulting in impairing the cooling performance of the winding.

Therefore, when it is attempted to obtain the same gas flow rate as in the case of FIG. 6, in the structure of FIG. 8, the average thickness of the vertical duct 7 {(d ₁ +
It is necessary to make d ₂ ) / 2} larger than d, and even if the thickness of the interlayer insulator 6 is partially reduced, the radial dimension of the winding does not become so small.

(Problems to be Solved by the Invention) Even if the thickness of the interlayer insulator is reduced according to the required insulation degree as described above, the increase in the cooling duct thickness due to the reduction is sufficient for improving the winding cooling. There was a problem that it could not be reflected effectively.

The present invention has been made to solve this problem, and an object of the present invention is to provide a self-cooling gas-insulated transformer that can improve cooling performance and reduce the amount of interlayer insulation, and has a compact winding structure. It is in.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve this object, in the self-cooling type gas insulation transformer according to the present invention, a large number of tubular windings are arranged in a multiple tubular configuration and these tubular windings are arranged. The inter-layer insulation is placed between every other layer of the spiral winding, and a vertical duct is formed between every other layer where the inter-layer insulation is not placed by using a supervisor, etc. The thickness of the interlayer insulating material in the radial direction is increased downward, and the radial gap length of the vertical duct is increased upward.

(Operation) According to this configuration, the interlayer insulator becomes thinner as the voltage between two adjacent cylindrical windings, that is, the position where the interlayer voltage is lower, and not only that the radial gap length of the vertical duct is lower at the position where the interlayer voltage is lower. Is shortened. As a result, from the viewpoint of insulation, the space occupied by the interlayer insulator and the space occupied by the vertical duct can be minimized, and the volume of the entire winding can be reduced, while the radial gap length of the vertical duct can be reduced. As a result of the upward expansion, it is possible to reduce the pressure loss when the insulating gas, which is the cooling medium, is circulated, and thus the gas flow rate is increased and the cooling performance is improved.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

Reference numeral 21 denotes an inner insulating cylinder that is inserted into an iron core leg (not shown), and 22 is a large number of cylindrical windings formed by winding insulation-coated wire conductors in a cylindrical shape, and these cylindrical windings form multiple concentric circles. It is arranged in a cylindrical shape. An interlayer insulator 23 is interposed in every other gap between the cylindrical windings 22, and upper and lower ends are opened by interposing a spacer between every other interlayer in which the interlayer insulator 23 is not interposed. A vertical duct 24 for cooling is secured. Further, since the winding directions of the respective cylindrical windings 22 are opposite to each other with respect to the adjacent windings, the interlayer connection by the crossover wire 25 is made by connecting the upper end and the lower end of the cylindrical winding 22. They are conducted alternately with each other, forming a so-called U-shaped connection.

As shown in FIG. 2, the interlayer insulator 23 includes a large number of insulating sheets 26a, 26b, ... 26n having different width dimensions (vertical dimension).
Are wound in multiple layers, and in particular, by forming the insulating sheets 26a, 26b, ... having a smaller width dimension toward the inner layer, the thickness of the interlayer insulator 23 becomes thicker toward the lower end and thinner toward the upper end. There is. Especially in this case, the insulating sheet 26
Among a, 26b, ... 26n, as shown by the dimension H in the height direction in FIG. 2, a low heat resistant insulator is used for those located in the low temperature region, and a high heat resistant insulation is used for those extending to the high temperature region. I use things. The interlayer insulator 23 is a crossover wire shown in FIG.
As can be understood from the connection state of 25, the interlayer voltage is formed such that it becomes thinner at the portion between the cylindrical windings 22, 22 having a lower interlayer voltage at the upper end, in other words, the interlayer insulator 23 has the same thickness. Is thickened as the interlayer voltage increases. Due to the shape and arrangement of the interlayer insulator 23, the radial gap length of the vertical duct 24 becomes a taper shape that increases toward the upper end. That is, the gap length d ₂ at the upper end is larger than the gap length d ₁ at the lower end. This duct structure is the third in consideration of pressure loss.
It can be represented as the structure shown in the figure.

Also, cylindrical windings located on both sides of the vertical duct 24 in the radial direction.
As is clear from the state where 22 is connected at the lower end by the crossover wire 25, the insulation distance by the vertical duct 24 becomes larger at the upper end, that is, as the interlayer voltage becomes higher.

In the transformer having such a structure, during operation, the insulating gas is circulated by moving upward in the vertical duct 24 by natural convection due to a temperature difference, thereby cooling the winding.

When the insulating gas is circulated in this manner, the pressure loss h in the vertical duct 24 can be approximated by the equation (III), assuming that the duct has a shape as shown in FIG. Further, the average gap length of the vertical duct 24 is equal to that of the conventional vertical duct 4 shown in FIG. 6 (d ₁
Assuming that + d ₂ = 2d), the formula (V) is established, and the pressure loss of the vertical duct 24 becomes smaller by the degree that d ₁ / d ₂ becomes larger than _{1 according to the} pressure loss characteristic shown in FIG. The gas flow rate in the winding is increased and the cooling performance of the winding is improved.
On the other hand, the thickness of the interlayer insulator 23 becomes thinner at a position where the voltage between the cylindrical windings 22 and 22 becomes lower, and accordingly, the vertical duct
The gap length of 24 is also reduced as the voltage between the cylindrical windings 22 and 22 decreases, so that the interlayer insulator 23 and the vertical duct
Since the space occupied by 24 can be suppressed to the minimum required for insulation, the winding structure becomes compact. Further, according to the present embodiment, since the insulating sheets 26a, 26b, ... Forming the interlayer insulator 23 are made of low-priced, low-heat-resistant insulators for the portions located below the middle portion where the temperature is relatively low, Economically advantageous.

FIG. 5, which shows the same parts as those in FIG. 2 with the same reference numerals, shows another embodiment of the present invention. The interlayer insulator 27 partially wraps a narrow insulating sheet 27a in the radial direction. However, the winding is performed in multiple layers, and such winding is performed in multiple steps in the height direction, and the number of windings is reduced toward the upper side to form a tapered cross-section. According to this embodiment, all the materials of the insulating sheet 27a arranged in the low temperature region can be low heat-resistant insulators, and only the insulating sheet located thereabove is a high heat-resistant insulator, which is expensive. It is possible to significantly reduce the amount of high heat-resistant insulating material used. In addition, since insulating sheets of the same size can be used to form the interlayer insulating material, it is advantageous in that the number of types of constituent parts can be reduced.

[Advantages of the Invention] According to the present invention, as described above, the thickness of the interlayer insulator is made thinner as it goes upward, and at the same time the radial gap length of the vertical duct is made higher as it goes up. In addition, it is possible to provide a self-cooling type gas-insulated transformer with improved cooling performance.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part showing an embodiment of the present invention, and FIG.
1 is an enlarged vertical sectional view of a portion shown in FIG. 1, FIG. 3 is an explanatory view of the action of the duct, FIG. 4 is a pressure loss characteristic curve diagram, and FIG. 5 is a view equivalent to FIG. 2 showing a modified example of the present invention. FIG. 6 is a longitudinal sectional view of a main part showing a conventional example, FIG. 7 is a view for explaining the action of a conventional vertical duct, and FIG. 8 is a view corresponding to FIG. FIG. 9 is a view corresponding to FIG. 7 with respect to FIG. In the figure, 22 is a cylindrical winding, 23 and 27 are interlayer insulators, and 24 is a vertical duct.

Claims (1)

[Claims] 1. A number of tubular windings, each of which is formed by winding a wire conductor into a tubular shape and arranged in a multi-tubular shape so as to be concentric with each other, and alternate layers of these tubular windings. A self-cooling type having an interlayer insulating material arranged in the vertical duct and a vertical duct secured by spacers or the like between every other layer in which no interlayer insulating material is arranged, and the insulating gas is naturally circulated in the vertical duct. In the gas-insulated transformer, the self-cooling type gas-insulated transformer characterized in that the radial thickness of the interlayer insulator is increased downward and the radial gap length of the vertical duct is increased upward. vessel.