JPH03120804A - Gas-insulated transformer - Google Patents

Abstract

PURPOSE:To obtain a compact transformer wherein insulating characteristics of a high-voltage winding, the balance of insulating gas circulation between the high-voltage winding and a low voltage winding, and cooling characteristics of the whole part of the winding are improved, by using a sheet winding as the high-voltage windings, and forming gas ducts vertically to the sheet winding. CONSTITUTION:A transformer main body wherein windings are wound on the outer periphery of an iron core 1 is accommodated in a transformer tank; insulating gas is sealed with a specified pressure; windings wherein a high-voltage winding 7 is coaxially arranged on the outer periphery of a low-voltage winding 2 are used as the windings constituting the above-mentioned transformer main body. In this gas-insulated transformer, a multiple cylindrical winding formed by using insulated copper wire is used as the low-voltage winding 2, and a sheet winding wherein a conductor sheet and an insulating film are stacked and wound is used as the high-voltage winding 7. The sheet winding 15 is provided with vertical gas ducts 17 at arbitrary intervals. For example, electrostatic rings 16 for relieving electric field at the end part are arranged at upper and lower end parts on the outermost side of the sheet winding 15, and the potential is made equal to that of a lead wire 9 on the line side.

Description

Detailed Description of the Invention [Purpose of the Invention (Industrial Field of Application) The present invention is directed to storing the contents of a transformer consisting of a winding wound around the outer periphery of an iron core in a transformer tank, and The present invention relates to a gas insulated transformer filled with insulating gas, and particularly to a gas insulated transformer with improved cooling and insulation structure.

(Prior Art) In recent years, substations are increasingly being installed in the suburbs of cities or underground due to constraints on their installation sites. Therefore, there is an even higher demand for flame retardancy for transformers installed in substations in such locations.

Therefore, recently, instead of conventional oil-immersed transformers, gas insulated transformers have been put into practical use, which insulate and cool transformers by using an insulating gas such as SF6 gas, which has excellent insulating properties, as an insulating cooling medium. ing.

However, this gas-insulated transformer has a drawback in that its cooling characteristics are inferior to that of conventional oil-immersed transformers. In other words, the specific heat and heat exchange efficiency of insulating gas are significantly lower than those of insulating oil, so the cooling efficiency of gas-insulated transformers using this insulating gas is considerably lower than that of oil transformers. .

- in the shell, the losses L (kW) occurring in the winding, the cooling medium ff1Q (1/min) flowing in the winding per unit time to cool the winding, and the inlet to the winding and The temperature difference of the cooling medium at the outlet, that is, the temperature difference Δ between the upper and lower windings
Between T, 8T=1/(k-Cp-r)×(L/Q)...■ To: Constant (kW/kcal/min) Cp: Specific heat of cooling medium (kcal/kg・℃ ) r: specific gravity of cooling medium (kg/i).

When concrete physical constants are substituted into this equation 0, when SF6 gas is used as the cooling medium, (1/ (k
-Cp-r)) is approximately 6,500 to 7,000. On the other hand, when insulating oil is used as the insulating medium, this value is about 35, which is about 1/200 of the value when SF6 gas is used.

In other words, in the case of a gas-insulated transformer, if the same loss occurs in the windings as in an oil-immersed transformer, and the amount of circulating coolant is also the same, the temperature difference between the two ends of the winding will be greater than that of an oil-immersed transformer. This would be 200 times more expensive than a transformer.

In order to efficiently cool the windings of gas-insulated transformers with poor cooling efficiency, it is necessary to use SF6 as a cooling medium.
It is required to feed a large amount of gas into the winding without stagnation. As a technology to meet this demand, it is possible to form many vertical gas flow paths within the winding, and a large amount of SF can be formed within the winding.
There are multiple cylindrical windings capable of circulating six gases.

FIG. 3 is a diagram showing a winding structure (multiple cylindrical winding structure) of a conventional core type gas insulated transformer. In FIG. 3, a low voltage winding 2 and a high voltage winding 7 are wound around the outer periphery of the iron core 1. They are arranged coaxially on the outside.

The low voltage winding 2 is constituted by a multilayer cylindrical winding 5 extending from the neutral point side outlet 3 side to the line side outlet 4 side. This multiple cylindrical winding is manufactured by the following process.

That is, on the neutral point side outlet 3 side, a first layer of cylindrical winding 5 is formed on the outer periphery of an insulating cylinder (not shown), a plurality of pieces of insulating spacers 6 are distributed and arranged around the outer periphery, and The second layer of cylindrical winding 5 is formed on the outer periphery, and the cylindrical winding 5 is subsequently formed in sequence via insulating spacers 6 in the same manner. Further, each cylindrical winding 5 is formed by winding an insulated copper wire.

Similarly to the low voltage winding 2, the high voltage winding 7 also has a neutral point side outlet 8.
It is composed of multi-layered cylindrical windings 10 from the side to the track side outlet 9, and each cylindrical winding 10
are formed by winding an insulated copper wire, and an insulating spacer 11 is inserted between adjacent cylindrical windings 10. Note that, as a unique configuration of the high-voltage winding 7, a conductive cylindrical electrostatic shield 12 is provided on the outer periphery of the outermost cylindrical winding 10 to improve potential distribution characteristics against lightning surges. The electrostatic shield 12 is at the same potential as the line side outlet 9.

Further, a gas flow path 13 is secured by the insulating spacer 6.11 between the adjacent cylindrical windings 5 and 10 of the low voltage winding 2 and the high voltage winding 7 configured as described above, Each winding 2.7 is cooled by an insulating gas (gas flow 14) such as SF6 gas flowing through this gas flow path 13.

(Problem to be Solved by the Invention) In the gas insulated transformer shown in FIG. , has excellent cooling properties, but has problems with insulation properties, especially lightning surge properties in gas insulation. This point will be explained below.

In other words, in the gas insulated transformer shown in Fig. 3, when the neutral point side outlet 8 of the high voltage winding 7 is grounded and a lightning surge is applied to the line side outlet 9, potential oscillations occur inside the winding, and the adjacent cylinder A very high voltage is generated between the windings 10 (between layers). In the case of the configuration shown in FIG. 3, empirically, the interlayer voltage is about 1.5 times the voltage shared by the ratio of the number of turns (number of turns) of the cylindrical winding 10. Assuming that the high voltage winding 7 in Fig. 3 has insulation class 605-5 (lightning impulse test voltage 350 kV) and is composed of four layers of cylindrical winding 10 with the same number of turns, the The voltage distributed to the ends is 350X (2/4)Xi, 5 to about 263 kV, and a high voltage of 70 to 80% of the applied voltage is applied between the layers. A very high electric field is generated at the end corners.

If such a high electric field occurs at the end corner of the winding,
Oil insulation does not necessarily lead to a decrease in dielectric strength, but gas insulation has the drawback of significantly decreasing dielectric strength.

In other words, in the case of oil insulation, the dielectric strength does not decrease due to the presence of a high electric field area itself, but the dielectric strength of the insulating oil decreases as the amount of insulating oil exposed to the high electric field area increases, and The smaller the amount of insulating oil, the higher the dielectric strength of the insulating oil. Therefore, in the case of oil insulation, even if the corner of the winding receives a very high electric field, the breakdown electric field at that part will be much higher than the general part of the layer, and the withstand voltage will be improved accordingly. , there is no problem of reduced dielectric strength.

On the other hand, in the case of gas insulation, the presence of the high electric field part itself reduces the breakdown voltage of the part, so the third
As shown in the figure, if the structure is such that local electric field concentration occurs in the high-voltage winding 7, the dielectric strength will drop significantly. In order to deal with such drawbacks, conventional methods have been used to increase the size between the layers of the cylindrical winding 10 in the high voltage winding 7 or increase the number of layers of the cylindrical winding 10 to lower the shared voltage. The electric field concentration at the end of the cylindrical winding 10 of the wire 7 is relaxed. However, in both methods, the high voltage winding 7
This increases the radial dimension of the gas insulated transformer, which has the disadvantage of increasing the size of the gas insulated transformer.

Furthermore, in the gas insulated transformer shown in FIG. 3, if the inter-layer dimension of the cylindrical winding 10 constituting the high voltage winding 7 is increased, the balance of the amount of circulating gas between the layers and the low voltage winding 2 will be poor, This results in the disadvantage of deteriorating cooling properties. That is,
In gas insulated transformers, there is a technique for increasing the cooling capacity by forcibly circulating an insulating gas such as SF6 gas as described above within the windings using a blower. In this case, the interlayer dimension of the high voltage winding 7, that is, the cross-sectional area of the gas flow path 13 is equal to the gas flow path 1 of the low voltage winding 7.
If the cross-sectional area is larger than 3, the amount of insulating gas will be largely biased toward the high-voltage winding 7 side, and as a result, the gas flow rate of the low-voltage winding 2 will be insufficient, and the cooling capacity of that part will deteriorate, causing the winding There is a risk that the cooling characteristics of the wire as a whole will deteriorate.

The present invention was proposed in order to solve the problems of the prior art as described in 2.The purpose of the present invention is to improve the insulation properties of high voltage windings, and to improve the insulation properties of high voltage windings and low voltage windings. It is an object of the present invention to provide a gas-insulated transformer which can improve the clearance of the amount of insulating gas circulated between the windings and the windings, and improve the cooling characteristics of the entire winding.

[Structure of the Invention] (Means for Solving the Problem) The gas insulated transformer of the present invention uses multiple cylindrical windings formed of insulated copper wire as the low voltage winding, and It is characterized in that a sheet winding formed by overlapping and winding a conductor sheet and an insulating film is used as the wire, and vertical gas ducts are formed in the sheet winding at arbitrary intervals.

(Function) In the gas-insulated transformer of the present invention having the configuration described below, sheet winding is used as the high-voltage winding, so the high-voltage winding has insulation properties with excellent anti-surge properties. Can be made to have.

In addition, by appropriately selecting the dimensions and number of vertical gas ducts in the high-voltage winding, it is possible to optimally balance the amount of cooling gas circulating between the low-voltage winding and the high-voltage winding, thereby improving the cooling characteristics of the entire winding. There are also benefits that can be improved.

Furthermore, the radial dimension of the vertical gas duct does not need to be increased for insulation reasons, and can be reduced to the minimum dimension necessary for cooling, resulting in the advantage that the dimensions of the winding can be reduced.

(Embodiment) An embodiment of the gas insulated transformer according to the present invention will be specifically described below with reference to FIGS. 1 and 2. In addition,
Components that are the same as those in the prior art shown in FIG. 3 are designated by the same reference numerals, and their explanation will be omitted, and only the features of this embodiment that are different from the prior art will be described.

First, in this embodiment, as shown in FIG. 1, multiple cylindrical windings (low-voltage windings 2) consisting of cylindrical windings 5 and insulating spacers 6 are arranged around the outer periphery of the iron core 1, as in the conventional case. ing. Then, the sheet winding 15 of the present invention, that is, the sheet winding 15 (high voltage winding 7 ) are placed. This sheet winding 150 winding start end (inner peripheral end)
At the end of the winding (outer peripheral end), a neutral point side outlet 8 and a line side outlet 9 made of copper wire are joined to the conductor sheet of the sheet winding 15.

Further, electrostatic rings 16 are arranged at the outermost upper and lower ends of the sheet winding 15 for relaxing the electric field at the ends, and the potential of this ring is the same as that of the line side opening 9. Furthermore, vertical gas ducts 17 are provided at appropriate intervals in the radial direction of the sheet winding 15.

FIG. 2 is a diagram showing a method of forming this vertical gas duct 17. That is, the conductive sheet 18 and the insulating film 19
After winding the duct sheet 20 a predetermined number of times, the vertical gas duct 17 is wound by sandwiching the duct sheet 20.
is formed. In this case, the duct sheet 20 is made up of a large number of square rod-shaped insulating spacers 20b successively pasted at regular intervals in the winding direction on one side of an insulating sheet 20a. Further, the direction of each insulating spacer 20b is the width direction orthogonal to the winding direction. Note that FIG. 2 exemplifies the process of forming the second vertical gas duct 17 from the inner peripheral side of the sheet winding 15.

The operation of this embodiment having the above configuration is as follows.

First, as many vertical gas ducts 17 as necessary are connected to the high voltage winding 7.
can be easily configured. That is, unlike the conventional high voltage winding having a multiple cylindrical winding configuration, the high voltage winding 7 of this embodiment
Since the sheet winding 15' is used, when a lightning surge enters, the voltage distributed to the vertical gas duct 17 is only one voltage, and the sheet winding 15 has anti-lightning surge characteristics. Since the internal potential fluctuation is also small, the voltage distributed to the vertical gas duct 17 becomes very small. Therefore,
It is not necessary to increase the cross-sectional area of the vertical gas duct 17 for insulation reasons, and the radial dimension of the vertical gas duct 17 is
Since the size can be minimized by considering only the cooling performance, the winding can be made smaller, which can contribute to making the entire transformer smaller.

Further, the configured vertical gas duct 17 is connected to the sheet winding 1
5, it is extremely convenient to flow a large amount of insulating gas as a cooling medium. In addition, by freely selecting the dimensions and number of the vertical gas ducts 17 of the high-voltage winding 7, it is possible to easily balance the circulating gas flow rate with the low-voltage winding 2, which is composed of multiple cylindrical windings. Since the balance can be optimized, cooling characteristics can be improved.

By the way, in this embodiment, as the low voltage winding 2, a multiplex cylindrical winding using conducting wire is used as in the conventional case.
The low-voltage winding 2 has a low insulation class and the incoming lightning surge voltage is small, so there are no insulation problems, and the dimensions of the gas flow path required for cooling are balanced with the insulation dimensions required for insulation. There is.

Furthermore, even in consideration of economic efficiency, the configuration of this embodiment is extremely practical because multiple cylindrical windings are cheaper.

Note that the present invention is not limited to the above embodiments, and the specific configuration of the vertical gas duct can be selected as appropriate.

As explained in "Effects of the Invention" 2, the present invention uses a sheet winding as the high-voltage winding and provides a vertical gas duct to the sheet winding. In comparison, it is possible to significantly improve the insulation properties of the high-voltage winding, and at the same time improve the balance of the amount of insulating gas circulation between the high-voltage winding and the low-voltage winding, improving the cooling characteristics of the entire winding. It is possible to provide a gas-insulated transformer that is both possible and compact.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view schematically showing an embodiment of a gas insulated transformer according to the present invention, Fig. 2 is a perspective view showing the process of forming a vertical gas duct in the same embodiment, and Fig. 3 is a conventional gas insulated transformer. FIG. 2 is a cross-sectional view schematically showing. 1... Iron core, 2... Low voltage winding, 3... Neutral point side outlet, 4... Line side outlet, 5... Cylindrical winding, 6...
... Insulating spacer, 7... High voltage winding, 8... Neutral point side outlet, 9... Line side outlet, 10... Cylindrical winding, 1.1... Insulating spacer, 12... ... Cylindrical electrostatic shield, 13... Gas flow path, 14... Gas flow, 15.
... Sheet winding, 16... Electrostatic ring, 17... Vertical gas duct, 18... Conductor sheet, 19... Insulating film, 20... Duct sheet, 20a... Insulating sheet I. , 20b... Insulating spacer.

Claims (1)

[Claims] The transformer tank contains the contents of a transformer consisting of a winding wound around the outer periphery of an iron core, and is filled with an insulating gas at a predetermined pressure. In a gas insulated transformer using a winding in which a high voltage winding is arranged coaxially around the outer periphery of a low voltage winding, the low voltage winding is formed of an insulated copper wire. Multiple cylindrical windings are used, and the high-voltage winding is a sheet winding formed by overlapping a conductor sheet and an insulating film, and vertical gas ducts are formed in this sheet winding at arbitrary intervals. A gas insulated transformer characterized by: