JP3460702B2 - Transformers for gas insulated instruments - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas-insulated instrument transformer used for converting a high voltage into a measurable voltage level in electric power equipment.

[0002]

2. Description of the Related Art A gas-insulated voltage transformer (gas V) is used as one of the components of a gas-insulated switch in electric power equipment.
T) is used. Gas insulation instrument transformer is SF
Placed in a space filled with insulating gas such as ₆ gas,
It is a transformer that transforms the high voltage on the primary side to a measurable voltage with high accuracy. This type of transformer includes an iron core, a secondary coil (low-voltage coil) wound on the iron core, and a primary coil (high-voltage coil) coaxially wound on the secondary coil.
Between the secondary coil and the primary coil, the potential fixing plate connected to the winding start of the primary coil and connected to the grounding terminal through the lead wire, and between the potential fixing plate and the secondary coil A ground electrode plate which is provided in an insulated state with respect to the potential fixing plate and is connected to an iron core or a ground point set at a portion having the same potential as the iron core, and the potential fixing plate is a ground electrode plate. It is connected to the grounding point via the electrostatic capacity between and.

FIG. 6 shows the structure of a conventional transformer of this type, and an equivalent circuit of the same transformer is shown in FIG. In these figures, 1 is an iron core made of a laminated body of steel plates, 2 is a secondary coil (low-voltage coil) wound around a leg of the iron core 1 through a secondary winding form 3, and 4 is the outside of the secondary coil 2. A primary coil (high voltage coil) wound on a primary winding form 5 coaxially arranged with a secondary coil via a ground electrode plate 6, an insulating layer 7 made of an insulating film, and a potential fixing plate 8. ).

In the example shown in FIG. 6, a transformer is constituted by an iron core 1, a secondary coil 2, a secondary winding type 3, a primary winding type 5, a ground electrode plate 6, an insulating layer 7, a potential fixing plate 8 and a primary coil 4. A main body is configured, and the main body of the transformer is housed in a metal container 9 (see FIG. 5) of a gas-insulated switchgear in which an insulating gas such as SF ₆ gas is sealed and kept at the ground potential.

The potential fixing plate 8 is connected to the winding start of the primary coil 4 and is connected to the grounding terminal 11 electrically connected to the container 9 through the low voltage side primary lead wire 10. In order to enable measurement of the ground insulation resistance of the primary coil 4 by a megger, the low-voltage side primary lead wire 10 is drawn to the outside of the container 9 while being insulated from the container 9, and then on the outer surface of the container 9. It is connected to the grounding terminal 11 provided.

The ground electrode plate 6 is insulated from the potential fixing plate 8 by the insulating layer 7, and the core 1 is passed through the grounding lead wire 12 having a minimum reactance and a minimum necessary length.
Or a part having the same potential as the iron core (for example, iron core tightening fitting)
Is connected to the ground point e set to. Therefore, the potential fixing plate 8 is connected to the ground point e via the electrostatic capacitance C between the potential fixing plate and the ground electrode plate 6.

FIG. 7 is an enlarged view of the Z portion of FIG. 6, and as is clear from the figure, in the conventional instrument transformer of this type, the secondary coil 2 and the primary coil 4 are measured in the winding axis direction. The lengths of the potential fixing plate 8 and the ground electrode plate 6 are set to be equal, and the end portions 6a and 8a at both ends of the potential fixing plate 8 and the ground electrode plate 6 in the longitudinal direction are arranged at the same position. It was

[0008]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention In a gas-insulated instrument transformer, it is possible to measure the ground insulation resistance of the primary coil 4 by a megger at the time of assembling the gas-insulated switchgear and at the time of periodic inspection. As described above, the low-voltage side primary lead wire 10 is once pulled out of the container 9 while being insulated from the container 9, and then connected to the grounding terminal 11 provided on the outer surface of the container 9. Therefore, the low voltage side primary lead wire 10 becomes considerably long, and its reactance X becomes large. Therefore, when a high frequency surge flows from the high voltage side of the primary coil, the reactance X of the lead wire 10
(See FIG. 5), the potential of the potential fixing plate 8 rises, and there is a possibility that dielectric breakdown may occur near the potential fixing plate 8. This dielectric breakdown may appear in the form of layer dielectric breakdown occurring between the layers of the primary coil, or in the form of creeping discharge breakdown with the end of the potential fixing plate 8 as a base point. Whether it appears depends on the design insulation strength.

When the potential of the potential fixing plate 8 rises, electrostatic induction between the potential fixing plate 8 and the secondary coil 2 causes
High voltage may be transferred to the secondary coil 2 and dielectric breakdown may occur on the secondary side.

In order to prevent the above-mentioned dielectric breakdown from occurring, the instrument transformer shown in FIG. 6 is connected to the iron core 1 by the minimum necessary length of the lead wire 12 having a small reactance and is connected to the ground potential. By making the ground electrode plate 6 which is the opposite to the potential fixing plate 8 to form a capacitance C between the potential fixing plate 8 and the ground, and by bypassing the high frequency surge through this capacitance C, the potential The rise in the potentials of the fixed plate 8 and the secondary coil 2 is suppressed. As described in Japanese Patent Publication No. 61-69107, there is a technique for suppressing the potential rise of the potential fixing plate and the secondary coil when the high frequency surge enters by making the ground electrode plate face the potential fixing plate. It is known.

However, as described above, even when the ground electrode plate is provided, when a surge (for example, a switching surge of a disconnecting switch) enters the primary coil 4, its frequency is a high frequency of several MHz or more. However, there is a possibility that dielectric breakdown may occur near the end of the potential fixing plate 8.

An object of the present invention is to provide a gas-insulated instrument transformer capable of further improving the insulation performance against high frequency surges.

[0013]

SUMMARY OF THE INVENTION The present invention provides an iron core, a secondary coil wound around the iron core, a primary coil coaxially wound around the secondary coil, and a secondary coil. A potential fixing plate that is provided between the primary coil and connected to the winding start of the primary coil and that is also connected to the grounding terminal through the lead wire, and between the potential fixing plate and the secondary coil with respect to the potential fixing plate. And a ground electrode plate connected to a ground point set at the same potential as the iron core and the iron core, and the potential fixing plate is provided between the potential fixing plate and the ground electrode plate. It is applied to the transformer for gas-insulated instrument which is connected to the ground point through the capacitance of.

In the present invention, the longitudinal dimension of the potential fixing plate measured in the winding axis direction of the primary coil and the secondary coil is made longer than the longitudinal dimension of the ground electrode plate measured in the same direction. The both ends of the potential fixing plate in the longitudinal direction are terminated at positions beyond the both ends of the ground electrode plate in the longitudinal direction.

With the above arrangement, the radius of curvature of the equipotential line in the vicinity of both ends of the potential fixing plate can be increased, so that the electric field near the ends of the potential fixing plate is relaxed and the dielectric strength against high frequency surge is increased. Can be improved.

Further, in the present invention, it is preferable that both ends of the potential fixing plate in the longitudinal direction are folded back so that the ends of the respective end portions of the potential fixing plate in the longitudinal direction are rounded.

According to this structure, the both ends of the potential fixing plate have no edges, and the end portion of the potential fixing plate has a thickness of 2 mm.
Since it is doubled, the electric field near the end of the potential fixing plate can be further relaxed, and the dielectric strength near the end of the potential fixing plate can be further improved.

[0018]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a longitudinal sectional view of a half portion of a transformer for gas-insulated instrument according to the present invention, FIG. 2 is a transverse sectional view showing a quarter of the transverse section of the transformer, and FIG. 3 is A in FIG.
It is an enlarged view of a part. FIG. 4 is an enlarged view showing a modified example of the portion A of FIG.

1 to 3, the same parts as those of FIGS. 6 and 7 are designated by the same reference numerals. In these figures, 1 is an iron core, 2 is a secondary coil, and the secondary coil 2 is wound around the outer circumference of a cylindrical secondary winding shape 3 and fitted on the leg portion of the iron core 1.

Reference numeral 4 denotes a primary coil wound on a cylindrical primary winding 5 with a ground electrode plate 6, an insulating layer 7 and a potential fixing plate 8 interposed therebetween. The ground electrode plate 6 is provided so as not to form one turn, and is composed of a conductive plate arranged along the outer periphery of the primary winding shape 5, and the insulating film has a predetermined thickness on the ground electrode plate 6. The insulating layer 7 is formed by winding. The potential fixing plate 8 is a conductive plate which is provided so as not to form one turn and is arranged along the outer periphery of the insulating layer 7, and the primary coil 4 is provided on the outer periphery of the potential fixing plate 8 between the layers. It is wound in multiple layers with an insulating film interposed.

The iron core 1, the secondary coil 2, the secondary winding type 3, the primary winding type 5, the ground electrode plate 6, the insulating layer 7, the potential fixing plate 8 and the primary coil 4 constitute a transformer body. The main body is housed in a metal container of a gas-insulated switchgear in which an insulating gas such as SF ₆ gas is sealed and kept at the ground potential.

The equivalent circuit of the transformer for a meter according to the present invention can be represented by FIG. 5 like the conventional transformer for a meter, and the potential fixing plate 8 is connected to the winding start of the primary coil 4. At the same time, it is connected to the grounding terminal 11 electrically connected to the container 9 through the low voltage side primary lead wire 10. The low-voltage side primary lead wire 10 is pulled out of the container 9 while being insulated from the container 9, and then connected to a grounding terminal 11 provided on the outer surface of the container 9.

The ground electrode plate 6 is provided with the core 1 through the grounding lead wire 12 having a minimum reactance and a minimum necessary length.
Or a part having the same potential as the iron core (for example, iron core tightening fitting)
Is connected to the ground point e set to.

Although the basic construction described above is the same as that of the conventional instrument transformer, in the present invention, as shown in FIG. 3, the primary coil 4 and the secondary coil 2 are wound in the axial direction. The longitudinal dimension of the potential fixing plate 8 measured in the above is longer than the longitudinal dimension of the ground electrode plate 6 measured in the same direction, and both ends of the potential fixing plate 8 in the longitudinal direction of the ground electrode plate 6 are It is terminated at a position beyond both ends in the longitudinal direction. In FIG. 3, reference numerals 8a and 6a denote the end portions of the potential fixing plate 8 and the ground electrode plate 6, respectively.

In the conventional instrument transformer, as shown in FIG. 7, the equipotential line V is curved with a small radius of curvature near the end of the potential fixing plate 8. Therefore, the potential gradient of the equipotential line becomes large in the vicinity of the end of the potential fixing plate 8, and there is a risk of dielectric breakdown.

On the other hand, when both ends of the potential fixing plate 8 are terminated at positions beyond both ends of the ground electrode plate 6 as in the present invention, the equipotential line V is formed near the terminal end 6a of the ground electrode plate 6. Since it is curved to the inner diameter side and then largely curved toward the outside of the potential fixing plate 8, the radius of curvature of the equipotential line V near the terminal end of the potential fixing plate 8 can be increased. Therefore, the electric field near both ends of the potential fixing plate 8 can be relaxed, and the dielectric strength against high frequency surge near both ends of the potential fixing plate 8 can be improved.

In the present invention, as shown in FIG. 4, both ends of the potential fixing plate 8 in the longitudinal direction are folded back so that the ends of the respective end portions 8a in the longitudinal direction of the potential fixing plate 8 are rounded. The attached shape is preferable.

With this structure, it is possible to eliminate sharp edges from both ends of the potential fixing plate 8 (tips of the terminal end portions 8a) and double the thickness of the end portion of the potential fixing plate 8. Therefore, the electric field near both ends of the potential fixing plate can be further relaxed. Therefore, as shown in FIG. 3, as compared with the case where both ends of the potential fixing plate 8 are not folded back,
The dielectric strength near both ends of the potential fixing plate can be further improved.

[0029]

As described above, according to the present invention, the longitudinal dimension of the potential fixing plate is made longer than the longitudinal dimension of the ground electrode plate so that both ends of the potential fixing plate exceed both ends of the ground electrode plate. Since it is terminated at a different position, there is an advantage that the electric field near both ends of the potential fixing plate can be relaxed and the dielectric strength against high frequency surge can be improved.

Particularly, according to the invention described in claim 2,
By folding back both ends of the potential fixing plate to eliminate sharp edges from both ends of the potential fixing plate and increasing the thickness of the terminal end portions of both ends of the potential fixing plate, the electric field near both ends of the potential fixing plate was further relaxed, There is an advantage that the dielectric strength against high frequency surge can be improved.

[Brief description of drawings]

FIG. 1 is a half longitudinal sectional view showing the structure of a gas-insulated instrument transformer according to the present invention.

FIG. 2 is a cross-sectional view showing a quarter of the cross section of the instrument transformer of FIG.

FIG. 3 is an enlarged view of a portion A of FIG.

FIG. 4 is an enlarged view showing a modified example of a portion A of FIG.

FIG. 5 is an equivalent circuit diagram showing an electrical configuration of a voltage transformer for an instrument according to the present invention.

FIG. 6 is a half longitudinal sectional view showing a configuration of a conventional instrument transformer.

FIG. 7 is an enlarged view of a Z portion of FIG.

[Explanation of symbols]

1 ... Iron core, 2 ... Secondary coil, 3 ... Secondary winding type, 4 ... Primary coil, 5 ... Primary winding type, 6 ... Ground electrode plate, 7 ... Insulating layer, 8 ... Potential fixing plate, 10 ... Lead wire, 11 ... Grounding terminal.

Continuation of the front page (56) References JP-A-61-69107 (JP, A) Actually opened 60-49613 (JP, U) Actually opened 60-133615 (JP, U) Actually opened 4-42721 (JP , U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01F 27/28

Claims (2)

(57) [Claims] 1. An iron core, a secondary coil wound around the iron core, a primary coil coaxially wound around the secondary coil, and provided between the secondary coil and the primary coil. And a potential fixing plate connected to the winding start of the primary coil and connected to a grounding terminal through a lead wire, and insulated from the potential fixing plate between the potential fixing plate and the secondary coil. And a ground electrode plate connected to a ground point set in the iron core or a portion having the same potential as the iron core, wherein the potential fixing plate is between the potential fixing plate and the ground electrode plate. In a gas-insulated instrument transformer that is connected to the ground point via capacitance, the longitudinal dimension of the potential fixing plate measured in the winding axis direction of the primary coil and the secondary coil is the same direction. The longitudinal dimension of the ground electrode plate measured in Even longer,
A gas insulation instrument transformer, wherein both ends in the longitudinal direction of the potential fixing plate are terminated at positions beyond both ends in the longitudinal direction of the ground electrode plate. 2. The both ends of the potential fixing plate in the longitudinal direction are folded back, and the ends of the respective end portions of the both ends of the potential fixing plate in the longitudinal direction are rounded. The transformer for gas-insulated instruments described in.