JP2010092915A - Electrostatic board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic board of a transformer, having excellent transition response characteristics against a shock voltage, having sufficient potential followability and sufficiently improved in potential vibration suppressing effect of a line end coil. <P>SOLUTION: The electrostatic board to be installed adjacent to a line end coil of the transformer has an insulative substrate and a conductive layer formed on the surface of the insulative substrate, wherein the insulative substrate has the surface shape substantially the same as the coil surface shape of the line end adjacent thereto, and the conductive layer is a layer formed with a conductive paint. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrostatic plate installed adjacent to a line end coil of a transformer, and relates to an electrostatic plate that suppresses potential vibration when an impact voltage enters the transformer.

  An electrostatic plate is connected adjacent to the line end coil of the transformer in order to suppress potential vibration of each part of the winding when an impact voltage such as lightning surge enters the transformer. The electrostatic plate has a large capacitance with respect to the line end coil, and suppresses potential vibration of the entire winding by suppressing potential vibration of the line end coil.

  The electrostatic plate has an electrode having the same surface shape as the surface shape of the adjacent coil, and has a large electrostatic capacity between the adjacent coil by facing the adjacent coil. Such an electrostatic plate is provided with a conductive layer on the surface, and conventionally, this conductive layer has been formed using a metal foil. However, since the metal foil has a low sheet resistance, when a conductive layer is formed over a wide area, a circulating current or eddy current is generated by the magnetic flux, and a large loss occurs in the transformer. In order to prevent this loss, conventionally, an electrostatic plate having a conductive layer having a structure in which a metal foil is subdivided and wound alternately with an insulator has been employed.

  The structure of a conventional electrostatic plate having a conductive layer formed of a segmented metal foil is shown in FIGS. 3 shows a schematic view of the electrostatic plate viewed from the adjacent coil side, and FIG. 4 shows a cross-sectional view taken along line IV-IV in FIG. When the conductive layer is formed of a metal foil, it is necessary to subdivide the metal foil in order to prevent the occurrence of a large loss due to the generation of circulating current or eddy current due to magnetic flux as described above. In this case, the conductive layer has a structure in which the metal foils 6 and the insulating paper 7 are alternately wound on the insulating substrate 4 as shown in FIG. 4, and as a result, as shown in FIG. An electrode having the same surface shape as that of the adjacent coil is formed by the metal foil 6 thus made. 3 and 4, the metal foil 6 and the insulating paper 7 provided on the surface of the insulating substrate 4 are the same, but the hatching is omitted in FIG. 3.

On the other hand, as shown in Patent Document 1, in an electrostatic shield intended to alleviate an electric field and prevent incompatibility by grounding a conductive layer directly or indirectly through a ground plate, the conductive layer is coated with a conductive paint. A method of forming the film using the same has been studied.
Japanese Utility Model Publication No. 60-61716

However, the conventional work for forming a conductive layer of an electrostatic plate using a metal foil has the following problems (1) to (4).
(1) It is difficult for one person to wrap a metal foil around a large electrostatic plate.
(2) It is necessary to wind the metal foil and the insulator (insulating paper) alternately and to keep the winding tension uniform, and requires a well-trained technique.
(3) The end of the metal foil becomes a sharp blade due to the winding tension, which is dangerous.
(4) When winding around the corner of the insulating base, the metal foil and the insulator (insulating paper) must be wound while cutting their width so that the overlap of the metal foil and the insulator (insulating paper) is not necessary. I must.

Further, the electrostatic shield as disclosed in Patent Document 1 is grounded, and the surface resistivity required for the electrostatic plate and the surface resistivity required for the grounded electrostatic shield may differ greatly. Are known. Here, it is described in Patent Document 1 that the surface resistivity of the conductive layer exceeds 10 ⁵ ohms. When the conventional conductive paint having such a high surface resistivity is applied to the electrostatic plate installed at the end of the line, the transient response characteristic is delayed with respect to the impact voltage, and sufficient potential followability is obtained. However, it has been clarified by the present inventors that there is a problem that a potential difference is generated in the electrostatic plate and the potential vibration suppression effect of the line end coil cannot be sufficiently obtained.

  This invention is made | formed in view of the said subject, Comprising: It is an electrostatic board arrange | positioned adjacent to the line end coil of a transformer, Comprising: A conductive layer is a layer formed with the conductive paint. Features.

  In this invention, since the conductive layer of the electrostatic plate is formed by applying a conductive paint, the work of forming the conductive layer is significantly improved compared to the conventional electrostatic plate having a conductive layer formed by winding a metal foil. Can be made. Moreover, the problem etc. in the winding around the corner portion due to the presence of the metal edge can be solved.

  Hereinafter, the present invention will be described in more detail. In the following description of the embodiments, the description is made with reference to the drawings. In the drawings of the present application, the same reference numerals denote the same or corresponding parts.

<Embodiment>
FIG. 1 shows a schematic view of the electrostatic plate of the present invention viewed from the line end coil side. In the electrostatic plate shown in FIG. 1, a conductive layer 1 is formed by applying a conductive paint on an insulating substrate (not shown). FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1 and shows a cross-sectional structure of the electrostatic plate of the present invention. As shown in the cross-sectional structure of FIG. 2, in the electrostatic plate of the present invention, the conductive layer 1 is formed by applying a conductive paint around the insulating substrate 4. By forming the conductive layer of the electrostatic plate with a conductive paint, the manufacturing efficiency of the electrostatic plate is improved as compared with a conventional electrostatic plate having a conductive layer using a metal foil, and the metal foil in the corner portion There is no need for processing. Such an electrostatic plate of the present invention can be applied to, for example, a transformer intended for a high voltage region of 100 kV or higher.

  In the electrostatic plate of the present invention, when a conductive paint is applied to the entire surface of the electrostatic plate, a circulating current flows by forming one turn by the magnetic flux passing through the electrostatic plate. In order to prevent loss due to the generation of the circulating current, it is desirable to provide a portion where the conductive paint is not applied as insulation. For example, by providing a strip-shaped one-turn insulation portion 2 as shown in FIG. Give. For example, the one-turn insulating portion 2 may be formed by masking the one-turn insulating portion 2 when a conductive paint is applied to the electrostatic plate. Moreover, the area | region of 1 turn insulation part 2 is not specifically limited, According to the scale etc. of a transformer, what is necessary is just to set suitably in the range in which the said insulation is confirmed.

  The coating film (conductive layer 1) formed by the conductive paint is formed so that the surface shape of the insulating substrate 4 provided with the conductive layer 1 is substantially the same as the surface shape of the line end coil. Further, the thickness of the conductive layer 1 is not particularly limited, and may be adjusted so as to have a surface resistivity described later, but is preferably provided with a uniform thickness on the insulating substrate 4. Such a thickness can be achieved by adjusting the coating conditions. In addition, the said substantially the same does not necessarily mean only the completely same, but the shape where 90% or more of each surface area of the surface of a line end coil and the insulating board | substrate 4 opposes is included.

  In order to obtain the potential vibration suppression effect of each part of the winding when the impact voltage of the electrostatic plate enters, the potential of the electrostatic plate must be the same as the potential of the adjacent coil when the impact voltage enters. . If the resistivity of the conductive paint (or the conductive layer formed of the conductive paint) is high, the follow-up of the potential of the obtained electrostatic plate becomes slow, and the function of suppressing the potential vibration of the electrostatic plate may not be sufficiently performed. is there. For this reason, the surface resistivity of the conductive layer is lower than the surface resistivity of the conductive layer formed by the conductive paint applied to the conventional electrostatic shield, and is in the range of 10Ω / □ to 1000Ω / □. Desirably, it is more preferably 10Ω / □ to 50Ω / □. When the conductive layer has the above surface resistivity, the potential vibration suppressing effect is good. The unit Ω / □ of the surface resistivity is an eigenvalue that does not depend on the measurement method, and is a value after the conductive paint is dried.

  As the conductive paint for forming the conductive layer, a paint whose viscosity is adjusted so that it can be uniformly applied to an electrostatic plate applicable to a transformer intended for the high voltage region as described above is used. It is preferable that the surface resistivity of the conductive layer formed at the same time is sufficiently reduced. Such a conductive coating material preferably contains spherulitic carbon having an average particle size of 5 to 50 μm. By using spherulitic carbon having such an average particle diameter, the surface of the conductive layer to be formed is maintained while maintaining a low viscosity by suppressing an increase in the viscosity of the conductive paint due to the addition of a conductive material such as carbon. The resistivity can be adjusted to a low resistance. The average particle diameter can be determined from the scattering maximum angle of the scattered image measured with crossed Nicols using a light scattering measuring device.

  The composition of the conductive paint preferably includes spherulitic carbon, a resin varnish, and a curing agent. Moreover, it is preferable to contain the said carbon 50 mass%-70 mass% with respect to the whole electroconductive coating material. When setting it as such a composition, the viscosity and surface resistivity of the said coating material can be improved with sufficient balance. In addition, you may contain a well-known additive in such a conductive coating material. Further, the composition of the conductive paint preferably has a viscosity of 1 Pa · s to 100 Pa · s at room temperature. If the viscosity is within such a range, the conductive paint on the insulating substrate can be used. Good applicability. The conductive paint can be diluted with thinner or the like at the time of application. In this case, the carbon content in the diluted conductive paint is 12% by mass to 13% by mass. The viscosity is preferably 0.4 Pa · s to 40 Pa · s at room temperature. The conductive paint can appropriately contain known additives and the like. In addition, when the carbon content in the conductive layer to be formed is 60% by mass to 70% by mass, and more preferably about 65% by mass, good surface resistivity can be imparted.

  Specifically, the conductive paint is composed of 60 mass% to 65 mass% of spherulitic carbon, 20 mass% to 25 mass% of a polyester resin varnish, and 5 mass% to 10 mass% of xylene. And 5% by mass to 10% by mass of ethylbenzene and 1% by mass to 5% by mass of n-butyl acetate are adjusted so as to be 100% by mass in total, and 100% by mass of polyisocyanate solution is used as a curing agent. May be mixed so that these volume ratios are 4: 1. At the time of application, the conductive paint includes, for example, 20% by mass to 30% by mass of isobutyl acetate, 5% by mass to 10% by mass of an aromatic hydrocarbon mixed solvent, and 40% by mass to 50% by mass of xylene. It is diluted to a dilution rate of about 25% using a known diluent such as thinner composed of 10% by mass to 20% by mass of propylene glycol monomethyl ether acetate. The diluted conductive coating is applied and dried by a known method to form a conductive layer.

  The electrostatic plate of the present invention is preferably provided with a short-circuit plate 3 as shown in FIG. When the short-circuit plate 3 is provided, the short-circuit plate 3 has a structure connected to the line end 8 where the impact voltage enters. The short-circuit plate 3 can further adjust the surface resistivity of the conductive layer in addition to the adjustment by the conductive paint. Such a short-circuit plate 3 is made of a metal foil or the like, is brought into contact with the conductive layer 1 and is connected to the conductive layer 1 by fastening and fixing. For example, as shown in FIGS. 1 and 2, the short-circuit plate 3 is provided in the central portion of one side of the conductive layer. Arrangement | positioning of the short circuit board 3 is not restricted to the aspect shown in FIG. 1, You may arrange | position so that the surface periphery may be enclosed. The adjustment of the surface resistivity by the short-circuit plate 3 can be performed by adjusting the distance d from the short-circuit plate 3 to the farthest point 5 of the conductive layer.

  FIG. 5 shows the response magnification (%) of the conductive layer with respect to the impact voltage entering from the line end 8 [((measured voltage at potential measurement point) − (impact voltage entered)) / (impact voltage entered) × 100]. It is a graph to show. The potential measurement point on the horizontal axis corresponds to the distance from the line end 8 where the impact voltage enters, and the vertical axis represents the response magnification (%) at that position. The wavefront length of the impact voltage is 1.2 μS, and the surface resistivity of the conductive paint is 100Ω / □. Without the short-circuit plate 3, as the distance from the impact voltage intrusion point increases, the potential follow-up worsens and the response magnification increases, and it is difficult to obtain the potential vibration suppression effect of the electrostatic plate. On the other hand, the short-circuit plate 3 is disposed on the conductive paint application surface, and the distance d from the short-circuit plate 3 to the farthest point 5 on the conductive paint application surface is within an appropriate range so as to have a desired surface resistivity. As a result, the follow-up of the potential is adjusted appropriately and the potential oscillation is suppressed.

Thus, in the present invention, by providing a conductive layer formed by applying a conductive paint on the electrostatic plate, workability is greatly improved as compared to the conventional formation of a conductive layer by winding a metal foil, and the potential is increased. An electrostatic plate excellent in followability and the like can be provided. Moreover, the electrostatic plate which adjusted the surface resistivity more effectively can be produced by arrange | positioning a short circuit board.
The electrostatic plate is formed by applying the conductive paint by keeping the resistivity of the conductive paint to be applied within an appropriate range and additionally arranging a short-circuit plate.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is the schematic of the electrostatic plate of this invention seen from the track end coil side. It is sectional drawing in the II-II line of FIG. It is the schematic of the conventional electrostatic plate which has the conductive layer formed with the metal foil. It is sectional drawing in the IV-IV line of FIG. It is a graph which shows the followable | trackability of the electric potential of a conductive layer with respect to the approach of an impact voltage.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Conductive layer, 2 1 turn insulation part, 3 Short circuit board, 4 Insulation board | substrate, 5 Farthest point from a short circuit board, 6 Metal foil, 7 Insulation paper, 8 Line end.

Claims (6)

An electrostatic plate installed adjacent to the line end coil of the transformer,
The electrostatic plate has an insulating substrate and a conductive layer provided on the surface of the insulating substrate,
The insulating base is substantially the same as the adjacent line end coil surface shape of the surface shape,
The electrostatic plate, wherein the conductive layer is a layer formed of a conductive paint.   2. The conductive plate according to claim 1, wherein the insulating substrate is provided with a portion where the conductive paint is not applied so that current does not flow in a circumferential direction of the adjacent line end coil.   The electrostatic plate according to claim 1, wherein the conductive layer has a surface resistivity in a range of 10Ω / □ to 1000Ω / □.   The electrostatic plate according to claim 1, wherein the conductive paint includes spherulitic carbon having an average particle diameter of 5 μm to 50 μm. The conductive paint includes at least spherulitic carbon having an average particle diameter of 5 μm to 50 μm, a resin varnish, and a curing agent,
The electrostatic plate according to claim 1, wherein the carbon is contained in an amount of 50% by mass to 70% by mass with respect to the entire conductive paint. The conductive layer has a short-circuit plate disposed on at least a part of its surface,
The electrostatic plate according to claim 1, wherein a surface resistivity of the conductive layer is adjusted by the short-circuit plate.

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