JP2660302B2 - Gas-filled film capacitors - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a gas-filled film capacitor, and more particularly to an insulating structure thereof.

[Conventional technology]

FIG. 2 is a simplified diagram showing the internal structure of a conventional film capacitor. In the figure, (1) is a case obtained by appropriately shaping a metal plate, and (2) is a film capacitor element (hereinafter simply referred to as an element) housed in a case (1) and connected in series with each other. As the dielectric material, a polyolefin-based polypropylene film, a polyester-based polyethylene terephthalate film, or the like is used. (3) is an extraction terminal, and (4) is an insulating medium filled in the case (1). There are cases where insulating oil is used and cases where insulating gas is used. (5) is a main insulating layer for providing electric insulation between each element (2) and the case (1). As shown in the perspective view of FIG. 3, a plurality of assembled elements (2). Are wrapped together in a sheet-like insulator. This insulating sheet has a high electric insulation performance and is economically employed for the element (2).
A polypropylene film or the like having good workability is usually used. In FIG. 3, the connection between the elements (2) is not shown.

As described above, the insulation between the element (2) itself and the element (2) and the element (2) is the dielectric material, and the insulation between the element (2) and the case (1) is the main insulation. An insulation design performed in layer (5) is employed.

Next, the role of the main insulating layer (5) will be described by assuming a dielectric breakdown failure of the capacitor. now,
For example, a material defect exists in the specific element (2),
It is assumed that the element (2) breaks down during the operation of the capacitor. The destruction portion of the faulty element (2) is gradually enlarged. However, after a predetermined time, when an external fault detection device (not shown) detects the occurrence of an internal fault of the capacitor, the circuit breaker on the power supply side is immediately turned on. To disconnect the faulty capacitor from the circuit. In addition, as a method of this failure detection, an insulating medium (4) and a failure element (2)
There is a method of mechanically detecting the bulge of the case (1) based on thermal decomposition, and a method of electrically detecting a change in current or voltage of a circuit due to element short-circuit.

However, if the destruction of the element (2) is expanded to reach the case (1) by the time of detection of the failure, the fault will develop into a ground fault and the effect on the circuit will be greatly expanded.

Therefore, as the main insulating layer (5), it is necessary to prevent the spread of fire from the faulty element (2) and to achieve protection coordination of maintaining the insulating performance at least within the time until the fault detection.

[Problems to be solved by the invention]

Since the conventional film capacitor is configured as described above, there is a problem that it is difficult to achieve the above protection coordination, particularly when an insulating gas is used as the insulating medium (4).

That is, when the insulating oil is used as the insulating medium (4), the insulating oil is vaporized by the heat generated at the destruction portion of the element (2), and the volume thereof is greatly increased, so that the case (1) is rapidly deformed. However, failure detection is performed relatively quickly and reliably. Further, since the latent heat of vaporization of the insulating oil acts in a direction to suppress the heat generation at the destruction part, the above-described protection coordination is relatively easily realized.

However, in the case of a gas-filled film capacitor using an insulating gas, since oil having a large specific heat does not exist, the temperature of the destruction portion of the element (2) rapidly increases, and the failure detection time tends to be long. As a result, the melting point is 16
The element film at about 0 to 260 ° C. is melted at the above temperature, fluidized, and comes into contact with the main insulating layer (5). For this reason, a part of the main insulating layer (5) is melted, a through hole is generated, and a ground fault is likely to occur in a short time, so that there is a high possibility that the target protection coordination cannot be achieved.

The present invention has been made in order to solve the above-described problems, and it is an object of the present invention to obtain a gas-filled film capacitor that achieves protection coordination with a failure detection device and can prevent the occurrence of a ground fault. Aim.

[Means for solving the problem]

In the gas-filled film capacitor according to the present invention, the main insulating layer includes a first film layer having heat resistance equivalent to that of the film used for the film capacitor element and having electric insulation resistance, and the first film layer. And a second film layer having a heat resistance at a temperature higher than the melting temperature of the film capacitor element.

In a further embodiment, the second film layer is made of a polyimide film or an aramid film.

[Action]

When dielectric breakdown occurs in some of the film capacitor elements, the film of the element melts and flows due to the heat generated at the broken portion, and may reach the main insulating layer. However, since the inside of the main insulating layer is formed of a second film layer having high heat resistance (more specifically, a polyimide film or an aramid film), the second film layer is formed of the first film layer. Of the main insulating layer, and the original electrical insulation resistance as the main insulating layer is maintained.

〔Example〕

FIG. 1 is a perspective view showing a main part of a gas-filled film capacitor according to an embodiment of the present invention, and corresponds to the conventional FIG. In the figure, the main insulating layer (5) is different from the conventional one in that an insulating sheet (5a) made of a polypropylene film as a first film layer and an insulating sheet (5b) made of a polyimide film as a second film layer
Is a double structure. And the insulating sheet (5b) is arranged inside. In this case, the packaged element (2) may be wrapped with an insulating sheet (5b) first, and then wrapped with an insulating sheet (5a) from above, but the two sheets (5a) and (5b) may be overlapped in advance. Alternatively, the element (2) may be wrapped with the insulating sheet (5b) inside.

Here, as a polyimide film, Kapton (a trade name of a polyimide film manufactured by DuPont, USA) is famous, and this Kapton has a heat-resistant performance that allows use at 400 ° C. or higher. Therefore, it usually has a heat resistance sufficiently higher than the melting temperature of the polypropylene film or the like used for the element (2), and even if the melt of the film flows due to the dielectric breakdown of the element (2). The insulating sheet (5b) is not damaged at all. As a result, the insulation sheet (5a) maintains its electric insulation performance, insulation between the element (2) and the case (1) until the time of failure detection is ensured, and the above-described protection coordination is achieved.

However, from the viewpoint of heat resistance alone, it is conceivable that the main insulating layer (5) is entirely made of a polyimide film. However, a polyimide film is inferior in electrical insulation performance, particularly in corona discharge life, and extremely expensive, as compared with a polypropylene film or the like. Therefore, by adopting the double structure of the above-mentioned sheets (5a) and (5b), an economical and highly reliable gas-filled film capacitor capable of minimizing the increase in price and reliably achieving protection coordination can be obtained. It can be realized.

In the above embodiment, the case where polypropylene or polyethylene terephthalate is used as the dielectric material of the element (2) has been described. However, for example, polyphenylene sulfide or the like may be used. Therefore, the same applies to the first film layer.

Further, the second film layer is not limited to a polyimide film, and may be, for example, an aramid film.

That is, this aramid film (aromatic polyamide film) also has high heat resistance close to that of the above-described polyimide film, and does not change at all even when exposed to a solder bath at 260 ° C. for 2 minutes.

〔The invention's effect〕

As described above, in the present invention, the main insulating layer is constituted by the predetermined first film layer and the second film layer, so that at the time of an internal failure, protection coordination with the failure detection device can be reliably achieved. An economical and highly reliable gas-filled film capacitor can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main part of a gas-filled film capacitor according to one embodiment of the present invention, FIG. 2 is a structural view showing a simplified internal structure of a conventional film capacitor, and FIG. It is a perspective view which shows the principal part of a thing. In the figure, (1) is a case, (2) is a film capacitor element, (4) is an insulating gas, (5) is a main insulating layer, (5)
a) and (5b) are insulating sheets as first and second film layers, respectively. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (2)

(57) [Claims] A case, a film capacitor element housed in the case together with an insulating gas, and a main insulating layer enclosing the film capacitor element and providing electric insulation between the film capacitor element and the case. In the above, the main insulating layer has a heat resistance equivalent to that of the film used for the film capacitor element and has a first film layer which bears the electric insulation resistance, and is disposed inside the first film layer. A gas-filled film capacitor, comprising: a second film layer having a heat resistance higher than a melting temperature of the film capacitor element. 2. The method according to claim 1, wherein the second film layer is a polyimide film or an aramid film.
A gas-filled film capacitor as described.