JP5128023B1 - Current transformer for instrument - Google Patents

Abstract

The instrument current transformer 50 includes a current transformer mounting frame 5 to which the current transformer core 4 is attached. The current transformer mounting frame 5 includes a cylindrical member 5a and a support member 5b. The cylindrical member 5a is coaxially disposed around the center conductor 2, the annular end 6 in the axial direction is thicker than the other portions, and the inner diameter side of the annular end 6 is more central than the other portions. The trap hole 20 is provided at a position adjacent to the annular end 6 on the bottom surface thereof.
[Selection] Figure 1

Description

  The present invention relates to an instrument current transformer installed in a gas-insulated switchgear, and more particularly to an instrument current transformer with a metal foreign substance trap structure.

A gas insulated switchgear is configured by storing various devices such as circuit breakers, busbars, disconnectors, and current transformers in a tank filled with an insulating gas such as SF ₆ (sulfur hexafluoride) gas. The

  Patent Document 1 describes a current transformer for an instrument installed in a gas insulated switchgear. The current transformer for instrument described in Patent Document 1 is a so-called horizontal and penetrating instrument current transformer, and has an annular shape that circulates around a central conductor (high voltage portion) horizontally disposed in a tank. It includes a current transformer core and a mounting frame that is also used to attach the current transformer core in a cylindrical shape that circulates around the central conductor.

  By the way, there are cases where minute metallic foreign matter may be mixed in the tank of the gas insulated switchgear, but this metallic foreign matter behaves due to the electric field generated by the high-voltage part in the tank and causes a decrease in insulation performance. Therefore, it is a problem to capture or remove foreign metal.

  When a metallic foreign object exists on the inner bottom surface of the instrument current transformer mounting frame, if this metallic foreign object behaves due to an electric field and contacts the central conductor, a flashing or the like may occur, causing a dielectric breakdown. Conventionally, an electric field design has been performed so that metal foreign objects existing on the inner bottom surface of the mounting frame are not captured and the metal foreign objects are not harmful.

JP-A-56-70616

  However, there is a great demand for reducing the installation area of gas-insulated switchgear, and reducing the tank diameter to reduce the size of the equipment increases the electric field strength. It is necessary to capture or remove the metallic foreign matter.

  The present invention has been made in view of the above, and is a current transformer for an instrument with a trap structure capable of capturing and detoxifying minute metallic foreign matters that may exist on the inner bottom surface of the current transformer mounting frame. The purpose is to provide.

  In order to solve the above-described problems and achieve the object, the current transformer for an instrument according to the present invention uses a current flowing through a central conductor disposed horizontally in a metal tank filled with an insulating gas. A current transformer for measuring, which is coaxially arranged around the central conductor, and has one end in the axial direction that is thicker than the other part, and the inner diameter of the one end is larger than the inner diameter of the other part. Also has a small diameter, a current transformer mounting frame having a cylindrical member provided with a through hole in a position adjacent to the one end in the axial direction on the bottom surface, and penetrated by the cylindrical member A current transformer core disposed around the central conductor.

  According to the present invention, there is an effect that it is possible to capture and detoxify minute metallic foreign matters that may exist on the inner bottom surface of the current transformer mounting frame.

FIG. 1 is a longitudinal sectional view showing an example of the configuration of a gas insulated switchgear including an instrument current transformer according to an embodiment. 2 is a cross-sectional view taken along line AA of FIG. FIG. 3 is a diagram showing a configuration of a main part of FIG. FIG. 4 is a diagram showing a configuration in the case where a trap hole is not provided in the instrument current transformer, and corresponds to FIG. FIG. 5 is a diagram showing a configuration in the case where no trap hole is provided in the instrument current transformer, and corresponds to FIG.

  Hereinafter, an embodiment of a current transformer for an instrument according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
FIG. 1 is a longitudinal sectional view showing an example of the configuration of a gas-insulated switchgear including an instrument current transformer according to this embodiment. 2 is a cross-sectional view taken along line AA of FIG. In FIG. 2, the display of the current transformer core 4 is omitted. FIG. 3 is a diagram showing a configuration of a main part of FIG.

  As shown in FIGS. 1 to 3, the gas insulated switchgear includes a tank 1, a central conductor 2, and a current transformer 50 for an instrument. The instrument current transformer 50 includes a current transformer core 4, a current transformer mounting frame 5, an adapter 7, a screw rod 8, and the like.

The tank 1 is a grounded cylindrical metal container in which an insulating gas such as SF ₆ gas is sealed. The tank 1 is arranged with its axis line horizontal, for example. The center conductor 2 constitutes a high voltage part through which current flows. The center conductor 2 is horizontally disposed along the axis of the tank 1, for example.

  The current transformer mounting frame 5 includes a cylindrical member 5a and a support member 5b. The cylindrical member 5 a is a cylindrical metal member, for example, and is arranged so as to go around the central conductor 2. For example, the axis of the cylindrical member 5a and the axis of the central conductor 2 coincide with each other, and the central conductor 2 penetrates the cylindrical member 5a in the axial direction. The current transformer mounting frame 5 is at the same potential (ground potential) as the tank 1.

  The annular end 6 which is one end of the cylindrical member 5a in the axial direction is thicker than the other part of the cylindrical member 5a, and the inner diameter side thereof is closer to the central conductor 2 side than the inner diameter side of the other part. It is exciting. That is, the inner diameter of the annular end 6 is smaller than the inner diameter of the other part in the axial direction. The inner diameter of the cylindrical member 5 a is constant except for the annular end 6. Moreover, the outer diameter of the cylindrical member 5a is constant in the axial direction, for example. Further, the longitudinal cross-sectional shape on the inner diameter side of the annular end portion 6 is a smooth shape having a finite curvature so that there is no corner portion.

  Furthermore, a trap hole 20 (through hole portion) is provided in a portion adjacent to the annular end portion 6 in the axial direction on the bottom surface portion of the cylindrical member 5a. The trap hole 20 penetrates the bottom surface of the cylindrical member 5a vertically downward, and captures the metal foreign object 30 when a minute metal foreign object 30 exists on the inner bottom surface of the current transformer mounting frame 5. Then, it falls on the bottom surface of the tank 1 below the trap hole 20 and plays a role of detoxification.

  The other end of the cylindrical member 5a in the axial direction is attached to the support member 5b. The support member 5b is made of, for example, an annular metal member and is connected to the tubular member 5a in a bowl shape. The periphery of the support member 5b is sandwiched between the flange portions 10 of the tank 1, and is fixed to the tank 1 with bolts or the like, for example.

  The current transformer core 4 is composed of, for example, three current transformer cores 4a to 4c having an annular shape, and is supported by a cylindrical member 5a. That is, the current transformer core 4 is attached to the cylindrical member 5a so as to penetrate the cylindrical member 5a. The current transformer cores 4 a to 4 c are each configured by winding a coil around an iron core, and are arranged side by side in the axial direction of the center conductor 2 so as to circulate around the center conductor 2. The number of current transformer cores 4 is not limited to the illustrated example.

  The current transformer core 4 is fixed to the current transformer mounting frame 5 via the adapter 7. The adapter 7 has an annular shape arranged so as to circulate around the central conductor 2, and the end surface in the axial direction of the annular end portion 6 is attached to the surface facing the cylindrical member 5 a. Note that the adapter 7 is attached to the annular end portion 6 by, for example, a plurality of bolts 9 arranged in the circumferential direction. Further, on the outer diameter side of the position where the annular end portion 6 is attached to the adapter 7, for example, the screw rod 8 penetrates in the axial direction at a plurality of locations in the circumferential direction, and the tip portion of the screw rod 8 is changed. The current transformer core 4 is fixed to the current transformer mounting frame 5 so as not to move in the axial direction by being brought into contact with and pressed against the current transformer core 4.

  The instrument current transformer 50 circulates around the central conductor 2, outputs an induced current caused by the current flowing through the central conductor 2, and measures the magnitude of the current flowing through the central conductor 2.

  4 and 5 show a configuration in the case where the trap hole 20 is not provided for comparison. That is, FIG. 4 is a diagram illustrating a configuration in the case where the trap hole 20 is not provided in the instrument current transformer, and corresponds to FIG. FIG. 5 is a diagram showing a configuration when the trap hole 20 is not provided in the instrument current transformer, and corresponds to FIG. 4 and 5, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals. As shown in FIGS. 1 to 5, the trap hole 20 is formed with a predetermined width in the axial direction and a predetermined length in the circumferential direction on the bottom surface portion adjacent to the annular end portion 6 in the axial direction. .

  Next, the operation of the present embodiment will be described with reference to FIG. A minute metal foreign object 30 exists on the inner bottom surface of the cylindrical member 5a. The electric field value around the cylindrical member 5a is closer to the central conductor 2 and becomes a higher electric field. Therefore, the electric field of the A part around the annular end 6 is higher than the electric field of the B part around the central part of the cylindrical member 5a.

  The foreign metal 30 has a greater weight than the attractive force of the electric field to the center conductor 2 side (high voltage side) due to the electric field, and does not float to reach the center conductor 2. However, although it does not reach the center conductor 2, it may move in the axial direction while repeatedly jumping up and down, and may move toward the A portion where the electric field is higher than the B portion. In this case, since the A part has a higher electric field, the A part itself has an effect of attracting the metal foreign object 30, and the metal foreign object 30 is reliably attracted toward the A part as it approaches the A part.

  However, since the metal foreign object 30 is captured by the trap hole 20 provided in front of the A portion and falls downward before reaching the A portion, it does not reach the A portion (annular end portion 6). It is rendered harmless between the bottom of the tank 1 and the tubular member 5a. Note that the portion C around the ridge of the trap hole 20 has a higher electric field than the portion B due to the effect of the shape of the ridge itself. Therefore, the provision of the trap hole 20 itself has an effect of attracting the metal foreign object 30. That is, by making the inner diameter of the annular end 6 closer to the central conductor 2 side, the electric field of the A part is made higher, and the metal foreign object 30 is drawn toward the A part, and the trap provided in front of the A part The hole 20 itself also has a synergistic effect in attracting the metal foreign object 30, and the metal foreign object 30 can be more reliably attracted and dropped into the trap hole 20.

  On the other hand, in the configuration in which the trap hole 20 is not provided (FIGS. 4 and 5), the metal foreign object 30 reaches the A part due to the inducing effect of the A part, and the electric field strength of the A part reduces the weight of the metal foreign object 30. If it exceeds, the metallic foreign object 30 floats up to the center conductor 2 and flashes. When the electric field strength of the part A does not exceed the dead weight of the metal foreign object 30, the metal foreign object 30 repeats up and down behavior on the inner surface of the annular end 6, but even in this case, there is a possibility that it will eventually flash. Therefore, a structure in which the metal foreign object 30 is dropped into the trap hole 20 before reaching the part A is preferable.

  Note that the width of the trap hole 20 in the axial direction is larger than the stroke of the behavior of the metal foreign object 30. That is, the metallic foreign object 30 is approximately a certain distance in the axial direction (behavior of the behavior) from when it is present on the inner bottom surface of the cylindrical member 5a until it falls on the inner bottom surface again due to the effect of its own weight after floating on the inner surface. This distance is determined by various conditions such as the magnitude of the voltage applied to the center conductor 2 and the distance between the center conductor 2 and the cylindrical member 5a, so the width of the trap hole 20 in the axial direction. Is made larger than the stroke of the behavior of the metal foreign object 30, the metal foreign object 30 can be reliably dropped into the trap hole 20.

  As described above, according to the present embodiment, the cylindrical member 5a is provided in which the annular end 6 is thicker than the other part and the inner diameter of the annular end 6 is smaller than the inner diameter of the other part. Further, since the trap hole 20 is provided adjacent to the annular end 6 on the bottom surface portion, the minute metal foreign matter 30 that may exist on the inner bottom surface of the current transformer mounting frame 5 is captured by the trap hole 20. It can be detoxified.

  In particular, in the present embodiment, since the annular end 6 serving as a higher electric field portion has an effect of attracting the metal foreign object 30, the capture of the metal foreign object 30 becomes more effective. In addition, the trap hole 20 itself has an effect of attracting the metal foreign object 30 due to the height of the electric field in the cage.

  Further, the annular end portion 6 has a shape in which the inner diameter side is raised toward the central conductor 2 side, and is provided toward the inner side in the radial direction. Therefore, there is no need to increase the diameter of the tank 1, and the device can be downsized. Contribute to.

  In addition, the annular end portion 6 is thick, but this is suitable as a connection portion with the adapter 7, facilitating the fixing of the adapter 7 necessary for mounting the current transformer core 4, and as described above. It also has an incentive effect for the metallic foreign object 30.

  On the other hand, the conventional instrument current transformer described in Patent Document 1 is not provided with a trap structure for capturing metallic foreign matter, and the diameter of the inner cylinder for attaching the instrument current transformer is also axial. There is no structure in which the end of the inner cylinder is arranged on the inner diameter side as in the present embodiment.

  As described above, the present invention is useful as a current transformer for an instrument with a trapping structure for metallic foreign matters.

DESCRIPTION OF SYMBOLS 1 Tank 2 Center conductor 4,4a-4c Current transformer core 5 Current transformer mounting frame 5a Cylindrical member 5b Support member 6 Annular end 7 Adapter 8 Screw rod 9 Bolt 10 Flange part 20 Trap hole

Claims (4)

A current transformer for an instrument for measuring a current flowing through a central conductor disposed horizontally in a metal tank filled with an insulating gas,
It is coaxially arranged around the central conductor, one end in the axial direction is thicker than the other part, and the inner diameter of the one end is smaller than the inner diameter of the other part, A current transformer mounting frame having a tubular member provided with a through hole at a position adjacent to the one end in the axial direction;
A current transformer core that is penetrated by the tubular member and arranged around the central conductor;
A current transformer for an instrument characterized by comprising:   2. The current transformer for an instrument according to claim 1, wherein the one end has a shape that rises smoothly toward the center conductor as compared with the other portion. An annular adapter disposed around the central conductor and attached to the end face in the axial direction of the one end;
Threaded rod that presses and fixes the current transformer core by penetrating the adapter in the axial direction on the outer diameter side from the position where the one end is attached, and with the tip abutting against the current transformer core When,
The current transformer for an instrument according to claim 2, comprising: The current transformer mounting frame has an annular support member connected in a hook shape to the other end of the cylindrical member,
The current transformer for an instrument according to claim 3, wherein the support member is attached to the tank.

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