JPH0627940Y2 - Mold type voltage transformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial field of application) The present invention relates to a molded instrument transformer in which the arrangement of the primary terminals is improved.

(Prior Art) Conventionally, as a transformer for a meter that supplies voltage exclusively to a meter for measurement in a power distribution system, a mold is used because of its high insulation reliability and suitability for miniaturization and the like. Many of the shapes are used. On the other hand, the distribution board to which the measuring transformer is attached tends to adopt a gas insulation method instead of the conventional air insulation method by the atmosphere because it is compact and can save space.

FIG. 2 shows a general example of a molded instrument transformer mounted on such a gas-insulated switchboard. The molded instrument transformer has an iron core 1, a secondary winding 2 and a primary winding 3
Are sequentially wound concentrically via the insulators 4 and 5, respectively, and the primary terminals 6 are arranged at the outer positions of the windings 2 and 3 in the radial direction (downward in the figure). The high-voltage bushing 7 for housing and the insulating wall 8 for housing the iron core 1, the windings 2, 3 are integrally formed by a molding material such as epoxy resin using a mold not shown. And the metal box body 9 that constitutes the outer wall of the gas-insulated switchboard
The high pressure bushing 7 is inserted into the through hole 10 formed in the above, the high pressure bushing 7 is located inside the gas-insulated switchboard, and the insulating wall 8 is located outside the gas-insulated switchboard. The transformer is attached to the gas-insulated switchboard using bolts (not shown). In the above structure, the thickness t of the insulating wall 8 between the primary winding 3 of high potential and the box 9 of ground potential is more sufficient than the others in order to relax and reduce the electric field between them. It is largely set in.

(Problems to be solved by the device) In the secondary circuit of the transformer for the meter, there are relatively many short circuits due to two-point grounding etc. due to connection error or forgetting to remove the temporary ground during modification or modification of the circuit wiring. is doing. When such a secondary circuit is short-circuited, an excessive secondary current flows and copper loss rapidly increases in the winding portion. On the other hand, when the fuses are not provided in the secondary circuit due to the consideration of measurement and protection of the power distribution system, or even if the fuses are provided, a short circuit occurs at the upstream side of the place where the fuses are provided. In such a case, if the short-circuited state continues for a long time, the winding portion becomes overheated, and the coating insulation of the wire, the insulating materials 4, 5 and the mold insulating wall 8 around the winding portion are melted and gasified. Progress to. Further, due to the melting and gasification, the gas pressure inside the insulating wall 8 rises, and then the insulating wall 8 cracks and scatters, which also leads to the flow and release of the melt and gas inside the insulating wall 8.

The cracks due to the increase in the gas pressure inside the insulating wall 8 start from mainly the outer peripheral portion of the winding portion and propagate from there to various directions depending on the thickness of the insulating wall 8, but only in the radial direction (Fig. Middle downward). Further, in that case, as the thickness of the insulating wall 8 is larger, the withstand pressure is larger, so that the gas pressure inside the insulating wall 8 is correspondingly increased, and when the crack is generated, the gas pressure becomes very large. Gas flow,
The situation of release and scattering of molding material also becomes severe.

In the conventional structure shown in FIG. 2, the primary terminal 6 and the high voltage bushing 7 are arranged at the radially outer positions of the windings 2 and 3, and the high voltage bushing 7 is arranged inside the switchboard. Since the molded instrument transformer is attached to the switchboard in such a manner as to be located at the position, the cracks and scattering of the insulating wall 8 due to the radial direction of the windings 2 and 3, that is, the secondary short circuit, Since the switchboard is present in the direction of progress and the thickness (t) of the insulating wall 8 between the switchboard and the windings 2 and 3 is larger than the others, as a result, the insulating wall 8 scatters. The object and the melted material inside the insulating wall 8 spread to the inside of the switchboard to a great extent and cause a great deal of damage, so that there has been a problem that the recovery work also requires a great deal of cost and time.

The present invention has been made in view of the above circumstances, and therefore an object thereof is to prevent the damage caused by a secondary short circuit from spreading to the inside of power distribution equipment, and thereby to minimize the damage.
At the same time, it is an object of the present invention to provide an excellent molded instrument transformer capable of improving the overall stability in the state of being attached to power distribution equipment and achieving miniaturization.

[Structure of the Invention] (Means for Solving Problems) A molded instrument transformer according to the present invention has a secondary winding and a primary winding wound around an iron core, and these windings are provided outside the windings. A primary terminal is arranged, a high-voltage bushing having the primary terminal, the iron core, and an insulating wall that houses the winding are integrally formed with a molding material, and in a power distribution device, the high-voltage bushing is located inside thereof. In an installation in which the insulating wall is located outside, the thickness of the insulating wall radially outside the winding portion on the side where the iron core is not located is defined as the insulating wall axially outside the winding portion. It is characterized in that the primary terminal is arranged at an axially outer position of the winding portion and the primary terminal and the winding portion are connected by a thin wire.

(Operation) According to the above means, in the mounted state where the high voltage bushing of the molded instrument transformer is located inside the power distribution device, cracks in the insulating wall due to the radial direction of the winding portion, that is, a secondary short circuit The distribution device is not located in the direction of the scattering, and the damage caused by the cracks and scattering does not spread to the inside of the distribution device. Also, in this case, while obtaining the required thickness of the insulating wall between the primary winding and the power distribution equipment, the thickness of the insulating wall at the outer radial position of the winding portion can be reduced, and In addition, the thickness of the radial insulating wall of the winding part on the side where the iron core is not located is thinner than the thickness of the insulating wall axially outward of the winding part. The cracks and splashes of the insulating wall that have formed rapidly occur in the thin portion, and the cracks and
It is possible to more reliably prevent the damage caused by the scattering from spreading to the inside of the power distribution device. In addition, when the insulating wall cracks or scatters, it is possible to prevent the thin wire connecting the primary winding and the winding part from breaking due to its thinness and exerting tensile force on the primary terminal. It is possible to more reliably prevent the damage from spreading to the inside of the power distribution device without damaging the high-voltage bushing located inside the device. Further, when the transformer is attached to the power distribution device, the iron core having a large weight approaches the power distribution device in the transformer, and the position of the center of gravity of the entire transformer can be lowered accordingly. Since the thickness of the insulating wall at the outer radial position of the winding portion can be reduced, the transformer can be miniaturized.

(Embodiment) An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, the same parts as those in FIG. 2 are designated by the same reference numerals. Therefore, in FIG. 1, 1 is an iron core, 2 is an iron core 1 wound around an insulator 4 The secondary windings 3, 3 are wound around the secondary winding 2 via the insulator 5, and thus the primary winding is wound around the iron core 1 concentrically with the secondary winding 2, and 9 is a gas-insulated switchboard. Boxes 10 forming the outer wall are through holes formed in the box 9.

On the other hand, reference numeral 11 denotes a primary terminal connected to the primary winding 3 by a thin wire 11a. The primary terminal 11 is arranged at an outer position in the axial direction (downward in the figure) of the windings 2 and 3 parts. There is. 12 is a high-voltage bushing containing the primary terminal 6,
Reference numeral 3 denotes an insulating wall that houses the iron core 1 and the windings 2 and 3, and these are integrally formed by a molding material such as epoxy resin using a mold not shown. Regarding this, the thickness t ₁ of the insulating wall 13 at the radially outer position of the windings 2 and 3 on the side where the iron core 1 is not located (left side in the figure) is the same as that of the conventional _one (second It is formed thinner than the thickness t of the portion below the primary winding 3 in the drawing) and thinner than the thickness t ₂ of the insulating wall 13 which is axially outward of the windings 2 and 3.

In the molded instrument transformer formed as described above, the high voltage bushing 12 is inserted in the through hole 10 of the box body 9.
By inserting the high voltage bushing 12 inside the switchboard and the insulating wall 13 outside so that the molded instrument transformer is attached to the switchboard using bolts not shown. There is.

In the case of the structure as described above, the cracks and scattering of the mold insulating wall 13 caused by the above-mentioned secondary short circuit are in the radial direction of the windings 2 and 3, and the primary terminal 12 is in that direction.
The primary terminal 12 is disposed at an outer position in the axial direction at right angles to the radial direction of the windings 2 and 3. Therefore, when this high-voltage bushing 12 is located inside the switchboard and the insulating wall 13 is located outside the transformer, the molded transformer is mounted in the switchboard in a radial direction of the windings 2 and 3. That is, the switchboard is not located in the direction of the cracks and scattering of the mold insulating wall 13 caused by the above-mentioned secondary short circuit, and the damage due to the cracks and scattering does not reach the inside of the switchboard. Also in this case, the primary winding 3 of high voltage potential
Between the switchboard and the switchboard (box 9) at the ground potential, the insulating wall 13 can secure a necessary thickness t ₂ for relaxing and reducing the electric field therebetween. The thickness t ₁ of the insulating wall 13 at the radially outer position of the three parts can be made thin, so that the crack of the insulating wall 13 caused by the secondary short circuit,
Scattering occurs rapidly in the thin wall portion of the insulating wall 13 at the radially outer position of the windings 2, 3 and cracks,
It is possible to more reliably prevent the damage caused by the scattering from spreading to the inside of the switchboard. Furthermore, when the insulating wall 13 cracks or scatters, the thin wire 11a connecting the primary terminal 11 and the primary winding 3 is broken due to its thinness, which may exert a tensile force or the like on the primary terminal 3. Since it can be avoided, damage to the high voltage bushing 12 located inside the switchboard can be prevented, and the spread of damage to the switchboard can be prevented more reliably. Therefore, these cause cracks in the insulating wall 13,
The damage caused by the scattering can be minimized, and in particular, it can be avoided that a great amount of cost and time are required for restoration of the inside of the switchboard. Further, when mounted on the switchboard, the iron core 1 having a large weight approaches the switchboard in the transformer, and the position of the center of gravity of the whole can be lowered accordingly.
The stability can be improved and the seismic strength can be increased. Further, by reducing the thickness t ₁ of the insulating wall 13 at the radially outer position of the windings 2 and 3 described above, it is possible to achieve miniaturization of the transformer.

The device to which the molded instrument transformer is attached is not limited to the gas-insulated switchboard, but may be another switchboard device such as a gas-insulated switch.

[Effects of the Invention] As is clear from the above description, the present invention has the secondary winding and the primary winding wound around the iron core, and the primary terminals are arranged outside the windings. A high-voltage bushing having a primary terminal and an insulating wall that houses the iron core and the winding are integrally formed of a molding material, and the high-voltage bushing is located inside the distribution device and the insulating wall is located outside. In this way, the thickness of the insulating wall radially outside the winding portion on the side where the iron core is not located is thinner than the thickness of the insulating wall axially outside the winding portion. It is characterized in that the primary terminal is arranged at an axially outer position of the winding portion and the primary terminal and the winding portion are connected by a thin wire, whereby a secondary short circuit is caused. Minimize the damage because it can prevent the damage from spreading to the inside of power distribution equipment. It has an excellent effect that it can be kept to the limit and, at the same time, the overall stability in the state of being attached to the power distribution device and the miniaturization can be achieved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention, and FIG. 2 is a vertical sectional view of a conventional device. In the drawing, 1 is an iron core, 2 is a secondary winding, 3 is a primary winding, 4 and 5 are insulators, 9 is a box of a switchboard, 11 is a primary terminal, 1
1a is a thin wire, 12 is a high pressure bushing, 13 is an insulating wall, t
Reference numeral ₁ denotes the thickness of the insulating wall on the radially outer side of the winding portion on the side where the iron core is not located, and t ₂ denotes the thickness of the insulating wall on the axially outer side of the winding portion.

Claims (1)

[Scope of utility model registration request] 1. A secondary winding and a primary winding are wound around an iron core, a primary terminal is arranged at an outer position of the winding portion, and a high voltage bushing having the primary terminal and the iron core and the winding are provided. In the case where the insulating wall to be installed is integrally formed with a molding material, and the high-voltage bushing is located inside of the distribution device and the insulating wall is located outside, the iron core is located. The thickness of the insulating wall on the outer side in the radial direction of the non-winding part is thinner than the thickness of the insulating wall on the outer side in the axial direction of the winding part, and the primary terminal is located outside the axial direction of the winding part. A transformer for a molded instrument, characterized in that it is arranged in one direction and the primary terminal and the winding part are connected by a thin wire.