JPH01266706A - Molded instrumentation transformer - Google Patents

Abstract

PURPOSE:To minimize secondary shorting induced-damage by providing, in the middle of winding sections and a high voltage bushing, an insulating layer having a tensile strength smaller than that of an insulating wall in such a manner that it is arranged along a surface for mounting switchboard equipment at dimensions larger than the winding section. CONSTITUTION:At the middle of winding sections 2, 3 and a high voltage bushing 7 in an insulating wall 8, an insulating layer 11 whose tensile strength is smaller than that of the insulating wall 8 is disposed along a surface for mounting switchboard equipment 9 at larger axial length and diameter than those of the winding sections 2, 3. Accordingly, when the secondary circuit of a molded instrumentation transformer is shorted and this shorting is so persistent for a long time that a crack in the insulating wall 8 grows toward the high voltage bushing 7, the crack is held in check at the insulating layer 11. This prevents damage due to cracks and flown strips from being introduced into the inside of the switchboard.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION (Industrial Field of Application) The present invention relates to a molded potential transformer with improvements in the wall of the molded insulating wall.

(Prior art) Traditionally, molded instrument transformers have been used as instrument transformers that supply voltage exclusively to measuring instruments in power distribution systems because of their high insulation reliability and their suitability for compact metering. Many shapes are used.

On the other hand, power distribution equipment such as switchboards to which the instrument transformers are attached tend to adopt gas insulation methods instead of the conventional atmospheric insulation method because they can be made smaller and space-saving.

Figure 2 shows a general example of a molded voltage transformer installed in such a gas-insulated switchboard.
are sequentially wound concentrically through insulators 4 and 5,
A primary terminal 6 is disposed on the outer circumferential side (lower side in the figure) of the windings 2.3, and a high-voltage bushing 7 that supports the primary terminal 6 and an insulating wall that houses the windings 2.3 of the iron core 12 are installed. 8 are integrally formed using a molding material such as epoxy resin using a mold (not shown). In the molded instrument transformer constructed in this way, the high-voltage bushing 7 is inserted into the through-hole 10 formed in the metal box 9 that constitutes the outer wall of the gas-insulated switchboard. It is mounted to the gas insulated switchboard using bolts (not shown), with the insulating wall 8 positioned on the inside of the insulated switchboard and on the outside. In the above configuration, the thickness of the insulating wall 8 between the primary winding 3 at high voltage potential and the box body 9 at ground potential is set to be sufficiently thicker than the others in order to moderate and reduce the electric field between the two. It is largely determined.

(Problem to be solved by the invention) In the secondary circuit of a voltage transformer, short circuits occur relatively often due to two-point grounding due to wiring errors, changes in circuit wiring, or forgetting to remove low grounding during remodeling. ing. When such a secondary circuit is short-circuited, an excessive secondary current flows, and copper loss rapidly increases in the windings 2 and 3.

On the other hand, there are cases where fuses are not installed in the secondary circuit due to measurement of the power receiving and distribution system, and protection is prioritized, or even if fuses are installed, a short circuit occurs upstream from the point where they are installed. In some cases, if the short circuit continues for a long time,
The windings 2 and 3 become overheated, which progresses to melting and gasification of the insulation coating of each of the wires, the insulators 4 and 5, and the mold insulating wall 8 around the windings 2 and 3. Furthermore, the gas pressure inside the insulating wall 8 increases by -1- due to its melting and gasification, which progresses to cracks and scattering of the insulating wall 8.
Flow of melt and gas inside the insulating wall 8.

leading to release.

Cracks caused by an increase in gas pressure inside the secondary insulating wall 8 originate mainly from the outer periphery of the windings 2 and 3, and propagate in various directions from there depending on the strength of the insulating wall 8. Furthermore, in this case, the greater the thickness of the insulating wall 8, the greater the withstand pressure, so the gas pressure inside the insulating wall 8 increases accordingly.Therefore, when a crack occurs, the gas pressure becomes extremely large, and the melted material Also, the flow and release of gas and the scattering of molding material become more intense.

In the conventional device shown in FIG. 2, in order to simplify the structure, facilitate manufacturing, and stabilize quality, the
Although the primary terminal 6 and the high voltage bushing 7 are arranged on the outer circumferential side of the secondary There is enough sexuality. If the crack develops in the high-voltage bushing 7 and its base and causes the high-voltage bushing 7 to scatter, the high-voltage bushing 7 is located inside the switchboard, and therefore the high-voltage bushing 7 and the primary Scattered objects from the terminals 6 and the insulating wall 8, as well as molten substances inside the insulating wall 8, enter the inside of the switchboard and cause great damage. Particularly in this case, since the insulating wall 8 is thicker at the base of the high-pressure bushing 7 than at other parts, the gas pressure increases accordingly.For the above-mentioned reason, the distribution board for the above-mentioned flying debris and melted matter is The situation of intrusion into the interior was serious, and the damage to the inside of the power distribution board was fundamental. Therefore, there was a problem in that the restoration work required a great deal of cost and time.

The present invention has been made in view of the above-mentioned circumstances, and therefore, its purpose is to effectively prevent damage caused by secondary short circuits from spreading to the inside of power distribution equipment, thereby minimizing the damage. To provide an excellent molded potential transformer.

[Means for Solving the Problems] The molded instrument transformer of the present invention has a secondary winding and a primary winding wound around an iron core, and a A primary terminal is placed at a position, a high voltage bushing supporting the primary terminal and an insulating wall housing the two iron core windings are integrally formed using a molding material, and the high voltage bushing is placed inside the power distribution equipment. and an insulating wall is located outward, and an insulating layer having a lower tensile strength than the insulating wall is provided at a position between the winding part and the high-voltage bushing in the insulating wall. , is characterized in that the length in the axial direction of the winding portion and the diameter I11 are larger than that, and the winding portion is arranged along the mounting surface for the power distribution equipment.

(Function) According to the above means, even if a crack in the insulating wall caused by a secondary short circuit in a molded potential transformer develops toward the high-voltage bushing, the insulating layer will be damaged in the winding part on the way. Due to its position being larger than its size, it bumps into this insulating layer, and since that insulating layer has a lower tensile strength than the insulating wall, the insulating layer is subsequently torn and the insulating wall along which this insulating layer runs along. It develops in a direction approximately parallel to the mounting surface for power distribution equipment. In this way, it is possible to prevent the crack from propagating to the high-voltage bushing, and furthermore, it is possible to prevent the damage caused by the crack from extending to the inside of the power distribution equipment where the high-voltage bushing is located.

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

In FIG. 1, the same parts as in FIG. A secondary winding, 3 is a primary winding wound around the secondary winding 2 via an insulator 5, 6 is a primary terminal located on the outer circumferential side of the windings 2 and 3 (lower in the figure); 7 is a high-voltage bushing that supports the primary terminal 6;
1 is an insulating wall in which the iron core 1 and the windings 2.3 are housed, and the high-voltage bushing 7 and the insulating wall 8 are integrally formed using a molding material such as epoxy resin using metal and a mold (not shown).

11 is the winding 2 in the insulating wall 8,
The insulating layer is provided at a position between part 3 and the high-pressure bushing 7, and in detail, it mainly has a lower tensile strength than the insulating wall 8, and also has good adhesion with the mold material, and The secondary winding 2 is made of a material such as cork, which does not leave any weak points such as electrical insulation on the interface with the material, does not impregnate the mold material, and can withstand external forces from the molding process. It has an area larger than the area S formed by the axial length and the diameter of the primary winding 3, and is arranged along the mounting surface 8a of the insulating wall 8 for power distribution equipment, which will be described later. The 2.3 part of the winding in the insulating wall 8 and the 2.3 part of the winding in the insulating wall 8 are set in advance at a position between the winding 2.3 accommodating part in the mold and the high-pressure bushing 7 molding part, and then molded. It is buried in a position between the high pressure bushing 7 and the high pressure bushing 7.

Regarding the arrangement of the insulating layer 11, the difference in relative dielectric constant with the mold hole is taken into consideration, and the arrangement is such that it does not disturb the electric field distribution. The dimension T1 between the insulation layer 11 and the mounting surface 8a of the insulation wall 8 is set smaller than the dimension T2 between the insulation layer 11 and the mounting surface 8a of the insulation wall 8.

Reference numeral 9 denotes a box constituting the outer wall of a gas-insulated switchboard, which is a power distribution device, and 10 denotes a through hole formed in the box 9. As described above, the winding 2 in the insulating wall 8 is inserted into the through hole 10. , 3 and the high-voltage bushing 7, the high-voltage bushing 7 of the molded instrument transformer with the insulation jW11 is inserted, so that the high-voltage bushing 7 is located inside the switchboard, and the high-voltage bushing 7 is located outside the switchboard. With the insulating wall 8 located, the mounting surface 8a is directed toward the box 9, and the molded instrument transformer is mounted to the box 9 and, in turn, to the gas-insulated switchboard using bolts (not shown).

Now, in the case of the structure as described above, if a short circuit occurs in the secondary circuit of the molded potential transformer and continues for a long time, windings 2 and 3 will become overheated, causing each element of the molded potential transformer to overheat. This progresses to melting and gasification of the wire coating insulation, the insulation materials 4 and 5, and the mold insulation wall 8 around the windings 2 and 3.
Furthermore, its melting.

As mentioned above, cracks develop in the insulating wall 8 due to an increase in gas pressure inside the insulating wall 8 due to gasification, but if the crack develops in the direction of the high-pressure bushing 7, then Since the insulating layer 11 intervening in the middle is hit and the tensile strength of the insulating layer 11 is lower than that of the insulating wall 8, the insulating layer 11 is subsequently torn and the insulating wall 8 along which the insulating layer 11 runs is attached to the switchboard. It develops in a direction substantially parallel to the mounting surface 8a. In this way, it is possible to prevent the crack from propagating to the high-voltage bushing 7 located inside the switchboard, and furthermore, the damage caused by the crack and scattering is prevented from reaching the inside of the switchboard. Therefore, damage caused by cracking and scattering of the insulating wall 8 can be minimized, and in particular, it is possible to avoid requiring a great deal of cost and time to restore the interior of the switchboard.

In addition to the above, especially in the case of the above embodiment, the dimension T1 between the outer periphery of the primary winding 3 in the insulating wall 8 and the insulating layer 11 is determined by the mounting surface 8a of the insulating layer 11 and the insulating wall 8. By setting the dimension T2 between the insulation wall 8 and the insulation wall 8 to be smaller than the dimension T2, cracks can easily occur at a stage when the gas pressure inside the insulation wall 8 does not become excessive, and the degree of cracking and scattering of the insulation wall 8 can be made smaller. In addition, the strength of the insulating wall 8 can be increased in the dimension 12 where the thickness of the insulating wall 8 is increased, and cracks can be propagated along the insulating layer 11 to improve quality.

Although one embodiment of the present invention has been described above, the present invention is not limited thereto, and in particular, the equipment to which the molded instrument transformer is installed is not limited to gas-insulated switchboards, but also other power distribution equipment such as gas-insulated switchgears. In addition, the insulating layer 11 is not limited to being made of cork material, but may be made of other materials as long as it has the same strength and insulation properties. .

[Effects of the Invention] As is clear from the above description, the molded potential transformer of the present invention has a structure having a lower tensile strength than the insulating wall at a position between the winding part in the insulating wall and the high-voltage bushing. The device is characterized in that an insulating layer with dimensions larger than the axial length and diameter of the winding section is provided along the mounting surface for the power distribution equipment, thereby reducing damage caused by secondary short circuits. This has the excellent effect of effectively preventing the damage from spreading to the inside of the power distribution equipment, thereby minimizing the damage.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing one embodiment of the present invention, and FIG. 2 is a vertical sectional view of a conventional device. In the drawing, 1 is the iron core, 2 is the secondary winding, 3 is the primary winding, 6 is the primary terminal, 7 is the high-voltage bushing, 8 is the insulation wall, 9 is the box of the switchboard (power distribution equipment), and 11 is the insulation layer. shows. Agent Patent Attorney Kensuke Norichika Ken Daishimaru

Claims (1)

[Claims] 1. A secondary winding and a primary winding are wound around an iron core, a primary terminal is arranged on the outer periphery of the winding, and a high-voltage bushing that supports the primary terminal and an insulator that houses the core and the winding are provided. The wall is integrally formed with molded material, and the power distribution equipment is
The high-voltage bushing is located inside the high-voltage bushing, and the insulating wall is located outside the high-voltage bushing. A molded potential transformer, characterized in that an insulating layer having a low tensile strength is provided with a dimension larger than the axial length and diameter of the winding portion and arranged along a mounting surface for the power distribution device.