JPH0337223Y2 - - Google Patents

Description

[Detailed explanation of the invention] [Purpose of the invention] (Field of industrial application) This invention is a gas-insulated instrument transformer (hereinafter referred to as gas-insulated
(hereinafter abbreviated as PT), and in particular relates to improvements in the mounting structure of grounding shields for mitigating electric fields.

(Prior Art) In general, the voltage transformation element of an instrument transformer consists of a pair of left and right side legs, and an upper and lower yoke that magnetically couple the upper and lower parts of the side legs, forming a closed magnetic path. It consists of an iron core, and a low-voltage coil and a high-voltage coil that are sequentially wound coaxially around the upper yoke from the inner surface.In the case of a gas-insulated method, dielectric breakdown is dependent on the electric field, so In order to avoid local concentration of stress, electric field mitigation shields are provided at high potential parts such as high voltage coils and ground potential parts such as iron cores.

Conventionally, this type of gas-insulated PT is a voltage insulator in which a low-voltage coil 3 and a high-voltage coil 2 are sequentially coaxially wound from the inside around an upper yoke 1a of an iron core 1 forming a closed magnetic path, as shown in FIGS. 6 and 7. A structure is adopted in which the metamorphic elements are housed together with high-pressure insulating gas in an outer box (not shown) that is made as a container that can withstand high pressure. In this way, in a gas-insulated PT that uses high-pressure insulating gas and has been miniaturized, the insulation distance between the high-potential part and the opposing ground potential part is extremely small, so electrical stress is locally concentrated. In terms of insulation design, it is important to create a structure that prevents this from occurring. Therefore, as shown in FIGS. 6 and 7, in order to alleviate the electric field around the ground potential portions, such as the iron core 1 and the iron core tightening member 7, the side of the lower yoke 1b facing the high voltage coil 2 is In addition, the side of the side leg 1c facing the high voltage coil 2 is completely covered by the ground shield 5, and a cylindrical high voltage shield 4 coaxial with the high voltage coil 2 is provided around the outer periphery of the high voltage coil 2. is attached to cover the end of the winding of the high voltage coil 2. At the part where the upper yoke 1a of the gas-insulated PT iron core 1 penetrates the side grounding shield 6, the side grounding shield 6 is cut into the side grounding shield 6 so as not to form a one-turn short circuit at the penetration part. A divided portion 13 in which a notch is formed is provided.

The side grounding shield 6 is 1 as shown in FIG.
It is formed into a thin flat plate shape with studs 11
It is fixed by tightening nuts 12 to a core tightening member 7 that tightens the side legs 1c of the iron core 1 from both sides. Therefore, when assembling a conventional insulated PT, first one side leg 1c and the upper and lower yokes 1 are assembled.
After assembling the U-shaped iron core 1 using steps a and 1b, and attaching one of the iron core tightening members 7 and the side grounding shield 6 to this iron core 1, insert the low voltage coil 3, high voltage coil 2, and high voltage shield 4 into the iron core 1. and then attach the other side grounding shield 6 to the upper yoke 1a.
After penetrating the other side leg 1c, perform the core assembly of the other side leg 1c. Next, the core insulating member 8 is brought into contact with the side leg 1c, and the L-shaped core tightening member 7 is tightened from both sides of the side leg 1c with the tightening bolt 9 and the tightening nut 10 to fix the iron core 1. Side grounding shield 6
Tighten the stud 11 to the core tightening member 7 with the tightening nut 1.
Fix by 2. Note that the studs 11 of the side grounding shield 6 must be insulating studs at necessary locations depending on the structure of the gas-insulated PT so as not to form a one-turn circuit surrounding the iron core.

(Problem that the invention attempts to solve) However, such conventional gas-insulated PT
In this grounding shield mounting structure, the stud 11 is attached by welding to the side grounding shield 6 made of a thin flat plate, so it cannot be firmly fixed to the side grounding shield 6, and the welding work is very difficult. This is difficult, and there are concerns that bonding defects may occur. Further, after welding the stud 11 to the side grounding shield 6, surface treatment and inspection of the strength of the welded portion are required, which increases the cost. Furthermore, the work of attaching the side grounding shield 6 to the core tightening member 7 must be done with great care, which has the disadvantage of impairing workability.

This invention was made taking the above points into consideration.
The objective is to provide a gas-insulated PT that is easy to manufacture and assemble, is inexpensive, and has high reliability.

[Structure of the idea]

(Means and effects for solving the problem) According to the present invention, in order to achieve this purpose,
The side grounding shield of the gas-insulated PT is divided into multiple parts, further formed into an L-shape, and attached and fixed to the core by sandwiching it between the side legs of the core and the core clamping member that tightens the side legs. As a result, the grounding shield can be easily designed and installed, and its reliability is improved at low cost.

(Example) The gas-insulated instrument transformer of the present invention (gas-insulated
A first embodiment of PT) will be described with reference to FIGS. 1 to 3. In FIGS. 1 to 3, the same parts and parts having the same functions as those in FIGS. 6 to 8 are designated by the same reference numerals. That is, a voltage transformation element in which a low-voltage winding 3 and a high-voltage winding 2 are coaxially wound around an iron core 1 forming a closed magnetic path is placed under high pressure in an outer box (not shown) made as a container that can withstand high pressure. Store with insulating gas. A high voltage shield 4, a lower earth shield 5, and a divided earth shield 6a for mitigating electric fields are provided at the high potential parts of the wound low voltage winding 3 and high voltage winding 2, and the ground potential part of the iron core 1, etc., which are opposed to these, respectively. 6b, 6c, and 6d are arranged so that the electric field is not locally concentrated.

In this embodiment, the side grounding shield 6 is not formed into an integral structure as shown in the drawings, but is constructed by being divided into a plurality of divided grounding shields 6a, 6b, 6c, and 6d as shown in FIG. This split ground shield 6
a, 6b, 6c, and 6d are each made by bending a thin flat plate into an L shape, and are connected to the side leg 1c of the iron core 1 via the core insulating member 8 so that they face the high voltage coil and form the same plane. One end of the L-shape is sandwiched between the core tightening members 7, and the core is tightened and fixed to the side leg 1c with a tightening bolt 9 and a core tightening nut 10.
Between the divided grounding shields 6b and 6c is a divided part 13 in advance.
, which prevents the core 1 from forming one turn due to the ground shield.

The gas insulation of this embodiment 1 configured in this way
According to PT, the side grounding shield 6 is divided into a plurality of split grounding shields 6a, 6b, 6c, and 6d, and these are combined to obtain the same effect as an integrated flat plate, so that the electric field stress can be partially concentrated. This allows the electric field to be relaxed and maintain sufficient insulation strength. In addition, the divided grounding shields 6a to 6d
It can also be produced by simply bending a flat plate.
Attachment of the iron core 1 to the side leg 1c can also be easily and reliably performed. Further, since there is no need to weld studs for fixing the side grounding shield 6, surface treatment and mechanical strength inspection after welding are no longer necessary.
Also, in the assembly work of gas-insulated PT, the iron core 1
At the same time as the assembly, the side grounding shield 6 and the core tightening member 7 can be assembled together. Even when checking the 1-turn circuit of the ground shield, since the split ground shields 6b and 6c are completely separated by the split part 13, it is possible to check the 1-turn circuit and between the side ground shield 6 and the core tightening member. Tests such as the same potential can be easily performed.

Next, second and third embodiments of the present invention will be described with reference to FIGS. 4 and 5. Figures 1 to 3
The same parts as in the figures are given the same reference numerals. The second embodiment of the present invention, as shown in FIG. 4, is made by bending one thin flat plate as shown in divided grounding shields 6c and 6f, and bending the two L-shapes continuously to separate the flat plate side. I'm trying to form it.

Further, in a third embodiment of the present invention, as shown in FIG. 5, the side grounding shield 6 is divided into four divided grounding shields 15a, 6b, 6c, and 15b.
is made of a member with high mechanical strength, and is constructed so that it also serves as a core clamping member, that is, the core clamping member 7 of the first embodiment of the present invention is omitted.

In this way, in the second embodiment, the divided ground shields 6e and 6f are completely separated by the divided part 13, so that it is possible to check the one-turn circuit and to check the same potential between the ground shield and the core clamping member. can be easily done.

Further, in the third embodiment, since the iron core tightening member is omitted, the cost can be reduced by this amount.

[Effect of idea]

As explained above, according to the present invention, the side grounding shield for electric field relaxation is formed by forming a plurality of thin flat plates with a cross section L.
By combining divided grounding shields that are bent to form a letter shape, it is possible to prevent the concentration of electric fields, and it is inexpensive and easy to assemble, thus reducing assembly time and ensuring the installation of the grounding shield. A highly reliable gas-insulated instrument transformer can be provided.

[Brief explanation of the drawing]

1 to 3 show a first embodiment of the gas-insulated instrument transformer of the present invention, and FIG. 1 is a front view;
Fig. 2 is a side view, Fig. 3 is an enlarged sectional view showing the side grounding shield attached to the core, and Figs. 4 and 5 are main parts of the second and third embodiments of the present invention, respectively. Figures 6 to 8 show a conventional gas-insulated instrument transformer, Figure 6 is a front view, Figure 7 is a side view, and Figure 8 is a side grounding shield attached to the core. FIG. 1... Iron core, 1c... Side leg, 2... High voltage coil, 3... Low voltage coil, 4... High voltage shield, 5
...Lower grounding shield, 6...Side grounding shield, 6a, 6b, 6c, 6d, 6e, 6f, 15
a, 15b...divided grounding shield, 7... core tightening member, 8... core insulating member, 9... tightening bolt, 10... core tightening nut, 13... split portion.

Claims (1)

[Scope of utility model registration request] It is divided into multiple pieces, each with an L-shaped cross section, consisting of an iron core, high-voltage and low-voltage coils coaxially wound around this iron core, and a high-voltage shield for electric field mitigation attached to cover the high-voltage coil. Bend it so that it forms, and place one end of the L shape against the side leg of the iron core.
A side grounding shield is inserted between this side leg and the core clamping member and is tightened and fixed, and the other end is placed between the core and the coil.The side grounding shield is enclosed in a container together with the front core and the coil. A gas-insulated voltage transformer consisting of an insulating gas.