JP2772094B2 - Barrier in insulating gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a barrier for improving the dielectric strength of a storage device in an electric device filled with a low-pressure insulating gas.

(Prior Art) FIG. 6 is a side view showing an example of a conventional gas insulated switchgear. In this gas insulated switchgear, a circuit breaker 2, a disconnector 3, a busbar 4, a cable head 5, a spacer 6, and a main circuit conductor 7 for electrically connecting the circuit breaker 2, the disconnector 3, the busbar 4, and the spacer 6 are housed in a closed box 1, and a low-pressure insulation is provided. Gas 8 is sealed and insulated.

FIG. 7 is a sectional view of one side cut along the center line of the circuit breaker 2 described above. The conventional circuit breaker 2 shown in FIG.
A vacuum valve 9 is used. This vacuum valve 9
An end cover 9a made of Kovar material is fixedly provided on an insulating cylinder, and the outer periphery of the end cover 9a is an edge.

In order to alleviate the electric field of the end cover 9a, metal shields 10 are mounted above and below the vacuum valve 9.

The circuit breaker 2 needs to be opened and closed in order to fulfill its responsibilities. The circuit breaker 2 is operated via a movable electrode shaft 11, an insulating rod 12 connected thereto, and an operating mechanism connected to the insulating rod 12 and not shown. Like that. Therefore, the lower metallic shield 10 needs a hole 10a through which the movable electrode shaft 11 penetrates. When the circuit breaker 2 is in the closed state, the insulating rod 12 approaches the lower metallic shield 10, so that
To avoid triple junctions, the movable electrode shaft 11
It is necessary to increase the diameter of the hole 10a through which the hole 10a passes.

However, when the diameter of the hole 10a is increased, the electric field strength of the metallic shield 10 at that portion increases, and the withstand voltage decreases. Therefore, in order to prevent this, it was necessary to enlarge the lower metallic shield 10.

On the other hand, when the circuit breaker 2 is closed, a load of about 1 ton or more may be applied upward. Therefore, it is necessary to support the circuit breaker 2 with the insulating support 13 as shown in FIG.
In order to prevent triple junction at the mounting portion of the metallic shield 10, the metallic shield 10 had to be sufficiently large.

(Problem to be Solved by the Invention) In the case of a three-phase circuit, the closed box 1 of the closed device of the gas insulated switchgear has the inter-phase and ground insulation distances determined by the metallic shield 10 of the circuit breaker 2. For the reasons described above, when the size of the metallic shield 10 was increased, its width had to be increased. The same can be said for the height direction. That is, disconnector 3, cable head 5, switch
The circuit breaker 2 is insulated from the pacer 6 and the like in a manner in which the height and the height are not coordinated with each other, and the size of the electric device is increased. Further, as a method of supporting the circuit breaker 2, the insulating support 13 is attached to the upper and lower metallic shields 10, so that the vertical dimension is determined by this, and there is no allowance for centering with the spacer 6, and the closed box 1 It took a long time for processing and assembling as an opening / closing device, which was expensive.

On the other hand, when a barrier is used in an insulating gas, if the barrier and the high-voltage electrode are too close to each other, the withstand voltage is improved, but the partial discharge starting voltage is reduced, which may cause long-term insulation deterioration of the barrier.

Therefore, an object of the present invention is to reduce the metallic shield of the circuit breaker and eliminate the upper insulating support,
Reduce the external insulation dimensions of the circuit breaker, match the insulation between the disconnectors, cable heads, spacers, etc. with the phase and ground, reduce the size of the switchgear, and eliminate the upper insulating support of the circuit breaker, With a margin for centering, it is easy to process the closed box and assemble the switchgear, and it is possible to reduce the cost.Insulating gas that improves the partial discharge starting voltage without lowering the withstand voltage To provide a barrier.

[Configuration of the invention]

(Means for Solving the Problems) According to the present invention, when an electrode that forms an uneven electric field is present in a barrier in an insulating gas attached to an electric device in which a low-pressure insulating gas is sealed, a high electric field having a high electric field strength is used. The three-dimensional periphery of the side electrode is covered with an insulating barrier having a sufficiently large curvature than this electrode, a thickness that does not cause breakthrough at a predetermined withstand voltage, and a conductor layer provided on a concave surface facing the high voltage electrode. It is like that.

That is, in FIG.
The inside of the insulating cylinder 14 has a U-shape so as to surround the end cover 9a, and the vacuum valve 9 constituting the shut-off portion of the circuit breaker is U-shaped. It has a coaxial shape facing the center, and a conductor layer 14
a is provided. Further, through holes for main circuit conductors electrically connected to the movable electrode shaft 11 of the vacuum valve 9 and other devices are provided above and below the insulating cylinder 14.

(Operation) The operation will be described with reference to FIG. 2 to FIG.

FIG. 2 shows that the recess of the bowl-shaped barrier 17 having a distance G from the tip of the hemispherical rod is inserted into the gap between the hemispherical rod 15 and the flat plate 16 toward the hemispherical rod 15. Alternatively, a conductor layer 17a made of a conductive paint is provided.
Here, the outer radius of curvature A / 2 of the bowl-shaped barrier 17 is
Is larger than the radius of curvature B / 2 of the tip, and is equal to or greater than the radius of curvature of the sphere in the sphere-to-plate gap that can satisfy the withstand voltage with the gap length L between the hemispherical rod 15 and the plate 16. The gap G is spaced such that partial discharge does not occur at a predetermined voltage. A bowl-shaped barrier from the tip of the hemisphere rod 15
Projecting distance l 17, if the maximum field strength of the hemispherical rod 15 tip and E _1, the E ₂ = E _1/2 when the field strength at any location on the hemispherical rod 15 surface and E ₂ position To protrude. The thickness t of the bowl-shaped barrier 17 is a thickness that does not penetrate even if all of the predetermined withstand voltage is applied in the penetration direction of the bowl-shaped barrier, for example,
At a nominal voltage of 33 kV, lightning impulse withstand voltage of 200 kV / destructive electric field strength of epoxy resin of 40 kV / mm = 5 (mm) or more, and at a nominal voltage of 77 kV, similarly considered, 400 kV / 40 kV / mm = 10 (mm)
Above.

As described above, may be by enclosing the hemispherical rod 15 in the recess of the bowl-shaped barrier 17 having a conductive layer 17a in the recess, can be reduced E _1, to improve the withstand voltage and the partial discharge inception voltage.

 The results of this experiment are shown in FIG. 3 and FIG.

Fig. 3 shows a diameter φ12.5 (mm) and a radius of curvature R6.25 (m
m), a gap length of 50 (mm), an outer radius of curvature R25 (mm) inserted into the gap at a distance of 10 (mm) from the tip of the hemisphere rod, a thickness of 5 (mm), and a concave portion. A bowl-shaped barrier with a conductor layer provided on the surface and a bowl-shaped barrier without a conductor layer inserted, and a diameter φ50 instead of this bowl-shaped barrier (with and without a conductor layer) (M
m) and a disk-shaped barrier with a thickness of 5 (mm) inserted,
About six electrode configurations of the sphere-to-plane gap length 50 of the same curvature as the outer radius of curvature of the bowl-shaped barrier radius R25 (mm) (mm), the gas pressure is 0.10 (MPa) at SF ₆ gas concentration of 95% or more of the air 5 shows a partial discharge start voltage, an AC flashover voltage, and a 50% flashover voltage of a lightning impulse in a mixed gas of (1) and (2). In the same figure, comparing the electrical characteristics of a hemispherical rod-to-plate electrode with a barrier inserted therein, a disk-shaped barrier is inserted in the case of a lightning impulse 50% flashover voltage. Thus, a negative barrier effect is exhibited, a positive barrier effect is exhibited by inserting a bowl-shaped barrier, and a bowl-shaped barrier without a conductor layer is the same as a ball-to-plate one, The body layer is 90% of the ball-to-plate type. Next, in the case of AC flashover voltage, a negative barrier effect is also exhibited by inserting a disk-shaped barrier, and a bowl-shaped barrier is inserted. By doing so, a positive barrier effect is exhibited, and the barrier effect is higher than that of a sphere-to-flat plate, and is higher with the conductor layer provided than without the conductor layer. Finally, in the case of the partial discharge inception voltage, the insertion of a disc-shaped barrier and a bowl-shaped barrier without a conductor layer allows the hemispherical rod to flat plate to be inserted.
It is reduced to 90% value and becomes equivalent to that of a hemispherical rod-to-flat plate by inserting a disc-shaped barrier with a conductor layer, and becomes equivalent to that of a bowl-shaped barrier with a conductor layer by inserting a bowl-shaped barrier with a conductor layer About 140%, and about 70% of ball-to-plate. From this, it can be seen that it is effective to insert a bowl-shaped barrier to improve the electrical characteristics of an electrode system that forms an uneven electric field such as a hemispherical rod versus a flat plate. The electrical characteristics of the bowl-shaped barrier differ slightly depending on the presence or absence of a conductor layer on the surface of the recess. The AC flashover voltage and the partial discharge starting voltage show higher characteristics when the conductor layer is provided than when the conductor layer is not provided. However, since these electric characteristics are evaluated independently, it is not clearly understood whether the conductive layer is present or not.

Therefore, in order to evaluate these jointly, although a conductor layer is provided between the hemispherical rod and the flat plate electrode, a bowl-shaped barrier is inserted, and the distance between the tip of the hemispherical rod and the barrier is changed to 0 to 30 (mm). FIG. 4 shows the results of calculating the lightning impulse 50% flashover voltage and the AC flashover voltage by changing the partial discharge starting voltage and using these as parameters. The figure shows that the lightning impulse 50% at the same partial discharge starting voltage
It can be seen that both the flashover voltage and the AC flashover voltage are higher with the conductor layer provided. For this reason, in order to improve the electrical characteristics by inserting a barrier into an electrode system that forms an uneven electric field in low-pressure SF ₆ gas, it is necessary to use a bowl-shaped barrier provided with a conductor layer on the surface of the concave portion. The best.

Therefore, by surrounding the end cover 9a of the vacuum valve 9 with the insulating cylinder 14 provided with the conductor layer 14a on the inner surface, the electric field intensity of the end cover 9a can be reduced, and the partial discharge starting voltage and the withstand voltage can be improved. it can. The insulating cylinder 14 is an integrally cast product, and can withstand a large force of about 1 ton when the circuit breaker is closed.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
This embodiment embodies the basic configuration of FIG. 1 described above.
An opening is provided in the upper part of 14 and a shield is provided in this opening. FIG. 5 shows this configuration.

That is, in the same figure, the insulating cylinder 20 has a thickness that does not break through at a predetermined withstand voltage, has an opening 20a in which the vacuum valve 9 can be inserted, and has an opening inside the middle part. A partition wall 20b for fixing the vacuum valve 9 inserted from the center 20a is provided, and a plurality of support legs 20c are provided equidistantly along the circumferential direction below the intermediate portion.
A conductor layer 20e is provided on the inner surface of the upper insulating cylinder 20. Here, the upper shield 21 is provided on the edge surface of the opening 20a.
A plurality of bosses (not shown) with screw holes for screwing bolts (not shown) for fixing are molded along the circumferential direction. The upper shield 21 is provided with a conductor layer 21a on the surface on the insulating cylinder 20 side, covers the opening 20a of the insulating cylinder 20, is fixed to the insulating cylinder 20 via a bolt (not shown), The fixed electrode shaft 22 is fixed by bolts (not shown). The main circuit conductor 7 is fixed to the upper surface of the upper shield 21 via a coupling 7a, and the coupling 7a is connected to the fixed electrode shaft 22. On the other hand, the partition wall 20b is provided with a screw hole or a through hole for screwing a bolt (not shown) for fixing the vacuum valve 9, and a screw hole for screwing a bolt (not shown) for fixing the lower shield 23. The movable electrode shaft 11 of the valve 9
There is provided a hole 20d that allows the shaft to move in the axial direction. A lower shield 23 is fixed to the lower surface of the partition wall 20b via a bolt (not shown) so as to cover the hole 20d. The lower shield 23 has a movable electrode shaft 11 of the vacuum valve 9.
Is provided with a hole 23a that penetrates.

With the above configuration, the electric field strength of the end cover 9a of the vacuum valve 9 can be reduced, and the partial discharge starting voltage and the withstand voltage can be improved. The thickness of the insulating cylinder 20 is
The flashover voltage is determined by the radius of curvature of the upper shield 21 or the lower shield 23, the ground, and the distance between the phases, since the thickness is such that the breakdown does not occur at a predetermined withstand voltage. In general, the distance between the lower shield 23 is larger than the distance between the lower shield 23 and the ground. The upper shield 21 is fixed to the opening 20a of the insulating cylinder 20 and applies a large force acting upward when the circuit breaker is closed.
20 can be absorbed throughout.

Therefore, the embodiment configured as described above can be downsized while maintaining the same insulation performance as that of the conventional metal shield, and the partial discharge starting voltage is improved because the semiconductor layer is provided inside the insulating cylinder, thereby improving the long-term operation. And the inter-phase pitch of the circuit breaker can be adjusted to other storage devices. In addition, the large mechanical force that acts when the breaker is turned on is absorbed by being housed in an integrally cast insulating cylinder, and the vertical dimension of the breaker can be reduced by eliminating the need for an upper insulating support. In addition, the incorporation into the opening / closing device and the processing of the closed box can be facilitated, and the size of the opening / closing device can be reduced and the cost can be significantly reduced.

〔The invention's effect〕

As described above, according to the present invention, the non-uniform electric field present in the electric device in which the low-pressure insulating gas is sealed is surrounded by the insulating barrier having the conductor layer, and the conventional barrier is reduced when the barrier is inserted into the gap. And the long-term reliability can be improved.
In addition, the size can be reduced by relaxing the electric field, and the cost of electric equipment can be reduced accordingly.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of the barrier in the insulating gas of the present invention cut along one side along the center line, FIG. 2 is an explanatory view showing the operation of the present invention, and FIG. FIG. 4 is an explanatory view showing an operation of the present invention which is different from FIGS. 2 and 3, and FIG. 5 is a side view of one embodiment of the present invention cut along a center line. FIG. 6 is a side view of a switchgear accommodating a conventional circuit breaker, and FIG. 7 is a cross-sectional view of a conventional circuit breaker external insulation cut along one side along a center line. 9 Vacuum valve, 10 Metal shield 14 Insulating cylinder, 14a Conductor layer 17 Bowl-shaped barrier

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-191415 (JP, A) JP-A-60-226707 (JP, A) JP-A-60-226706 (JP, A) 63009 (JP, U) Actually open sho 59-78811 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H02B 13/00-13/06

Claims (1)

(57) [Claims] When an electrode system for forming an uneven electric field is present in a barrier in an insulating gas mounted on an electric device in which a low-pressure insulating gas is sealed, three-dimensional surroundings of a high-voltage side electrode having a large electric field intensity. Is covered with an insulating barrier having a curvature that is sufficiently larger than this electrode and a thickness that does not cause breakthrough at a predetermined withstand voltage, and a conductor layer is provided on the surface of the concave portion of the insulating barrier facing the high-voltage electrode. Characteristic barrier in insulating gas.