JPH0435858B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a gas circuit breaker, and particularly to a nozzle with excellent advanced small current interrupting performance.

[Background of the invention]

With the miniaturization of gas circuit breakers, the voltage applied to one breaking section of the circuit breaker has become more than twice as high as in the past. In order to deal with this, conventionally, as shown in FIG. 1, performance has been improved by changing the divergent angle of the nozzle having the divergent portion A-D with a straight cross section and the opening speed of the circuit breaker.

In FIG. 1, the movable arc contact 6 moves in unison with the puffer cylinder 4 and the nozzle 1, and the gas compressed within the cylinder is blown onto the movable arc contact 6 and the fixed arc contact 2 by the nozzle 1. . The compressed gas is accelerated at the throat of the nozzle and becomes subsonic or supersonic at the wide end. In the figure, 3 is a nozzle holder, 5 is a piston, and 7 is a current collector. When gas flows at such a high speed, the gas pressure at the diverging section varies depending on the cross-sectional area of the flow path. Here, A ₁ , A ₂ : Cross-sectional area at any two positions of the wide end part, M ₁ , M ₂ : Matsuha number at the positions corresponding to A ₁ and A ₂ , P ₁ , P ₂ : A ₁ and A If A _{1 <} A 2, then in general P 1 > P ₂ with the gas pressure at the position corresponding to _2.
become. In the diverging portion A-D, the flow path cross-sectional area increases toward the downstream side, so the gas pressure continues to decrease. In a circuit breaker, a fixed arc contact is located at the wide end of the nozzle, but as opening progresses at the tip opposite to the movable arc contact, the cross-sectional area of the flow path increases, so the gas pressure always decreases. There is. The solid line in FIG. 2 is a typical measured example.
When the distance between poles d is d ₁ , the tip of the fixed arc contact passes through the throat part T-A of the nozzle, and when the distance between poles is d ₂ , the tip of the fixed arc contact passes through the throat, and the tip passes through the throat of the nozzle with a distance of 10 to 20 mm. position has been reached. Since the gas pressure H at the tip of the fixed arc contact, which has a strong electric field, is reduced by the charging pressure of the circuit breaker, the dielectric strength between the fixed arc contact and the movable arc contact decreases even when the circuit breaker is stationary. As shown in Figure 2, the dielectric strength decreases significantly compared to the dielectric strength when it is present. This transient drop in gas pressure cannot be essentially avoided even by changing the inclination angle of the divergent portion or the moving speed of the puffer cylinder, and has been an essential drawback. In addition,
In the figure, E is the interelectrode dielectric strength at rest, F is the dielectric strength during contact opening operation, and G is the filling pressure.

Recently, as a method to overcome this drawback, a flow transformation part with a reverse taper part that narrows the cross-sectional area of the flow path is installed in the diverging part of the nozzle to prevent sudden gas expansion. Attempts are being made to prevent this decline. FIG. 3 is a schematic structural diagram thereof, in which A-B is a forward tapered portion, B-C-D is a current transformation portion 8, and B-C is a reverse taper portion. Due to variable fluid 8, sudden expansion of gas in the space surrounded by curve A-B-C and fixed arc contactor 2 is almost avoided, resulting in a pressure almost equal to the filling pressure of the circuit breaker, and the dielectric strength at the time of opening is reduced. is almost equivalent to the dielectric strength at rest. However, even with this method, vortices are generated in the triangular region connected by B-C-D, resulting in a microscopic drop in gas pressure and preventing a significant increase in dielectric strength.

[Purpose of the invention]

An object of the present invention is to provide a nozzle equipped with a flow transformation section with a reverse tapered portion, which has a shape that prevents the generation of vortices.

[Summary of the invention]

The present invention provides a gas circuit breaker that extinguishes an arc generated between a fixed contact and a movable contact in an arc extinguishing chamber by blowing an arc extinguishing gas through an insulating nozzle when the arc is interrupted. The base end is attached to the movable contact and is formed to move relative to the fixed contact, and a forward tapered part is provided continuously in the circumferential direction at a diverging part on the downstream side of the throat part of the insulating nozzle. A reverse tapered part is continuously provided in the circumferential direction in connection with the forward tapered part, and the arc-extinguishing gas is blown in the insulating nozzle from the movable contact side to the fixed contact side. In addition, the angle formed by the straight line connecting the throat outlet and the base of the inversely tapered portion and the inversely tapered portion is 95 degrees or more. The basis of the present invention will be explained below.

The inventors conducted various analyzes on the shape of the current transformation section with the reverse taper section, and as a result, the following facts were clarified.

The stator position where the transient pressure drop at the tip of the stator is large and is most severe in terms of insulation (distance between poles d ₂ in Figure 2)
The presence or absence of vortices in the vicinity of the forward tapered part A
-B and the angle θ ₁ (Fig. 4) formed by the reverse tapered portion BC was analyzed as a variable. As shown in FIG. 5, the vortex is generated in an area surrounded by the main flow of gas and ABC as indicated by the arrow, and in an area approximately shaped like a triangle ABC. The analysis was carried out under flow path cross-sectional area conditions ((throat section cross-sectional area)≈(cross-sectional area surrounded by point C and fixed arc contactor 2)) under which this vortex is difficult to generate. As a result, the 6th
As shown by the ● mark in the figure, it was found that when θ ₁ ≦90°, a vortex is generated in the triangular region, and when θ ₁ ≧100 ^∞ , no vortex is generated. It can be easily inferred that the boundary lies at 95°.

Also, the angle θ ₂ between the divergent part A-B and the nozzle center axis
When we analyzed the generation of vortices between the interpolar lengths d ₁ and _{d 2} in Figure 2 using the parameters as shown in Figure 7, we found that no vortices are generated when θ ₂ ≦40 _° , but At ≧50°, vortices occur in the triangular region. It can be easily inferred that the boundary is 45°. Incidentally, the relationship shown in FIG. 7 also holds true for a cross-sectional straight nozzle as shown in FIG. 1, which does not have the reverse tapered portion B--C.

Therefore, if θ ₁ ≧95° and θ ₂ ≦45°, the generation of vortices can be prevented.

[Effect]

During the breaking operation, the movable contact moves away from the fixed contact, and arc-extinguishing gas is blown onto the arc generated between both contacts, but the insulating nozzle moves together with the movable contact. The arc-extinguishing gas is blown in a flow from the movable contact side to the fixed contact side, and by forming the inner surface of the insulating nozzle into a predetermined shape described later, the pressure can be reduced. It becomes possible to spray gas onto a relatively moving fixed contact, that is, an arc, without deterioration, thereby making it possible to maintain a high interelectrode dielectric strength. In the present invention, the predetermined shape of the inner surface of the insulating nozzle means that a forward tapered part is provided continuously in the circumferential direction in the diverging part on the downstream side of the throat part of the insulating nozzle, and a reverse tapered part is continuous with this forward tapered part. It is provided continuously in the circumferential direction, and has a shape in which the angle formed by the inverted tapered portion is 95 degrees or more. Because of this shape, when compressed arc-extinguishing gas flows into the fixed arc contact side through the throat part of the nozzle during the shutoff operation, the gas is guided by the reverse taper part and does not generate a vortex. It collides with the reverse taper, where it is reflected and blown toward the axis of the nozzle. Therefore, the amount of gas blown increases, that is, there is no pressure drop and the interelectrode dielectric strength does not decrease.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described using FIG. 8. The insulating gas compressed by the cylinder 4 and piston 5 is guided through a nozzle 1 made of an insulating material, and is guided through a fixed arc contact 2 and a movable arc contact 6.
The arc that occurs during this time is blown out and the arc is blown out. The nozzle 1 is fixed to a cylinder 4 by a nozzle holder 3, and the movable arc contact 6 is engaged and fixed to the cylinder. A large current is collected by the current collector 7, and at the time of opening, the time when the current collector 7 and the nozzle holder 3 are separated is earlier than the time when the movable and fixed arc contacts 6 and 2 are separated. Nozzle 1
A current transformation section 8 (B-C-D) is provided in the diverging section downstream of the throat T-A to suppress rapid expansion of the insulating gas flow. The angle between straight line A-B and the nozzle center axis is 43°, and the angle between straight line A-B and straight line B-C is
ABC is selected to be 110°. In addition, the flow path cross-sectional area of the throat T-A section and the maximum constriction section C of the current transformation section 8
is approximately equal to the cross-sectional area of the flow path surrounded by the fixed arc contact 2. In this way, by forming the diverging part of the nozzle, the transient pressure drop at the interpolar distance d ₂ shown in Fig. 2 is not only significantly reduced and becomes almost equal to the filling pressure of the circuit breaker, but also the pressure drop shown in Fig. 5 The generation of vortices as shown in can be prevented. the result,
As shown by the curve of θ ₁ =110° in FIG. 9, the dielectric strength of F increases significantly during the opening operation and becomes equal to that during the static state. Accordingly, the advanced small current interrupting performance is significantly improved.

The figure shows the case without variable fluid.

〔Effect of the invention〕

According to the present invention, the insulating nozzle moves together with the movable contact, and the arc-extinguishing gas flows from the movable contact toward the fixed contact and is blown onto the arc within the insulating nozzle. In addition, by making the angle between the forward tapered part, the reverse taper part, and the reverse taper part of the inner surface of the insulating nozzle 95 degrees or more, it is possible to prevent the generation of vortices that locally reduce the gas pressure at the tip of the stator, where the electric field is strong. Since this can be prevented, the dielectric strength is significantly increased, and the low current resistance and breakage performance are significantly improved.

[Brief explanation of drawings]

Figure 1 is a schematic structural diagram of a conventional breaking section of a circuit breaker.
Figure 2 is an explanatory diagram of the transient gas pressure and decrease in dielectric strength of the conventional interrupting section of a circuit breaker, Figure 3 is a schematic structural diagram of the improved interrupting section, and Figure 4 is an explanation of the principle of the present invention. Figure 5 is a schematic diagram showing the flow of gas and the generation of vortices, Figures 6 and 7 are diagrams showing the critical conditions for the generation of vortices, and Figure 8 is a schematic diagram of an embodiment of the present invention. 9th
The figure is a diagram showing dielectric strength actually measured in an example of the present invention. DESCRIPTION OF SYMBOLS 1... Nozzle, 2... Fixed arc contact, 3... Nozzle holder, 4... Cylinder, 5... Piston, 6... Movable arc contact, 7... Current collector, 8... Current transformation part.

Claims (1)

[Claims] 1. A gas circuit breaker that extinguishes an arc generated between a fixed contact 2 and a movable contact in an arc extinguishing chamber by blowing an arc extinguishing gas through an insulating nozzle 1 at the time of interruption, The insulating nozzle has a proximal end attached to the movable contact and is formed to move relative to the fixed contact, and a forward tapered part is formed in the diverging part downstream of the throat part of the insulating nozzle in the circumferential direction. A reverse tapered portion is provided continuously in the circumferential direction in series with the forward tapered portion, and the arc-extinguishing gas is blown in the insulating nozzle from the movable contact side to the fixed contact side. 2. A gas circuit breaker characterized in that the gas circuit breaker is formed so as to face the inversely tapered portion, and the angle formed between the straight line connecting the throat outlet and the base of the inversely tapered portion and the inversely tapered portion is 95 degrees or more. 2. The gas circuit breaker according to claim 1, wherein the angle between the straight line connecting the throat outlet and the base of the reverse tapered portion and the center line of the nozzle is 45 degrees or less.