JPH0481291B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a sulfur hexafluoride (SF ₆ ) gas circuit breaker.

[Background of the invention]

The breaking structure of an SF ₆ gas circuit breaker generally consists of a fixed arc contact 1, a movable arc contact 2, a fixed main contact 3, a movable main contact 4, an insulating nozzle 5, a puffer cylinder 6, and a puffer cylinder as shown in Figure 1. piston 7
It is formed from a powder chamber 8 formed by.
When this SF ₆ gas circuit breaker is energized, the fixed arc contact 1 and the movable arc contact 2 are connected as shown in the upper part of Figure 1.
The fixed main contact 3 and the movable main contact 4 are electrically connected to each other. During the opening operation, as shown in the lower part of FIG. 1, the movable arc contact 2, the movable main contact 4, and the insulating nozzle 5, which are fixed to the puffer cylinder, move to the left in the illustrated example. In this process, the fixed main contact 3 and the movable main contact 4 are separated,
After this, the fixed arc contact 1 and the movable arc contact 2 are separated. Therefore, at the time of opening, an arc is generated between the fixed arc contact 1 and the movable arc contact 2, but no arc is generated between the fixed main contact 3 and the movable main contact 4. On the other hand, the puffer piston 7 is fixed and the puffer cylinder ₆ moves to the left in FIG. This SF ₆ gas then flows through the arc extinguishing chamber 11 and out of the insulating nozzle 5 through the space between the fixed arc contact 1 and the widening part of the insulating nozzle 5 .

When a large current is interrupted, the current value is large, so even if the fixed arc contact 1 and the movable arc contact 2 are separated, the arc continues between the poles, and when the fixed arc contact 1 is inside the insulating nozzle 5. The current cannot be interrupted, and after the fixed arc contact 1 has completely escaped from the throat of the insulating nozzle 5, SF ₆ gas compressed in the puffer chamber 8 is blown onto the arc to extinguish it. Therefore, to interrupt large currents, it is effective to control the gas flow after the fixed arc contact 1 exits the throat part of the insulating nozzle 5, and the fixed arc contact 1 becomes insulated in about 0.5 cycles after opening. Nozzle 5
The structure is such that the gas escapes through the throat of the arc and is sprayed onto the arc.

However, in the case of advanced small current interruption, since the interruption current is small, the current may be interrupted at the same time as the fixed arc contactor 1 and the movable arc contactor 2 are separated and the arc time is 0. In the case of a small leading current, the phase difference between voltage and current is approximately 90 degrees in electrical angle, so when the arc is extinguished, the load side of the circuit breaker is charged with the peak value of the ground voltage at this time. , a ground voltage at the power frequency is applied to the power supply side of the circuit breaker. As a result, in the case of three phases, for example, a potential difference V expressed by the following equation occurs between the poles.

V=V _P /√3×√2 (1-coswt) …(1) However, V _P : Power supply voltage (effective value of phase voltage) ω : Angular velocity of power frequency t : Time This value is determined after 0.5 cycle of power frequency Maximum. In practical circuit breakers, the rate of voltage increase in equation (1) is greater than the rate of increase in the length between poles when the circuit is opened, so the electric field strength between the poles is highest after 0.5 cycles of opening. , especially when the arc time is 0. Therefore, as the voltage burden between poles increases, the duty to interrupt small currents is becoming one of the major issues that must be solved in the development of circuit breakers.

Figure 2 shows the pressure change at point Q at the tip corner of the fixed arc contact 1 during the opening operation when using the insulated nozzle with the conventional structure shown in Figure 1, and the gap between the poles during the opening operation. Indicates the dielectric strength and inter-electrode dielectric strength at rest without contact opening operation. During the electrode opening operation, the pressure at point Q rises higher than the filling pressure until the distance between poles d ₁ is reached, and thereafter, the pressure at point Q rapidly decreases until the distance between poles reaches d ₂ . When examined in relation to the stroke characteristics of the circuit breaker, the interpole distance d ₁ corresponds to the position where the end Q of the fixed arc contact 1 begins to pass through the throat of the insulating nozzle 5, and d ₂ corresponds to the position where the end Q of the fixed arc contact 1 begins to pass through the throat of the insulated nozzle 5. This corresponds to a position where the cross-sectional area of the gas flow path between the arc contacts is slightly larger than the cross-sectional area of the throat portion of the insulating nozzle 5. In other words, _d2 is the position where the gas flow velocity near point Q of the tip corner of the fixed arc contact 1 is maximum, and is the position where the static pressure on the surface of the fixed arc contact 1 suddenly decreases due to the increased gas flow velocity. It can be said. On the other hand, looking at the dielectric strength during electrode opening operation in Figure 2, it increases until the electrode distance d ₁ as in the case of stationary gas, then decreases suddenly when the electrode distance exceeds d ₁ , and decreases at the electrode distance d ₂ . It shows the same tendency as the pressure change, which shows a minimum value and then increases again, and it can be seen that the inter-electrode dielectric strength during the opening operation depends on the pressure on the surface of the fixed arc contact 1. As mentioned above, in order to improve the interrupting performance of large currents, if you try to spray gas strongly onto the arc from about 0.5 cycles after opening, the arc will be fixed at a distance between the electrodes where the voltage between the electrodes is highest when interrupting small currents. There is a drawback that the gas pressure at the tip of the contact decreases, resulting in a decrease in inter-electrode dielectric strength.

Another known example is shown in FIG. Fixed arc contact 1, movable arc contact 2, fixed main contact 3,
The movable main contact 4, the insulating nozzle 5, the puffer cylinder 6, and the puffer piston 7 are the same as the example shown in FIG. Protrusions 9 are scattered. This is done immediately before the interruption of a large current, that is, when the distance between poles becomes sufficiently large and the current to be interrupted becomes small, a part of the gas flow at the wide end of the insulating nozzle 5 is transferred to the center of the insulating nozzle 5. The aim is to encourage arc extinction in the region. Therefore,
There is no effect on the advanced small current interrupting performance at a point in time when the distance between poles is short. In addition, dispersing the protrusions in this manner generates vortices in the gas flow, which reduces the gas pressure at the center of the vortex, resulting in a decrease in dielectric strength. Therefore, it is not preferable to attach this kind of protrusion at a position where the distance between the electrodes is short and the electric field strength between the electrodes is high, which affects the interruption of small currents.

[Purpose of the invention]

An object of the present invention is to prevent a pressure drop in the vicinity of a fixed arc contact during the opening operation of a gas circuit breaker, and to improve the small current breaking performance.

[Summary of the invention]

The present invention provides a variable fluid on the downstream side of the insulated nozzle throat of a gas circuit breaker, and applies dynamic pressure due to gas flow to the surface of a fixed arc contact near 0.5 cycles after opening during the opening operation, and applies a dynamic pressure to the surface of the fixed arc contact in the vicinity of the fixed arc contact. This is to prevent a drop in gas pressure.

Further, in the case where the variable fluid is a discontinuous ring-shaped variable fluid, the variable fluid is connected to the fixed arc near the position where the tip corner of the fixed arc contact passes after 0.5 cycles of opening. The structure is such that (S ₂ /S ₁ ) ^1/2 is 0.15 or less, where S ₁ is the gas flow area between the contacts and S ₂ is the gas flow area between the variable fluids.

[Embodiments of the invention]

FIG. 4 shows the structure of the interrupting part of the gas circuit breaker according to the present invention. The structure is exactly the same as the conventional one in that it is composed of a fixed arc contact 1, a movable arc contact 2 fixed to a puffer cylinder (not shown), an insulating nozzle 5, and the like. The feature of the present invention is that a variable fluid 13 is provided on the downstream side of the throat of the insulating nozzle 5.
According to the present invention, the small current interrupting performance can be greatly improved. This will be explained in detail with reference to FIG. 4 below. Patshua chamber (not shown) during electrode opening
The compressed SF ₆ gas passes through the arc extinguishing chamber 11, passes through the throat of the insulating nozzle 5, and flows from around the fixed arc contact 1 to the outside of the insulating nozzle 5 (on the right side of the figure).
In this process, the SF ₆ gas hits the G surface forming the tapered part of the variable fluid 13 attached to the divergent part A-D of the insulating nozzle 5, and a part of the gas flow flows toward the fixed arc contact 1 side. This gas flow applies dynamic pressure to the surface of the fixed arc contact.
As a result, the gas pressure on the surface of the fixed arc contactor 1 increases, increasing the dielectric strength between the electrodes. The tip C of the variable fluid is provided at a position where point Q of the tip corner of the fixed arc contact 1 passes approximately after 0.5 cycles of contact opening. Therefore, the pressure at the end of the fixed arc contactor 1 at the time when the electric field becomes the highest in advanced small current interruption becomes high, and the advanced small current interruption performance can be improved. This variable fluid 13 is annular and continuous. Further, as shown in FIG. 4, the grooves 14 may be discontinuous, but if they are discontinuous, the characteristics will vary depending on the dimensions of the grooves 14 formed between the variable fluids 13. FIG. 5 shows the value of the interelectrode dielectric strength at the time of contact opening, obtained by changing the gas flow path area between variable fluids 13, at a position 0.5 cycle after contact opening. The cross-sectional area of the gas flow path between the tip C of the variable fluid 13 and the fixed arc contact 1 is _S1 , and the cross-sectional area of the gas flow path between the variable fluid 13, that is, the width W of the groove 14 and the height of the variable fluid shown in FIG. If the product of h and the number of grooves n is S ₂ S, and the horizontal axis is (S ₂ /S ₁ ) ^1/2 and the vertical axis is dielectric strength, the value of (S ₂ /S ₁ ) ^1/2 is greater than 0.1. It can be seen that the dielectric strength decreases rapidly. The dielectric strength (relative value) when using the conventional insulated nozzle shown in Figure 1 is 0.7, and in order to improve the advanced small current interrupting performance, (S ₂ /S ₁ ) ^1/2 must be 0.15 or less. I know it has to be. This is because when the cross-sectional area of the gas flow path between the variable fluids 13 increases, the variable fluids 13
This is because not only is there a small increase in gas pressure on the surface of the fixed arc contactor 1 that faces the fixed arc contactor 1, but also a vortex of gas flow is generated around the variable fluid 13, which lowers the pressure at the center of the vortex and lowers the dielectric strength. . According to the theory of fluid mechanics, the pressure in the vortex is expressed by equation (2).

P ₀ /P _∞ = exp (-C ² /RT) ...(2) Here, P ₀ : Pressure at the center of the vortex P _∞ : Pressure at the chamber wall C: Speed of sound T: Absolute temperature of the gas R: Gas constant SF For ₆ gases, C=134.9 (m/s), R=56.9
(m ² /s ² K), and if T = 288 (〓), then P ₀ /P _∞
It becomes ≒1/3. Therefore, in the worst case, the pressure at the center of the vortex in SF ₆ gas will drop to 1/3 of the ambient pressure, and the dielectric strength will also drop in proportion to this.
As mentioned above, the variable fluid 13 is provided so that the gas flow path becomes the smallest near the position where point Q of the end of the fixed arc contactor 1 passes 0.5 cycles after opening on the downstream side of the throat of the insulating nozzle 5 (S ₂ / _S1 ) ^1/2 ≦0.15
By making it possible to significantly improve the advanced small current interrupting performance.

〔Effect of the invention〕

According to the present invention, it is possible to prevent a drop in gas pressure near the fixed arc contact when the gas circuit breaker is opened.
It is effective in improving the interelectrode dielectric strength during contact opening operation and improving the small current interrupting performance.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the structure of a conventional gas circuit breaker, Figure 2
The figure is an explanatory diagram of the dielectric strength between poles and the gas pressure change at the fixed arc contact terminal during the opening operation of the gas circuit breaker in Figure 1, and Figure 3 is an explanatory diagram of the structure of the breaking part of another conventional gas circuit breaker. Figure 4A is a cross-sectional view of the insulating nozzle of the embodiment of the gas circuit breaker of the present invention, B is a side view of A, and Figure 5 is a comparative explanatory diagram of the dielectric strength when the dimensions of the insulating nozzle in Figure 4 are changed. It is. 1... Fixed arc contact, 2... Movable arc contact, 3... Fixed main contact, 4... Movable main contact, 5... Insulating nozzle, 6... Puff cylinder, 7... Puff piston, 8... Patshua chamber, 9... Protrusion, 11... Arc extinguishing chamber, 13... Variable fluid, 14... Groove.

Claims (1)

[Claims] 1. A device comprising a fixed arc contact, a movable arc contact, a device for compressing arc-extinguishing gas, and an insulating nozzle for guiding the compressed arc-extinguishing gas; In a gas circuit breaker that extinguishes the arc generated between the contacts by spraying arc-extinguishing gas, it is located downstream of the throat of the insulating nozzle, near the position where the tip corner of the fixed arc contact passes after 0.5 cycles of opening. A gas circuit breaker characterized by being provided with a variable fluid whose gas flow path area is minimized. 2 Equipped with a fixed arc contact, a movable arc contact, a device for compressing arc-extinguishing gas, and an insulated nozzle that guides the compressed arc-extinguishing gas. In a gas circuit breaker that extinguishes an arc by spraying an arc extinguishing gas, a discontinuous annular variable fluid is provided downstream of the throat portion of an insulating nozzle, and the variable fluid is
The gas flow area between the variable fluid and the fixed arc contact near the position where the tip corner of the fixed arc contact passes after the cycle is S 1 , and the gas flow area between the variable fluid is S ₁ .
A gas circuit breaker characterized in that, when S ₂ , (S ₂ /S ₁ ) ^1/2 is 0.15 or less.