JPH0244621A - Gas breaker for electric power - Google Patents

Abstract

PURPOSE:To construct a grounded metal vessel in a small size by forming an insulation layer with an appropriate thickness at the inner wall of the vessel, and lessening out of equilibrium in the insulation margin for withstand voltage and heat gas. CONSTITUTION:An insulation layer of 3-5mm thick consisting of ethylene tetrafluoride resin is formed on the inner wall of a grounded metal vessel 30 over an extent covering to insulation cylinders 28, 31, which support the main live part insulatively from the ground potential, except the region of gas space accommodating a link mechanism 3. Accordingly electric charges supplied to glass space from the inner wall of vessel in the initial period of transient recovery voltage rising from zero immediately after the current being shut off consists of displacement current with insulation layer made of dielectric substance, so that the quantity is suppressed, and propagation of charged particles in the gas space will be delayed. Therefore, the heat gas space exhibits an insulation strength to sustain this wave height value even when the transient recovery voltage is at wave height value, and there is no risk of shortcircuting to provide recovered voltage in normal state.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a circuit breaker used in power systems with a transmission voltage of several hundred volts or more, which is installed in a grounded metal container filled with insulating arc-extinguishing gas. The present invention relates to a power gas circuit breaker in which a breaking contact is housed in the grounded metal container, and insulating arc-extinguishing gas heated by an arc generated between the breaking contacts when current is interrupted spreads within the grounded metal container.

[Conventional technology]

An example of a conventional configuration of such a power gas circuit breaker is shown in FIG. Inside a cylindrical grounded metal container 30 filled with several atmospheres of SF6 gas as an insulating arc-extinguishing gas, there is a current-carrying fixed contact 1 supported from the left end plate 29 via an insulating cylinder 28.
0 and a bar-shaped fixed breaking contact 11, and a movable energizing contact 12 and a movable breaking contact 13 that contact and separate from these fixed contacts, respectively, are accommodated. The figure shows the circuit breaker in the closed state, but in order to cut off the current, the bow of the hydraulic actuator is removed from the coil 18a.
When the oil passage 6b on the back side of the hydraulic piston 5 is switched to the oil tank 9 side as shown by the arrow, the oil on the back side is discharged into the oil tank 9 and is constantly applied to the front side of the hydraulic piston 5. The operating rod 4 is driven downward by the hydraulic pressure from the hydraulic source 7, and the bell crank of the link mechanism 3 connected to this operating rod rotates clockwise to move the insulating rod 2 to the right, and the energizing rod 15, the energizing movable contact 12 and the breaking movable contact 13 are driven to open and open, and an arc is generated between the breaking fixed contact 11 and the breaking movable contact 13, which open late. This arc is extinguished by compressing the gas in the gas space 20 formed between the fixed piston 16 and the movable cylinder 17 as the movable contacts 12 and 13 break strokes, and this compressed gas flows through the insulating nozzle 21. This is done by blowing the arc through the inside. The gas blown by the arc becomes a hot gas heated to a high temperature by the arc, spreads in the radial direction from the opening gap of the breaking contact, and heads toward the inner wall surface of the grounded metal container 30. During this time, the density of the hot gas becomes thinner, the temperature drops, the hot gas recovers its dielectric strength, and the power supply side metal member inside the metal container 30 is kept insulated from the ground potential.

[Problem to be solved by the invention]

The problems with the power gas circuit breaker configured as described above are as follows. In recent years, continuous efforts have been made to downsize electric power gas circuit breakers and closed gas switchgear using these circuit breakers, and as a result, miniaturization of these switchgear devices is approaching its limits. Downsizing of opening/closing equipment is
This effect becomes more noticeable when the container containing functional components such as contacts and opening/closing mechanisms is made smaller; however, in the case of the electric power gas circuit breaker targeted by the present invention, the dimensions of the container are: (1) withstand voltage; Dimensions determined above (2) are determined by the larger of the dimensions that do not cause a flashover between the main conductive part and the metal container due to the hot gas caused by the arc at the time of current interruption, and in reality, it is often determined by item (2). For this reason, the size of the container was larger than the size determined by the withstand voltage.

It is an object of the present invention to provide an insulation structure for a circuit breaker that reduces the imbalance in insulation tolerance with respect to withstand voltage and hot gas and allows for smaller container dimensions.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, an insulating layer of an appropriate thickness is formed on the inner wall surface of a grounded metal container.

[Effect]

First, a description will be given of the applied voltage waveform when the main conductive part and the metal container flash over due to hot gas at the time of current interruption. This applied voltage waveform is the waveform of the recovery voltage that appears between the breaking contacts following the current interruption (in this case, the load side of the breaker is assumed to be at ground potential), and this recovery voltage is the waveform of the recovery voltage that appears between the breaking contacts following the current interruption. It consists of a transient recovery voltage that appears during the period, and a steady recovery voltage that follows this transient recovery voltage. The steady-state recovery voltage is the AC voltage at the operating frequency, and the transient recovery voltage is defined as the AC voltage when the peak value is higher than the AC voltage peak value in the current range of the rated breaking current or about 60% of it, where insulation deterioration due to hot gas is a problem. It has a waveform with a duration of about 0.2 to 1 millisecond or less. Therefore, by creating an insulating structure that can withstand this short-term transient recovery voltage, it is possible to significantly reduce the container dimensions.

As is well known, the flashover phenomenon between two metals is a phenomenon that occurs when charged particles moving between the two metals increase their density and this density exceeds a certain value. , an insulating layer is formed on the inner wall of a grounded metal container, and at the beginning of the transient recovery voltage that rises from zero immediately after the current is interrupted, the charge bottle supplied from the inner wall of the container to the gas space is suppressed, and the charged particles in the gas space are suppressed. By slowing down the proliferation of the current, it becomes possible to connect the transient period immediately after the current cutoff to the stationary phase without reaching a flashover. Therefore, the area of the insulating layer formed on the inner wall surface of the grounded metal container does not need to cover the entire inner wall surface of the container, but may be wide enough to sufficiently cover the high-density hot gas region.

〔Example〕

FIG. 1 shows an embodiment of the present invention. In the figure, the same members as those in the second embodiment are denoted by the same reference numerals, and their explanations will be omitted. The area is large enough to sufficiently cover the gas area near the separation gap formed between the fixed breaking contact 11 and the movable breaking contact 13, in which the main current part is excluded except for the area of the gas space where the link mechanism 3 is accommodated. Insulating cylinder 28.31 supporting insulation from earth potential
An insulating layer made of polytetrafluoroethylene resin and having a thickness of 3 to 5 mm is formed on the inner wall surface of the grounded metal container 30 so as to cover the entire area. When an insulating layer is formed on the inner wall of a grounded metal container in this way, the charge supplied from the inner wall of the container to the gas space at the initial stage of the transient recovery voltage that rises from zero immediately after the current is cut off is transferred to the insulating layer as a dielectric. Since it is caused by a displacement current, the amount is suppressed, and the increase in charged particles in the gas space is delayed compared to the case where no insulating layer is formed.

Therefore, even at the time of the peak value of the transient recovery voltage, the hot gas space exhibits an insulating strength that can withstand this peak value, and a steady state recovery voltage is reached without causing a flashover.

〔Effect of the invention〕

As described above, according to the present invention, the breaking contact is housed in a grounded metal container filled with insulating arc-extinguishing gas, and the insulating arc-extinguishing gas is heated by the arc generated between the breaking contacts when current is interrupted. In the power gas circuit breaker that spreads within the grounded metal container, an insulating layer is formed on the inner wall of the grounded metal container, so that at the beginning of the transient recovery voltage that rises from zero immediately after the current is cut off, the The charge supplied to the gas space is caused by a displacement current using the insulating layer as a dielectric, and the amount is suppressed, and the proliferation of charged particles in the gas space is delayed compared to when no insulating layer is formed.
Even at the peak value of the transient recovery voltage, the hot gas space exhibits an insulating strength that can withstand this peak value, and the steady recovery voltage continues without causing flashover. Therefore, it is possible to reduce the size of the grounded metal container, and the imbalance between the withstand voltage required by the standard and the insulation margin for hot gas during current interruption is reduced, and there is no waste in the use of materials and the circuit breaker is The effect is that the size is significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is an explanatory sectional view of a gas circuit breaker for electric power according to an embodiment of the present invention, and FIG. 2 is an explanatory sectional view showing the structure of a conventional gas circuit breaker for electric power. 1 Insulating layer, 11 Breaking fixed contact, 13 Breaking movable contact, 30 Grounded metal container. Figure 1 Figure 2

Claims (1)

[Claims] 1) A power gas interrupter in which a breaking contact is housed in a grounded metal container filled with insulating arc-extinguishing gas, and the insulating arc-extinguishing gas heated by the arc generated between the breaking contacts when the current is interrupted spreads within the grounded metal container. 1. A gas circuit breaker for electric power, characterized in that an insulating layer is formed on an inner wall surface of the grounded metal container.