JP2004039411A - Vacuum circuit breaker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum circuit breaker capable of stabilizing the breaking performance, enhancing the reliability, and reducing the loss in the vacuum circuit breaker with the use of a commutation device. <P>SOLUTION: The commutation device 20 is connected in parallel with a vacuum valve 11 of the vacuum circuit breaker. In the commutation device 20; a capacitor 21, a reactor 22, and a commutation current starting switch 24 are serially connected, and further an arrester 23 to be a non-linear resistive element is connected in parallel with this as an energy absorbing device. The capacitance of the capacitor is made not less than 1000 μF, the reactor is made not less than 3 μH, the resonance frequency is made not less than 1000 Hz and less than 2000 Hz, the resistance of the serial circuit consisting of the capacitor, the reactor, and the turned-on commutation current starting switch is made not less than 20 mΩ. The operating voltage (the voltage value at which a current of 1 mA begins to flow) of the energy absorbing device is made 1.5-2.5 times the rated voltage of the system. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vacuum circuit breaker, and more particularly, to a vacuum circuit breaker having a stabilized breaking performance in which a commutation current from a commutation device is superimposed on a breaking current when a current is cut off to break the current.
[0002]
[Prior art]
In recent years, vacuum circuit breakers have been used in various fields. When shutting off a vacuum circuit breaker using a vacuum valve, the current cannot be cut off unless the current becomes zero. For this reason, in the case of DC current, a method is used in which a high-frequency current is superimposed on a cutoff current by a commutation device connected in parallel to a vacuum valve to forcibly form a current zero point and cut off the current.
[0003]
In the case of an air circuit breaker, when a contact is opened to interrupt a current, an extremely high arc voltage of several volts or more occurs, and the current is limited by the influence of the arc voltage, so that interruption can be performed. In this air circuit breaker, it is known that the energy consumed at the contacts, that is, the product of the current and the arc voltage is very large, and therefore, the contacts are greatly deteriorated due to the interruption.
[0004]
Therefore, it is necessary to frequently perform maintenance and the like, and furthermore, since the arc is cut off in the air and cut off, a loud shut-off sound is generated at the time of cut-off, and environmental problems have also been raised. When a vacuum circuit breaker is used as compared with such an air circuit breaker, the arc voltage is several tens of volts, and the energy consumed between the contacts is reduced to about one-hundredth of the air circuit breaker. For this reason, damage to the contacts is small and the life can be extended.
[0005]
Furthermore, the arcs are processed in the vacuum vessel, since the contacts that come into and away from each other are arranged in the vacuum vessel. As a result, the influence of the scattering of the arc and the interruption sound at the time of interruption can be significantly reduced, and it can be said that it is suitable for the environment. From these backgrounds, a vacuum circuit breaker using a vacuum valve has come to be used even when direct current is cut off.
[0006]
In addition, even in the case of performing high-speed cutoff with an alternating current, there has been a case where a commutation device connected in parallel to the above-described vacuum valve is used. As a result, it is possible to perform a cut-off with a cut-off time close to that of a semiconductor circuit breaker (GTO circuit breaker). Compared with a semiconductor circuit breaker, a vacuum circuit breaker can reduce energy loss when a rated current is supplied and save energy. I can plan.
[0007]
As described above, the vacuum circuit breaker has been widely used for interrupting a DC current or for interrupting a current at a very high speed. In such a case, it is necessary to connect a commutation device in parallel with the vacuum valve, as described above, with respect to a conventional vacuum circuit breaker used for alternating current.
[0008]
By the way, when the commutation device is connected in parallel with the vacuum valve, a current zero point is created by the superimposed current from the commutation device, and thus the current gradient at the current zero point greatly affects the breaking performance. The arc between the vacuum valve electrodes in the cutoff state is in a plasma state.
[0009]
As the current attenuates toward the current interruption, the plasma between the electrodes decreases, and ideally, if the plasma diffuses completely from between the electrodes at the current zero point and the environment between the electrodes becomes a vacuum state, after the current interruption, Since there is a sufficient dielectric strength against the recovery voltage applied between the electrodes, the cutoff is surely completed.
[0010]
In a vacuum circuit breaker, the diffusion speed of this plasma is high, and it is possible to cut off even with a high current gradient. However, if the current gradient is too large, the amount of residual plasma that cannot be diffused at the current zero point increases, and as a result, there is a possibility that shutoff may fail. It is known that when using a commutation device, the current gradient condition of the commutation current is important.
[0011]
On the other hand, in the method of cutting off by creating a current zero point by the commutation current, it is necessary to release the energy remaining in the circuit inductance because the current is forcibly cut off. It is necessary to connect an energy absorbing device such as a non-linear resistor.
[0012]
As this kind of technology, a DC high-speed circuit breaker mounted on a vehicle described in Japanese Patent Application Laid-Open No. 3-67429 is known. According to this, it is shown that the oscillation frequency of the commutation circuit is 2 kHz or more, the commutation current is 5,000 A or more, and the commutation inductance is 1 μH or more.
[0013]
However, when this condition is applied to a DC high-speed vacuum circuit breaker used in a track circuit on the ground, there may be a case where a current gradient at the time of a large current interruption becomes large and interruption cannot be performed.
[0014]
That is, in the case of a railroad circuit breaker, the detected current value of the accident current (scale value in the general name of the air circuit breaker) is 12,000 A, and the circuit breaker operates at the rated break current and scale value. The maximum current value during the period until the current is cut off is 25,000 A. This is because the time from the detection of the fault current to the interruption is several ms, and the current rise rate is 3 × 10 ⁶ A / s, so the current at the interruption point has a large value.
[0015]
In the case of interrupting such a large current, the arc form between the electrodes of the vacuum valve may cause a self-pinch force to act on the arc and concentrate, possibly causing extreme damage to the electrodes. For this reason, the current gradient that can be cut off is smaller than in the case where the current is diffused at about 10,000 A or less.
[0016]
Therefore, in order to stably cut off the current even in the case of cutting off a large current exceeding about 10,000 A, it is necessary to reduce the current gradient near the current zero point of the current flowing by superimposing the commutation current.
[0017]
A circuit shown in FIG. 3 is known as a technique for reducing a current gradient near a current zero point of a current on which a commutation current is superimposed. In FIG. 3, a saturable reactor 15 is connected in series to a vacuum valve 11 of a vacuum circuit breaker, and a commutation device 20 is connected in parallel to this series circuit.
[0018]
In the commutation device 20, a capacitor 21, a reactor 22, and a commutation current start switch 24 are connected in series, and an arrester 23 as an energy absorbing device is connected in parallel with this series circuit. The capacitor 21 is charged by a charging device (not shown).
[0019]
In this method, the supersaturated reactor 15 is connected to a portion where the cutoff current flowing through the vacuum circuit breaker and the commutation current overlap. According to this method, the reactor component of the supersaturated reactor 15 increases near the current zero point of the vacuum valve 11, and the current gradient at the current zero point can be reduced.
[0020]
When interrupting the current, the vacuum valve 11 is first opened, and then the commutation current start switch 24 is turned on. As a result, the electric charge charged in the capacitor 21 flows to the vacuum valve 11 as a commutation current in a direction opposite to the cutoff current. A current zero point is created by this superimposed current to interrupt the current.
[0021]
FIG. 4 shows the current waveform at this time. FIG. 2A shows a superimposed current waveform diagram of a cutoff current and a commutation current, and FIG. 2B shows a current waveform diagram when only a commutation current flows. The superimposed current has a small current gradient near the current zero point. Looking at only the commutation current, the portion A near the current peak is a portion where the supersaturated reactor 15 has an effect.
[0022]
However, on the side of the commutation device 20, the effect of reducing the current gradient with respect to the current zero point of the commutation current flowing through the commutation current start switch 24 for starting the discharge of the capacitor 21 cannot be expected.
[0023]
[Problems to be solved by the invention]
With such a configuration, since the supersaturated reactor 15 needs to be attached to a portion where a normal current flows, there is a loss due to the supersaturated reactor 15 even when the normal current is flowing.
[0024]
Further, an arrester 23, which is a non-linear resistance element, is connected as an energy absorbing device for releasing residual energy corresponding to the reactance of the circuit due to current interruption. However, the limiting voltage of the arrester 23 is too high. The voltage generated in the circuit may cause discharge in parts other than the arrester. If the limit voltage is too low, the operation frequency of the arrester 23 increases, and the life of the arrester 23 is reduced.
[0025]
Further, the capacity of the capacitor 21 for flowing the commutation current can be reduced by increasing the charging voltage in order to flow the same commutation current, but it is necessary to consider the shunt to the arrester 23 and the like. When the charging voltage is reduced, the capacity of the capacitor 21 needs to be increased, and the limiting voltage of the arrester 23 is applied to both ends of the capacitor 21, which leads to hasten deterioration of the capacitor 21 depending on the allowable voltage of the capacitor 21. .
[0026]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a vacuum circuit breaker using a commutation device, which stabilizes the breaking performance and provides a highly reliable, low-loss vacuum circuit breaker. It is.
[0027]
[Means for Solving the Problems]
To achieve the above object, according to the vacuum circuit breaker of the present invention, a commutation device is connected in parallel to a vacuum valve, and when a current is interrupted, a commutation current is superimposed on the interruption current from the commutation device to create a current zero point. In a vacuum circuit breaker for interrupting a current, the commutation device is connected to a circuit in which a commutation current start switch for discharging a charged charge of a capacitor and a reactor and a capacitor charged by a charging device is connected in parallel to a circuit. Elements are connected, the capacitor of the commutation device is 1000 μF or more and the reactor is 3 μH or more, the resonance frequency is 1000 Hz or more and less than 2000 Hz, and the capacitor and the reactor of the commutation device and the commutation current start switch are provided. The series circuit resistance in the input state is set to 20 mΩ or less, and the operating voltage of the energy absorbing device (1 mA starts flowing) The pressure value), characterized in that it was 1.5 to 2.5 times the rated voltage of the system.
[0028]
As a result, the commutation device can be reduced in size, the life of the energy absorbing device can be extended, and the current gradient at the current zero point of the superimposed current can be reduced to 200 A / μs or less, and stable interruption can be performed. Can be made.
[0029]
According to the vacuum circuit breaker according to the present invention, a commutation device is connected in parallel with the vacuum valve, and when the current is interrupted, the commutation current is superimposed on the interruption current from the commutation device to form a current zero point and the current is interrupted. In the device, the commutation device is configured by connecting an energy absorption element in parallel to a circuit in which a commutation current start switch for discharging a charged charge of the capacitor and the reactor and the capacitor charged by the charging device is connected in series. The charging voltage of the capacitor of the commutation device is lower than the operating voltage of the energy absorbing element and higher than the rated voltage of the system.
[0030]
As a result, deterioration of the life of the capacitor can be reduced, and stable shutoff can be performed.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows an embodiment of the present invention. In FIG. 1, a commutation device 20 is connected in parallel with a vacuum valve 11 of a vacuum circuit breaker. The commutation device 20 includes a capacitor 21, a reactor 22, and a commutation current starting switch 24 connected in series, and further connected in parallel with an arrester 23 as a non-linear resistance element as an energy absorbing device. The capacitor 21 is charged by a charging device (not shown).
[0032]
When interrupting the current, the vacuum valve 11 is first opened, and then the commutation current start switch 24 is turned on. As a result, the electric charge charged in the capacitor 21 flows to the vacuum valve 11 as a commutation current in a direction opposite to the cutoff current. A current zero point is created by this superimposed current to interrupt the current.
[0033]
FIG. 2 shows the relationship between the frequency of the commutation current and the current gradient. The current gradient can be suppressed to 200 A / μs or less by setting the resonance frequency to less than 2 kHz in 20 kA interruption, which is a large current interruption region. It is also appropriate to set the capacity of the capacitor 21 to 1,000 μF or more and the reactor 22 to 3 mH or more from the viewpoint of reducing the size of the commutation device 20.
[0034]
As an example in the present invention, the capacitance of the capacitor was 1,200 μF, and the reactor was 15 μH. Thus, under the conditions of an estimated short-circuit current of 50 kA, a DC current increase rate of 3 × 10 ⁶ A / s, and a scale value of 12,000 A, the current gradient at the current zero point of the superimposed current of the commutation current and the breaking current is 200 A / μs or less, and could be cut off without any problem.
[0035]
By inserting the reactor 22 into the commutation device 20 in addition to the floating inductance, the influence of the fluctuation of the floating inductance due to the manufacturing state can be eliminated, and a commutation device with stable performance can be manufactured.
[0036]
Further, in order to reduce the resonance frequency of the commutation current to less than 1 kHz, it is necessary to increase the size of the capacitor 21 and the reactor 22, so that the size of the commutation device 20 is not good.
[0037]
Further, the circuit resistance when the capacitor 21, the reactor 22, and the commutation current start switch 24 are turned on is preferably 20 mΩ, and was set to 10 mΩ in the embodiment of the present invention. Thereby, the attenuation of the commutation current could be reduced. As a result, it was possible to cut off the DC current without any problem even under the condition of 13,200 A flowing in the reverse direction.
[0038]
Further, the limit voltage (voltage value of 1 mA flowing through the arrester) of the arrester 23 used in the energy absorbing element is set in a range of 1.5 to 2.5 times the rated voltage of the system. In the embodiment of the present invention, the limit voltage of the arrester is set to 2,500 V with respect to the rated voltage of the system of 1,500 V.
[0039]
As a result, the maximum generated voltage of the arrester at the time of interruption can be limited to 4,000 V or less, and interruption without any problem such as insulation breakdown at a portion other than the arrester can be achieved. By setting the limit voltage of the arrester 23 to 1.5 times or more of the rated voltage of the system, the arrester does not operate under conditions such as small current switching and the life of the arrester can be extended.
By setting the maximum of the limit voltage to 2.5 times or less, it is possible to perform stable interruption without dielectric breakdown of parts other than the arrester.
[0040]
By setting the charging voltage of the capacitor 21 of the commutation device 20 lower than the limit voltage of the arrester 23 and equal to or higher than the rated voltage of the system, a stable commutation current can be superimposed on the vacuum valve 11 of the circuit breaker. As a result, deterioration of the life of the capacitor 21 can be reduced.
[0041]
In the embodiment of the present invention, the charging voltage of the capacitor 21 is set to 2,300 V with respect to the rated voltage of the system of 1,500 V and the limit voltage of the arrester of 2.500 V. As a result, a stable commutation current could be superimposed on the vacuum valve 11 without diverting the commutation current to the arrester 23 side.
[0042]
The contact material of the vacuum valve 11 used was Cu or Ag as a conductive component, and a material made of an alloy containing at least one of Cr, W, Mo, Ti and a carbide thereof as an arc resistant component. .
[0043]
With such a contact material configuration, it is possible to reduce the amount of neutral metal vapor and metal plasma generated from the contact per unit charge amount of the breaking current, as compared to a material containing a high vapor pressure material or the like. Interruption was possible even under conditions where the current gradient of the interruption current was larger than before. Therefore, there is an advantage that the current frequency of the commutation current can be increased and a small commutation device can be obtained.
[0044]
As an example of the present invention, a CuCr alloy was used as a contact material. As a result, high blocking performance could be obtained.
[0045]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the vacuum circuit breaker of this invention, the commutation current of a commutation apparatus can be stabilized, and while being able to stabilize interruption | blocking performance, miniaturization is possible. Further, the deterioration of the commutation device can be reduced and the life can be prolonged.
[Brief description of the drawings]
FIG. 1 is a circuit diagram illustrating an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a relationship between a frequency of a commutation current and a current gradient.
FIG. 3 is a circuit diagram showing a conventional vacuum circuit breaker.
4A and 4B are a superimposed current waveform diagram and a commutation current waveform diagram in the vacuum circuit breaker of FIG.
[Explanation of symbols]
11 Vacuum valve 15 Supersaturated reactor 20 Commutation device 21 Condenser 22 Reactor 23 Arrestor 24 Commutation current start switch

Claims (5)

In a vacuum circuit breaker in which a commutation device is connected in parallel to a vacuum valve and a current is cut off by superimposing a commutation current from the commutation device on the interruption current when the current is interrupted to cut off the current, the commutation device includes a capacitor and a reactor. And an energy absorbing element connected in parallel to a circuit in which a commutation current starting switch for discharging the charged charge of the capacitor charged by the charging device is connected in series, and the capacitor capacity of the commutation device is set to 1000 μF. With the above, the reactor is set to 3 μH or more, the resonance frequency is set to 1000 Hz or more and less than 2000 Hz, and the series circuit resistance in a state where the commutation device capacitor and the reactor and the commutation current start switch are turned on is set to 20 mΩ or less. Operating voltage (voltage value at which 1 mA starts to flow) is 1.5 to 2.5 times the rated voltage of the system. Vacuum circuit breaker according to. The vacuum circuit breaker according to claim 1, wherein the energy absorbing device is a non-linear resistance element. In a vacuum circuit breaker in which a commutation device is connected in parallel to a vacuum valve and a current is cut off by superimposing a commutation current from the commutation device on the interruption current when the current is interrupted to cut off the current, the commutation device includes a capacitor and a reactor. And an energy absorbing element connected in parallel to a circuit in which a commutation current start switch for discharging the charged charge of the capacitor charged by the charging device is connected in series, and the capacitor charging of the commutation device is performed. A vacuum circuit breaker characterized in that the voltage is lower than the operating voltage of the energy absorbing element and higher than the rated voltage of the system. 2. The vacuum valve according to claim 1, wherein the contact material comprises Cu or Ag as a conductive component, and an alloy containing at least one of Cr, W, Mo, Ti and carbide thereof as an arc-resistant component. The vacuum circuit breaker according to any one of claims 1 to 4. The vacuum circuit breaker according to claim 4, wherein the contact material of the vacuum valve is a CuCr alloy.

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