The present invention relates to a switch, more specifically relates to a switch including a plurality of switching units disposed in series.
A rapid-transit railway such as the Shinkansen adopts an AC electrification system to secure large power. Since power is supplied from individual substations, a section is provided to isolate a neighbor power source. Such a configuration is specifically illustrated in
Examples of existing switches include a switch described in Patent Literature 1 that is however different from the above-described switch for the rapid-transit railway. Patent Literature 1 describes a DC breaker for DC current breaking in which a plurality of energizing vacuum breakers and breaking vacuum breakers disposed in parallel to the energizing vacuum breakers are provided between a DC power supply and a reactor as a load, and the breaking vacuum breakers are disposed in parallel to one another. In Patent Literature 1, the energizing vacuum breakers are provided separately from the breaking vacuum breakers. During energization, the breaking vacuum breakers are opened, while the energizing vacuum breakers are closed. On the other hand, during braking, the breaking vacuum breakers are first closed, and then the energizing vacuum breakers are opened to commutate a current to each breaking vacuum breaker, and then the breaking vacuum breakers disposed in series are sequentially opened, so that the DC current is finally decreased to zero through attenuation according to a predetermined time constant given by a series circuit of resistances provided in parallel to the breaking vacuum breakers and the reactor.
When the above-described operating method is applied to the section switches VS1 and VS2, the following problem occurs. The section switch VS2 is closed during passing of the train 101 to make a load current. When the section switch VS2 is opened, the train 101 has passed through the dead section 100, and the section switch VS2 is opened at no load. If the load current is repeatedly made, a contact surface in the switch is roughened due to pre-arc. If the load current is broken, the electrode surface is smoothed by arc generated during the breaking. In the case of the section switch VS2, however, since load making and no-load breaking are repeated, the contact surface is gradually roughened, leading to a possibility of lowering of withstanding voltage. If interelectrode breakdown occurs in the section switch VS2, short circuit occurs between the power supplies G1 and G2, which leads to a serious accident that may disturb train service. Patent Literature 1 basically does not consider such roughening of the contact surface.
An object of the invention is therefore to provide a reliable switch having a contact surface that is prevented from being roughened.
To solve the above-described problem, according to the invention, there is provided a switch including a plurality of switching units each including a fixed electrode and a movable electrode that is disposed to be opposed to the fixed electrode and is closed or opened with respect to the fixed electrode, the switch being characterized in that the switching units each make or break a current to be applied to the switch, the switching units are electrically connected in series to each other, and the switching units are configured such that a first switching unit is first closed, and then a second switching unit is closed.
According to the present invention, it is possible to provide a reliable switch having a contact surface that is prevented from being roughened.
Hereinafter, some preferred embodiments of the present invention will be described with reference to the accompanying drawings. The following description merely shows example embodiments, and the subject matter of the invention is not limited to the following specific modes. It will be appreciated that the invention can also be modified or altered into various modes in addition to the following modes.
A switch according to Embodiment 1 is now described with reference to
The vacuum interrupters 2 and 3 internally accommodate electrode pairs 4 and 5 each including a fixed electrode and a movable electrode that is disposed to be opposed to the fixed electrode and is closed or opened with respect to the fixed electrode. Each of the electrode pairs 4 and 5 is opened or closed (is into a contact or separate state) while the vacuum state is maintained, thereby the circuit is allowed to be made or broken. The breaking vacuum interrupter 2 has a current breaking function, and the disconnecting vacuum interrupter 3 has an anti-surge function. Conductors 6 and 7 for connection to a power supply or a load are fixed to upper sides of the vacuum interrupters 2 and 3, respectively. Movable conductors 8 and 9 are provided on the lower sides of the vacuum interrupters 2 and 3 while being connected to movable-side electrodes and disposed to penetrate through the vacuum interrupters 2 and 3, respectively. The movable conductors 8 and 9 extend to the respective outsides of the vacuum interrupters and are electrically connected to current collectors 10 and 11, respectively. The current collectors 10 and 11 are fixed to conductors 12 and 13, respectively, and are connected to each other by a connecting conductor 14. Specifically, the breaking vacuum interrupter 2 and the disconnecting vacuum interrupter 3 are connected in series via the connection conductor 14. The movable conductor 8 is connected to an insulative operating rod 46 that is connected to a wipe spring 42 to be connected to the insulative operating rod 46 and a shaft 40. The movable conductor 9 is connected to an insulative operating rod 47 that is connected to a wipe spring 43 to be connected to the insulative operating rod 47 and a shaft 41. The shaft 41 is connected to an electromagnet 22.
The breaking vacuum interrupter 2 and the disconnecting vacuum interrupter 3 are peripherally covered with insulators 15 and 16, respectively, and are fixed to a housing 17 on an electromagnet side with the respective insulators 15 and 16 in between, so that electrical isolating performance under high voltage is secured.
An operating unit for the breaking vacuum interrupter 2 and the disconnecting vacuum interrupter 3 is now described. The breaking vacuum interrupter 2 and the disconnecting vacuum interrupter 3 are connected to electromagnets 21 and 22, respectively. As illustrated in
To describe the operation of the electromagnet 21 or 22, when the electromagnet 21 or 22 is closed, the coil 29 is excited such that magnetic flux is generated in the same direction as that of the magnetic flux generated by the permanent magnet 30. When the electromagnet 21 or 22 is opened, the coil 29 is excited in a direction opposite to that in closing to cancel the magnetic flux generated by the permanent magnet 30, so that the electromagnet 21 or 22 is allowed to operate by the force of the wipe spring 42 or 43 and the force of the breaking spring 44 or 45.
The coil 29 is excited using power stored in the capacitor 50 or 51.
Specifically, the timing is set as illustrated in
Effects of the invention are now described. A vacuum switch is typically used for the section switches VS1 and VS2 illustrated in
To avoid pre-arc of the disconnecting vacuum interrupter 3 in closing operation, operation time is desirably shifted by 10 ms or more to sufficiently secure an gap distance of the breaking vacuum interrupter 2 connected in series to the disconnecting vacuum interrupter 3. The reason for setting the shift time to 10 ms or more is as follows: a half cycle of 50 Hz passes within such a period at least one time, and thus at least one voltage peak exists in the period. To generalize this, operation time should be shifted by at least a half cycle of an AC frequency, i.e., by at least (1×103)/(2×X) [ms] with respect to a power supply of an AC frequency X [Hz]. In breaking operation, assuming that arc is iginiting during one cycle in breaking, the disconnecting vacuum interrupter 3 is desirably opened by 20 ms or more later than the breaking vacuum interrupter 2. The reason for setting the delay to 20 ms or more is as follows: one cycle of 50 Hz passes within such a period at least one time, and thus at least two current zero point exists in the period, and consequently the AC current can be broken. To generalize this, operation time should be shifted by at least one cycle of an AC frequency, i.e., by at least (1×103)/X [ms] with respect to a power supply of an AC frequency X [Hz].
Although Embodiment 1 has been described with a case where the electromagnets 21 and 22 are used in the operating unit, it is obvious that the electromagnets do not exclusively perform one or both of (1) making (closing) operation where the disconnecting vacuum interrupter 3 is made (closed) prior to the breaking vacuum interrupter 2 and subsequently the breaking vacuum interrupter 2 is made, and (2) opening operation where the disconnecting vacuum interrupter 3 first starts opening and then the breaking vacuum interrupter 2 starts opening, and an electric motor charged spring operating unit or pneumatic operating unit is also allowed to provide similar effects.
According to Embodiment 1, a plurality of switching units are electrically connected in series to each other, and the switching units are configured such that the disconnecting vacuum interrupter 3 as a first switching unit is first closed, and then the breaking vacuum interrupter 2 as a second switching unit is closed; hence, since one vacuum interrupter (the disconnecting vacuum interrupter 3 in the above-described operation) is closed at no load in each case, a reliable switch having a contact surface being prevented from being roughened can be provided without degrading electrical isolating performance.
Embodiment 2 is now described with reference to
In other words, when the gap distance (a distance between the movable electrode and the fixed electrode of the switching unit) of the disconnecting vacuum interrupter 3 in the opened state is set shorter than the gap distance of the breaking vacuum interrupter 2 in the opened state, the disconnecting vacuum interrupter 3 is first made, so that effects similar to those described in Embodiment 1 can be exhibited.
According to Embodiment 2, the number of components such as the electromagnets and the capacitors can be decreased, and the control circuit can be simplified, and consequently the switch can be achieved in a simple configuration.
Embodiment 3 is now described with reference to
In this case, vertical power of a rod 75, which is driven in a vertical direction, is converted into horizontal power. Hence, an operating-unit-side link unit 72 is connected to the rod 75, and a shaft 71 that moves in a horizontal direction is connected to the operating-unit-side link unit 72. In addition, a switching-unit-side link unit 74, which is vertically branched across the shaft 71, is provided on a vacuum interrupter side of the shaft 71. Each of ends of the switching-unit side link unit 74, the end being opposite to an end close to the shaft 71, is connected to each of the movable conductors of the two vacuum interrupters.
The power transmission mechanism such as the link unit is not limited to the mode described herein. When a plurality of switching units are disposed in a vertical direction, and if each switching unit can be operated at one of the above-described timings, the footprint can be reduced while the effects described in Embodiments 1 and 2 are provided.
As a possible measure for achieving such a timing, specifically, the gap distance of the disconnecting vacuum interrupter 3 in the opened state is set shorter than the gap distance of the breaking vacuum interrupter 2 in the opened state, thereby the disconnecting vacuum interrupter 3 is first closed, so that effects similar to those in Embodiment 1 can be provided.
It will be appreciated that the electromagnet may not be necessarily provided in the operating unit not only in Embodiment 1 but also in each of Embodiments 2 and 3. Moreover, although the vacuum interrupter is used in the switching unit in each of Embodiments, the vacuum interrupter may not be exclusively used. Using the vacuum interrupter allows the switch to be small and reliable.
Number | Date | Country | Kind |
---|---|---|---|
2012-163215 | Jul 2012 | JP | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/JP2013/067433 | 6/26/2013 | WO | 00 |