EP1352407A1

EP1352407A1 - Vacuum circuit-breaker and a method for controlling the same

Info

Publication number: EP1352407A1
Application number: EP01273291A
Authority: EP
Inventors: Bernd-Heiko Krafft; Karl Mascher
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2001-01-19
Filing date: 2001-11-29
Publication date: 2003-10-15
Also published as: WO2002058091A1; US20040061504A1; CN1486499A; DE10104392A1; DE10104392C2; JP2004517455A

Abstract

The aim of the invention is to improve the interrupting capacity of a vacuum switch. to achieve this, the contact parts (4, 5) that can be displaced in relation to each other are separated at a variable speed. Separation takes place in such a way that during a predetermined time period a predetermined distance between the contacts is not exceeded. To prevent said predetermined distance from being exceeded, a braking element is allocated to the vacuum circuit breaker.

Description

description

Vacuum switch and system and method for its control

The present invention relates to a control system for controlling a vacuum switch, the contact system of which has at least two contact pieces which can be moved relative to one another and which are separated from one another at a changing speed during a switch-off process and between which an arc to be extinguished burns during the switch-off process.

Such a control system is known for example from the patent DE 38 15 805 C2. By means of an eccentric drive element, the switch-off movement becomes one

Contact arrangement of a vacuum switch controlled. The design of the mechanical lever chain is selected so that after a very short acceleration phase (1.3 ms) of a movable contact piece, an opening path of the contact pieces of 1 mm is achieved. Furthermore, it is described that it has proven to be particularly favorable if a contact piece separation speed of 2 m / s is reached after 0.8 ms. This technical solution is based on the consideration of extinguishing an arc which ignites after the contact separation as quickly as possible in order to avoid melting of the contact material of the contact pieces. It is assumed that the highest possible breaking capacity of a vacuum switch can be achieved if the contact separation speed is as high as possible.

However, any increase in the contact separation speed is not technically possible. In addition, when switching off high currents, it should be noted that these are only Get cheaply deleted within a certain range of the distance of the contact pieces. Outside of this quenching area, it is technically very complex to influence an arc in such a way that it is finally extinguished as quickly as possible.

The present invention is therefore based on the object of designing a control device of a vacuum switch in such a way that arcs occurring during a switch-off process are extinguished more reliably with a justifiable technical outlay.

The object is achieved according to the invention in a control system of the type mentioned at the outset in that the control means that a given distance of the contact pieces is only exceeded after a period of time predetermined for the control system.

In order to promote the extinguishing of the switch-off arc, it is necessary to influence the arc so that it burns as diffusely as possible. The behavior of the arc is essentially influenced by the shape of the contact pieces and the distance between the contact pieces. If the given distance of the contact pieces is not exceeded within a predetermined period of time, the extinguishing of the arc proves to be a problem that can be solved with reasonable technical effort. The specified period of time is the maximum interval required for the respective switch configuration until the arc is finally extinguished. If the given distance were exceeded during the specified period, much more extensive technical constructions would be necessary. In this case, the electromagnetic forces acting on the arc would which are caused by the current to be interrupted and support the rotation and thus the cooling and extinguishing of the arc, are not available to a sufficient extent.

In addition to the control system, a method for switching a vacuum switch is also provided, the contact system of which has at least two contact pieces which can be moved relative to one another and which are separated from one another at a changing speed during a switch-off process and between which an arc to be extinguished during the switch-off process burning.

This method provides that until the arc is finally extinguished, the average speed of contact separation in a first phase is greater than the average speed of contact separation in a second phase immediately following the first phase.

So far it has been assumed that the deletion of a

Arc in a vacuum switch should always take place with the highest possible contact separation speed. It was assumed that a higher switching capacity of the vacuum switch is directly connected when a higher contact separation speed is reached.

In order to control the breaking currents that occur in the high-voltage range, it has proven to be advantageous to select the average speed of the contact separation in a first phase greater than the average speed of the contact separation in a phase immediately following the arc until the arc is finally extinguished second phase. This makes it possible to switch off the electromagnetic forces over a longer period of time Use _S tromes to make the arc rotate and make it as diffuse as possible. Furthermore, a relatively low-power drive for moving the contact pieces can be used with such a speed profile.

Another method for switching a vacuum valve comprising at least the contact system comprises two relatively movable contact pieces which are separated from each other during a turn-off _V organges at a varying speed and between which organges during the turn-off _V a sees burns to extinguishing the arc before that in a first time period before the final arc extinguishing, the distance of the contact pieces from a predeterminable first contact distance is increased at least up to a predeterminable second contact distance and at most up to a predeterminable third contact distance and in a second time period following the first time period before the final arc extinguishing, the distance the contact pieces remain between the second contact distance and the third contact distance.

_S teuert to the separation of the contact pieces so that the contact gap change in a first time range and is carried out as described above in a second time range is ensured even at high voltages, that the arc in a short time will be securely deleted. In the first time range, the contact distance can vary within a relatively large range. By limiting the variation range of the contact distance in the second time range is ensured with great SECURITY _S, that even with the occurrence of the _S a recovery voltage-peak value of a reignition of the arc is not possible. The first contact distance is the distance at which, depending on the respective switch configuration, the arc can be extinguished for the first time. The extinguishing of the switch-off arc can already begin in the first time range. If the conditions are favorable, the arc can be extinguished in the first period. Such favorable conditions are essentially determined by the point in time at which the switch-off movement begins with regard to the phase position of the current to be switched off at that moment.

_F urthermore can advantageously be provided that the first _Z starts eitbereich once the first Kontakta stand is reached.

If the first time period begins at the point in time at which the first contact has been reached, this ensures that the time required for the entire switch-off process is minimized.

_A u _ß addition it may be advantageous provided that the end of the second time range being different from the time of reaching the Ausschaltendlagen of the contact pieces.

If the time at which the contact pieces are switched off is separated from the end of the second time range, it is possible to optimize the switch-off movement with regard to the arc quenching. After the arc has been extinguished, the contact pieces can be moved to their switch-off positions at any speed. The

_G AAGER of restrike of the arc is no longer present after the end of the second time range. Provision can furthermore advantageously be made for the speed of the contact separation to be controlled as a function of the current to be switched off.

The control of the speed of the contact separation as a function of the current to be switched off is particularly effective, since when a very large current, such as a short-circuit current, is switched off, other requirements are placed on the sequence of the contact separation than, for example, when a rated current is switched off.

Furthermore, it can be provided to design a vacuum switch for carrying out one of the methods described above and for operation by means of the control system described so that an electromagnetic braking device is assigned to a movable contact piece.

Electromagnetic braking devices are able to brake movements almost free of signs of wear. They are therefore ideally suited for braking a movable contact piece on a vacuum switch. This makes it possible to influence the movement sequence of the contact separation in such a way that it can be combined with the control system described and the intended forms of movement, contact distances and time periods are observed.

It can also be advantageously provided that an electromechanical braking device is assigned to a movable contact piece.

Electromechanical braking devices are extremely inexpensive to procure and are adequately suited to delay movement. Provision can furthermore advantageously be made for parts connected to a movable contact piece to be movable in a magnetorheological fluid.

Magneto-rheological liquids react extremely quickly with a change in their viscosity when exposed to a magnetic field. As such, such liquids are well suited for braking assemblies moving in them. Braking devices which take advantage of this effect can be metered very well in their braking action in a wide range ".

_T he method and apparatus described are suitable for use on loading Sonders vacuum switches, which are for interrupting short-circuit currents of 30 kA and used in higher voltage levels from 50kV.

In the following, the invention is shown on the basis of an exemplary embodiment in a drawing and described in more detail below.

The shows

1 shows a path-time diagram with a course of the change in the distance of the contact pieces during a

2, a path-time diagram with a first time range and a second time range, FIG. 3 a plurality of possible path-time characteristics with a first and a second time range,

FIG. 4 shows a vacuum interrupter of a vacuum interrupter with an electromagnetic braking device, Figure 5 shows a vacuum holding tube of a vacuum switch with an electromechanical braking device and the

Figure _{6 shows} a vacuum holding tube of a vacuum switch with a liquid brake device.

Figures 1, 2 and 3 show path-time diagrams of switch-off movements of a vacuum switch. The time t advancing during a switch-off process is plotted on the abscissa of the coordinate system, the galvanic isolation of the contact pieces taking place in the coordinate origin. _A t the ordinate is plotted the distance s of the contact pieces from each other. 1 shows a possible _V erlauf an inventive disconnection. The switch-off movement begins at time t = 0. The contact pieces are galvanically isolated. First, there is a constant increase in the distance between the two contact pieces. At a first point in time tl, a first contact distance sl _{d the} contact pieces _is reached. Up to a point in time t2, the contact pieces are separated at a constant speed. At time t2, a second contact distance s2 is reached. After reaching the second contact distance s2, the relative contact separating movement takes place with a reduced _G eschwindigkeit up to a third time point t3. At no time lying between the first time t1 and the third time t3 does the contact distance of the contact pieces exceed a given third distance s3. The third point in time t3 is chosen such that an arc burning between the two contact pieces is definitely extinguished at this point in time. After reaching the third point in time t3, it is possible to exceed the third distance s3. As a rule, the contact pieces are moved into their end positions after the third point in time t3. A typical value for time t2 is 8-9 ms after galvanic isolation of the contact pieces. There should be a time interval of 12 ms between the first time t1 and the third time t3. The third distance s3 is approximately 3-5 times as large as the first distance sl. The second distance s2 is determined by the voltage level in which the vacuum switch is to be used.

FIG. 2 shows the times described in FIG. 1, first time t1, second time t2, third time t3 and the associated distances between the contact pieces, first contact distance s1, second contact distance s2 and third contact distance s3. A first time range 1 is formed between the first time t1 and the second time t2. The second point in time t2 and the third point in time t3 delimit a second time range 2. The permissible contact distance of the contact pieces moves in the first time range between the first distance sl and the third distance s3. In the second time range, the permissible contact distance of the contact pieces moves between the second distance s2 and the third distance s3. At the third point in time t3, the arc burning between the contact pieces is finally extinguished. Any change in the spacing of the contact pieces is possible within the permitted minimum and maximum spacings of the contact pieces provided in the two time ranges 1, 2.

In FIG. 3, the superimposition of the movement sequence from FIG. 1 (shown with a continuous line in the coordinate system) and the permissible contact distances from FIG. 2 are superimposed. Within the two time periods 1, 2 the distance between the contact pieces is always within the permissible limit values. In order to extinguish the arc as quickly as possible during a switch-off process, the movement sequence shown with the continuous line shows the start of the first time range 1 and the time at which the first distance s 1 of the contact pieces was reached at the same time.

Before the third distance s3 is reached, the speed of the separation of the contact pieces is reduced so that the distance of the contact pieces is within the permissible limit values at any time in the second time period 2. This ensures that the electric field caused by the current to be interrupted is always sufficiently large to support the rotation of the arc and to promote diffuse burning. After reaching the third point in time t3, the separation of the contact pieces is continued until they have reached their end positions. The dashed line shows an example of a further movement sequence. In addition, there are others

Forms of movement possible. However, these forms of movement must ensure that the contact distances in the first time range 1 and in the second time range 2 are within the permissible limits.

The braking devices shown in FIGS. 4 to 6 serve to brake a switch-off movement of the second contact piece 5. The braking devices are controlled with the aid of a control system 13. Alternatively or in combination with the braking devices, it can be provided to have the drive device 14 controlled by the control system 13 in order to achieve the desired movement sequence of the contact separation. FIG. 4 shows a vacuum holding tube 3 of a vacuum switch with the contact pieces 4, 5 forming a contact system in its switched-off position. The first contact piece 4 is mounted in a stationary manner, the second contact piece 5 can be driven by means of a switching rod 6. A ferromagnetic core 7 is arranged at the coupling point of the switching rod 6 and the second contact piece 5. This ferromagnetic core 7 is surrounded by a coil 8. This coil 8 is flowed through by the current flowing through the contact pieces 4, 5. The combination of the coil 8 and the ferromagnetic core 7 constitutes an electromagnetic brake. During a switch-off process, the ferromagnetic core 7 moves through the coil 8, the forces occurring between the coil 8 and the ferromagnetic core 7 being directed in such a way that they counteract the switch-off movement. This slows down the switch-off movement. Only after the switch-off arc is finally extinguished and the final interruption of the electrical current associated therewith is this force effect reduced and the switching rod moves the second contact piece 5 attached to it unaffectedly. The electromagnetic braking device, as well as the braking devices shown in FIGS. 5 and 6, are arranged on the vacuum switches in such a way that the described movement sequences and limit ranges are complied with. It proves to be advantageous to let the braking effect begin after the second distance s2 has been reached.

FIG. 5 shows a further embodiment of a vacuum switch in its switched-off position with an electromechanical brake. The switching rod 6 and the second switching contact piece 5 are concentrically surrounded by contact fingers 9 clamped on one side. The contact fingers 9- an additional friction-enhancing brake pad 10 on their inner sides. If an electrical current flows through the contact fingers 9, the electromagnetic forces then acting press the contact fingers 9 with the brake pads 10 against the switching rod 6 or against the movable contact piece 5. If the contact pieces 4, 5 are separated, the brake pads 10 brake them Movement off immediately. Only after the arc is finally extinguished and the associated interruption of the electrical current does the contact force of the contact fingers 9 decrease due to the lack of electromagnetic forces and the contact separation of the contact pieces 4, 5 can take place almost unaffected by the electromechanical braking device.

Figure 6 shows another embodiment of a vacuum switch in its off position. Ontaktstück to the second _K 5 attachments 11 are fixed, which are moved during movement of the second contact piece 5 within a magneto-rheologisehe liquid 12th The magneto-rheological fluid is around the second contact piece

₅ arranged that it is exposed to the electromagnetic field of the current flowing through the contact pieces 4, 5. This electromagnetic field increases the viscosity of the magneto-rheological fluid 12 and counteracts the movement of the second contact piece 5 in a braking manner when the device is switched off. Depending on the design of the attachments 11 connected to the second contact piece 5, the intensity of the braking effect can be adjusted. In addition to this possibility of variation, it is also possible to influence the viscosity of the magnetorheological fluid 12 by applying an external electric field.

Claims

claims

1. Control system for controlling a vacuum switch whose contact system has at least two contact pieces (4, 5) which can be moved relative to one another and which are separated from one another at a changing speed during a switch-off process and between which an arc to be extinguished burns during the switch-off process, thereby drawing nn, that the control has the effect that a given distance (s3) of the contact pieces is only exceeded after a period of time (t3-tl) predetermined for the control system.

2. Method for switching a vacuum switch whose contact system has at least two contact pieces (4, 5) which can be moved relative to one another and which are separated from one another at a changing speed during a switch-off process and between which an arc to be extinguished burns during the switch-off process, characterized in that, until the arc is finally extinguished, the average speed of contact separation in a first phase is greater than the average speed of contact separation in a second phase immediately following the first phase.

3. Method for switching a vacuum switch whose contact system has at least two contact pieces (4, 5) which can be moved relative to one another and which are switched off during a switch-off.

Process are separated from one another at a changing speed and between which an arc to be extinguished burns during the switch-off process, characterized in that in a first time period (1) before the final arc quenching, the distance of the contact pieces (4, 5) from a predeterminable first contact distance (sl) at least up to a predeterminable second contact distance (s2) and at most up to a predefinable third contact distance ( s3) is increased and the distance of the contact pieces (4, 5) between the second contact distance (s2) and the third contact distance (s3) is maintained in a second time period (2) following the first time period (1) before the final arc quenching.

4. The method for switching a vacuum switch according to claim 3, so that the first time range (1) begins as soon as the first contact distance (sl) is reached.

5. A method for switching a vacuum switch according to one of claims 3 or 4, so that the end of the second time range (2) is different from the point in time when the contact elements (4, 5) have reached the switch-off end positions.

6. A method for switching a vacuum switch according to one of claims 1 to 5, d a d u r c h g e k e n z e i c h n e t that the speed of the contact separation is controlled depending on the current to be switched off.

7. Vacuum switch for performing the method according to one of claims 2 to 6 and for operation by means of a control system according to claim 1, characterized in that a movable contact piece is an electromagnetic

Brake device is assigned.

8. Vacuum switch for carrying out the method according to one of claims 2 to 6 and for operation by means of a control system according to claim 1, that a electromechanical braking device is assigned to a movable contact piece.

9. Vacuum switch for performing the method according to one of claims 2 to 6 and for operation by means of a control system according to claim 1, d a d u r c h g e k e n n z e i c h n e t that parts (11) connected to a movable contact piece are movable in a magneto-rheological fluid (12).