CA2189322A1

CA2189322A1 - Electrical switching device

Info

Publication number: CA2189322A1
Application number: CA 2189322
Authority: CA
Inventors: Herbert Schifko; Andrzej Kaczkowski; Olav Knudsen; Andreas Laubi; Erwin Manz; Marta Lacorte
Original assignee: ABB Management AG
Current assignee: ABB Asea Brown Boveri Ltd
Priority date: 1995-11-02
Filing date: 1996-10-31
Publication date: 1997-05-03
Also published as: BR9605408A; CZ319396A3; JPH09167549A; EP0772214A2; DE19540777A1; PL316668A1

Abstract

The electrical switching device is provided with at least two contact supports (32, 28) which are arranged spaced apart on an axis (3), with at least one contact (switching pin 36) which moves along this axis (3) and, in the connected state of the switching device, electrically conductively bridges the distance between the at least two contact supports (32, 28), with a drive (39) which acts on the moving contact and is driven by a superordinate control system.
It is intended to specify an electrical switching device which is designed to be more user-friendly and which has an increased switching capacity.
This is achieved in that the at least one moving contact (switching pin 36) can be moved during at least one switching process at at least two different speeds, and in that at least one of the at least two speeds is optimally matched to the respective physical characteristics which govern the relevant switching process.

Description

Se 30.10.95 95/133 TITLE OF THE lNV~NllON

Electrical switching device BACKGROUND OF THE INVENTION

Field of the Invention The invention is based on an electrical switching device according to the preamble of claim 1.

Discussion of Background The invention in this case refers to a prior art as results, for example, from the Laid-Open Specification DE-A1-42 10 545. This publication describes as an electrical switching device an angled disconnector for a metal-encapsulated, gas-insulated high-voltage switching installation, having two switching pieces which are arranged in the insulating-gas-filled metal encapsulation, can make contact with one another or can be disconnected from one another along one axis and have in each case one pre-arcing contact which is in the form of a pin, extends axially and is designed, in the case of one of the two switching pieces, as an overtravel contact, and having a fixed contact, which coaxially surrounds the pre-arcing contact of a fixed one of the two switching pieces, and a moving contact, which is provided on a moving one of the two switch pieces and forms a continuous current path with the fixed contact in the connected position.
In the case of this disconnector, after the acceleration phase, the moving contact is moved both in the disconnection direction as well as in the connection direction at an approximately constant speed.

SUMMARY OF THE lNv~NlION

Accordingly, one-object of the invention, as it is defined in the independent patent claims, is to provide a novel electrical switching device which is designed to be more user-friendly and which has an increased switching capacity and, in addition, a method for its operation is provided.
It is particularly advantageous that the switching movements of the switching device can be matched to the physical requirements of the respective switching process, so that its switching capacity is improved, or the influences on the power supply caused by the switching process are minimized.
The electrical switching device is provided with at least two contact supports which are arranged spaced apart on an axis, with at least one contact, which is designed as a switching pin, moves along this axis and, in the connected state of the switching device, electrically conductively bridges the distance between the at least two contact supports, with a drive which acts on the moving contact and is driven by a superordinate control system. During the at least one switching process, the at least one moving switching pin can move at at least two different speeds, and at least one of the at least two speeds is optimally matched to the respective physical characteristics which govern the respective switching process.
Further exemplary embodiments of the invention and the advantages which can be achieved thereby are explained in more detail in the following text with reference to the drawing, which illustrates only one possible configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the atten~nt advant~gee thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
Fig. 1 shows a section through a housing of an electrical switching device according to the invention, Fig. 2 shows a simplified section through one embodiment of an electrical switching device according to the invention, Fig. 3 shows a schematic illustration of a profile of a disconnection movement of a contact of an electrical switching device according to the invention, and Fig. 4 shows a schematic illustration of a profile of the contact speed during disconnection of a contact of an electrical switching device according to the invention.
Only those elements which are essential for direct underst~n~;ng of the invention are illustrated.
DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, a disconnectQr will be considered first as the electrical switching device.
Fig. 1 shows a section through a schematically illustrated housing 1 of this disconnector. As a rule, the housing 1 is filled with an insulating gas under pressure, sulfur hexafluoride (SF6) being particularly suitable for this purpose. In order to assist clarity, the visible edges of the housing 1 are only indicated.
As a rule, this housing 1 is at ground potential, together with the other encapsulation parts of a metal-encapsulated, gas-insulated switching installation. The housing 1 has two axes 2, 3 which lie on a plane and intersect at an angle a. As a rule, the angle a is designed as a right angle but, for special applications, angles other than a right angle can also be envisaged. As a rule, the housing 1 is cast from an aluminum alloy in a pressure-tight manner. The housing 1 has at least four circular openings 4, 5, 6 and 7, which are provided with flanges 8, 9, 10 and 11. In this case, the flange 8 is assigned to the opening 4, the flange 9 to the opening 5, the flange 10 to the opening 6, and the flange 11 to the opening 7. The openings 4, 5, 6 and 7 are arranged such that the axes 2, 3 pass through them at the center, to be precise the axis 2 passing through the openings 4 and 6 and the axis 3 passing through the openings 5 and 7. The flanges 8, 9, 10 and 11 have surfaces which are arranged at right angles to the respective axes 2, 3.
In this case, the opening 4 is closed by an insulator 12, which is designed in the form of a disk and has an electrically conductive cast-in fitting 13.
The cast-in fitting 13 is screwed to a conductor 14.
The insulator 12 is held by means of an outer ring 15, in which grooves are incorporated for the accommodation of sealing rings which are not illustrated. The outer ring 15 is composed of two identically designed, metallic, electrically conductive rings. The insulator 12 and the outer ring 15 are held in position by a connecting flange 16, which is screwed to the flange 8, of an adjacent housing 17. The opening 5 is in this case closed by a cover flange 18. An outer ring 15, which accommodates the necessary sealing rings (which are not illustrated), is mounted between the cover flange 18 and the flange 9. However, it is also possible to dispense with this outer ring 15 and, for this purpose, to provide the bearing surface of the cover flange 18 or the bearing surface of the flange 9 with a groove for the accommodation of a sealing ring.
The cover flange 18 is provided with a connecting piece 19, which is closed in a pressure-tight manner by means of a threaded cover 20. If required, a bursting disk as well as connections for the gas supply of the housing 1 can be installed in the cover flange 18 or in the cover 20.

21 8~322 The opening 6 is in this case closed by an insulator 12 which is designed in the form of a disk and has an electrically conductive cast-in fitting 13.
The cast-in fitting 13 is screwed to a conductor 21.
The insulator 12 is held externally by means of an outer ring 15 in which grooves are incorporated for the acco~o~tion of sealing rings (which are not illustrated~. The insulator 12 and the outer ring 15 are held in position by a connecting flange 22, which is screwed to the flange 10, of an adjacent housing 23.
The opening 7 is in this case closed by a cover flange 18. An outer ring 15, which accommodates the necessary sealing rings (which are not illustrated), is mounted between the cover flange 18 and the flange 11. However, it is also possible to dispense with this outer ring 15 and, for this purpose, to provide the bearing surface of the cover flange 18 or the bearing surface of the flange 11 with a groove for the accommodation of a sealing ring. The cover flange 18 is provided with a connecting piece 19, which is closed in a pressure-tight manner by means of a threaded cover 20.
The housing 1 and the closure parts described above enclose an internal area 24 in which the active parts, to which high voltage is applied, of electrical switching devices can be installed, these being the active parts of a disconnector, as already mentioned, in this case. The covers 20 can be used for the installation of the widely different accessories which are used in metal-encapsulated, gas-insulated switching installations. The housing 1 can also be provided with additional connecting pieces, which can be used for the installation of sensors and viewing windows for optical inspection of the disconnector position. In Fig. 1, a viewing window 25 is provided in the center of the housing 1 and is installed in a cylindrically designed connecting piece whose center axis runs at right angles to the plane on which the axes 2 and 3 are located and which, in addition, passes precisely through the intersection of the axes 2 and 3. An identically 2~ 89322 designed viewing window is provided in the opposite wall of the housing 1, at precisely the same point. The disconnection point of all disconnector versions is in each case arranged centrally in the housing 1 such that it can be inspected through the viewing window 25 described above.
Fig. 2 shows a simplified section through a schematically illustrated first embodiment of an electrical switching device, which is designed as a disconnector for metal-encapsulated, gas-insulated high-voltage switching installations, in the disconnected state. This disconnector is designed as a bus-tie switch-disconnector, as is provided, for example, in the course of metal-encapsulated, gas-insulated busbars. In this case, the conductors 14 and21 represent the respective ends of the busbar sections which are at high-voltage potential. The conductor 14 is screwed to the metallic cast-in fitting 13 of the left-hand insulator 12. An electrically conductive angled connecting piece 26, which is designed to be dielectrically favorable, is connected on the side of the cast-in fitting 13 facing away from the conductor 14, and has a connecting surface which is inclined through an angle ~ with respect to the axis 2. In this case, the value of the angle ~ is 30~, but other values of the angle ~ are also conceivable, corresponding to the geometry of the housing 1, and an angle range of from 25~ to 35~ can sensibly be implemented, as a rule, for this angle ~. The inclined connecting surface is screwed to a cylindrically designed spacer 27. The side of the spacer 27 opposite the connecting surface is screwed to a contact support 28. The spacer 27 extends along an axis 29 which is on the same plane as the axes 2 and 3 and is inclined through the angle ~ with respect to the axis 2. The contact support 28 is designed in a dielectrically favorable manner and is manufactured from metal. A cylindrically designed mating contact 30, which i8 used as the fixed pre-arcing electrode of the disconnector, is incorporated 2~ 89322 .

in the contact support 28. In addition, spiral contacts 31, which carry the current when the disconnector is closed, are incorporated in the contact support 28. The mating contact 30 extends in the direction of the axis 3, which at the same time forms the central axis of the mating contact 30.
The conductor 21 is screwed to the metallic cast-in fitting 13 of the right-hand insulator 12. An electrically conductive angled connecting piece 26, which is designed in a dielectrically favorable manner, is connected on the side of the cast-in fitting 13 facing away from the conductor 21, and has a connecting surface which is inclined through an angle ~ with respect to the axis 2. Care must be taken in this case to ensure that these two angles ~ always have the same value. The value of this angle ~ in this case is accordingly likewise 30~. The inclined connecting surface is screwed to a cylindrically designed spacer 27. The side of the spacer 27 opposite the connecting surface is screwed to a contact support 32. The spacer 27 extends along an axis 33, which is on the same plane as the axes 2 and 3 and is inclined through the angle ~
with respect to the axis 2. The axis 33 runs parallel to the axis 29.
The contact support 32 is designed in a dielectrically favorable manner and is manufactured from metal. Spiral contacts 34 for carrying the current are incorporated in the contact support 32. The moving disconnector contact 35 is arranged in the center of the contact support 32. The moving disconnector contact is designed cylindrically and its axis coincides with the axis 3. The moving disconnector contact 35 has a switching pin 36 which is surrounded by a contact tube 37 of tubular design. When the disconnector is connected, the contact tube 37 makes contact, after the switching pin 36, with the spiral contacts 31 of the contact support 28 and, during disconnection of the disconnector, the contact tube 37 i8 released first from the spiral contacts 31 of the contact body 28, and 21 ~322 the switching pin 36 is thus released from the mating contact 30. An insulating rod 38, which is operated by a drive 39, sets the moving disconnector contact 35 in motion. The drive 39 is mounted on the upper connecting piece 19. The drive 39 has a speed-controlled DC motor whose rotor is fitted with permanent magnets. The control instructions for the speed-controlled DC motor are generated by a superordinate control system which is not illustrated. The insulating rod 38 is passed out of the housing 1 in a pressure-tight manner. The insulating rod 38 is moved by the speed-controlled DC
motor via a lever drive, and a rotating bushing is used, as a rule, as a pressure-tight bushing. The side of the moving disconnector contact 35 facing the drive 39 is covered by a shield 40, which is designed in a dielectrically favorable manner and is composed of an electrically conductive material. The moving disconnector contact 35 extends along the axis 3 which, at the same time, forms the central axis of this contact. The spiral contacts 34 surround the contact tube 37 and connect it to the contact support 32 in an electrically conductive manner.
When the disconnector is in the connected state, the current flows from the conductor 14, through the cast-in fitting 13, the angled connecting piece 26, the spacer 27, the contact support 28, the spiral contacts 31, the contact tube 37, the spiral contacts 34, the contact support 32, the spacer 27, the angled connecting piece 26 and the cast-in fitting 13 into the conductor 21.
Fig. 3 shows a schematic illustration of the profile of the disconnection movement s of the switching pin 36 as a function of the time t. The movement of the contact tube 37, which is intended to carry the rated current, will not be considered any further here. The closed disconnector receives a disconnection instruction at the instant To. The disconnection movement of the switching pin 36 start~
shortly after this, at the instant T1. The drive 39 .
_ 9 _ 95/133 accelerates the switching pin 36 to an increasingly great extent until the contact disconnection between the switching pin 36 and the mating contact 30 takes place at the instant T2. The switching pin 36 is accelerated even further until it reaches its maximum speed. In the case of this disconnector, for example, this m~;mll~ speed is in the region of 300 m~m/s, but generally is somewhat above 300 ~m~/s, and the speed of 330 mm../s has proven to be particularly favorable.
Shortly after reaching this maximum speed, the switching pin 36 is braked again so that, from the instant T3, it continues to move at a slower speed in the disconnection direction, this speed being in the region of 50 ~m~/s. ~owever, after the instant T4, the switching pin 36 is accelerated more sharply again, to be precise to a speed of about 300 ~m~/s. Shortly before reaching the disconnected position, the switching pin 36 is braked again, and then runs into the definitive disconnected position at the instant Ts.
Fig. 4 shows a schematic illustration of the profile of the speed v of the switching pin 36 as a function of the ti~me t during the disconnection of the disconnector. This illustration likewise shows the three essential speed ranges A, B and C of the switching pin 36 which have been described in conjunction with Fig. 3. The range A comprises the time interval between T2 and T3, the range B comprises the time interval between T3 and T4, and the range C
comprises the time interval between T4 and Ts.
The comparatively high ma~;mllm speed in the region A brings with it the advantage that only a comparatively short time interval r~m~; ns for the restrikes which may occur in this region A as a result of so-called loop current switching operations. The life of the switching pin 36 and of the mating contact 30 is advantageously lengthened as a result of this advantageous limiting of the possible nu~mber of restrikes and a reductlon in the erosion llnked thereto, and this results in a considerably increased 21 ~9322 .

availability of the disconnector. In the case of a switching installation which is provided with a double or multiple busbar system, loop current switching operations are understood to be operational changeover operations, under load, from one busbar system to another, which are carried out with the assistance of the disconnector.
The comparatively low speed in the region B
brings with it the advantage that, when capacitive currents are being disconnected, only a comparatively small trapped charge rc~-;ns in the metal-encapsulated, gas-insulated high-voltage installation after passing through this region B. Capacitive residual charges which remain on the active parts of the high-voltage installation are called a trapped charge. These residual charges are dissipated to a considerable extent by restrikes, which occur in the region B, between the mating contact 30 and the switching pin 36.
These residual charges also influence the size of the transient overvoltages, that is to say the smaller these residual charges are, the smaller are the values of the transient overvoltages to be expected, as well.
However, the speed of the switching pin 36 in the region B should once again not be so slow that the number of restrikes occurring in this region becomes too great, since each of these restrikes causes corresponding compensation processes and thus undesirable sharp voltage spikes as well (VFT, very fast transients).
In the region C, the switching pin 36 is then once again accelerated to a comparatively high speed in order that the position of the switching pin 36 which corresponds to the full disconnection travel is reached as quickly as possible, that is to say that distance between the switching pin 36 and the mating contact 30 which withstands any voltage spike occurring in the relevant metal-encapsulated, gas-insulated switching installation. The switching pin 36 has reached its - 21 ~q322 definitive disconnected position at the time Ts, and it has moved through its full disconnection travel.
During connection of the disconnector, the moving disconnector contact 35 is moved by the insulating rod 38, which is operated by the drive 39, along the axis 3 toward the fixed mating contact 30.
Any pre-arcing between the switching pin 36 and the fixed mating contact 30, which may be caused by residual charges and/or by an operating-frequency voltage being present between the contact support 32 and the contact support 28, is coped with correctly by the disconnector. As a result of the geometrical arrangement of the disconnector active parts, it is impossible for any spreading of the pre-arcing arc to occur toward the wall of the housing 1. The drive 39 of the disconnector is designed such that it moves the moving contact arrangement 35 reliably into the intended connected position in every possible operational case, so that this always ensures that the current is carried correctly via the contact tube 37, which is intended for this purpose, and the spiral contacts 31 and 34. As a rule, when a disconnector is being switched on, it is desirable for the speed of the switching pin 36 to be as high as possible throughout the entire connection process, but the stepping of the connection movement, which would likewise be possible per se, is not used in the case of this electrical switching device, since it would physically be pointless.
This drive principle, which is used here for a disconnector and optimally matches the movement profile of the switching pin 36 to the physical characteristics to which disconnector switching processes are subject, can, of course, also be used, appropriately modified, for other switching devices and other switching processes. In this case, power circuit breakers having non-uniform contact movements can primarily be envisaged, and, in particular, it i8 al~o conceivable for different contact movements to be provided 21 ~39322 - 12 - 95tl33 depending on the switching operation to be carried out.
For example, when small inductive currents are being disconnected in the case of a puffer circuit breaker, the disconnection movement could take place so slowly that the blowing of the arc takes place sufficiently smoothly that the arc is prevented from turning off before the zero crossing, so that no overvoltages caused by the turning off can occur and there is therefore no need to provide protective measures against such overvoltages, the advantageous consequence being considerable reduction in the cost of the switching installation in which this power circuit breaker is used. In the case of power disconnection, the same puffer circuit breaker would, however, operate at a comparatively high contact speed in order to produce the necessary gas pressure for blowing out the arc in the shortest possible time in a conventional piston-cylinder arrangement.
The movement sequences of switching devices can advantageously be matched to the physical characteristics of the corresponding - switching operations in all areas relating to distribution of electrical power, that is to say at all voltage levels, in open-air and encapsulated switching installations as well as in DC and AC power supplies. The influences of different insulating and/or quenching media, for example of liquid or gaseous media, could also be taken into account in a very simple manner with respect to the optimal matching of the contact movement.
Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

LIST OF DESIGNATIONS

1 Housing 2, 3 Axes 5 4, 5, 6, 7 Openings 8, 9, 10, 11 Flanges 12 Insulator 13 Cast-in fitting 14 Conductor 10 15 Outer ring 16 Connecting flange 17 Adjacent housing 18 Cover flange 19 Connecting piece 15 20 Cover 21 Conductor 22 Connecting flange 23 Adjacent housing 24 Internal area 20 25 Viewing window 26 Angled connecting piece 27 Spacer 28 Contact support 29 Axis 25 30 Mating contact 31 Spiral contacts 32 Contact support 33 Axis 34 Spiral contacts 30 35 Moving disconnector contact 36 Switching pin 37 Contact tube 38 Insulating rod 39 Drive 35 40 Shield a, ~ Angles s Travel t Time v Speed A, B, C Regions

Claims

1. An electrical switching device having at least two contact supports (32, 28) which are arranged spaced apart on an axis (3), having at least one contact (switching pin 36) which moves along this axis (3) and, in the connected state of the switching device, electrically conductively bridges the distance between the at least two contact supports (32, 28), having a drive (39) which acts on the moving contact and is designed such that it can be driven by a superordinate control system, - wherein the at least one moving contact (switching pin 36) can be moved during at least one switching process at at least two different speeds, and - wherein at least one of the at least two speeds is optimally matched to the respective physical characteristics which govern the relevant switching process.

2. The electrical switching device as claimed in claim 1, - wherein an electric motor is provided as the drive (39).

3. The electrical switching device as claimed in claim 2, - wherein a speed-controlled DC motor is provided as the electric motor.

4. The electrical switching device as claimed in one of claims 1 to 3, - wherein a disconnector having a moving contact which is designed as a switching pin (36) is provided as the electrical switching device, the disconnection movement of the switching pin (36) being at different speeds in each of three regions (A, B, C).

5. The electrical switching device as claimed in claim 4, - wherein a maximum speed of more than 300 mm/s, but in particular 330 mm/s, is provided in the first region (A), - wherein a speed in the region around 50 mm/s is provided in the second region (B), which follows the first, and - wherein a speed in the region around 300 mm/s is provided in the third region (C), which follows the second region.

6. The electrical switching device as claimed in one of claims 1 to 3, - wherein a power circuit breaker is provided as the electrical switching device.

7. The electrical switching device as claimed in claim 6, - wherein the drive (39) is energized by the superordinate control system such that the at least one moving contact of the power circuit breaker moves, as a function of the present switching case, through a travel corresponding to this switching case at an appropriately matched speed or at at least two different speeds.

8. The electrical switching device as claimed in one of claims 1 to 3, - wherein a grounding disconnector, a rapid grounding device or a load disconnector is provided as the electrical switching device.

9. A method for operation of an electrical switching device having at least two contact supports (32, 28) which are arranged spaced apart on an axis (3), having at least one contact (switching pin 36) which moves along this axis (3) and, in the connected state of the switching device, electrically conductively bridges the distance between the at least two contact supports (32, 28), having a drive (39) which acts on the moving contact and is driven by a superordinate control system, - wherein the at least one moving contact (switching pin 36) moves during at least one switching process at at least two different speeds, and - wherein at least one of the at least two speeds is optimally matched to the respective physical characteristics which govern the relevant switching process.