DE29709084U1 - Gas pressure switch - Google Patents

Description

General power of attorney: 4.3,5.-No.270/97AV

Title:

0122126

Pressure gas switch

21.05.1997 sch / lbe

DESCRIPTION

The invention relates to a gas pressure switch with two contact pieces that can move relative to one another.

Such a gas pressure switch is described in the article Toda, H. et al.: Development of 550 kV 1-Break GCB {Part II)-

Development of prototype;

in: IEEE Transactions on Power Delivery, Vol. 8, No. 3,

July 1993, pp. 1192 - 1198

known. The displacement of one contact piece is transferred to the other via a lever mechanism. For this purpose, two reversing levers are provided symmetrically to the central axis of the gas pressure switch, to which two rods are each attached in a rotating manner. Both contact pieces are symmetrically connected to opposite ends of the reversing levers via the rods. The lever mechanism with the rods must contain electrical insulation, as it is connected to both contact pieces and thus bridges the switching gap. Insulation and electrical shielding are complex. The reversing levers inevitably protrude laterally beyond the circumference of the switching chamber; this results in a fairly

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large diameter.

Encapsulating the gas pressure switch with a porcelain insulator, as is usual for outdoor switches, would be very expensive with such a large diameter. The mechanism is therefore more suitable for metal-encapsulated gas-insulated gas pressure switches. The known gas pressure switch works according to the conventional autopneumatic principle. This means that the pressure required to extinguish the arc, even at high currents, is mainly generated by a compression device in the switching chamber. Accordingly, the known gas pressure switch has a compression device with the help of which insulating gas is compressed during a break-out process by the movement of a compression cylinder against a fixed piston and is then used to extinguish an arc.

The compression of the insulating gas to the required pressure is only possible if the compression cylinder and the contact piece connected to it are moved at a relatively high minimum speed. Consequently, the switch drive must be dimensioned for this speed. The minimum speed increases as the diameter of the compression device decreases. For economic reasons, as already mentioned, efforts are made to keep the diameter as small as possible.

EP 0 313 813 also discloses a high-voltage switch with two contact pieces that move against each other, of which only one is directly driven. An insulating nozzle with a conductive shield that coaxially surrounds it is attached to this contact piece. This carries two parallel toothed racks, each of which interacts with an associated gear wheel.

Each of the two gears engages on the one hand with one of the two racks and on the other hand with another rack to which the contact piece not connected to the insulating nozzle is coupled. The gears cause a reversal of the

Direction of movement, so the contact pieces always move in the opposite direction. The gears must be designed for very high loads, as they are suddenly exposed to high speeds during switching off processes.

The high-voltage switch works with a blow-out device for the arc. This means that decomposition products, which the arc generates with its high energy, are distributed very far inside the switch and thus also reach the rack gear. This reduces the reliability of the high-voltage switch in the event of several years of operation.

The fact that the insulating nozzle has a shield coaxially surrounding the insulating nozzle at its end facing the second contact piece has the disadvantage that this shield, if it is to fulfil its function, must be arranged approximately in the same plane as the electrodes.

The electrodes control the electric field in the open circuit. The flash distance along the outer wall of the insulating nozzle cannot therefore be made significantly larger than the flash distance in SF6.

The lay distance is the distance between two conductive parts along a thread that is stretched along the shortest path between these parts.

The invention is based on the object of creating a low-maintenance and reliable pressure gas switch with which a high contact separation speed with low drive energy is achieved during a switching-off process.

This object is achieved according to the invention by a pressure gas switch according to claim 1.

Since the rotation axis of each reversing lever is in the central axis of the pressure gas switch, it can be manufactured with the same diameter as conventional pressure gas switches. This is particularly

advantageous if it is used as an outdoor switch and is encapsulated gas-tight with a porcelain insulator. The cost of a porcelain insulator increases considerably with its diameter. The lever mechanism is a particularly simple and robust means of causing the contact pieces to move in opposite directions. Since the force is transmitted via the insulating nozzle, the lever mechanism itself does not need to contain any insulating elements (e.g. insulating rods).

The pot-shaped contact unit body according to claim 2 ensures a dielectric shielding of the reversing lever with its swivel joints against the interruption point.

By means of the force transmission element on the insulating nozzle according to claim 3, the pivot point of the first rod attached to the insulating nozzle is guided in a straight line.

Preferably, the force transmission element, which is located between the insulating nozzle and the deflection lever with respect to the force flow, is arranged at a greater distance from the opposite contact body inside the contact unit body according to claim 5. As a result, the metal connecting elements of the force transmission element are electrically shielded. These important transmission elements can thus be optimally designed without regard to the electrical field strength. Further advantages of this design are:

1. The flash distance along the outside wall of the nozzle can be significantly greater than the flash distance in SF6. This is important because the dielectric strength on the insulating surface on the outside of the nozzle can be reduced by contamination and foreign particles compared to SF6. This already applies to the new condition, but even more so to many years of operation.

2. The arc distance along the inner wall of the nozzle is also increased to a similar extent. This inner wall of the nozzle is subjected to great stress due to the arc stress during operation.

3. This also ensures that the dielectric stress on the solid insulating material of the nozzle is greatly reduced. This is important for long-term trouble-free operation, because damage can accumulate in the solid insulating material.

The polytetrafluoroethylene ring(s) according to claim 8 ensure good, maintenance-free sliding of the force transmission element on the inner wall of the hollow cylinder.

If the power supply has the shape of a tube and the reversing lever is housed in this tube, this is dielectrically shielded using simple means and in a particularly effective way. It is very easy to provide additional protection for the lever mechanism against decomposition products. A tubular power supply can be used that is used in conventional pressure gas switches (for example in a pressure gas switch according to page 4 in the company brochure "SF6 circuit breaker with spring energy drive. 72.5-170 kV", A22 V.7.104/0993 DE of AEG Aktiengesellschaft, D-34123 Kassel-Bettenhausen). The diameter of the pressure gas switch disengaged with a lever mechanism therefore remains unchanged compared to conventional pressure gas switches.

The encapsulation according to claim 12 protects the plain bearings in particular against the penetration of decomposition products that arise under the influence of the arc energy. This makes such a lever mechanism more reliable than a gear mechanism with gears in terms of long-term use.

A lever mechanism made of metal according to claim 13 is characterized by its stability; this is particularly advantageous in the case of the two {long) rods which are attached to the reversing lever.

If both contact pieces move in opposite directions to each other by means of the lever mechanism, the

Relative speed between them is greater than the speed at which the drive sets one of the two contact pieces in motion. In this way, a high contact separation speed is achieved with little drive energy.

This is particularly useful in the case of gas pressure switches according to claim 14, which operate according to the pressure chamber principle. In such switches, the arc provides the energy for blowing out the arc when switching off large currents. To do this, insulating gas heated by the arc first penetrates into a pressure chamber. Close to the current zero crossing, this heated insulating gas then triggers an insulating gas flow from the pressure chamber into the area between the contact pieces. A compression device is only required for interrupting small currents, but this only has to generate low extinguishing pressures and can be moved at a correspondingly low speed. For arc blowing, only a very low drive speed is therefore required for such high-voltage switches. A high contact breaking speed is also necessary for such switches for interrupting capacitive currents without re-ignition.

A further reduction in the drive energy can be achieved by dividing the speed differently between the two contact systems in accordance with claim 15. In this case, it is advantageous to select a higher speed for the contact system that has a lower mass. When dividing the speed, the following must be taken into account: the stroke of the other contact system also decreases with the speed. Both variables determine the compression in the compression device that is coupled to the contact system. This results in an additional condition for optimizing the drive energy.

With the switch type according to the invention, a high contact separation speed is achieved during a switch-off process with low drive power. The energy for the switch-off is significantly reduced, while still a fairly

high breaking capacity is achieved. The advantages of the lever mechanism according to the invention are therefore particularly evident in switches based on the pressure chamber principle.

Further preferred embodiments of the invention are characterized in the remaining subclaims.

In the following, an embodiment of the invention is described in more detail with reference to two drawings from which further details and advantages emerge.

Show it

Fig. 1 a gas pressure switch in the off position in section,

Fig. 2 the pressure gas switch from Fig. 1 in the switched-on position and

Fig.3 shows another embodiment of the gas pressure switch of Fig. 1 and 2.

Fig. 1 shows a longitudinal section through a vertical switch pole of a gas pressure switch in the off position.

The gas pressure switch is filled with insulating gas, for example SF ₆ , and is surrounded on the sides by a tubular insulator 1. Regarding the switch type, it is an outdoor switch.

The gas pressure switch has two contact pieces 2 and 3 that can be moved in opposite directions along its central axis M, which form an interruption point. The contact piece 2 is a contact pin and is attached to the bottom of a pot-shaped contact unit body 4.

The contact unit body 4 surrounds the contact piece 2 and the central axis M of the gas pressure switch coaxially and has its

Opening in the direction of the interruption point, namely downwards.

The contact unit body 4 extends telescopically into a tubular part of a power supply 5 (for the contact piece 2) that is open in the direction of the interruption point and can be moved out of it. The power supply 5 also coaxially surrounds the central axis M of the gas pressure switch. Within this power supply 5, a deflection lever 6 is arranged above the contact unit body 4, the axis of rotation 17 of which intersects the longitudinal axis of the gas pressure switch at a right angle.

The reversing lever 6 has two lever arms, at the outer ends of which a rod 7, 8 is rotatably attached. Both rods 7, 8 protrude downwards. The rod 7 is rotatably attached at its lower end in the upper end area of an insulating nozzle 9. The insulating nozzle 9 laterally surrounds the ends of the contact piece 3 and the contact piece 2 facing each other.

The insulating nozzle 9 is attached to the upper end of a hollow cylindrical metal contact body 10, which coaxially encloses both the central axis M of the gas pressure switch and partially the contact piece 3.

This contact piece 3 is a tulip contact which, when the pressure gas switch is switched on, touches the contact piece 2 at its end area on the circumference.

The contact piece 3 is attached to the bottom of the contact body 10 and is electrically connected to it.

There is a small gap between the contact piece 3 and the insulating nozzle 9, which creates a connection between the area between the contact pieces 2 and 3 (switching gap) on the one hand and the interior of the contact body 10 on the other hand.

The pressure gas switch works according to the pressure chamber principle.

The interior of the contact body 10 is closed by a base at the end facing away from the point of interruption. The interior of the contact body 10 serves as a pressure chamber 19. During a switching-off process, insulating gas heated by the arc initially penetrates into this pressure chamber 19. In the vicinity of the current zero crossing, the gas pressure in the switching gap decreases and the insulating gas temporarily stored in the pressure chamber 19 flows through a narrow point in the insulating nozzle 9 into the area of the switching gap and blows the arc.

At low breaking currents, the arc is blown out by means of a compression device consisting of the front part of the power supply 14, which is designed as a fixed cylinder, and a movable piston 21, which is also the bottom of the pressure chamber 19. The movable piston 21 and the cylinder enclose a compression chamber 20.

When the arc is blown out, the extinguishing gas flows from the compression chamber 20 via check valves 23 to the pressure chamber 19 and from there to the insulating nozzle 9. Overpressure valves 24 limit the pressure in the compression chamber 20 and thus relieve the load on the drive 11.

When switched on, check valves 25 release the gas flows into the compression chamber 20.

By means of a motor drive 11, which is arranged in the lower part of the gas pressure switch, a drive rod 12 arranged vertically in the central axis M of the gas pressure switch is moved upwards during a switch-on process and downwards during a break-off process. The drive rod 12 continues in the direction of the interruption point in a blow-back tube 26. The drive rod 12 is coaxially surrounded by a tubular insulator 13. The end of a power supply 14 for the tulip contact piece is connected to the insulator 13 at the top.

The power supply 14 coaxially surrounds the central axis M of the

Pressure gas switch and is tubular, with its lower end extending horizontally outwards in a plate shape. There are electrical connection options to the outside of the pressure gas switch. Inside, in the plate-shaped end of the power supply 14, there is an opening for the drive rod 12. This opening corresponds to the inner cross-sectional area of the tubular part of the power supply.

The insulator 1 is attached to the plate-shaped end of this power supply 14. The transitions from the insulator 1 and from the insulator 13 to the plate-shaped end of the power supply 14 are each designed to be gas-tight.

The contact body 10 can be moved telescopically into and out of the power supply 14 during switching operations. Via spring contacts that are attached to the upper edge of the power supply 14, there is a conductive contact between the power supply 14 and the contact body 10 with the contact piece 3 in every switch position.

The contact body 10 with the insulating nozzle 9 is attached to the end of the drive rod 12 facing away from the drive 11. The insulating nozzle 9 has a plate-shaped force transmission element 15 made of metal at its end facing away from the contact piece 3, which extends radially from the insulating nozzle 9 to the inner wall of the cup-shaped contact unit body 4. There is a sliding connection to the inner wall of the contact unit body 4 with one or more rings made of PTFE. In this way, the insulating nozzle 9 is guided with the rod 7 rotatably attached to it.

At the same time as the rod 7, the other rod 8 attached to the reversing lever 6 moves. Its lower end is attached to the bottom of the contact unit body 4 via a swivel joint, on the side facing away from the point of interruption.

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The contact unit body 4 is guided through the tubular part of the power supply 5. This also ensures a straight-line guide of the force transmission element 15, which in turn is slidably mounted within the contact unit body 4. Spring contacts 22 on the inner wall of the power supply 5 ensure a conductive contact between the power supply 5 and the outer wall of the (metal) contact unit body 4.

The power supply 5 passes into a cover at the top, which seals the insulator 1 gas-tight at the top and on which electrical connection options are available on the outside.

During a switch-on process, the drive rod 12 with the blow-back tube 26 and the contact body 10 is moved upwards, while the contact unit body 4 is moved downwards.

When a certain stroke is reached, the contact pieces 2 and 3 first come into contact with each other. During the further switching-on movement, the rated current contacts 16, which are attached in the lower area of the contact unit body 4, come into contact with the outer wall of the contact body 10 and enable a current to flow via the upper current lead 5, the contact body 10 and the lower current lead 14. The (rated) current also flows via the above-mentioned elements in the switched-on position.

Fig. 2 shows the gas pressure switch in the switched-on position. The individual parts are provided with the same reference numerals as in Fig. 1. In comparison with this figure, it can be clearly seen that the reversing lever 6 is now inclined in the other direction.

During a switch-off process, the electrical connection between the contact body 10 and the nominal current contacts 16 is first broken. The current then commutates to the contact pieces 2 and 3.

As the switching-off movement continues, these contact pieces 2 and 3 also separate and an arc forms between them.

The relative speed between the contact body 10 and the contact unit body 4 is the sum of the absolute speed of the contact body 10 and the absolute speed of the contact unit body 4.

For the interruption of capacitive currents without re-ignition, the relative speed of the "contact systems" (contact body 10/contact piece 3 and contact unit body 4/contact piece 2) to one another is crucial. On the other hand, the absolute speed of the compression device is of secondary importance in switches that work according to the pressure chamber principle. With the described pressure gas switch, it is therefore possible - while maintaining the same breaking capacity - to significantly reduce the absolute speed of the contact body 10. The drive therefore requires significantly less energy.

Fig. 3 shows a gas pressure switch which essentially corresponds to the gas pressure switch shown in Figs. 1 and 2 and described above. Corresponding parts are therefore provided with the same reference numerals.

The difference to the gas pressure switch of Fig. 1 and 2 is that the gas pressure switch of Fig. 3 is provided with a reversing lever 27, the two arms 28, 29 of which are of different lengths. In particular, the lengths of the two arms 28, 29 are 2 to 3. The rod 8, which is coupled to the contacts 2, 16, is connected to the longer arm 29, and the rod 7 is connected to the shorter arm 28. This means that the speed of the contacts 2, 16 is greater.

List of reference symbols

1 insulator

2 (second) contact piece

3 (first) contact piece

4 Contact unit body

5 Power supply

6 reversing lever

7 (first) bar

8 (second) bar

9 Insulating nozzle

10 contact bodies

11 Drive

12 Drive rod

13 Insulator

14 Power supply

15 Power transmission element

16 rated current contacts

17 Rotation axis

18 Spring contact

19 Pressure chamber

20 Compression chamber

21 (movable) piston

22 Spring contact

23 Check valve

24 Pressure relief valve

25 Check valve

26 Blowback pipe

27 reversing lever

28 short arm

29 long arm

Claims (17)

PROTECTION CLAIMS 1. Gas pressure switch with the following features: the gas pressure switch has at least one interruption point; each interruption point has a first and a second contact piece (3, 2); the contact pieces (2, 3) of at least one interruption point are coupled via a lever mechanism with at least one reversing lever (6, 27) having two lever arms; the contact pieces (2, 3) of this The interruption point(s) can be moved in opposite directions along the central axis (M) of the gas pressure switch by means of a single drive {11). an insulating nozzle (9) arranged coaxially to the central axis (M) is attached to the first contact piece (3) of said interruption point(s); the axis of rotation of the reversing lever(s) (6, 27) crosses the central axis (M) of the gas pressure switch at a right angle; a rod (7, 8) is attached to each of the lever arms via a swivel joint; the first rod (9) is rotatably connected to the insulating nozzle (6) and the second rod (8) is rotatably coupled to the second contact piece (2). 2. Gas pressure switch according to claim 1, characterized by the following features: the second contact piece (2) is fixed to the bottom of a cup-shaped contact unit body (4) which coaxially surrounds it; the contact unit body (4) is attached to the second rod (8) via a swivel joint; its open end faces the interruption point; it is arranged coaxially to the central axis (M) of the gas pressure switch; in its bottom there is an opening through which the first rod (7) is passed; the contact unit body (4) is electrically conductive at least on its outer wall, the outer wall is electrically conductively connected to the second contact piece (2); it is connected via at least one sliding contact to a fixed power supply (5) for the second contact piece (2). 3. Pressure gas switch according to claim 1 or 2, characterized by the following features: a single- or multi-part force transmission element (15) is attached to the insulating nozzle (9); the force transmission element (15) extends from the insulating nozzle (9) radially to the inner wall of the contact unit body (4); it slides on the inner wall of the contact unit body 4. Gas pressure switch according to claim 3, characterized in that the force transmission element (15) has webs which engage in grooves of the insulating nozzle (9). 5. Gas pressure switch according to one of the preceding claims, characterized in that the force transmission element (15) is arranged within the contact unit body (4) such that the striking distance along the outer wall of the insulating nozzle (9) in the off position is greater than the striking distance in the insulating gas. 6. Pressure gas switch according to claim 5, characterized in that the edge of the contact unit body (4) facing the interruption point projects beyond the force transmission element (15) by a certain length in the direction of the interruption point in the off position. 7. Gas pressure switch according to claim 6, characterized in that the length is at least 2 cm. 8. Gas pressure switch according to one of the preceding claims, characterized in that the Energy transmission element (15) is guided on its outer circumference with one or more rings made of polytetrafluoroethylene (PTFE) in the contact unit body (4). 9. Gas pressure switch according to one of the preceding claims, characterized by the following features: the power supply (5) for the second contact piece (2) has, at least in its part facing the point of interruption, the shape of a tube aligned coaxially to the central axis (M); it laterally encloses the deflection lever (6); the sliding contact is an electrically conductive, spring-loaded element attached to the power supply; the contact unit body (4) can be moved telescopically into and out of the power supply (5). 10. Gas pressure switch according to one of the preceding claims, characterized by the following features: the first contact piece (3) is attached to the bottom of a hollow cylindrical contact body (10); the contact body (10) surrounds the contact piece (3) coaxially; the insulating nozzle (9) is attached to the end of the contact body (10) facing the interruption point; the insulating nozzle (9) extends in the longitudinal direction from the contact body (10) in the direction of the interruption point; the contact body (10) is electrically conductive at least on the lateral outer wall; it is always provided with a fixed power supply (14) electrically connected. 11. Gas pressure switch according to claim 10, characterized by the following features: the power supply (14) has the form of a tube arranged coaxially around the central axis (M); the contact body (10) can be telescoped out of and into the power supply (14); a spring contact (18) is attached to the power supply (14); the spring contact (18) touches the outer wall of the contact body in all switch positions (10) . 12. Gas pressure switch according to one of the preceding claims, characterized in that the rotary joints on the reversing lever (6) and on the rods (7, 8) are encapsulated plain bearings. 13. Gas pressure switch according to one of the preceding claims, characterized in that the deflection lever (6) and the rods (7, 8) are made of metal. 14. Pressure gas switch according to one of the preceding claims, characterized in that it is a switch operating according to the pressure chamber principle. 15. Gas pressure switch according to one of the preceding claims, characterized in that the two lever arms (28, 29) of the deflection lever (27) have different lengths. 16. Gas pressure switch according to claim 15, characterized in that the ratio of the lengths of the two lever arms (2 8, 29) is approximately 2 to 3. 17. Gas pressure switch according to claim 15 or 16, characterized in that the longer arm (29) is coupled to the second contact piece (2).