EP0061992B1

EP0061992B1 - High-voltage gas-blast puffer type circuit-breaker

Info

Publication number: EP0061992B1
Application number: EP19820730040
Authority: EP
Inventors: Ernst Slamecka
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-03-30
Filing date: 1982-03-23
Publication date: 1986-11-20
Also published as: EP0061992A3; EP0061992A2

Description

This invention relates to a high-voltage gas-blast puffer-type circuit-breaker according to the precharacterizing features of claim 1.
Such a circuit-breaker is disclosed in the document DE-C-2741357.
In particular, major features needing further improvement are the following:
The nozzles exhibit a rather rudimentary shape, impairing thus the gas flow.
Both nozzles are made of electrically conductive material. This feature in particular brings about basically at higher rated voltages an unfavorable effect.
Speaking specifically, the extension of the axial distance between the nozzles on the one hand necessary for increasing the dielectric resistance to breakdown at higher rated voltages reduces, on the other hand, the velocity of the gas flow in the ring duct between the nozzles.
As a consequence, hot arc plasma may penetrate into the gas compression space and impair therein the dielectric quality of the quenching gas.
Concerning the gas compression system, only a simple single compression cylinder of constant diameter is used. The front cap and the inner bottom of it are engaged with a fixed and with a movable ringshaped compression piston respectively necessarily exhibiting the same inner and outer diameter.
Thus the gas compression rate is limited.
The fixed inner bottom of the gas compression cylinder is traversed by a gas pipe, ensuring the communication of the two gas compression chambers. Such a solution, however, implicates constructional expenditure.
The object of the present invention is to improve the afore mentioned circuit-breaker in the range described above.
According to the invention a high-voltage gas-blast puffer-type circuit-breaker comprises:

a fixed dual-blast nozzle arrangement, having two nozzles facing each other in a fixed axial distance;
the dual-blast nozzles, each ending in a gas flow absorbing volume, being temporarily surrounded by a movable single compression cylinder which is equipped with front cap and an inner bottom;
the cap and the inner bottom of the compression cylinder being engaged with a fixed and a movable compression piston respectively;
the fixed compression piston being traversed by a gas pipe mounted on said inner bottom of the movable compression cylinder;
separated contact pieces for carrying continuous and arc current respectively;
characterized by:
in the dual-blast nozzle arrangement the first nozzle is made of electrically conducting material and the second nozzle is made of electrically insulating material;
the movable compression cylinder being made of electrically insulating material bearing a
cylindrically shaped contact piece intended for carrying continuous current;
the arcing contact piece being connected to the movable contact piece in a mechanically rigid and electrically conducting manner.

Advantageous embodiments of the invention set out in claim 1 are to be found in the dependent claims 2 to 7.
An embodiment of a circuit-breaker in accordance with the present invention will now be described with reference to the accompanying drawings, of which:
Fig. 1 shows a longitudinal sectional view of an embodiment of a circuit-breaker constructed in accordance with the invention. The specific feature represents the stationary dual-blast nozzle arrangement with one nozzle made of electrically conductive material whereas the opposite nozzle consists of electrically insulating material. The circuit-breaker is illustrated in three switching positions: closed, arc quenching, open,
Fig. 2 shows a view similar to that of Fig. 1 but showing the embodiment improved by a dual- cylinder high-performance compression system characterized by a fixed and a movable piston. The circuit-breaker is illustrated in the closed and open positions,
Fig. 3 shows a preferred clicking system for the movable compression piston according to Fig. 2.
Referring to Fig. 1 the description will follow the substantial functional groups as there are: gas compression system, gas flow system, system for carrying the continuous and short time current, system for carrying the arc current, dielectric system and actuating system.

Gas compression system

The gas compression employed here is of single-acting type. It is realized in the volume 1 made up by the movable compression cylinder 3 with a cap 2 fixed at its front end and the fixed compression piston 4 at the other end. Further the walls of the volume 1 also comprise the external surfaces of the nozzles 5, 6, the pipe 7 for carrying one part of the down stream gas flow, the arcing contact tube 8 and the filling component consisting of the electrically conductive member 10b and at the front side thereof the electrically insulating member 10a.
Advantageously the compression piston 4 as well as the filler and the insulating nozzle 6 are mounted on the pipe 9 provided for carrying the other part of the down stream gas flow.
Between the- netallic part of the filler and the compression piston a movable flat ring 11 serves as a valve, in conjunction with a spring, however, being not shown here. Said valve closes the compression volume 1 when during an opening operation the inside pressure exceeds the outside pressure.
During a closing operation the valve opens thus making possible a refilling of the volume 1.
The pressure of the arc quenching gas may be controlled by the overlapping length between the arcing contact tube 8 and the electrically conductive nozzle 5.

Gas flow system

The gas flow starts during an opening operation as soon as the arcing contact tube 8 separates from the inside surface of the electrically conductive nozzle 5.
Provided a voltage is applied to the terminals of the circuit-breaker an electric arc is initiated between the two electrodes immediately within the nozzle space.
This represents a basic progress compared with other existing solutions mentioned previously.
During a first time interval after the arcing contact separation the gas flow can make use only of the full cross-section of the electrically conductive nozzle. At the other side the gas flow is controlled by the smaller cross-section of the arcing contact tube being shaped like a nozzle, too.
As a result of the reduced gas flow in the case of switching small inductive currents the arc current remains stable until shortly before its natural zero crossing point.
Switching overvoltages being proportional to the value of the instable (chopped) current are thus limited automatically.
The interruption of short-circuit currents needs a longer arc length due to the increased input of thermal energy into the gap. In this case the reduced gas flow offers the advantage of a reduced arc power due to reduced arc cooling until the minimum arc length. Beyond this arc length the throat of the insulating nozzle is cleared by the retracting arcing contact enabling its full participation in the arc quenching process. Such an arc quenching position is illustrated in the figure.
It should be emphasized here that due to the combination of an electrically conductive nozzle with a nozzle being electrically insulating the gap length between the nozzles and the diameter of them can be dimensioned taking into account only the gas flow conditions being not influenced by the dielectric conditions and vice versa. Furthermore it is well known that a stationary symmetrical dual-blast nozzle arrangement represents the most effective means for the de-ionization of the arc plasma.
The tube 8 of the movable arcing contact is connected by means of the ribs 14 with the sliding and guiding cylinder 15 transmitting at the same time the current to the contact fingers 24. From the electrically conductive nozzle 5 the gas flows through the pipe 7 into the adjacent support pipe 16. This pipe is connected with the end flange of the porcelain housing, not visible in the drawing.
The quenching gas escaping the electrically insulating nozzle 6 passes first into the pipe 9, and further, not visible in the drawing, into the gear box.
Additionally the quenching gas can escape through longitudinal slots 18 in the pipe 9. If necessary a screening cylinder 20 can be provided, for protecting the surface of the porcelain housing 17 from hot gases.

Contact system for carrying the continuous current and the short time current

This contact system consists of two fixed contact pieces and a movable contact bridge. One of the fixed contacts is realized by elastic contact fingers on the support 21.
The other fixed contact piece is represented by the down stream gas pipe 9.
The movable contact bridge between the two fixed contacts pieces is made up as follows: On the outer surface of the compression cylinder 3 of insulating material a copper tube 23 is shrink fitted. At the one end of the contact tube the contact fingers are resting.
The other end of the contact tube is connected electrically with the movable contact fingers 24 by means of the structural component 19. Due to this arrangement of the contact system outside the compression cylinder 3 it is protected against all sorts of influences of the arc and hot gases.

Contact system for carrying the arc current

During the separation of the contact pieces for carrying the continuous and short time current in the course of a current interruption they are paralleled by the arc contact system. This contact system consists of the surface of the throat of the electrically conductive nozzle 5 and the outer surface of the movable contact tube. 8. Where necessary the transition of the current between the arc contacts can easily be further improved by application of contact ribs 26 inside of the nozzle. The influence of such ribs on the gas flow is small.
After building up an appropriate gas pressure in the volume 1 and commutation of the current the arcing contacts separate. Here again the arcing contact system exhibits the advantage that the arc drawn is immediately exposed to the gas flow preparing its interruption.
Thus, any time delay needed elsewhere for moving the arc from the outer surface of the nozze 5 into its throat is avoided.
From the arcing contact tube 8 the current flows through the ribs 14 to the sliding cylinder 15. This cylinder is connected by means of other ribs fixed on its surface with the structural component 19 providing a further current path to the contact fingers 24 and gas pipe 9.

Dynamic dielectric system

Immediately after the separation of the arcing contacts the dynamic dielectric system consists of the stationary electrically conductive nozzle 5 and the arcing contact tube 8.
With increasing contact distance the influence of the field grading electrodes becomes more and more relevant. At the side of the fixed contact pieces the ring electrode 28 is attached to the rim of the cylinder 25. At the side of the movable contact pieces the arcing contact 8 is electrically screened by the ring electrode 29 attached to one end of the contact tube 23 on the compression cylinder 3.
With further increasing contact distance the influence of the ring electrode 29 on the electric field disappears, when the influence of the large sized electrode represented by the metallic filler 10b becomes dominant.

Static dielectric system

Belonging to the open position of the circuit-breaker this system is characterized by the electrically conductive nozzle 5 with the appropriate field grading electrode 28 at one side of the open gap and the metallic filler 10b at the other side. The optimization in particular of the static dielectric system can be implemented independently of the optimization of the gas flow system.
This feature in combination with electrodes of large surface at both sides of the gap may be deemed as a considerable progress in the technique of stationary dual-blast nozzle arrangements.

Actuating system

The actuating energy for the movable contact pieces and compression cylinder is transmitted from the operating mechanism through a gearing-both not shown in the figure-by means of two rods 30 being pivotally fixed at 31.

Housing of the active parts for current interruption

The example given describes the interrupting chamber of an outdoor life-tank type circuit-breaker. Accordingly the housing 17 is realized by a porcelain vessel having at both ends connecting flanges, not shown in the drawing.
At the side of the fixed contact pieces on the flange is mounted a cap providing an expansion volume for the hot gas and serving outside the terminals to connecting the circuit-breaker to the bus conductor. At the side of the movable contact pieces the porcelain cylinder is connected by its flange to the gear box of the circuit-breaker in the case of a two- or three-unit per pole type.
Referring to Fig. 2 the single-acting gas compression system shown in Fig. 1 has now been improved by the introduction of a dual- acting gas compression system of high performance. As before the gas compression being decisive for the current interruption is realized in the first compression volume 1. It surrounds the dual-nozzle arrangement during the precompression and arcing period.
In the same manner as with the embodiment shown in Fig. 1 to the compression cylinder 3, being called here the first one, is attached a contact tube 23. However, this contact tube now makes up additionally together with the compression cylinder 3 a channel 32 for the gas communication between the first 1 and the second 33 gas volume. A check valve 42 controls the gas flow through the openings 38 being possible only in the direction from the volume 33 to the volume 1.
In the first time interval of an opening operation the movable compression piston 35 remains held by means of spring loaded balls 40 and a notch round the surface of tha gas-pipe 9. Another check valve 43 prevents the gas from escaping during an opening operation and enables the refilling of the volume 33 to be done during a closing operation.

Run of a gas compression

The actuating rods 30 move the contact pieces 23 and 8 in connection with the compression cylinders (3, 34) into the opening direction. Thereafter the gas pressure rises in both volumes 1, 33, however, with different rates of rise. Due to its comparatively smaller height the rate of rise of the gas pressure in the volume 33 is superior to that in the volume 1. Hence a flow of gas is forced from volume 33 into the volume 1.
In the example as just described the rate of precompression is about 1.7. Inspite of this comparatively high compression rate the total stroke of the compression and contact system is only 180 mm.
If necessary a further increase of the compression rate would be easily feasible by increasing only slightly the outside diameter of the second compression cylinder (34). Alternatively in this way, with an unchanged compression rate, the time needed for it can be reduced appreciably. This again results in a very small breaking time - unsurpassed by the conventional SF₆ puffer type circuit-breakers.
Furthermore the compression system according to the invention can be easily designed to provide quenching gas even after the release of the gas flow into the nozzles thus compensating the pressure drop.
This feature is of high importance for restrike free switching of capacitive currents at very high voltages.
In the course of the opening operation a volume is produced between the fixed piston 4 and the cap 36 on the cylinder 34. For the ventilation of this volume holes 39 are provided at the end of the wall of the compression cylinder 3.
Referring now to Fig. 3, there is illustrated a favourable variant of the notching system for the compression piston 35. Following this design the movable compression piston is mounted on the tips of three rods 44 being distributed along the circumference of a circle. At the other end each rod dips into a ring of elastic fingers 46 catching a notch 47 round the rod surface.
By means of a tube 48 surrounding these fingers their resilience can be easily adjusted.
Thus the piston 35 remains fixed until the maximum gas pressure is reached. Then the cap 36 takes along the piston 35 into the open position.

Claims

1. A high-voltage gas-blast puffer-type circuit-breaker comprising:

(a) a fixed dual-blast nozzle arrangement, having two nozzles (5, 6) facing each other at a fixed axial distance;

b) the dual-blast nozzles (5, 6) each ending in a gas flow absorbing volume, being temporarily surrounded by a movable single compression cylinder (3) which is equipped with a front cap and an inner bottom;

c) the cap and the inner bottom of the compression cylinder (3) being engaged with a fixed and a movable compression piston (4, 35) respectively;

d) the fixed compression piston (4) being traversed by a gas pipe mounted on said inner bottom of the movable compression cylinder (3);

e) separated contact pieces for carrying continuous and arc current respectively; characterized by:

f) in the dual-blast nozzle arrangement the first nozzle (5) is made of electrically conducting material and the second nozzle (6) is made of electrically insulating material;

g) the movable compression cylinder (3) being made of electrically insulating material bearing a cylindrically shaped contact piece (23) intended for carrying continuous current;

h) the arcing contact piece (8) being connected to the movable contact piece (23) in a mechanically rigid and electrically conducting manner.

2. Circuit-breaker according to claim 1, characterized by:

the compression piston (4) being fixed on the gas pipe (9) next to the second nozzle (6) made of electrically insulating material.

3. Circuit-breaker according to claim 1, characterized by:

a first piston-cylinder structure (3, 4) and a second piston-cylinder structure (34, 35), both being mechanically interconnected, forming two compression spaces (1, 33) having the same inner diameter and different outer diameters.

4. Circuit-breaker according to claim 3, characterized by:

the two compression spaces (1, 33) communicating pneumatically with each other, for which purpose a pneumatical communication structure (32) being arranged outside of the fixed compression piston (4).

5. Circuit-breaker according to claim 4, characterized by:

the communication structure (32), connecting pneumatically the two compression spaces (1, 33), being arranged between the outer wall of the compression cylinder (3) and the inner wall of the tube shaped contact piece (23).

6. Circuit-breaker according to claim 5, characterized by:

in said pneumatical communication structure (32) a check valve being positioned.

7. Circuit-breaker according to claim 3, characterized by:

the clear distance between the cap (36) on the second compression cylinder (34) made of electrically conducting material and the second catchable compression piston (35) being larger compared with the overlapping length between the movable arcing contact piece (8) and the first nozzle (5) made of electrically conducting material.