Electrical medium or high voltage switching device

Abstract

An electrical switching device for medium or high voltage circuits having at least a nominal contact arrangement, wherein the nominal contact arrangement includes at least a first nominal contact including a plurality of contact fingers forming a finger cage concentric with respect to a longitudinal axis, wherein the contact fingers are separated from one another by empty slots extending up to a free end of the contact fingers. The empty slots include first and second empty slots, wherein the second empty slots are shorter than the first empty slots, and wherein the contact fingers are grouped in groups, with the contact fingers of each group being separated by second empty slots and the contact fingers of adjacent groups being separated by first empty slots.

Claims

1. An electrical switching device for medium or high voltage circuits comprising: a chamber enclosed by an enclosure which is cylindrical around a longitudinal axis, at least one nominal contact arrangement, wherein the nominal contact arrangement comprises: at least one first nominal contact comprising a plurality of contact fingers forming a finger cage concentric with respect to the longitudinal axis, wherein the contact fingers are separated from one another by empty slots extending up to a free end of the contact fingers, and at least one mating second nominal contact, the at least one second nominal contact is tube-shaped, wherein at least one of the nominal contacts is movable parallel to the longitudinal axis and cooperates with the other nominal contact for closing and opening the electric switching device, the empty slots having first and second empty slots, wherein the second empty slots are shorter than the first empty slots, and wherein the contact fingers are grouped in groups, with the contact fingers of each group being separated by the second empty slots and the contact fingers of adjacent groups being separated by the first empty slots; wherein each group comprises at least two contact fingers, and wherein the contact fingers are formed by a tubular metal section, wherein the first empty slots and the second empty slots extend from a first end into the tubular metal section, and wherein the contact fingers are interconnected at a second end of the tubular metal section.

2. The electrical switching device according to claim 1, wherein each contact finger is adjacent to at least one of the second empty slots.

3. The electrical switching device according to claim 1, wherein the groups each have the same number of contact fingers.

4. The electrical switching device according to claim 1, wherein a total number of the contact fingers is not a prime number.

5. The electrical switching device according to claim 1, wherein all of the second empty slots have the same length.

6. The electrical switching device according to claim 1, wherein the second empty slots are shorter than the first empty slots by at least 50%.

7. The electrical switching device according to claim 1, wherein the contact fingers are elastically deformed in a radial direction upon closing the electrical switching device.

8. The electrical switching device according to claim 1, being an earthing switch, a fast-acting earthing switch, a disconnector, a combined disconnector and earthing switch, a load break switch, a circuit breaker, or a generator circuit breaker.

9. The electrical switching device according to claim 1, wherein each group comprises at least three contact fingers.

10. The electrical switching device according to claim 1, wherein each contact finger extends linearly.

11. The electrical switching device according to claim 1, wherein the second empty slots have different lengths.

12. The electrical switching device according to claim 11, wherein a largest length of the second empty slots exceeds a smallest length of the second empty slots by at least 20%.

13. An electrical switching device for medium or high voltage circuits comprising: a chamber enclosed by an enclosure which is cylindrical around a longitudinal axis, at least one nominal contact arrangement, wherein the nominal contact arrangement comprises: at least one first nominal contact comprising a plurality of contact fingers forming a finger cage concentric with respect to the longitudinal axis, wherein the contact fingers are separated from one another by empty slots extending up to a free end of the contact fingers, and at least one mating second nominal contact, wherein at least one of the nominal contacts is movable parallel to the longitudinal axis and cooperates with the other nominal contact for closing and opening the electric switching device, the empty slots having first and second empty slots, wherein the second empty slots are shorter than the first empty slots, wherein the contact fingers are grouped in groups, the contact fingers within the same group being separated by the second empty slots, and wherein the contact fingers that are from different groups and that are adjacent to one another are separated by the first empty slots; wherein each group comprises at least two contact fingers; wherein the contact fingers are formed by a tubular metal section, wherein the first empty slots and the second empty slots extend from a first end into the tubular metal section, and wherein the contact fingers are interconnected at a second end of the tubular metal section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further embodiments, advantages and applications of the invention result from the dependent claims and from the following description of the figures.

(2) FIG. 1 shows a partial sectional view of a simplified basic embodiment of a high voltage circuit breaker;

(3) FIG. 2 shows a detailed view, in radial direction, of three contact fingers of a finger cage of the high voltage circuit breaker of FIG. 1 according to the prior art; and

(4) FIG. 3 shows a detailed view, in radial direction, of two groups of contact fingers of the finger cage of the high voltage circuit breaker of FIG. 1 according to one embodiment of the invention.

(5) FIG. 4 shows a detailed view, in radial direction, of two groups of contact fingers of the finger cage of the high voltage circuit breaker of FIG. 1 according to another embodiment of the invention.

(6) FIG. 5 shows a perspective view of contact fingers of the finger cage of the high voltage circuit breaker of FIG. 1 according to one embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(7) The invention is described for the example of a high voltage circuit breaker, but the principles described in the following also apply for the usage of the invention in other switching devices, e.g. of the type mentioned in the Background-section, such as in an earthing switch, fast-acting earthing switch, disconnector, combined disconnector and earthing switch, load break switch, generator circuit breaker, and generally in any switch. The most preferred use is in switches for high voltage and medium voltage.

(8) FIG. 1 shows a partial sectional view of a simplified basic embodiment of a high voltage circuit breaker 1 in a closed configuration. In FIG. 1 partial sectional view means that only a part of the upper half of the circuit breaker is shown, for reasons of clarity. The device is rotationally symmetric about a longitudinal axis z. Only the elements of the circuit breaker 1 which are related to the present invention are described in the following, other elements present in the figures are not relevant for understanding the invention and are known by the skilled person in high voltage electrical engineering.

(9) A closed configuration as used herein means that nominal contacts of the circuit breaker are closed and are thus conducting a nominal current.

(10) The circuit breaker 1 comprises a chamber enclosed by a shell or enclosure 5 which normally is cylindrical around the longitudinal axis z. It further comprises a nominal contact arrangement formed by a first nominal contact comprising a plurality of contact fingers 3a, of which only one is shown here for reasons of clarity. The nominal contact arrangement is formed as a finger cage around the longitudinal axis z. The term finger cage as used herein refers to an arrangement, for example a cylindrical or conical or oval arrangement, of the contact fingers around the longitudinal axis z. A shielding 9 can be arranged around the finger cage. The nominal contact arrangement further comprises a second mating contact 3b which normally is a metal tube. The contact fingers 3a and the second contact 3b are movable relatively to one other from the closed configuration shown in FIG. 1, in which they are in electrical contact to one another, into an opened configuration, in which they are apart from one another, and vice versa. It is also possible that only one of the contacts 3a, 3b moves parallel to the longitudinal axis z and the other contact 3b, 3a is stationary with respect to the longitudinal direction z.

(11) The contact fingers 3a are attached to or can be a part of a finger support 2, particularly a metal support cylinder 2.

(12) The circuit breaker 1 furthermore comprises an arcing contact arrangement formed by a first arcing contact 4a and a second arcing contact 4b.

(13) The first nominal contact and the first arcing contact 4a are typically not movable relatively to one another. In the same way, the second nominal contact 3b and the second arcing contact 4b are not movable with respect to one another. For the explanatory purposes of the present invention it is assumed that only the second nominal contact 3b and the arcing contact 4b are movable and the finger cage is stationary along the z-axis.

(14) When the closed circuit of FIG. 1 shall be disconnected, the second nominal contact 3b and the second arcing contact 4b are moved parallel to the direction of the z-axis into the direction indicated by the z-arrow, such that the nominal contact arrangement disconnects first. Thereafter, the current commutates to the arcing contact arrangement, which is still closed. With further movement of the second nominal contact 3b and the second arcing contact 4b into the direction of the z-arrow, the arcing contact arrangement also disconnects, thereby creating an electric arc between the arcing contacts 4a, 4b, which is normally blasted out in a very short time. These principles are known and are therefore not explained in more detail here.

(15) FIG. 2 shows a detailed view of three contact fingers 3a of a finger cage of the high voltage circuit breaker 1 of FIG. 1 according to the prior art. This view shows the contact fingers 3a as they are seen from within the finger cage. This also applies for FIG. 3. The contact fingers 3a are attached to or can be a part of the finger support 2 of FIG. 1. The contact fingers 3a are separated by empty slots 10, the purpose of which has been mentioned above. Furthermore, the contact areas 11 for the second nominal contact 4b (not shown) are denoted by the circles 11. Thus, the second nominal contact 3b contacts the contact fingers 3a in the area 11 of their free end.

(16) FIG. 3 shows a detailed view of two groups 5 of contact fingers 6, 7 of the finger cage of the high voltage circuit breaker of FIG. 1 according to the invention. In this configuration there are three contact fingers 6, 7 per one group 5 of contact fingers 6, 7. However, as mentioned above, the groups can comprise only two contact fingers 6, 7 or more than three contact fingers 6, 7, depending on the configuration of the circuit breaker 1. As can be seen, the groups of contact fingers 6, 7 are separated from each other by first empty slots 10, which are basically similar to those of the prior art configuration of FIG. 2. The contact fingers 6, 7 of one group 5 are separated from each other by second empty slots 8 which are shorter than the first empty slots 10.

(17) In embodiments, each contact finger 6, 7 is adjacent to at least one second empty slot 8. Thus, there are no contact fingers which are adjacent to only first slots 10, which would again decrease their stiffness.

(18) In embodiments, the total number of the contact fingers 6, 7 is not a prime number. By this, it is ensured that all contact fingers 6, 7 can be grouped in suitable groups which all comprise the same number of fingers without occurrence of ungrouped contact fingers 6, 7. Of course, for this purpose the total number of contact fingers 6, 7 has to be a multiple of the number of contact fingers 6, 7 in one group 5.

(19) In one embodiment of the invention all the second empty slots 8 have the same length (FIG. 3), whereas in another embodiment of the invention the second empty slots 8 have different lengths (FIG. 4). In the latter case, a largest length of the second empty slots 8 may advantageously exceed a smallest length of the second empty slots 8 by at least 20%, as shown in FIG. 4. These options make the finger cage more flexible in terms of construction.

(20) In embodiments, the second empty slots 8 are shorter than the first empty slots 10 by at least 50%. This ensures that both criteria, a good radial flexibility and a good circumferential stiffness, are met.

(21) The contact fingers 6, 7 are elastically deformed in a radial direction upon closing the electrical switching device, here the circuit breaker 1.

(22) As mentioned, the contact fingers 6, 7 form the finger cage. Particularly, the contact fingers 6, 7 are formed by a tubular metal section 12. The first and second empty slots 10, 8 extend from a first end into the tubular metal section and the contact fingers 6, 7 are interconnected at a second end of the tubular metal section, as shown in FIGS. 3-5.

(23) While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may otherwise variously be embodied and practised within the scope of the following claims. Therefore, terms like preferred or in particular or particularly or advantageously signify optional and exemplary embodiments only.