WO2015154138A1

WO2015154138A1 - An electrical interrupter

Info

Publication number: WO2015154138A1
Application number: PCT/AU2015/050128
Authority: WO
Inventors: Joni Sahak Tortian; Fahmid KHONDAKER
Original assignee: Noja Power Switchgear Pty Ltd
Priority date: 2014-04-10
Filing date: 2015-03-24
Publication date: 2015-10-15
Also published as: AU2015245940A1; AU2015245940B2

Abstract

The present invention provides an electrical interrupter. The interrupter includes a housing defining a chamber. Three or more separable electrical contacts are located within the chamber. In one embodiment, the chamber is an air chamber. Advantageously, the separable contacts quench arcing to a sufficient extent so that the chamber may be filled with air rather mineral oil or SF6 for example. In particular, the separable contacts may effectively mitigate what would otherwise be greater arcing between two contacts by dividing the arc among the three or more contacts (compared with the prior art in which arcing occurs between two contacts). In an alternative embodiment, the chamber is a vacuum chamber to enable a higher voltage rating of the interrupter.

Description

AN ELECTRICAL INTERRUPTER

TECHNICAL FIELD

[0001] The present invention generally relates to an electrical interrupter. The present invention has particular application to electrical power switchgear such as switches which can include the electrical interrupter.

BACKGROUND

[0002] The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.

[0003] Vacuum interrupters have been used for decades in the medium voltage (up to between 72 and 145 kV) switchgear industry. The benefit of using vacuum

interrupters is largely financial, whereby they offer vastly longer life and greatly reduced maintenance costs when compared to other interrupters. Further, vacuum interrupters are environmentally friendly and provide the lowest environmental impact of all medium voltage switching technologies over the entire product life cycle.

[0004] At least part of the reason that vacuum interrupters last is because of their simple, yet rugged construction. Turning to Figure 1 , a known vacuum interrupter 100 includes a tubular ceramic insulating envelope 102 which holds opposing conductive end plates 104a, 104b forming an internal vacuum chamber. One end plate 104b is electrically connected to a fixed terminal 106, while an opposing end plate 104a is connected to a movable terminal 108. To cause interruption, one electrical contact 1 10 is pulled apart from the other electrical contact 1 12 by a few millimeters which results in arcing between the contacts 1 10, 1 12. The vacuum casing formed by the envelope 102 and plates 104, incorporates a bellows 1 14 to allow for this contact separation through movement of the movable terminal 108.

[0005] The voltage that is impressed across the open contacts 1 10, 1 1 2 in the vacuum chamber is also impressed externally across the end plates 104a,b and the terminals 106, 108 of the vacuum interrupter 100. For most modern interrupters the insulating envelope 102 is formed from a high-alumina content porcelain which is not, in itself, safe for isolation. Internal plate-like metallic end shields 1 16, a bellow shield 1 1 8 and a condensation shield 1 20 can also shield electromagnetic fields.

[0006] In a similar manner to a vacuum interrupter, the internal chamber can include mineral oil or SF6 to quench arcing between the contacts 1 10, 1 12.

[0007] Mineral oil, which has a dielectric strength about 5 times that of air, is extremely reliable and generally performs well. However, mineral oil has two distinct disadvantages, namely: (a) environmental, and (b) it is a potential fire hazard. The first disadvantage has now been alleviated with the development of biodegradable oils for high-voltage insulation.

[0008] In recent years, interrupters have included an SF6 ambient. Usually the SF6 at a pressure of just about 1 atm. gauge (i.e. 1 atm above the ambient atmosphere) has the breakdown voltage about five times that of air at 1 atm. This has permitted the use of relatively short-vacuum interrupters in rather compact designs especially at voltages of 24 kV, 36 kV, and higher voltages. Unfortunately the realization that SF6 is a potent greenhouse gas has led to a search for alternative methods of developing compact systems.

[0009] There is a need for an alternative interrupter. SUMMARY OF THE INVENTION

[00010] According to an aspect of the present invention, there is provided an electrical interrupter including:

a housing defining a chamber; and

three or more separable electrical contacts located within the chamber.

[00011 ] In one embodiment, the chamber is an air chamber. Advantageously, the separable contacts quench arcing to a sufficient extent so that the chamber may be filled with air rather mineral oil or SF6 for example. In particular, the separable contacts may effectively mitigate what would otherwise be greater arcing between two contacts by dividing the arc among the three or more contacts (compared with the prior art in which arcing occurs between two contacts). In an alternative embodiment, the chamber is a vacuum chamber to achieve a higher voltage rating. [00012] The electrical interrupter may further include biasing means located between each pair of adjacent contacts for biasing the contacts apart. Each biasing means may include a spring. The spring may be plastic.

[00013] Each contact may define one or more spinning formations for inducing spinning of arcs. Each formation may be shaped to cause the current to follow a path that causes an arc to spin thereby quickening arc dissipation. The formations may include slots or cuts. The formations may be bent or curved. The formations may extend outwardly. The formations of adjacent contacts may be opposed The formations of adjacent contacts may be aligned and/or superimposed.

[00014] Each contact may include a conductive core surrounded by an insulator. The core and insulator may form a complementary fit. The core may include copper, Aluminium or a metal alloy. The adjacent contact surfaces of the contacts may include copper, tungsten, silver or any other like material to limit thermal effect on the contacts. Each contact may be generally round in shape.

[00015] The core may protrude from either side of the insulator. Each contact may include a permanent magnet carried by the core. The magnet may be surrounded by the core. The contacts may be arranged in a stack. Adjacent magnets in the stack may be aligned with like facing poles. The core may define a lip for engaging with a lip of an adjacent contact. The interrupter may further include one or more limiters for limiting separation of adjacent contacts. Each limiter may be formed from insulator material. The limiters may be arranged so that the contacts are serially opened. The limiters may be arranged around the periphery of the contacts.

[00016] Each core may define a central hub conductor from which a conductor plate extends. The conductive plate may include an engagement lip for engaging with a lip of an adjacent plate so as to form a gap between the plates. The insulator may define a biasing channel for receiving biasing means. Each biasing channel may include a electric shield. The shield may be a cap.

[00017] The contacts may be configured so that arcs move laterally. The contacts may be configured so that current flows transverse to arcs. The contacts may be configured so that current flows in opposite directions between adjacent contacts. The contacts may be arranged in pairs. The contacts of each pair may make electrical contact with each other centrally, and with another pair laterally.

[00018] Preferably, the electrical interrupter further includes a moving terminal and a fixed terminal between which the contacts are located. Preferably, the housing includes an insulator. In one embodiment, the housing further includes one or more electric screens. The housing may include two screens embedded in the housing insulator on opposite sides of the contacts and for controlling electric fields emanating from the contacts. The housing may include one or more apertures so that the air chamber is at about atmospheric pressure and to facilitate the recovery of air after arc quenching.

[00019] The interrupter may include inhibition means for inhibiting rotation of the contacts within the housing. The inhibition means may include a tongue in groove arrangement. Alternatively, the inhibition means may include the shape of the contacts and housing.

[00020] The housing may define airways between adjacent contacts though which air can pass. The contacts may form a seal with the housing to drive air though the airways.

[00021 ] According to another aspect of the present invention, there is provided an electrical interrupter including three or more separable electrical contacts.

[00022] According to another aspect of the present invention, there is provided an electrical interruption method involving separating three or more separable electrical contacts.

[00023] According to another aspect of the present invention, there is provided a contact for an electrical interrupter, the contact including:

a conductive core;

an insulator surrounding the conductive core.

[00024] Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[00025] Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows:

[00026] Figure 1 is a side sectional view of a known vacuum interrupter;

[00027] Figure 2 is a side sectional view of an electrical interrupter in accordance with an embodiment of the present invention with contacts in a closed configuration;

[00028] Figure 3 is a side sectional view of the electrical interrupter of Figure 2 with contacts in an open configuration;

[00029] Figure 4 is an upper perspective sectional view of a contact of the electrical interrupter of Figure 2;

[00030] Figure 5 is a side sectional view of the electrical interrupter of Figure 2 showing current flow;

[00031 ] Figure 6 is a lower sectional perspective view of the electrical interrupter of Figure 3;

[00032] Figure 7 is an upper sectional perspective view of the electrical interrupter of Figure 6;

[00033] Figure 8 is an upper partially sectioned view of the electrical interrupter of Figure 8;

[00034] Figure 9 is a side sectional view of an electrical interrupter in accordance with another embodiment of the present invention with contacts in a closed configuration;

[00035] Figure 1 0 is an upper perspective sectional view of a contact of the electrical interrupter of Figure 9; [00036] Figure 1 1 is a side sectional view of an interrupter contact stack in accordance with another embodiment of the present invention with contacts in an open configuration;

[00037] Figure 1 2 is an upper perspective sectional view of a contact of the contact stack of Figure 1 1 ;

[00038] Figure 1 3a is a partial sectional view of the contact stack of Figure 1 1 showing a cleat arrangement prior to contact separation; and

[00039] Figure 1 3b partial sectional view of the contact stack of Figure 13b showing the cleat arrangement after contact separation.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[00040] According to an embodiment of the present invention, there is provided an electrical interrupter 200 for a switch as shown in Figures 2 and 3.

[00041 ] Turning firstly to Figure 2, the interrupter 200 includes a housing 202 defining an internal air chamber 204. In this particular embodiment, seven separable electrical contacts 10 are located within the air chamber 204. Advantageously, the separable contacts 10 quench arcing to a sufficient extent so that the chamber 204 can be filled with air rather mineral oil or SF6 for example. In particular, the separable contacts 10 effectively mitigate what would otherwise be greater arcing between two contacts by splitting the arcing among the contacts 10 (compared with the prior art in which arcing occurs between two contacts). A detailed description of the interrupter 200 is provided below.

[00042] The housing 202 includes a molded insulator case 60 and two, conductive or semi-conductive, electric screens 63, 64 embedded in the dielectric case 60. The screens 63, 64 are located on opposite sides of the stack of contacts 1 0, and screen and control electric fields emanating from the contacts 1 0. The electrical interrupter 200 further includes a fixed terminal 61 fixed to the housing 202, and a moving terminal 62 which is constrained to axially move relative to the housing 202. The contacts 10 are located between the terminals 61 , 62. [00043] Turning to Figure 3, the electrical interrupter 200 further includes metal leaf springs 50 (i.e. biasing means) located between each pair of adjacent contacts 1 0 for biasing the contacts 10 apart. The interrupter 200 further includes annular, conductive or semi-conductive, electric shields in the form of caps 51 for shielding the metal springs 50. Caps 51 embedded in adjacent contacts 10 come together to secure the flattened springs 50 as shown in Figure 2.

[00044] The structure of each round contact 10 is shown in Figure 4. Each contact 10 includes a circular conductive core 400 surrounded by an annular insulator 40. The core 400 and insulator 40 form a complementary tongue-in-groove fit. The core 400 includes copper, Aluminium or a metal alloy material. Each core 400 defines a protruding central hub conductor 1 1 for engaging with an adjacent hub conductor 1 1 so as to form a gap. Each core also defines a conductor plate 12 extending from the hub conductor 1 1 . The conductive plate 12 includes an outer protruding annular engagement lip for engaging with a lip of an adjacent plate 12 so as to form a gap between the plates 12. The hub inner contact surface 1 1 and lip outer contact surface 12 of the core 400 of each contact 10 includes copper, tungsten, copper beryllium, silver or any other like material to limit thermal effect on the contacts 1 0.

[00045] The insulator 40 defines a pair of outwardly facing spring channels 402 for receiving the caps 51 and springs 50. Each contact 1 0 defines two or more outwardly extending and curved cuts or slots 30 (i.e. formations). The curved slots 30 cause the current in the contacts 10 to follow a curved path which, in turn, causes the vertical arcs between the horizontal contacts 10 to spin thereby quickening arc dissipation.

[00046] Figure 5 shows the current flow 20 of the interrupter 200 operating in a non- interrupted configuration with the contacts 10 closed. The stack of contacts 10 is compressed between the terminals 61 , 62, the springs 50 are flattened and in the channels 402, and the air gaps 500 are formed between adjacent contacts 10. The contacts 10 are configured so that current 20 flows radially and in opposite horizontal directions between adjacent contacts 1 0. In use, the radially flowing horizontal current induces a transverse magnetic force on vertical electric arcs that laterally moves the arcs between the contacts 10. The lateral movement of the vertical arc causes the arc to stretch and skew which spreads the energy of the arc over a longer distance and quickens dissipation of the arc. Furthermore, the moving arc comes into contact with air which quickens cooling of the arc and contact surface temperature, thereby impeding erosion of the contacts 10.

[00047] The insulator 40 may provide a seal up against the inner surface of the housing 202. Apertures may be positioned at specific points in the housing 202, between the contacts 10, to allow air to be driven in and out of the chamber pulling in clean air and removing contaminated air, whilst providing a pressured environment to help quench the arc.

[00048] As can best be seen in Figures 6 and 7, the housing 202 includes end apertures 65 so that the internal air chamber 204 is at about atmospheric pressure and to facilitate the recovery of air after arc quenching.

[00049] Figure 8 best shows the arrangement of the bent leaf springs 50 in the contact channels 402 and caps 51 (see also Figure 3).

[00050] The interrupter 200 is compact, easy to manufacture, and easy to upgrade to different voltage levels by varying the number of contacts 10. Further, the use of air in the chamber rather than SF6, mineral oil or other hazardous material is far more environmentally friendly.

[00051 ] The operation of the interrupter 200 will now be briefly described.

[00052] Initially, the interrupter 200 is in a non-interrupted configuration with contacts 10 closed as shown in Figure 2, and the current 20 flows through the contacts 1 0 as shown in Figure 5.

[00053] During isolation of electricity supply, the movable terminal 62 is separated away from the fixed terminal 61 . In turn, the springs 50 between adjacent contacts 10 separate the contacts 1 0 thereby interrupting the current flow as shown in Figure 3. In turn, vertical arcing is split between various adjacent contacts 1 0, the effects of which are less detrimental when if instead the interruption and arcing is between only two contacts.

[00054] According to another embodiment of the present invention, there is provided an electrical interrupter 200 for a switch as shown in Figure 9. Like reference numerals refer to like features previously described. The interrupter 200 includes different contacts 10 to those previously described, as shown in Figure 10.

[00055] Turning to Figure 1 0, each contact 1 0 includes a conductor core 400 with a hub conductor 1 1 protruding from either side of the surrounding annular insulator 40. Adjacent hub conductors 1 1 engage when the interrupter 200 is in the non-interrupted configuration with contacts 10 closed as shown in Figure 9. The hub conductor 1 1 defines bent or curved slots 30. As before, the slots 30 cause the current in the contacts 10 to follow a bent or curved path which, in turn, causes the vertical arcs between the horizontal contacts 1 0 to spin thereby quickening arc dissipation.

[00056] According to another embodiment of the present invention, there is provided a contact stack 1 100 as shown in Figure 1 1 , with embedded permanent magnets 1202, for use with the interrupter 200. Like reference numerals refer to like features previously described.

[00057] As can best be seen in Figure 1 2, each contact 1 0 includes a circular conductive core 400 surrounded by an annular insulator 40. The core 400 forms a conductive outer housing 1 200, and an internal permanent magnet 1202 is housed within the housing 1 202. The permanent magnets 1 202 induce lateral movement, spinning, and speedy cooling of any arcs as previously explained which mitigates contact erosion. Adjacent permanent magnets 1 202 in the stack 1 100 are preferably aligned with like facing poles (e.g.N-N, S-S). The core 400 also defines protruding annular lips 1 204 on either side which contact with adjacent lips 1204 during non- interruption.

[00058] Turning to Figure 1 3, a cleat limiter arrangement 1300 is provided which includes a number of channel-shaped motion limiters 1302 (or cleats) for limiting separation of adjacent contacts 10 in the interrupted configuration by a fixed distance. Further, each limiter 1302 retains the adjacent contacts 10 when the stack 1 100 is removed from its housing 202 so that the stack 1 100 can be conveniently transported as a single unit without coming apart. Each limiter 1 302 is molded from insulator material (e.g. resilient plastic) and clips onto the edge of the stack 1 1 00.

[00059] During interruption, a fist pair of adjacent contacts 1 0 separate from a together configuration in Figure 13a to an apart configuration in Figure 13b. In turn, the momentum of the moving pair of separated contacts 10, connected by one or more limiters 1 302, causes the next contact 1 0 in the stack 1 100 to separate, and so on. Accordingly, the stack contacts 10 are serially opened in a controlled manner and break any welds in the process. The limiters 1302 are evenly arranged around the periphery of the stack 1 100 and adjacent limiters 1 302 are staggered so as to avoid interference.

[00060] A person skilled in the art will appreciate that many embodiments and variations can be made without departing from the ambit of the present invention.

[00061 ] In one embodiment, the spring 50 can be plastic and the caps 51 may not be provided.

[00062] The number of contacts 10 can be readily varied in excess of two, to achieve a desired voltage rating of the switch.

[00063] As described above, each contact 10 can be circular to fit within a cylindrical housing 202. Alternatively, each contact 10 and the housing 202 may be polygonal to inhibit rotation of the contacts 10 within the housing 202. Alternatively, the contacts 10 may define a peripheral groove for receiving an internal tongue of the housing to inhibit rotation of the contacts 10.

[00064] As can best be seen in Figure 6, the curved slots 30 in adjacent contacts 10 are opposed. In another embodiment, the curved slots 30 in adjacent contacts 10 may be aligned and/or superimposed.

[00065] In an alternative embodiment, the chamber 204 is a vacuum chamber enabling higher voltage rating (e.g. 1 1 0kV) of the interrupter 200.

[00066] In Figure 12, the permanent magnet 1202 is embedded within the housing 1202. In alternative embodiment, the magnet 1202 may instead be exposed, or fastened to the housing 1 202 in another manner.

[00067] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted by those skilled in the art.

[00068] Reference throughout this specification to One embodiment' or 'an embodiment' means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases 'in one embodiment' or 'in an embodiment' in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

Claims

The claims defining the invention are as follows:

1 . An electrical interrupter including:

a housing defining a chamber; and

three or more separable electrical contacts located within the chamber.

2. An electrical interrupter as claimed in claim 1 , wherein the chamber is an air chamber or a vacuum chamber.

3. An electrical interrupter as claimed in claim 1 , further including biasing means located between each pair of adjacent contacts for biasing the contacts apart.

4. An electrical interrupter as claimed in claim 3, wherein each biasing means includes a spring.

5. An electrical interrupter as claimed in claim 1 , wherein each contact defines one or more spinning formations for inducing spinning of arcs.

6. An electrical interrupter as claimed in claim 5, wherein the formations include slots or cuts.

7. An electrical interrupter as claimed in claim 5, wherein the formations are bent or curved.

8. An electrical interrupter as claimed in claim 5, wherein the formations extend outwardly.

9. An electrical interrupter as claimed in claim 1 , wherein each contact includes a conductive core surrounded by an insulator.

10. An electrical interrupter as claimed in claim 9, wherein the core includes copper, aluminium or a metal alloy.

1 1 . An electrical interrupter as claimed in claim 9, wherein the core protrudes from at least one side of the insulator.

12. An electrical interrupter as claimed in claim 1 , wherein adjacent contact surfaces of the contacts include copper, tungsten, silver or any other like material to limit thermal effect on the contacts.

13. An electrical interrupter as claimed in claim 1 , wherein each contact includes a magnet.

14. An electrical interrupter as claimed in claim 13, wherein the magnet is surrounded by a conductor.

15. An electrical interrupter as claimed in claim 1 , wherein the contacts are arranged in a stack and/or define a lip for engaging with a lip of an adjacent contact.

16. An electrical interrupter as claimed in claim 1 , further including one or more limiters for limiting separation of adjacent contacts.

17. An electrical interrupter as claimed in claim 1 , wherein each contact defines at least one biasing channel for receiving biasing means, and each biasing channel includes an electric shield.

18. An electrical interrupter as claimed in claim 1 , wherein the contacts are configured so that arcs move laterally.

19. An electrical interrupter as claimed in claim 1 , further including electric screens for screening and controlling electric fields emanating from the contacts.

20. A contact for an electrical interrupter, the contact including:

a conductive core; and

an insulator surrounding the conductive core.

21 . An electrical interrupter including three or more separable electrical contacts.

22. An electrical interruption method involving separating three or more separable electrical contacts.