DESC:BACKGROUND

FIELD OF THE INVENTION

The present invention generally relates to a disconnector and earth switch assembly, and, more particularly, to driving mechanism of a disconnector and earth switch assembly.

DESCRIPTION OF THE RELATED ART

Gas insulated switchgear (GIS) is a matured switchgear technology that is dominating the market due to its compactness and lifecycle cost. A switchgear is a combination of electrical disconnector switches, fuses, or circuit breakers that are used to control, protect and isolate electrical equipment. Disconnectors and earth switches are used to maintain circuit breakers within the switchgear assembly. The disconnectors are placed on either side of the circuit breakers to prevent aging of the circuit breakers in the high voltage electrical circuits as circuit breakers cannot isolate high voltages for prolonged time. The voltage ratings of the high voltage electrical circuits are typically in the range of kilovolts. These disconnectors are also termed as isolators. When maintenance work needs to be executed on the circuit breakers working under high voltages, the disconnectors and earth switches are required to isolate and discharge the circuit breakers before maintenance work is executed.

The gas-filled insulating chambers of disconnectors include insulating gases such as sulphur hexafloride (SF6). Moving contacts are utilized to open and close disconnecting switch and earth switch included in the disconnector. The motion of the moving contacts is achieved by employing various mechanisms. Some of the mechanisms that are used to facilitate the motion of the moving contacts are rack and pinion, ball and screw, and scotch and yoke. Thus, the aforementioned mechanisms are used to drive the moving contacts of the disconnector and earth switches to its open and closed configurations and are generally placed within the gas-filled insulating chamber. In an example, the rack and pinion mechanism is placed inside the gas-filled insulating chamber. The aforementioned mechanisms result in the wear and tear of the mechanical components that are utilized in the mechanisms due to friction. As a result, minute metallic particles are produced and deposited in the gas-filled insulating chamber of the disconnector. Thus, electric stress is concentrated on the minute metallic particles that are inside the gas-filled insulating chamber, thereby resulting in electrical breakdown of the gas insulation material that is included in the gas-filled insulating chamber.

In light of the foregoing discussion, there exists a need for a system that prevents introduction of minute metallic particles in the gas-filled insulating chamber, reduces dimensions of the gas-filled insulating chamber and hence, reduces the dimension of the enclosure of the disconnector, increases electrical stress handling capability and more importantly, increases the reliability of the overall switchgear system and the conventional disconnectors.

OBJECTS OF THE INVENTION

An object of the present invention is to provide disconnector and earth switch assembly that reduces the chances of insulating gas breakdown by placing mechanisms for driving moving contacts of the disconnector and earth switch assembly outside the high field region of a gas-filled insulating chamber that houses the disconnecting switch and earthing switch, thereby preventing the deposition of minute metallic particles inside the high field region of the gas-filled insulating chamber and reducing the electrical stress inside the gas-filled insulating chamber and preventing electrical breakdown of the gas insulation material.

Another object of the present invention is to reduce the operation and replacement costs of the disconnecting switch and earthing switch housed inside the gas-filled insulating chamber and provide a stable electrical environment in switchgear systems.

Embodiments of the invention provide a disconnector and earth switch assembly. The disconnector and earth switch assembly includes a gas filled enclosure containing the insulating gas. A housing is connected to a first terminal and is made up of a conducting material. A first fixed contact is connected to a second terminal, and a first moving contact is connected to the housing and moves within the housing. The first moving contact moves towards the first fixed contact to make an electrical connection with the first fixed contact. A second fixed contact is connected to the housing and a second moving contact is connected to an earth connection. The second moving contact moves towards the second fixed contact to make an electrical connection with the second fixed contact. Further, a first operating mechanism moves the first moving contact towards and away from the first fixed contact and
a second operating mechanism moves the second moving contact towards and away from the second fixed contact. The first and second operating mechanisms are placed outside the gas filled enclosure.

BRIEF DESCRIPTION OF DRAWINGS

The features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. Embodiments of the present invention will herein after be described in conjunction with the appended drawings provided to illustrate and not to limit the scope of the claims, wherein like designations denote like elements, and in which:
Fig. 1A is a sectional view of a disconnector and earth switch assembly along XY plane, in a disconnecting switch closed position, according to an embodiment of the present invention;
Fig. 1B is a sectional view of the disconnector and earth switch assembly along XY plane, in a neutral position, according to an embodiment of the present invention; and
Fig. 1C is a sectional view of the disconnector and earth switch assembly along XY plane, in an earth switch closed position, according to an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

As used in the specification and claims, the singular forms “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. For example, the term “an article” may include a plurality of articles unless the context clearly dictates otherwise.

Those with ordinary skill in the art will appreciate that the elements in the figures are illustrated for simplicity and clarity and are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated, relative to other elements, in order to improve the understanding of the present invention.

There may be additional components described in the foregoing application that are not depicted on one of the described drawings. In the event such a component is described, but not depicted in a drawing, the absence of such a drawing should not be considered as an omission of such design from the specification.

Before describing the present invention in detail, it should be observed that the present invention constitutes a novel disconnector and earth switch assembly, wherein the disconnecting switch and the earthing switch have increased reliability. Such disconnector and earth switch assembly finds applications in gas insulated switchgears (GISs). Further, the disconnector and earth switch assembly helps maintain vital electrical components like the circuit breakers that are in series with the disconnector and earth switch assembly. Accordingly, the components and the method steps have been represented, showing only specific details that are pertinent for an understanding of the present invention so as not to obscure the disclosure with details that will be readily apparent to those with ordinary skill in the art having the benefit of the description herein.

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting but rather to provide an understandable description of the invention.

FIGS. 1A-1C illustrate a disconnector and earth switch assembly 100 in accordance with an embodiment of the present invention. The disconnector and earth switch assembly 100 includes a reliable, electrical stress free, and breakdown resistant disconnecting switch and earthing switch. The disconnector and earth switch assembly 100 prevents breakdown of insulating gas that is filled inside a gas-filled insulating chamber and increases reliability of the disconnecting switch and earthing switch by placing mechanical components that result in the production of metal particles outside the high field region of the gas-filled insulating chamber. In an example, the disconnector and earth switch assembly 100 is used to isolate circuit breakers in high voltage electric circuits that support a high voltage of 245 kV.

Referring now to Fig. 1A, a sectional view of the disconnector 100 along XY plane, in a disconnecting switch closed position, according to an embodiment of the present invention, is shown.The disconnector and earth switch assembly 100 includes an aluminium enclosure 102, a sulfur hexafluoride (SF6) gas-filled insulating chamber 104, a first fixed contact 106 (hereinafter referred to as “disconnector fixed contact 106”), a first moving contact 108, a second fixed contact 109, a second moving contact 110, a housing 111, a first holder 112, a second holder 114, a first operating mechanism 116 (hereinafter referred to as “first rack and pinion mechanism 116”), a second operating mechanism 118 (hereinafter referred to as “second rack and pinion mechanism 118”), an insulating rod 120, a valve 122, a multi–lamella contact 124, a Teflon guide ring 126, a live conductor 127, a plurality of spacers including first and second spacers 128a and 128b (collectively referred to as spacers 128), and an earth connection 130. The first moving contact 108 and the disconnector fixed contact 106 are the parts of the disconnecting switch. The second moving contact 110 and the second fixed contact 109 are the parts of the earthing switch. The disconnector and earth switch assembly 100 is placed on either side of a circuit breaker (not shown) in order to provide isolation in the circuit. The epoxy compounds and the nozzles in the circuit breaker tend to age if kept under constant electrical stress caused due to prolonged exposure to high voltages.

The aluminium enclosure 102 houses the SF6 gas-filled insulating chamber 104. The SF6 gas is filled inside this chamber through the valve 122. The pressure of the SF6 gas is maintained at 5-7 bar to provide the required insulation to the live conductor 127 inside the aluminium enclosure 102 as the aluminium enclosure 102 is connected to ground. The spacers 128 provide support to the live conductor 127 from the aluminium enclosure 102 inside the disconnector and earth switch assembly 100. The spacers 128 also help in maintaining the pressure of the SF6 gas inside the gas-filled insulating chamber 104. Further, the housing 111, the second fixed contact 109, the first moving contact 108, the second moving contact 110 and, the disconnector fixed contact 106 are also placed inside the aluminium enclosure 102.

The first moving contact 108 is supported by the first holder 112 and the second moving contact 110 is supported by the second holder 114. The first and second rack and pinion mechanisms 116 and 118 are integrated into the first and second holders 112 and 114, respectively. Thus, the first holder 112 and the second holder 114 provide support and facilitate the motion of the first and the second of the moving contacts 108 and 110.

The housing 111 is made up of conducting material and is stationery with respect to the aluminium enclosure 102. The first moving contact 108 moves inside the housing 111 along Y-Y’ axis and is in a constant connection with the housing 111. Thus, the housing 111 acts as a guide for the translational motion of the first moving contact 108. Further, the second fixed contact 109 and the live conductor 127 are fixatedly connected to the housing 111. Thus, the first moving contact 108, the housing 111, and the second fixed contact 109 all are electrically connected to the live conductor 127.

The first rack and pinion mechanism 116 provides motion to the first moving contact 108 by way of the insulating rod 120. The first rack and pinion mechanism 116 drives the insulating rod 120 and provides a bidirectional motion to the first moving contact 108 along the Y-Y’ axis inside the housing 111. The insulating rod 120 is connected to the first moving contact 108 so that it helps in the motion of the first moving contact 108. Similarly, the second rack and pinion mechanism 118 provides a bidirectional motion to the second moving contact 110 along the X-X’ axis. The second moving contact 110 is connected to an earth connection 130. The second moving contact 110 discharges the charge accumulated in the gas-filled insulating chamber 104 when the disconnector and earth switch assembly 100 has operated in the electric circuit.

The first rack and pinion mechanism 116 and the second rack and pinion mechanism 118 are placed outside the aluminium enclosure 102. The first and second rack and pinion mechanisms 116 and 118 are placed outside the gas-filled insulating chamber and are fixatedly connected on the aluminium enclosure 102.

In an embodiment of the present invention, the first rack and pinion mechanism 116 provides a bidirectional motion to the first moving contact 108 along the Y-Y’ axis and the second rack and pinion mechanism 118 provides bidirectional motion of the second moving contact 110 along the X-X’ axis. Further, a disconnecting switch closed configuration is achieved when the first moving contact 108 is connected to the disconnector fixed contact 106 and the second moving contact 110 is isolated from the second fixed contact 109. FIG. 1A illustrates the disconnecting switch closed configuration of the disconnector and earth switch assembly 100. When the first moving contact 108 is in contact with the disconnector fixed contact 106, the electric circuit is completed and the current flows from a live conductor 127 to the electrical equipment or load connected to the disconnector fixed contact 106. The connection is achieved by the upward motion of the first moving contact 108 towards the Y direction of the Y-Y’ axis facilitated by the fist rack and pinion mechanism 116. Further, when the first moving contact 108 is isolated from the disconnector fixed contact 106, the electric circuit is broken and isolation is achieved. This disconnection is achieved by the downward motion of the first moving contact 108 towards the Y’ direction of the Y-Y’ axis facilitated by the first rack and pinion mechanism 116. This configuration in which the first moving contact 108 is isolated from the disconnector fixed contact 106 and the second moving contact 110 is isolated from the second fixed contact 109 is a neutral configuration of the disconnector and earth switch assembly 100. The disconnection is achieved by the downward motion of the first moving contact 108 towards the Y’ direction of the Y-Y’ axis facilitated by the fist rack and pinion mechanism 116. Fig 1B illustrates the neutral configuration of the disconnector and earth switch assembly 100. When the second moving contact 110 is connected to the second fixed contact 109, the live components inside the aluminium enclosure 102 namely the live conductor 127, the first moving contact 108, and the housing 111 are grounded and the accumulated charges flow into ground. The charges flow from the live conductor 127 and the first moving contact 108 by the way of the housing 111. This configuration in which the second moving contact 110 is in connection with the second fixed contact 109 and the first moving contact 108 is isolated from the disconected fixed contact 106 is referred to as the earth switch closed configuration of the disconnector and earth switch assembly 100. The connection is achieved by the horizontal motion of the second moving contact 110 towards the X’ direction of the X-X’ axis facilitated by the second rack and pinion mechanism 116. Fig. 1C illustrates the earth switch closed configuration of the disonnector and earth switch assembly 100. Further, when the second moving contact 110 is isolated from the second fixed contact 109, the discharge is stopped. The disconnection is achieved by the horizontal motion of the second moving contact 110 towards the X direction of the X-X’ axis facilitated by the second rack and pinion mechanism 116.

In an embodiment of the present invention, the first and the second rack and pinion mechanisms 116 and 118 are composed of metallic or non-metallic materials. The mechanical wear and tear of the first and the second rack and pinion mechanisms 116 and 118 produces metallic particles due to friction between the moving parts. However, since the first and second rack and pinion mechanisms 116 and 118 are placed outside the high field region of the aluminium enclosure 102, and hence outside the gas-filled insulating chamber 104, thereby ensuring that the metallic particles produced due to friction stay out of the high field region of SF6 gas-filled insulating chamber 104 and are not deposited in the gas-filled insulating chamber 104. This increases the reliability of the disconnector and earth switches, and hence, increases the reliability of the disconnector and earth switch assembly 100.

In another embodiment of the present invention, the disconnector and earth switch assembly 100 can also be used as only grounding switch when the disconnector fixed contact 108 is open and the second moving contact 110 connects the second fixed contact 109 and the earth connection 130 by the way of housing 111.

Thus, the GIS utilises the disconnector and earth switch assembly 100 that has higher stability and reliability, increased lifetime and reduces maintenance costs.

The present invention has been described herein with reference to a particular embodiment for a particular application. Although selected embodiments have been illustrated and described in detail, it may be understood that various substitutions and alterations are possible. Those having ordinary skill in the art and access to the present teachings may recognize additional various substitutions and alterations are also possible without departing from the spirit and scope of the present invention.
,CLAIMS:1. A disconnector and earth switch assembly, comprising:
a gas filled enclosure containing the insulating gas, the gas filled enclosure comprising;
a housing connected to a first terminal, wherein the housing is made up of a conducting material;
a first fixed contact and a first moving contact arrangement, wherein the first fixed contact is connected to a second terminal, and the first moving contact is connected to the housing and moves within the housing, and wherein the first moving contact moves towards the first fixed contact to make an electrical connection with the first fixed contact; and
a second fixed contact and a second moving contact arrangement, wherein the second fixed contact is connected to the housing and the second moving contact is connected to an earth connection and wherein the second moving contact moves towards the second fixed contact to make an electrical connection with the second fixed contact;
a first operating mechanism, wherein the first operating mechanism moves the first moving contact towards and away from the first fixed contact; and
a second operating mechanism, wherein the second operating mechanism moves the second moving contact towards and away from the second fixed contact,
wherein the first and second operating mechanisms are placed outside the gas filled enclosure.

2. The disconnector and earth switch assembly according to claim 1, wherein in a first configuration, the first moving contact is connected to the first fixed contact and the second moving contact is disconnected from the second fixed contact.

3. The disconnector and earth switch assembly according to claim 1, wherein in a second configuration, the first moving contact is disconnected from the first fixed contact and the second moving contact is disconnected from the second fixed contact.

4. The disconnector and earth switch assembly according to claim 1, wherein in a third configuration, the second moving contact is connected to the second fixed contact and the first moving contact is disconnected from the first fixed contact.

5. The disconnector and earth switch assembly according to claim 1, wherein the insulating gas includes sulfur hexafluoride (SF6) gas.

6. The disconnector and earth switch assembly according to claim 1, wherein the first terminal is connected to a live connection.

7. The disconnector and earth switch assembly according to claim 1, wherein the second terminal is connected to a circuit breaker terminal.

8. The disconnector and earth switch assembly according to claim 1, wherein the enclosure is made up of aluminum.

9. The disconnector and earth switch assembly according to claim 1, wherein the first, second, and third configurations are disconnector switch closed, neutral, and earth switch closed configurations, respectively.

10. The disconnector and earth switch assembly according to claim 1, wherein the first and second operating mechanisms include rack and pinion mechanisms.