WO2011080546A1

WO2011080546A1 - Electrical ring main unit

Info

Publication number: WO2011080546A1
Application number: PCT/IB2010/000586
Authority: WO
Inventors: Dukkaiappan Subbaiahthever; Ganesh Balkrishna Ghate; Vikas Vishwasrao Jakate
Original assignee: Abb Technology Ltd
Priority date: 2009-12-31
Filing date: 2010-03-19
Publication date: 2011-07-07

Abstract

The invention relates to an electrical ring main unit, in which the functionality of the isolator and earthing switch are integrated as a part of the circuit breaker unit instead of having a separate isolator unit for such functionality. The electrical ring main unit has circuit breaker, disconnector and earthing switch integrated therein. The said circuit breaker unit of the electrical ring main unit comprises a plurality of separate pole assemblies. Each of the said pole assembly comprises an interrupter with a contact blade fixed thereto for switching the electrical ring main unit to service or open or earth condition in accordance with the sequence of operation of the electrical ring main unit. The invention also relate to a method of operating the electrical ring main unit following the operation sequence of the said electrical ring main unit.

Description

ELECTRICAL RING MAIN UNIT

FIELD

The present invention relates to an electrical ring main unit and more particularly to an electrical ring main unit having disconnector and earthing switch integrated therein.

BACKGROUND OF THE INVENTION

Generally, ring main unit comprises a circuit breaker and isolators, where the circuit breaker is usually connected to a transformer. The circuit breaker and isolators in a ring main unit are two different units, which together perform the "Open and Earth" operation sequence. The said operation sequence follow the sequence of 1) opening the circuit breaker and disconnecting from the load; 2) opening the disconnector / isolator and 3) switching the disconnector to earth mode.

The circuit breaker and isolators being two separate units make the construction of the ring main unit complicated. Also importantly, the size of the ring main unit is considerably big occupying more space.

Hence there is a need for a ring main unit which occupies less space and simple in construction.

OBJECTS OF THE INVENTION It is an object of the invention to provide an electrical ring main unit which is simple in construction.

It is another object of the invention to provide an electrical ring main unit which is compact and occupies less space.

It is yet another object of the invention to provide an electrical ring main unit having disconnector and earthing switch integrated therein.

Further object of the invention is to provide an electrical ring main unit which is comparatively less expensive. SUMMARY OF THE INVENTION

According to one embodiment of the invention there is provided an electrical ring main unit. The electrical ring main unit has circuit breaker, disconnector and earthing switch integrated therein. The circuit breaker of the electrical ring main unit comprises a plurality of separate pole assemblies. The pole assemblies are coupled by a common operating shaft. Each of the said pole assembly comprises an interrupter connected to a rotary contact at the lower end of moving stem of the said interrupter.

According to other embodiment of the invention there is provided an electrical ring main unit having circuit breaker, double break disconnector and earthing switch integrated therein. The circuit breaker of the electrical ring main unit comprises a plurality of separate pole assemblies disposed within a common housing. Each of the pole assembly comprises an interrupter.

Accordingly, the invention also provides a method for operating an electrical ring main unit. The method comprises the steps of a) opening or closing the contact of the circuit breaker; rotating the contact blade by a mechanism for rotation, b) making contact with the contact connection bars for operating the said unit in service mode, c) rotating the contact blade further through a determined angle by the said mechanism for rotation to operate the said unit in isolation mode by isolation from the live contacts, d) rotating the contact blade still further through a determined angle by the said mechanism for rotation to operate the said unit in earthing mode by making contact with the earthing switch or terminal.

BRIEF DESCRIPTION OF THE INVENTION

With reference to the accompanying drawings in which: Fig. 1 depicts a single line diagram of the electrical ring main unit according to the state of art.

Fig. 2a shows the plan view of the electrical ring main unit according to one embodiment of the invention.

Fig. 2b shows the perspective view of the electrical ring main unit according to an embodiment of the invention shown in Fig 2a. Fig. 3a shows the circuit breaker of the electrical ring main unit illustrated in Figs. 2a and 2b.

Fig. 3b shows the cross sectional view of the circuit breaker depicted in Fig. 3a.

Fig. 4 shows the switching position of the electrical ring main unit illustrated in Figs. 2a and 2b.

Fig. 5a shows the switching position in service condition of an exemplary embodiment of the electrical ring main unit according to the embodiment of the invention illustrated in Fig. 2a.

Fig. 5b shows the switching position in open condition of the electrical ring main unit illustrated in Fig. 5a.

Fig. 5c shows the switching position in earth condition of the electrical ring main unit illustrated in Figs. 5a and 5b.

Fig. 6a illustrates the switching position in service condition of an exemplary embodiment of the electrical ring main unit in accordance with other embodiment of the invention.

Fig. 6b shows the switching position in open condition of the electrical ring main unit according to the invention depicted in Fig. 6a.

Fig. 6c shows the switching position in earth condition of the electrical ring main unit illustrated in Figs. 6a and 6b. DETAILED DESCRIPTION OF THE INVENTION

The invention is aimed at providing an electrical ring main unit, in which the functionality of the isolator and earthing switch are integrated as a part of the circuit breaker unit instead of having a separate isolator unit for such functionality. This to a great extent reduces the space and makes the electrical ring main unit compact. Also the integration herein above mentioned assures a simple construction devoid of complex arrangement whilst integrating the functionality of the isolator unit into the circuit breaker unit. The invention is explained hereinafter with reference to three exemplary embodiments. Fig. 1 shows a single line diagram of an electrical ring main unit (100) in accordance with the state of art. The electrical ring main unit (100) essentially comprises separate circuit breaker unit (101) having a circuit breaker and a separate isolator unit (102) and two cable switches (103, 104). The switching position considered herein are service, open and earth switching conditions / positions. In the electrical ring main unit (100), the circuit breaker unit (101) is required to perform "Close and Open" operation and the isolator unit (102) is required to perform the "Close, Open and Earth" operation sequence. The said operation sequence follow the sequence of 1) opening the circuit breaker and disconnecting from the load; 2) opening the disconnector / isolator and 3) switching the disconnector to earth mode. Generally, the electrical ring main unit at present are large in size and the construction is also complicated.

Figs. 2 to 4 show the electrical ring main unit (200) in accordance with one embodiment of the invention. Here, the electrical ring main unit (200) has the functionality of the isolator unit incorporated in the circuit breaker unit thereby eliminating the need for a separate isolator unit. This reduces the space occupied by the entire electrical ring main unit and hence provides compactness. The construction also becomes quite simpler in accordance with the invention, in having the circuit breaker and isolator functionalities integrated together therein in the electrical ring main unit.

The circuit breaker unit consists of three separate compact pole assemblies coupled by a common operating shaft (203). Each of the separate compact pole assembly comprises a circuit breaker (201). The circuit breaker referred here is a vacuum interrupter (201). The connection to the vacuum interrupter (201) and the pole assembly is made by suitable connector and through the bushing. The vacuum interrupter (201) has a moving stem, the lower portion of which is connected to a rotary contact. The rotary contact described herein is a combined assembly of plug (303) and hub (304), wherein the hub (304) is fixed to the moving stem of the said vacuum interrupter (201). A contact blade (305) is fixed to the plug (303) to have the switching position in service condition (401) when the contact blade (305) engages with the contact terminal (404). The switching position is in earth condition (403) when the contact blade (305) engages with the contact terminal (405). The switching condition is in open condition (402), when the contact blade (305) does not engage with any of the terminals (404, 405). The hub (304) is connected to a gear (301) for exhibiting rotation in clockwise or anticlockwise direction so as to change the switching position of the contact blade (305) and the switching condition thereof. The direction of the rotation depends upon the operation sequence and the functionality. The gear (301) fixed to each of the hubs (304) are driven by an operating gear (205) and by the common operating link (204) that connects the individual gears (301) that corresponds to each vacuum interrupter (201). The common shaft (203) is connected to a spring charged mechanism through suitable linkages. The open and close operation of the vacuum interrupter (201) is effected by the spring charges mechanism through the common shaft (203) and the breaker operation rod (202).

The switching position of the electrical ring main in accordance with one embodiment of the invention depicted in Figs. 2a to 4, in its service, open and earth condition are shown in Figs. 5a, 5b and 5c respectively, as an exemplary embodiment.

Fig. 5a shows the electrical ring main unit having three circuit breakers being the vacuum interrupters (506, 507, 508) corresponding to each of the bus namely R (501), Y (502) and B (503) bus. Each of the said vacuum interrupters (506, 507, 508) is disposed individually inside their respective and separate housing (504). Each of the said housing with its corresponding vacuum interrupters (506, 507, 508) is capable of being rotated about a pivot (505) of each of the housing (504). The rotation is caused by a suitable mechanism for changing the switching position. The mechanism for rotation here include a link (513) provided for each of the housing (504) and fixed thereto. The three links (513) corresponding to the three housings (504) are being connected to a common lever (514). The movement of the said lever (514) effects the rotation of the three housings (504) along with its vacuum interrupters (506, 507, 508).

The switching positions herein mentioned being the service, open and earth condition are affected by the rotation of the housing and the vacuum interrupters. A contact connection bar termed to be the contact blade (509) are provided for each of the three vacuum interrupters (506, 507, 508) and fixed thereto.

The rotation of the vacuum interrupters ascertains the movement of the contact blades (509) so as to define the switching position. The contact blade (509) of the three vacuum interrupters (506, 507, 508) when in contact with the bus R (501), Y (502) and B (503) relate the switching position to be in service condition as depicted in Fig. 5a. Further rotation of the vacuum interrupter (506, 507, 508) and the contact blades (509) thereof by the rotating mechanism disconnects the electrical ring main unit from the buses R (501), Y (502) and B (503) thereby having the switching position of the electrical ring main unit in open condition. On further rotation, the contact blades (509) make contact with the earthing switches (510, 511, 512) corresponding to each of the vacuum interrupters (506, 507, 508) to turn the switching position to earth condition. The operation sequence explained herein above follows the sequence of operation described above for the electrical ring main unit. # According to other embodiment of the invention, the electrical ring main unit has the functionality of the isolator unit incorporated in the circuit breaker unit thereby eliminating the need for a separate isolator unit. This makes the electrical ring main unit compact. Here, the electrical ring main unit comprises three vacuum interrupters being the circuit breaker with the double break disconnector and earthing switch functionality integrated therein. The switching position of the electrical ring main in its service, open and earth condition are shown in Figs. 6a, 6b and 6c respectively, as an exemplary embodiment.

Fig. 6a depicting the service condition of the electrical ring main unit shows three vacuum interrupters (606, 607 and 608) disposed within a common housing (604). The housing may be made of epoxy or any other housing made from suitable material. The shape of the housing may differ according to the requirement. Each of the three vacuum interrupters (606, 607, 608) corresponds to one of the bus namely R (601), Y (602) and B (603) bus of the electrical ring main unit, respectively. The housing (604) with the vacuum interrupters (606, 607, 608) are capable of being rotated about a pivot (605) located either at the top or bottom portion thereof by a suitable mechanism. The said mechanism referred herein is provided for rotating the housing (604) about the pivot (605). The housing (604) with the vacuum interrupters (606, 607, 608) are shown with the contact connection bars being the contact blades (609) for maintaining the contact at service condition or open condition or in earth condition. Here, the contact blades (609) corresponding to each of the vacuum interrupters (606, 607, 608) are seen in service condition making contact with the corresponding bus R, Y, B (601, 602, 603). Here, the switching position of the electrical ring main unit is in service condition.

The rotation of the housing (604) with the vacuum interrupters (606, 607, 608) disconnects the contact made by the contact blades (609) with the bus thereby isolating the unit and the switching position of the electrical ring main unit herein is in open condition as illustrated in Fig. 6b.

Fig. 6c shows the switching position of the electrical ring main unit in earth condition, in which the housing (604) with the vacuum interrupters (606, 607, 608) upon further rotation from the open position as depicted in Fig. 6b engages the contact blades (609) of each of the vacuum interrupters (606, 607, 608) with its corresponding earth switch (610, 611, 612), respectively. The operation sequence of the electrical ring main unit as described herein above is followed by the electrical ring main unit in accordance with the second embodiment and are being illustrated with the aid of Figs. 6a through 6c.

Accordingly, the invention also provides a method for operating an electrical ring main unit. The method essentially includes the operation sequence of the electrical ring main unit as herein above described.

The circuit breaker used herein is the vacuum interrupter. The vacuum interrupters are turned ON or OFF by a suitable mechanism. This constitutes to the opening or closing the contact of the circuit breaker. Besides this, the invention also includes integrating the functionality of the isolator unit as a part of the circuit breaker unit. Accordingly, the function of the isolator unit has to be performed. This is achieved by one of the three exemplary embodiments of the invention described herein above.

The contact blade which makes the contact with the bus or the earth switch has to be rotated in order to define the switching condition in accordance with the sequence of operation of the electrical ring main unit. This rotation of the contact blades fixed thereto to the vacuum interrupters is affected by the rotation embodied in one of the embodiments of the invention.

Contact blades making contact with the buses operates the electrical ring main unit in service mode. Rotation of the said contact blades through a determined angle disconnects or isolates the electrical ring main unit from the live contacts and operating it in isolation mode. Following this, the contact blades on further rotation through a determined angle establishes contact with the earthing switch causing the electrical ring main unit to operate in the earthing mode.

It is to be noted that the embodiments of the invention explained above are exemplary in nature and are not exhaustive. Any changes or modifications thereupon are construed to be within the scope of the invention.

Claims

WE CLAIM:

1. An electrical ring main unit having circuit breaker unit, disconnector and earthing switch integrated therein, said circuit breaker unit of the electrical ring main unit comprising a plurality of separate pole assemblies, each of the said pole assembly comprises an interrupter, and a mechanism for operating the electrical ring main unit.

2. The electrical ring main unit as claimed in claim 1, wherein the plurality of said separate pole assemblies is coupled by a common operating shaft.

3. The electrical ring main unit as claimed in claim 1, wherein each of the said pole assembly comprises an interrupter connected to a rotary contact at the lower end of moving stem of the said interrupter, the said rotary contact comprises an assembly of a plug and a hub, the said hub being fixed to the moving stem of the said interrupter and the said plug being fixed with a contact blade and assembled on the said hub.

4. The electrical unit as claimed in claim 1, wherein the mechanism comprises a gear mechanism for rotating the said rotary contact through corresponding links for providing rotational movement for the gear.

5. The electrical ring main unit as claimed in claim 1, wherein the mechanism further comprises a common operating shaft and capable of being operated by an operating mechanism for opening or closing the contact of the said circuit breaker.

6. The electrical ring main unit as claimed in claim 1, wherein the said disconnector is a double break disconnector.

7. The electrical ring main unit as claimed in claim 1, wherein the plurality of said separate pole assemblies is disposed within a common housing.

8. The electrical ring main unit as claimed in claim 6, wherein each of the said interrupter is fitted with contact connection bars, each disposed at top and bottom portion thereof, the said contact connection bars being the blades for maintaining contact with the earthing switch or being disconnected.

9. The electrical ring main unit as claimed in any one of claims 6 to 8 or a combination therefrom, wherein the mechanism is provided for rotating the said housing with the interrupter about a pivot located at the top or bottom portion thereof, the said mechanism may comprise a lever linking the said interrupters, the said rotation operates the electrical ring main unit in service mode or in isolation mode or in earth mode.

10. A method for operating an electrical ring main unit, the method comprising the steps of: opening or closing the contact of the circuit breaker; rotating the contact blade by a mechanism for rotation; making contact with the contact connection bars for operating the said unit in service mode; rotating the contact blade further through a determined angle by the said mechanism for rotation to operate the said unit in isolation mode by isolation from the live contacts; rotating the contact blade still further through a determined angle by the said mechanism for rotation to operate the said unit in earthing mode by making contact with the earthing switch.