FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A high voltage gas circuit breaker
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR
Chandalia Sandeep Kumar and Patil Ghansyam Narottam, both of Crompton Greaves Ltd, A-3 MIDC, Ambad, Nasik, Maharashtra, India, both Indian Nationals
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:


FIELD OF INVENTION
This invention relates to a high voltage gas circuit breaker.
BACKGROUND OF THE INVENTION
Typically, a high voltage gas circuit breaker is of a rating of 350 kilovolts or more and comprises of more than one interrupter assemblies. Each interrupter assembly comprises of a stationary contact and a moving contact. Each of the moving contacts are adapted to be closed and opened with the stationary contacts for marking or breaking a circuit connected across the stationary contacts. A conventional high voltage circuit breaker is constructed by connecting two sets of series connected interrupter assemblies in parallel. The device to be protected is supplied power through the stationary contacts of the series connected interrupter assemblies. Moving contacts of each of the series connected interrupter assemblies are electrically connected with each other albeit through a closing resistor in one of the sets for protecting the device from a sudden surge of current. Initially, moving contacts connected through the closing resistor are closed with the respective stationary contacts while the other set of moving contacts are kept open from the stationary contacts so as to allow the current to flow through the closing resistor. After the circuit is stabilized, moving contacts connected through the closing resistor are opened from the respective stationary contacts while the other set of moving contacts are closed with the respective stationary contacts thereby bypassing the closing resistor and
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establishing a normal flow of the current. Each of the interrupter assembly is housed in a gas filled porcelain housing for insulating purpose. The porcelain housings containing the interrupter assemblies connected in series are affixed to either sides of a gas filled tank. The porcelain housings along with the tank are mounted at an elevation with respect to the ground. Owing to the design of the circuit, the weight of the insulating bushings which are porcelain housings in this case, the high voltage gas circuit breaker is rendered heavy and costly. Also since the circuit breaker is required to be mounted at an elevation, it is prone to seismic dangers. The elevation of the circuit breaker is required to be increased with an increase in the rating of the circuit breaker resulting in further aggravation of the seismic dangers associated with it.
OBJECTS OF THE INVENTION
An object of the invention is to provide a high voltage gas circuit breaker which requires having a minimum number of insulating bushings thereby reducing its weight and cost.
Another object of the invention is to provide a high voltage gas circuit breaker having a low centre of mass thereby addressing seismic concerns associated with a heavy and elevated high voltage gas circuit breaker.
DETAILED DESCRIPTION OF THE INVENTION
In order to achieve the aforesaid and other objectives, according to the invention, a high voltage gas circuit breaker is provided comprising of a pair of interrupter
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assemblies connected in series. Each interrupter assembly comprises of a stationary contact, a first moving contact and a second moving contact wherein the first moving contacts of each interrupter assembly are electrically connected to each other through a closing resistor and adapted to close with the respective first stationary contact. The second moving contacts of each interrupter assembly are electrically connected to each other and adapted to close with the respective first moving contacts.
According to another embodiment of the invention, a high voltage circuit breaker is provided comprising of a pair of interrupter assemblies each comprising of a first stationary contact and a first moving contact. The interrupter assemblies are connected in series through a second stationary contact and a second moving contact adapted to close with the second stationary contact. The first moving contacts of each interrupter assembly are electrically connected with each other through a closing resistor and adapted to close with the respective stationary contacts. The second stationary contact is electrically connected to one of the first moving contact and the second moving contact is electrically connected to the other first moving contact.
These and other aspects, features and advantages of the invention will be better understood with reference to the following detailed description, accompanying drawings and appended claims, in which,
Fig la illustrates a high voltage gas circuit breaker according to one embodiment of the invention.
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Fig lb illustrates a circuit diagram corresponding to the high voltage gas circuit breaker as shown in Fig la.
Fig 2a illustrates a high voltage gas circuit breaker according to another embodiment of the invention.
Fig 2b illustrates a circuit diagram corresponding to a high voltage gas circuit breaker as shown in Fig 2a.
Fig la illustrates a high voltage gas circuit breaker according to one embodiment of the invention. The high voltage gas circuit breaker comprises of two series connected interrupter assemblies 1 & 2. Each interrupter assembly 1 & 2 is enclosed within a gas filled porcelain housing 3 affixed to either sides of a gas filled tank 4 for insulating purpose. Each interrupter assembly 1 & 2 comprises of stationary contact 5, a first moving contact 6 and a second moving contact 7. The first moving contact 6 and the second moving contact 7 of one assembly are electrically connected to the respective first 6 and second 7 moving contacts of the other interrupter assembly. However, to protect and stabilize a load connected to one end of the circuit breaker from a sudden surge of current when the power supply is resumed, a pair of series connected closing resistors 8 enclosed within the tank 4 are inserted in the electrical path of the first moving contacts 6. Practically, the closing resistors 8 are in the order of a few hundred ohms depending on the rating of the circuit breaker. The porcelain housings 3 along with the tank 4 are elevated by two gas filled porcelain towers 9 & 10 mounted on a drive block 11. The
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degree of elevation depends on the rating of the circuit breaker. The drive block 11 houses a drive mechanism for driving a drive rod 12 connected to each of the moving contacts 6 & 7 through the porcelain towers 9 & 10. The drive rod 12 enables the first moving contacts 6 in each interrupter assembly 1 & 2 to open and close with the respective stationary contacts 5 and the second moving contacts 7 in each interrupter assembly 1 & 2 to open and close with the respective first moving contacts 6. The stationary contact 5 of one interrupter assembly is connected to the power supply while the stationary contact 6 of the other interrupter assembly is connected to the load or the device to be protected. Initially on, before switching on the power supply, the first moving contacts 6 in each of the interrupter assembly are closed with the respective stationary contacts 5 and the second moving contacts 7 in each of the interrupter assembly is kept open from the respective first moving contacts 6 thereby enabling the current to flow to the device through the closing resistor 8. After a while when the device is stabilized, which is practically in the order of 10 milliseconds or more, depending upon the rating of the circuit breaker, the second moving contacts 7 in each of the interrupter assembly 1 & 2 is closed with the respective first moving contacts 6 thereby allowing the closing resistor 8 to be bypassed and establish a normal flow of current to the load. Fig lb illustrates a circuit diagram corresponding to the gas circuit breaker as shown in Fig la. Switches 13 & 14 correspond to the contact points between the stationary contacts 5 in each interrupter assembly and the respective first moving contact 6. Switches 15 & 16 correspond to the contact points between the first moving contacts 6 in each interrupter assembly and the respective second moving contact 7. When switches 13 &14 are closed and 15 & 16 are open, an electrical path is established is established between the two
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stationary contacts 5 of the two interrupter assemblies 1 & 2 through the closing resistor 8. When all the switches 13, 14, 15 & 16 are closed, an electrical path is established bypassing the closing resistor 8 from the circuit.
Fig 2a illustrates a high voltage gas circuit breaker according to another embodiment of the invention. The high voltage gas circuit breaker comprises of a pair of interrupter assemblies 1 & 2? each interrupter assembly 1 .& 2 comprises of a first stationary contact 5 and a first moving contact 6. The interrupter assemblies are connected in series through a second stationary contact 17 and a second moving contact 18 enclosed within a gas filled tank 4. Each interrupter assembly 1 & 2 is enclosed within a gas filled porcelain housing 3 affixed to either sides of the gas filled tank 4 for insulation purpose. One of the first moving contacts 6 of the interrupter assembly 1 is electrically connected to the second stationary contact 17 and the other first moving contact 6 is electrically connected to the second moving contact 18. To protect and stabilize a load connected to one end of the circuit breaker from a sudden surge of current when the power supply is switched on, a pair of series connected closing resistors 8 enclosed within the tank 4 are inserted in the electrical path of the first moving contacts 6. Practically, closing resistors 8 are in the order of a few hundred ohms depending on the rating of the circuit breaker. The porcelain housings 3 along with the tank 4 are elevated by two gas filled porceJain towers 9 & 10 mounted on a drive block 11. The degree of elevation depends on the rating of the circuit breaker. The drive block 11 houses a drive mechanism for driving a drive rod 12 connected to each of the moving contacts 6 & 18 through the porcelain towers 9 & 10. The drive rod 12 enables the first moving contacts 6
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in each interrupter assembly 1 & 2 to open and close with the respective first stationary contacts 5 and the second moving contact 18 to open and close with the second stationary contact 17. The first stationary contact 5 of one interrupter assembly is connected to the power supply while the stationary contact 6 of the other interrupter assembly is connected to the load or the device to be protected. Initially on, before switching on the power supply, the first moving contacts 6 in each of the interrupter assembly are closed with the respective first stationary contacts 5 while the second moving contact 18 is left open from the second stationary contact 17 thereby enabling the current to flow to the device through the closing resistor 8. After a while when the device is stabilized, which is practically in the order of 10 milliseconds or more, depending upon the rating of the circuit breaker, the second moving contact 18 is closed with the second stationary contact 17 thereby allowing the closing resistor 8 to be bypassed and establish a normal flow of current to the load. Fig 2b illustrates a circuit diagram corresponding to the high voltage gas circuit breaker as shown in Fig 2a. Switches 19 & 20 correspond to the contact points between the first stationary contact 5 in each interrupter assembly and the respective first moving contact 6. Switch 21 corresponds to the contact points between the second moving contact 18 and the second stationary contact 17. When switches 19 & 20 are closed and 21 is open, an electrical path is established is established between the two stationary contacts 5 of the two interrupter assemblies 1 & 2 through the closing resistor 8. When all the switches 19, 20, 21 are closed, an electrical path is established bypassing the closing resistor 8 from the circuit.
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According to the invention, since the high voltage circuit breaker comprises of only two porcelain housings instead of four, a substantial weight of the circuit breaker is eliminated thereby reducing the cost of the high voltage circuit breaker as well as addressing the seismic concerns associated with a bulky and elevated high voltage gas circuit breaker.
The constructional features of the high voltage circuit breaker may vary. Instead of using porcelain housings as insulating bushings, insulating bushings of some other type can be used. Instead of two porcelain towers elevating the gas tank, there can be one or of other type. There can be more than one pre-insertion resistors used in the circuit. The location of the drive mechanism may not be at the base and may be located elsewhere.
Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiment, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the invention as defined.
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We claim:
1. A high voltage circuit breaker comprising of a pair of interrupter assemblies
connected in series, each interrupter assembly comprising of a stationary contact,
a first moving contact and a second moving contact wherein
• said first moving contacts of each interrupter assembly are electrically connected to each other through a closing resistor and adapted to close with the respective stationary contacts;
• said second moving contacts of each interrupter assembly are electrically connected to each other and adapted to close with the respective first moving contacts.

2. The high voltage circuit breaker as claimed in claim 1, wherein said closing resistor is bypassed from the circuit while the second moving contacts in each assembly is closed with the respective first moving contacts.
3. An high voltage circuit breaker comprising of a pair of interrupter assemblies, each interrupter assembly comprising of a first stationary contact and a first moving contact, said interrupter assemblies connected in series through a second stationary contact and a second moving contact adapted to close with the second stationary contact, wherein
• said first moving contacts of each interrupter assembly are electrically
connected with each other through a closing resistor and adapted to close
with the respective first stationary contacts wherein said second stationary
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contact is electrically connected to one of the first moving contact and said second moving contact is electrically connected to the other first moving contact.
4. The high voltage circuit breaker as claimed in claim 1 and 3, wherein, each of the interrupter assembly is enclosed in gas filled porcelain housing mounted on either side of a gas filled tank for providing insulation to the interrupter assemblies.
5. The high voltage circuit breaker as claimed in claim 4, wherein said closing resistor is placed within the gas filled tank.
6. The high voltage circuit breaker as claimed in claim 3 and 4, wherein said second moving contact and the second stationary contact are enclosed within the gas filled tank.
7. The high voltage circuit breaker as claimed in claim 4, wherein said porcelain housings and the gas filled tank are elevated by at least one gas filled porcelain tower mounted on a drive block comprising of a drive mechanism for driving said moving contacts.
8. The high voltage circuit breaker as claimed in claim 7, wherein said porcelain tower encloses a drive rod driven by the drive mechanism and connected to each of the moving contacts.
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9. The high voltage circuit breaker as claimed in claim 1 & 3, wherein said closing resistor includes more than series connected closing resistors.

Dated this 22nd day of October 2008

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(Prita Madan)
ofKhaitan&Co
Agent for the Applicants