FIELD OF INVENTION :
The present invention generally relates to a process of current interruption in
a gas circuit breaker. More particularly, the present invention relates to a
pressure - propelled contact system for gas circuit breaker.
BACKGROUND OF THE INVENTION :
Puffer type gas circuit breakers are employed to interrupt normal and short
circuit current generated during fault conditions in a high voltage transmission
system. In a puffer type gas circuit breaker with insulating nozzle, gas is
stored in an enclosure at a predetermined high pressure and further
compressed by a cylinder piston to a higher pressure in a compression
chamber generally termed as a puffer or blast cylinder. The compressed gas
from the blast cylinder is discharged through an insulating nozzle at a very
high velocity to blow out the high temperature arc plasma that is struck
between a pair of arcing contacts. The arc that is surrounded by the
envelope of high pressure gas eventually gets lengthened and quenched to
interrupt the flow of current.
Indian Patent No.217361 disclosed a puffer type gas circuit breaker with
movable piston and metallic blast cylinder in which the moving piston
compresses the gas within a fixed metallic blast cylinder as opposed to the
then state of art circuit breakers, wherein a moving cylinder compresses the
gas against a fixed piston.
In the interrupter of the gas circuit breaker disclosed in the prior patent
No.217361 during the process of current interruption formation of an
insulating gap between a designated fixed arcing contact and the moving
arcing contact is entirely governed by the movement of the movable arcing
contact. The movable ...

arcing contact is driven by a circuit breaker operating mechanism. At any
instant, the speed of the movable contact for a given mass depends on the
energy supplied by the operating mechanism. During the process of current
interruption, the gap between the movable and fixed arcing contacts is
dependent on the speed of the movable contact. At the point of current
interruption, this gap plays a major role in withstanding the transient recovery
voltage for a successful current interruption. Thus, the gap between the two
arcing contacts at the instant of current interruption is one of the factors for
determining the total time required for arc extinction inside the interrupter
and designated as the arcing time of the interrupter. In order to achieve a
lower arcing time, the relative speed between the contacts has to be
improved by increasing the energy supplied by the operating mechanism
which in turn imposes additional stresses on the operating mechanism and
the movable system. The restrictions on speed thus imposed, limits the scope
for achieving further reduction in the arcing time of the interrupter for a
given configuration.
OBJECTS OF THE INVENTION :
It is therefore an object of the invention, to propose a pressure - propelled
contact system for gas circuit breaker, during the process current
interruption, which imparts movements to the designated fixed contacts
which is additional to the actuation provided to the moving contact by the
operating mechanism.
Another object of the invention is to propose a pressure - propelled contact
system for gas circuit breaker, which ensures a higher relative speed between
the contacts in a process of current interruption without increasing the energy
input to the operating mechanism.

A still another object of the invention is to propose a pressure - propelled
contact system for gas circuit breaker, which enables to reduce the arcing
time of the GCB for a given configuration of the gas circuit-breaker.
Yet another object of the invention is to propose a pressure - propelled
contact system for gas circuit breaker, which improves the voltage
withstanding capability of the interrupter at the instant of current interruption
by increasing the gap between the fixed and moving arcing contacts at a
faster rate by causing a movement of the designated fixed arcing contact in a
direction opposite to that of the movable arcing contact.
A further object of the invention is to propose a pressure - propelled contact
system for gas circuit breaker, which is enabled to improve voltage
withstanding capacity of the interrupter after current interruption for a given
energy level of the operating mechanism.
SUMMARY OF THE INVENTION :
Accordingly there is provided a pressure - propelled contact system for gas
circuit breaker, comprising a movable piston in a metallic blast cylinder for
interrupting high electric current; a pressure propelled fixed arcing contact
means; and a movable contact means enabled to move in opposed directions.
The invented system is capable to achieve improved interruption and reduce
the arcing time during current interruption process in a gas circuit breaker
interrupter.
According to the invention, a movement of the designated fixed arcing
contact facilitates early expulsion of arced gas through the throat of the
insulated nozzle resulting in faster current interruption.

An increased gap enables a higher voltage withstanding capability of the
Circuit breaker interrupter during the process of current interruption.
The inventive system with a dual contact movement improves the interrupting
capability in terms of higher voltage withstandability, lower arcing time at
higher currents without any additional mechanical energy input to the
operating mechanism of the Circuit breaker.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS :
The proposed invention will be better understood from the description with
reference to the accompanying drawings in which
Figure 1 represents a puffer interrupter for gas circuit breaker with a moving
Piston, a metallic blast cylinder, and an insulating nozzle with a designated
fixed arcing contact according to the prior art.
Figure 2 represents a puffer interrupter for gas circuit breaker with a moving
piston, a metallic blast cylinder, and an insulating nozzle with a pressure
propelled fixed arcing contact means in which movement of the designated
fixed arcing contact is effected in a direction opposite to that of the
designated movable contact by the pressure generated during the process of
current interruption, according to the invention.
Figure 3 represents a detailed view of the pressure propelled fixed arcing
contact means indicating the movement of the contact means during current
interruption including the direction of movements of both the arcing contacts
according to the present invention.

Figure 4 represents the detailed construction of the pressure propelled fixed
arcing contact system according to the invention.
DETAIL DESCRIPTION OF THE INVENTION :
An embodiment of the invention as depicted in the accompanying drawings
will now be described. However, there can be several other embodiments of
the same invention, all of which are deemed covered by this description.
As shown in figure 1, the prior art interrupter for gas circuit breaker
comprises an insulating chamber (1); a fixed contact system (2); a moving
contact system (3); a fixed contact terminal (4); a movable contact terminal
(5); a fixed contact support (6); a normal current contact (7); a designated
fixed arcing contact (8); a high voltage shield (9); a movable contact support
(10); a metallic blast cylinder (11); a movable piston (12); an insulating
nozzle (13); a moving arcing contact (14); a link to operating mechanism
(15); and a movable contact tube (16). The isolating gap and the
corresponding volume are represented respectively by the alphabets "A" and
"B" in figure 1.
Gas is stored at a high pressure in the insulating chamber (1), and the gas is
further compressed to higher pressure inside the metallic blast chamber (11)
and the movable piston (12) effects the gas compression. The insulating
nozzle (13) blows the high pressure compressed gas over the high
temperature arc that is stuck between the pair of designated fixed (8) and
moving (14) arcing contacts.
The efficiency of a gas circuit breaker depends upon how quickly the high
temperature arc can be extinguished or "blown out".

For the prior art, circuit breakers, which blow out an arc with compressed
gas, the breaking capacity is depended on unidirectional movement of the
movable contact system (3) only and such unidirectional movement limits the
relative speed and the gap between both the arcing contacts which play a
vital role in the process and capacity of current interruption. Interrupting
capability and arc extinction can be effected more easily and quickly, if the
relative speed and gap between the two arcing contacts are increased during
current interruption/arc extinction.
The present invention achieves an increase in the relative speed including an
improved gap between the two arcing contacts by providing an additional
movement ('E' shown in figure 3) in the designated fixed arcing contact with
the help of a differential pressure generated due to the cylinder-piston action
in a puffer type interrupter. Additionally, the magnitude of the differential
pressure thus generated is increased due to the heat generated during the
process of arc interruption, thereby further assisting the movement of the
designated fixed arcing contact (8).
Figure (3) shows the detailed view of the present invention showing the
relative directions of movements of the designated fixed arcing contact
(upward arrow) and movable arcing contact (downward arrow). The
designated fixed arcing contact (8) moves against a compression spring (18)
due to the differential pressure developed during the current interruption
process. This compression spring (18) enables the designated fixed arcing
contact (8) to restore to its initial position after completion of the process of
current interruption or arc extinction. The constituent components of the
interrupter are shown in figure (2).

The improvement on the prior art of figure 1 is characterized by
(a) additional movement (E) in the designated fixed arcing contact (8).
(b) a compression spring (18) fitted in the designated fixed arcing
contact (8) as shown in figure (3) to facilitate the additional
movement and improve the relative speed between the two arcing
contacts (8 & 14) without any physical coupling to the movable
contact system.
This additional gap enables faster building-up of dielectric across the contact
gap and there by shorten the arcing time during current interruption. Thus by
providing the designated pressure propelled fixed arcing contact system, the
total fault current duration in the electrical network is reduced, improving the
system reliability.

WE CLAIM :
1. A pressure-propelled contact system for gas circuit breaker
interrupter, comprising :
- an insulating chamber for storage of gas;
- a metallic blast cylinder having a movable piston for pressurizing the
gas supplied from the insulating chamber;
- an insulating nozzle for blowing compressed gas over a high
temperature arc when formed due to electrical fault between a pair of
designated fixed contact means, and a moving arcing contact means;
Characterized in that the designated fixed arcing contact is configured
as movable so as to move due to a differential and arc pressure
generated during the current interruption process, in that a
compression spring is provided to the fixed arcing contact to facilitate
increase the relative speed between the fixed arcing contact and the
moving arcing contact, and in that a substantial increase in the gap
between the contacts is achieved.
2. The system as claimed in claim 1, wherein the pressure energy
developed during the current interruption is adapted to effect a
movement in the designated fixed contact which is attached to the
fixed contact support.
3. The system as claimed in claim 1, wherein the insulated nozzle is
enabled an early expulsion of the arc gas due to movement in the
designated fixed arcing contact.

4. The system as claimed in claim 1, wherein the increased gap
between the two arcing contacts during the state of current
interruption enables the gas circuit breaker interrupter to withstand
higher voltage.
5. A pressure-propelled contact system for gas circuit breaker
interrupter, as substantially described and illustrated herein with
reference to the accompanying drawings.

The invention relates to a pressure-propelled contact system for gas circuit
breaker interrupter, comprising : an insulating chamber for storage of gas; a
metallic blast cylinder having a movable piston for pressurizing the gas
supplied from the insulating chamber; an insulating nozzle for blowing
compressed gas over a high temperature arc when formed due to electrical
fault between a pair of designated fixed contact means, and a moving arcing
contact means; Characterized in that the designated fixed arcing contact is
configured as movable due to a differential pressure generated during the
current interruption process, in that a compression ring is provided to the
fixed arcing contact to increase the relative speed between the fixed arcing
contact and the moving arcing contact, and in that a substantially physical
coupling between the contacts is achieved due to elimination of the gap
between the contacts.