FIELD OF INVENTION:
The present invention relates to extra high voltage gas circuit breakers in
general. More particularly directed towards improvement of interrupting
capabilities of such breakers by introduction of novel features of relative motion
contact system in which a movable pin which connects the moving and fixed
current carrying conductors during closing and operates on its own during
current interruption with accelerated speed without drawing energy from any
other drive and deploying a pair of dynamic field electrode to improve voltage
withstanding capabilities between contacts during arc extinction at current zero
by improving field uniformity in the inter-electrode gap.
BACKGROUND OF INVINTON
A Circuit Breaker (CB) is primarily used to interrupt normal/fault/capacitive/
inductive currents of high voltage power transmission and distribution systems.
When the CB is in closed condition it allows flow of normal electrical charge
(current) through a closed electrical system (circuit). The magnitude of current is
governed by the system characteristics and state. Short circuits, causing
abnormal flow of current, are sensed by current sensors and prevented by
isolating the source and the load by circuit breakers.
When fault current is interrupted by an interrupter, arc is struck between the
arcing contacts. The energy content of the arc depends on the current
magnitude, length of the arc and similar other parameters. As the temperature of

the arc is quite high it decomposes the insulating medium (gas) and materials
exposed to arc. Decomposed products accumulate in the vicinity destabilize
insulation and should be removed for sustaining the dielectric properties of the
inter-electrode gap for subsequent interruptions.
In conventional interrupters one of the two contacts is fixed, during interruption
the moving contact is driven by operating mechanism and an arc is struck on
contact separation (Fig.1 (a)). At current-zero the arc is extinguished naturally
exposing the developed inter-electrode gap to system and transient recovery
voltages. The gap reignites or the arc is re-struck should the gap fail to
withstand these voltages. For mechanical constraints limited inter-electrode gaps
only can be generated in conventional interrupters, promoting use of multiple
breaks for EHV circuit breakers. Up to 245kV voltage class single-break circuit
breaker designs are common, beyond this rating two or more breaks are used in
series to form a circuit breaker. The multiple breaks require voltage equalizing
devices like grading capacitors etc, affecting circuit breaker reliability and cost.
Additionally the conventional interrupters use static Meld profiling electrodes
resulting in varying field intensities as the contact separate. More clearly, when
shields are fixed the electrostatic field and voltage withstand capabilities of the
inter-electrode gap are limited. To overcome this constraint and to achieve
desired interrupter performance excess quantity of gas and higher differential
pressures are practiced by designers.
In general, to limit the voltage appearing across the contacts during interruption,
multiple breaks are preferred. The multiple break system is operated by same
drive which requires higher energy drive for its operation. To overcome this

problem, a dual motion contact system has been identified as an alternative
solution (Fig. 1.(b)). However, in all these systems, the second movable contact
i.e. other than primary moving contact takes sufficient portion of energy from the
operating mechanism. In some of the conventional breakers, such system have
relatively high energy requirements and are difficult to operate with the low
energy mechanisms (ref: US20080257866A1).
The electrostatic field, between movable and fixed contacts, is non-uniform for
various reasons like electrode profile and relative position of contacts. The field
intensification adversely affects voltage withstanding capabilities of the gap. The
availability of hot and conducting gas further complicates the situation
preventing successful interruption. Beyond particular instant of time during
current interruption, minimum arcing time is decided not only by the arc
quenching effectiveness with which arcing gas is being removed but also on the
uniformity of the electrostatic field between arcing contacts. The static shields
provided around the conventional contacts do not support uniform field during
the critical interruption process. Different methods have been employed by
researches to overcome this problem including higher creepage nozzles.
OBJECTIVE OF THE INVENTION
For successful interruption, the primary design requirements are: sufficient inter-
electrode gap; optimal dielectric properties of the gas and field uniformity in
inter-electrode gap. To address some of these requirements, a movable shield
approach has been innovated and notified, vide patent application No.
290/KOL/2009.

The main objective of the present invention is to improve the gas interrupter
performance both in terms of interrupting capacity and dielectric recovery by
inventing mainly:
1. Relative motion of contact system with a charging and toggling
mechanical system for pin and
2. A dynamic field electrode along with many other improvements.
The main objective of invention is to improve interrupting performance of higher
voltage circuit breakers as detailed hereunder:
Beyond 245 KV rating two or more breaks are used in series to form a circuit
Breaker. The multiple breaks necessitate additional features for voltage
equalizing devices like grading capacitors etc. affecting CB cost and reliability.
One of the objects of the invention is to reduce the breaks/pole of Circuit
Breakers of higher voltage class.
Another object of Invention is to provide a timed relative motion Contact System
in which a dynamic pin operates on its own during current interruption utilizing
the energy stored/gained during preceding closing operation.
Accelerated Contact Separation, another object of the invention is achieved by
designing speed of the pin based on dielectric recovery requirement of the CB at
minimum arcing time. Also the relative motion contact system introduced in the
present invention accelerates speed of contact separation as the first and second
movable contacts move in opposite direction (180 degrees orientation during
contact separation.

The conventional CB use static field profiling electrodes resulting in varying field
intensities as the contacts separate. More clearly when shields are fixed
electrostatic field and voltage withstand capabilities of inter-electrode gap are
limited. To overcome the constraint the invention proposes to ensure uniform
field intensity during contact separation through introduction of dynamic field
electrode in this invention.
One of the objective of the present invention, lowering of post-arc field intensity
is achieved by introduction of dynamic High Voltage electrode.
For mechanical constraints limited inter-electrode gap can be only be generated
in conventional circuit Breakers, promoting multiple breaks for EHV Circuit
Breaker.
One object of the invention is to optimize inter-electrode gap for a circuit Breaker
Voltage class for improvement of interruption capacity.
The arc struck between the arcing contacts when fault current is interrupted
gives rise to very high temperature depending on the current magnitude, length
of the arc etc. Such high temperature decomposes the insulating medium (gas)
and material exposed to arc. Decomposed product accumulate in the vicinity
destabilize insulation and have to be efficiently removed to sustain the dielectric
properties of the inter electrode gap for subsequent operation.
One of the object of the invention is to protect inter-electrode gap from
hot/conducting gas contamination and improved gas exhaust system.
The socket contact system, dynamic field electrode and the coupling system are
so arranged that the hot gas is vented to main volume through the guided

metallic path preventing stagnation/occupation of hot gas in the inter-electrode
gap of the contact system.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The invention is described with the help of Figures 1 to 6, where:
Figure 1: Conventional interrupters
Figure 2 : Socket contact Assembly
Figure 3 :Concept of Dynamic field electrode
Figure 4 : Invented interrupter with dynamic field electrode
Figure 5 : Concept of Relative motion contact system
Figure 6 : Invented interrupter with relative motion contact system and
Dynamic field electrode.
DESCRIPTION OF INVENTION
In the present invention, the socket [01], made of a high conductivity and low
erosion material is held on a socket support [02]. The socket is covered by a
socket contact shield [03] made from low erosion refractory material. The nozzle
[05] is fixed to dynamic current carrying (CC) contact [04] or first movable arcing
contact and to the socket contact assembly. The socket [01], socket contact
shield [03] and current carrying contact [04] are termed as the socket contact
assembly. Fig. 2 shows the socket contact assembly.
In interrupter fully open condition, the movable or second movable arcing
contact pin [06] is surrounded by a dynamic field electrode [07]. The pin is
located inside the dynamic field electrode and the arrangement is again inside

the stationary current carrying (CC) contact assembly. The pin Is dimensioned
such that it promotes uniform electrostatic field between the two contacts. The
static current carrying contact assembly comprising static current carrying (CC)
contact [08] and static current carrying contact shield [09].
In interrupter open condition, the dynamic field electrode [07] projects out from
the static current contact shield [09], and the gas gap between dynamic field
electrode and dynamic current carrying contact [04] decides the withstand
voltage. Fig. 3 shows the dynamic field electrode system. The entire contact
system is surrounded by SF6 at design density. The socket is separated from the
static current carrying contact shield by a design distance, proportional to the
system voltage and the SF6 gas density. To improve dielectric performance of the
circuit breaker, uniform electro-static field has been maintained, during
interruption, between following critical components:
1. Socket contact shield [03] and pin contact [06].
2. Dynamic field electrode [07] and dynamic current carrying
contact [04].
3. Static current carrying contact shield [09] and dynamic current
carrying contact [04].
In the invention, dynamic field electrode [07] is introduced between socket
contact assembly and static current carrying contact shield [09]. At the same
moment dynamic field electrode is guided between static current carrying
contact [08] and socket assembly. Dynamic field electrode improves electrostatic

field between socket contact assembly and static current carrying contact
assembly. Socket assembly is coupled to dynamic field electrode [07] through
nozzle [05] by means of a motion guide [10] whose profile is based on:
1. Distance to which dynamic field electrode [07] has to be moved.
2. Instant of presence of dynamic field electrode between static CC
shield [09] and socket contact assembly.
During opening operation, dynamic field electrode moves in downward direction
at a predefined instant of its operation depending on anticipated minimum arcing
time and the instant at which pin contact crosses the dynamic field electrode
[07]. More clearly, at current-zero, the voltage withstanding capabilities between
contacts is improved in the presence of dynamic field electrode [07]. Profile of
motion guide [10] is designed such that the location of dynamic field electrode
between the contacts can be adjusted for maximum benefit. The socket contact
system, dynamic field electrode [07] and the coupling system are arranged in
such a way that at first current-zero the hot gas is vented to main volume
through the guided metallic parts, preventing stagnation/occupation of hot gas in
the inter-electrode gap of the contact system.
The nozzle is connected to motion guide through suitable couplers known as
charging links [11] which in turn controls the movement of dynamic field
electrode [07]. The dynamic field electrode is clamped to motion guide by means
of guide rods [12]. The charging link [11] has a guiding slot whose length is
related to the stroke of breaker and distance by which pin [06] travels. Fig. 4
shows the interrupter with dynamic field electrode. The pin is compressed
against damper [13] force and guided by current collector [14] when the CB is in

open condition. The pin [06] is connected to the charging link [11] through a
mechanical arrangement [15]. This arrangement helps the pin [06] to engage
permanently with socket assembly and does not allow the pin to move
independently. At a particular instant of closing operation, the mechanical
arrangement [15] comes into operation and the pin guided by damper [13] gets
compressed. This in turn results in movement of pin and storage of energy in the
clamper. Once breaker is dosed, the toggle between mechanical arrangement
[15] and charging link [11] ensures pin location; the toggle is reactivated by
open command of the interrupter.
During opening operation, the pin is initially held by the socket and speed is
decided by, friction between pin and socket. The pin on release from socket
moves at a speed decided by energy stored, mass of the pin and friction offered
by current collector [14]. As the travel of the pin in controlled, pin acts as a static
contact beyond this travel. The travel of the pin is designed in conjunction with
speed of socket to suit; initial TRV, TRV and power frequency withstand
requirements. The distance to which pin [06] is displaced can be adjusted by
modifying the design parameters of mechanical arrangement [15]. Once opening
operation is completed, the pin is coupled to the charging link through
mechanical arrangement in such a way that it cannot operate on its own. Fig. 5
shows the invented interrupter with a relative motion contact system approach.
The relative motion Contact System introduced in the present invention
envisages first (04) and second movable arcing contact (06) which always move
in opposite direction, i.e. a relative motion is set between these arcing contacts.
This is a novel concept in respect of the earlier patent application No.

290/KOL/09 dated 16.2.2009 in which the second contact (06) was fixed and
the shield was movable. The concept of movable shield in the aforesaid patent
application has been further refined and termed as dynamic field electrode (07)
in the present patent application which focuses on relative motion Contact
System. The concept of dynamic field electrode is an extension to movable shield
approach of the earlier patent application. However, it differs in the following
manner.
1. The dynamic field electrode shall provide uniform field for all positions of
second movable arcing contact (06) during current interruption and
appearance of TRV across contacts.
2. At particular instant of current interruption, the second movable (06)
arcing contact comes out of the dynamic field electrode (07) and static
current carrying contact shield [09]. This may not be the situation for
movable shield approach where this may not be the design criteria.
3. The speed of dynamic field electrode and second movable arcing
contact is interrelated as they are connected to same drive. The concept
of relative motion again between the dynamic field electrode and second
movable arcing contact also plays critical role in the design of dynamic
field electrode.
The inventors propose and claim a relative motion system in which pin [06]
operates on it own during current interruption. The necessary energy required
for this movement is stored/gained during preceding closing operation. It is the
novelty of the design that the pin is again under the control of primary system
and proper dosing and opening of the contact system are ensured. The speed

of pin is designed based on dielectric recovery requirements of the interrupter at
minimum arcing time. Fig. 6 shows the invented interrupter with a relative
motion contact system and dynamic field electrode approach for gas interrupter,
in closed condition. The interrupter invented additionally features reduction in
operating energies for the interrupter.

WE CLAIM:
1. Extra high voltage gas Circuit Breaker with improved interrupting
capabilities comprising:
- a dynamic pin (06) or second movable arcing contact and a socket
assembly having a socket support (01), a socket contact shield (03) and a
dynamic current carrying contact (04) or first movable arcing contact.
- means for coupling of the socket assembly to the pin (06).
- a guiding arrangement for dynamic pin contact (06) with respect to nozzle
(05) which is fixed to dynamic current carrying contact (04) and socket contact
assembly.
- a pair of dynamic field electrode (07) so positioned that the pin (06) is
surrounded by it and the entire arrangement is again inside stationary current
carrying contact assembly comprising static current carrying contact (08) and
static current carrying contact shield (09) in CB fully open condition.
- a guiding arrangement for dynamic field electrode (07) through motion
guide (10) and charging link (11) with respect to nozzle assembly;
- a clamper (13) and charging link (11) for effective relative motion contact
system;

- an arrangement for storing energy in the damper (13) which is utilized by
the pin (06) during opening of contacts.
- a toggle between mechanical arrangement (15) and charging link (11)
ensures pin location during closing

- a means to reactivate the toggle during opening of the CB.
- an arrangement for operation of the pin (06) without consuming energy
from drive during interruption;
- an arrangement for so positioning socket contact system (01,03,04),
dynamic field electrode (07) and the coupling system that at first current zero
the hot gas is vented to main volume through guided metallic parts preventing
stagnation/occupation of gas in the inter-electrode gap of the contact system.

2. The socket (01) as claimed in claim 1 is made of high conductivity and low
erosion material.
3. The socket contact shield (09) as claimed in claim 2 is made of tow erosion
refractory material.

4. The socket assembly as claimed in claim l is coupled to dynamic field
electrode (07) through nozzle by means of motion guide (10).
5. The dynamic pin (06) or the second movable arcing contact comes out of
dynamic field electrode (07) and static current carrying contact shield (09) at a
particular instant of current interruption.

6. The first (04) and the second (06) movable arcing contacts as claimed in
claim 1 are so designed that they will always move in opposite direction (180
degrees orientation) so that a relative motion is set between the movable arcing
contacts.
7. The dynamic field electrode (07) as claimed in claim 1 is clamped to motion
guide by means of guiding rods (12).
8. The dynamic field electrode (07) as claimed in claim 1 shall provide uniform
field for all positions of the second movable contact (06) during current
interruption and appearance of transient recovery voltage (TRY) across contacts.
9. The speed of dynamic field electrode (07) as claimed in claim 1 and the
second movable contact (06) are inter-related as they are connected to the same
drive.
10. The dynamic field electrode (07) as claimed in claim 1 moves in
downward direction, during opening operation, at a predefined instant of its
operation depending on anticipated minimum arcing time and the instant at
which pin contact crosses the dynamic field electrode.
11. The pin (06) as claimed in claim 1 is so dimensioned that it promotes
uniform electrostatic field between the two contacts.
12. The entire contact system as claimed in claim 1 is surrounded by SF6
(sulphur hexaflouride) gas at design density.

13. The socket as claimed in claim 2 is separated from the static current
carrying contact shield (09) by a design distance proportional to the system
voltage and the SF6 gas density.
14. The charging link (11) as claimed in claim 1 has guiding slot whose length
is related to stroke of breaker and distance by which pin (06) travels.
15. The CB as claimed in claim 1 maintains uniform electrostatic field for
improvement of dielectric performance of the Circuit Breakers between the
following:
1. Socket contact shield (03) and pin contact (06)
2. Dynamic field electrode (07) and dynamic current carrying contact
(04).
3. Static current carrying contact shield (09) and dynamic current
carrying contact (04).
16. The motion guide of the CB as claimed in claim 1 which is responsible
for reliable operation of dynamic field electrode (07) has Its profile based on:
1. Distance to which dynamic field electrode (07) has to be
moved
2. Instant of presence of dynamic field electrode between
Static CC shield (09) and socket contact assembly.
17. The profile of motion guide (10) is designed such that the location of
dynamic field electrode between the contacts can be adjusted for maximum
benefit.

18. A system to operate EHV Gas Circuit breakers for improvement of
interrupting capabilities by introducing advance concepts of relative motion
contact system and dynamic field electrode and along with other arrangements
as substantially described herein with accompanying drawings.

The EHV Gas Circuit Breaker as disclosed in the present invention introduces
concepts of dynamic field electrode and relative motion contact system to
improve interruption capabilities of EHV gas circuit breakers.
A socket assembly (Fig. 2) comprising a socket (01), socket contact shield (03)
and current carrying contact (04) is fixed to a nozzle (05) which is connected to
a motion guide (10) through suitable coupler known as charging link (11) which
in turn control the movement of dynamic field electrode (07). The dynamic field
electrode is clamped to motion guide by means of guiding rods. The speed is
interrelated as they are connected to same d drive.
The invention also claims relative motion contact system in which pin (06)
operates on its own during current interruption drawing energy for this
movement from the stored/gained energy during preceding closing operation.
Also the first (04) and the second (06) moving contact always move in opposite
direction i.e. a relative motion is set between these two arcing contacts.
During opening operation when dynamic pin (06) moves upward, dynamic field
electrode moves in downward direction at predefined instant of its operation
depending on anticipated minimum arcing time and the instant at which pin
contact crosses the dynamic field electrode, improving withstand capabilities in
presence of the electrode, due to uniform field intensity in the inter-electrode
gap.