Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to puffer type circuit interrupters,
and more specifically relates to a novel arrangement whereby the movable ~ -
contact of a puffer type interrupter is flexibly connected to a gas
directing nozæle so that the arc between the separating interrupter con-
tacts is initially drawn downstream of the nozzle, with the movable
contact later returning to its preferred upstream position within the
nozzle after the initial arcing operation.
Single pressure SF6 type puffer interrupters are well known
in the art and commonly comprise a pair of separable contacts which are
contained within a sealed container filled with sulfur hexafluoride gas
or the like. One of the contacts is normally fixed to a nozzle~shaped
member which encloses the area of engagement between the two cooperating
contacts. The movable contact is connected to a piston and cylinder
arrangement such that, when the movable contact moves to a disengaged
position, the piston and cylinder force gas flow through the nozzle and
through the region at which the contacts separate. This then provides a
temporarily high-pressure region which moves gas through the arcing region
to assist in the extinction of the arc drawn between the separating
contacts and to sweep the space between the separating contacts clear of
ionized products.
In order to obtain interruption in this type breaker, two
conditions must be satisfied:
(1) The opening stroke of the movable contact must be suffic-
ient to establish an open gap large enough to withstand the crest of the
system recovery voltage; and
(2) The opening stroke must develop a sufficient pressure
differential across the nozzle to provide effective sweeping and deioniza-
tion of the arc space.
During the opening stroke of the movable contact, it is also
desirable to keep the energy released in the arc space to a minimum and to
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release this energy in such a manner as to minimize its effect on the -
interior components and to minimize the forces necessary to operate the
interrupter.
In puffer interrupters of this type, it is common practice to
fix a movable contact to the nozzle so that both move relative to a
stationary contact, and further to fix the end of the movable contact at
some fixed and preferred location which is upstream of the interrupter
nozzle throat. The arc which is drawn between the separating contacts in ;
such a device is then initiated upstream of the nozzle and will be drawn
through the nozzle throat during the first part of the opening stroke.
During the opening stroke and as pointed out above, the arc
produces various types of arcing products and ionized gas in the region
which is upstream of the nozzle so that these products and ionized gases
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must be swept free if interruption is to be obtained. Moreover, the arc
and heated gases produced by the arc are immediately adjacent to the
nozzle and the nozzle throat, thereby causing thermal deterioration of
the nozzle which can reduce the interrupting lifetime of the device.
A further disadvantage of the fixed positioning of the movable
contact upstream of the nozzle throat is that the initial arc which is
drawn will cause a high-pressure zone in the nozzle throat which results
in a back pressure which must be overcome by higher operating forces from
the operating mechanism. Note further that the back pressure in the
nozzle can result momentarily in a back flow of gas so that arc products
; could be brought into the puffer piston area.
In accordance with the invention, the movable contact and the
movable nozzle are movably connected to one another and the movable
contact is normally biased to a preferred location slightly upstream of the
nozzle throat. However, upon operation of the interrupter, the movable
contact and nozzle move relative to one another so that the end of the
movable contact is downstream of the nozzle throat at the time an arc is
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initiated between the separating contacts. Following the initial areing
interval, the movable contaet returns to its preferred upstream location
relative to the nozzle, when a sufficiently large open gap is formed to
withstand the erest of the system reeovery voltage and enough pressure
has developed to produce effective arc sweeping action.
Therefore, according to this invention, a puffer type circuit
interrupter comprises a stationary elongated contaet and a movable contact
movable between an engaged and disengaged position with said stationary
contact. An insulation nozzle surrounds said movable and stationary
contaets and an operating rod is eonneeted to said nozzle, said movable
contact being flexibly mounted on said operating rod and being axially
movable with respect thereto. Piston arc means connected to said oper-
ating rod for producing a flow of gas through said nozzle and through the
arc space produced by the separation of said movable and stationary
contacts. A housing surrounds said contacts, said nozzle and said piston
means and is filled with a relatively high dielectric gas. Said nozzle
has an internal nozzle throat restrietion and biasing means are provided
for biasing said nozzle and said movable eontaet to a position wherein
the end of said movable eontaet is upstream of said nozzle throat
restrietion. Said operating rod moves said nozzle throat restrietion
downstream of the end of said movable eontaet at a time following the
initial movement of said movable contact to its disengaged position,
whereby the initial areing between said movable and stationary eontaets
occurs in an arcing space downstream of said nozzle throat restriction,
and whereby said arcing space is thereafter located downstream of said
nozzle throat restriction and is swept free of arcing products by gas
flow from said piston means and through said nozzle throat restriction.
Said movable contact, said stationary contact and said nozzle are each
coaxially disposed and are each generally axially elongated. Preferably,
the dielectric gas is sulfur hexafluoride.
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The arrangement of the present invention permits release of
energy during the initial arcing period in a region which is downstream
of the nozzle, so that pressure release can be effected through the ~ ~ -
relatively open gap between the nozzle wall and the fixed contact as well
as through the hollow fixed contact if such an arrangement is used. Thus,
the undesirable effects on the nozzle of upstream reverse flow and early
contamination of the nozzle throat are largely overcome.
There is also a reduction of total energy release by elimin-
; ating or reducing gas blast in the early part of the opening stroke (when
interruption cannot be effected) so that arc voltage and thus arc energy
can be kept lower. There is also a reduction of the swept volume necessary
in the puffer piston due to the elimination of the need to clear away
initial upstream arc products which reach the piston region and a reduc-
tion of useless gas flow when the contact gap is too small to effect an
eruption. That is to say, the actual time at which contact separation ~ -
occurs may be slightly delayed while the nozzle moves relative to the
contact and toward a position in which the contact is-downstream of the
nozzle throat. This same time delay also allows time for a gas pressure ~ -
differential to build to a sufficiently high value to enable interruption
of the arc when the contacts open. A further advantage obtained by the
invention is an improvement in capacitor switching performance by mini-
mizing the possibility of interruption of the arc while the contacts are
still very close together so that restrike is more probable.
The invention will now be described further by way of example
only and with reference to the accompanying drawings, wherein:
~ FIGURE 1 is a cross-sectional view of a portion of an inter-
- rupter which incorporates the present invention, with the contacts in
- their closed position and wherein the nozzle is fixed to the operating rod
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-~- while the movable contact is flexibly connected to the operating rod.
- 30 FIGURE 2 shows the interrupter of Figure 1 immediately after
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the contacts have separated, with the separating contacts being downstream
of the nozzle throat; and
FIGURE 3 shows the interrupter of Figures 1 and 2, with the
contacts in their fully open position.
- Referring to Figures 1, 2 and 3, there is shown a portion of
a puffer breaker which includes a stationary conductive piston 10 which
can be connected to a first terminal 11 of the breaker. The member 10
may be contained within a suitable housing shown schematically by the
dotted block 12, which is filled with sulfur hexafluoride at some positive
pressure. Other gases and gas mixtures could also be used if desired.
A conductive operating rod 13 then terminates in an enlarged
head 14 which may be segmented if desired, and is in sliding engagement
with movable contact cylinder 15. The movable contact cylinder 15 may be
segmented into fingers at its right-hand end, where the fingers engage
the stationary tubular contact 16. Operating rod 13 is then electrically
connected to the stationary conductive member 10 by suitable sliding
contact members 17.
The conductive member 15 may then terminate in an annular
disk-shaped end region 18 and may have arcing contact finger type elements
19 at its right-hand end which engage the arcing contact end of stationary
contact 16. Movable contact 15 is then supported within an insulation
cup 20 which extends from disk 21 which is fixed to the interior of the
; baffle cylinder or nozzle 2Z. The baffle cylinder 22 then consists of a
- cylindrical body 23 having a restricted nozzle throat 24 where baffle
cylinder 23 is slidable on the stationary member 10 which serves as a
stationary piston for the puffer interrupter.
The disk 21 then has a plurality of openings including openings
25 and 26 therein which permit the flow of gas from the volume between
disk 21 and member 10 to flow to the right and through the nozzle throat
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24 when the circuit breaker is opened as will be later described.
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A sliding seal 30 may be provided between stationary member
10 and cylindrical portion 23 of nozzle 22 if desired. A biasing spring
35 is then captured within insulation cup 20 and biases contact cylinder
15 to the left and into its seat in the plate 21. Note that the movable
components of the breaker are all connected to one another and consist of
the operating rod 13, plate 21 and baffle 22. These components move as a
single unit when operating forces are applied to the operating rod 13.
In order to move contact 15 to the right and toward its
engaged position, the left-hand end of contact 15 is picked up by the
plate 21 and is driven to the right with the operating rod 13. In order
to move the contact to its open position, the operating rod 13 moves to the
left.
The operation of the interrupter shown in Figure 1 is as
follows:
The contacts are shown in their normally closed position in ~ -
Figure 1. In order to open the breaker, the operating rod 13 is moved to
the left. The initial movement of operating rod 13 and of disk 21 and
nozzle 22 to the left is inedpendent of the movement of contact 15 which
is held in position since the frictional engagement forces between
inwardly turned contact end 19 and the stationary contact 16 are greater
than the initial force from spring 35.
When the movable contacts reach the position of Figure 2, the
spring 35 has been compressed to a point where it is able to overcome the
engagement forces between contact 15 and stationary contact 16, and the
region of contact disengagement is now downstream of the nozzle throat 24.
Consequently, as the contacts separate in Figure 2, the initial arcing is
downstream of the nozzle throat 24 resulting in low-arc energy and minimum
pressure effect upstream of thP nozzle. It should be further noted that -
the pressure created by the initial downstream arc will bear against
surface 40 of throat 24, thereby to provide a pressure assi~t in the
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movement of the movable compo ~ ~s4 ~ot~e left during the opening of the
breaker. The spring 35 accelerates contact 15 to the left, thereby
increasing the effective speed with which a contact gap is achieved.
Furthermore, the contact 15 blocks nozzle 40 to eliminate gas flow and
pressure loss before the contacts reach a point where effective inter-
ruption can be obtained.
As the moving components continue to move to the left, the
movable contact ultimately reaches the preferred position which is up-
stream of the noæzle throat 24, which is most favorable for arc inter-
ruption and prevention of restrike. It will be noted that, during this
operation, relatively little ionized gas and contaminated arc products
will flow back toward the piston area or the region between disk 21 and
the end of stationary member 10.
Although this invention has been described with respect toits preferred embodiments, it should be understood that many variations
and modifications will now be obvious to those skilled in the art, and it
is preferred, therefore, that the scope of the invention be limited not
by the specific disclosure herein, but only by the appended claims.
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