Note: Descriptions are shown in the official language in which they were submitted.
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Reference ls made to th~ below-listed U.S. Patents
which are assigned to the ~ame assi8nee a~ the present invention.
1. U.S~ Patent No. 4~161,621 is~usd July 17~ 1979
; to P, C~ Bolin et al, entitled "Spacer Mount For A Gas In~ulated
Transmission Line".
2. UOS. Patent No. 4,085,807 i~l~ued April 25, lg78
to P0 C. Bolin~ entitled "Gas In~ulated Transmi~ion Line
With Closed Particle Trap".
. 3. UOS. Patent NoO 4,105,859 i~sued Augu~t 8, 1978
; 20 to Ao H. Cook~on et al~ entitled "Compartmentalized Ga~ Insulat~d
Tran~mission Line".
.~ ~
~ his invention relates generally ~o high ~oltage
electrlcal apparatu~, and more particularly ~o the use o~ a
polypropylelle felt ~ilt~r in ga~-in~ulated electrical app~ratus.
; . Ga~-insulated ele~trical equipment i~ being u~sd
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On an ever-increasing scale for the transmlssion and distri-
bution of electrical energy, particularly at higher volt-
ages. This equipment offers advantages in the reduced land
area required, the increased safety because of the typically
grounded outer enclosure of the equipment, the non-toxicity
of the insulating gas even in the presence of decomposition
products, and the quieter operation of the equipment. Also,
for gas-insulated transmission lines, there is no disturb-
ance of the surrounding environment by the intrusion of
electromagnetic fields from the high current-carrying con-
ductor, because of the grounded outer sheath.
In this gas-insulated equipment, there are numer- ;~
ous locations where it is desirable to provide a flexible
filter material within the outer enclosure of the equipment.
The purpose of this flexible filter is to prevent the pass-
age of particulate matter, which can cause deleterious
effects and a lessening of the dielectric strength of the
insulating gas, but which filter should allow the passage of
the insulating gas, which typically is sulfur hexafluoride.
For all of these apparatus~ it is required that the filter
material be compatible with the dielectric-type materials
present within the apparatus, and with the insulating gas.
` A critical requirement is that in the unlikely event of an
` arc in sulfur hexafluoride, for example due to a failure,
- the filter material should not be attacked by the arc pro-
ducts in the sulfur hexafluoride. This latter requirement
eliminates virtually all of the open cell foam materials
such as polyurethane and polystyrene,` which are attacked by
sulfur hexafluoride products and can disintegrate. Mater
ials that are not attacked by sulfur hexafluoride products~
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such as polypropylene and te:trafluoroethylene ~
cannot be made in an open cell foam structure to allow the
: passage of sulfur hexafluoride gas. Thus, what is needed is
. : a filter material for use in gas-insulated electrical appa-
-.............. ratus which will prevent the passage of particulate matter
but which will allow the passage of the insulating gas.
. SUMMARY OF THE INVENTION
In accordance with this invention, electrical
apparatus includes an enclosure which contains an insulating
gas, typical of which is sulfur hexafluoride, and a filter
is disposed at selected locations within the enclosure. The
filter is made Or polypropylene felt, which~ will allow the
passage of the insulating gas therethrough but prevent the
passage of particulate matter.
. BRIEF DESCRIPTION OF TH~ DRAWINGS
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. Reference is now made to the descriptlon o~ the
. preferred embodiments, illustrated in the accompanying
drawing, in which:
Figure 1 is a sectional view of a gas~insulated
~ 20 transmission line, typical of the electrical apparatus which
:: may utilize the invention;
Figure 2 is a cross-sectional view of the trans- ~
mission line taken along line II-II of Figure l; : ~-
Figure 3 is a detailed view of the filter utilized
~ in conjunction with a spacer ring in a transmission line; :.
:~ Figure 4 is a detailed view of the filter utilized
in conjunction with an insulating support;
Figure ~ is a view of the filter utilized with a
plug-in conductor Joint; and
Figure 6 is a view illustrating the filter used in
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47,93San insulating support spacerO
DESCRIPTION OF THE PR~F~RP~D EMBODIMENT
Figure 1 illustrates a gas~insulated kransmission
line, ~hich is ~ypical of the types of elec~rical apparatus
which may utilize the teachings of this inYention~ U7 So
Patent No~ 39~56,97~ issued December 24, 1974 to Sletten et al
illustrates numerous other examples of gas-insulated electrical
apparatus i~ which the invention of the present application
may be utilized. The transmission line 10 of Figure 1 is
comprised of an elongated, cylindrical outer sheath 12 which
is typically at low or ground potential7 an inner conductor
14 disposed within the outer sheath 12? and an insulating gas
16 which is generally sulfur hexafluorlde disposed within the
outer sheath 12 and which gas 16 electrically insulates the
inner conductor 14 from the grounded outer sheath 12. The
inner conductor 14 is typically at a high electrical potential,
for example 145-1200 kV, and both the ou~er sheath 12 and
the inner conducting member 14 l~ill be oP a good electrically
; conducting material such as aluminum~ Means 1~ are uti.lized
for insulatably supporking the inner conductor 1l~ wi~hin ~he
outer sheath 12. The support means 1~ illustrated in ~igures
: 1 and 2 are insulating supports 20 which compri~e a cen~ral
portion 22 and a plurality of legs 24 which extend from the
;: sentral portion 22 outwardly to the outer sheath 12
.. The support 20 is typically comprised of an epoxy resin
material. Secured to the insulating support 20 is a
particle trapping ring 26 which has a plurality of openings
2~ thereinO The ring 26 is electrically connected to the
.~ outer sheath 12, as by the contact 30, so as to form a low
field region 32 between the rlng 26 and the ou~er
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sheath 12. Elec~rically conducting or semiconducting par-
ticles which may be contaminaking the interior of the outer
`. sheath 12 can then pass through the openings 2~ in the ring
26 and be entrapped wlthin the low field region 32 there-
between so as not tQ cause electrical flashover or breakdo~
. within the transmission line 10~ One location where it may
be desirable to provide a filter is in the low field region
32 between the particle trapping ring 26 and the outer
sheath 12.
As shown in F~.gure 3, in some locations, the
transmission line 10 of Figure 1 may be disposed at an angle
to the horizontal, so that any particles which may have been
trapped within the low field region 32 would have a tendency,
due to gravity, to migrate out of the low field region 32~
: Because of this possible migration, it is desirable to in-
clude a barrier 34 at ~he longitudinal end 36 of the par-
ticle trapping ring 26 to prevent this migration of particles
from within ~he low field region 32. As descr-i.bcd in the
referenced U. S. Patent 4,0~5,~07, the barr~er 34 should ~.
be in contact with both the outer sheath 12 and the
:~ trapping ring 26. Thus, in this loca~lon, it may be desir- `
able to provide a seal or filter which will prevent the
passage oP particulate ma~ter~ and where it may be desirable
to allow the passage of the insulating5 sulfur hexafluoride
gas~ m e barrier 34t which would also be the filter9 is
made of a polypropylene Pelt material~ This filter 34 would
. not be attacked by sul~ur hexafluoride, and can operate
.` satisfactorily e~en in the even~ of a sulfur hexafluoride
arc. The Pilter~ of polypropylene felt, can be made ko khe
. 30 required porosity and ~ilter size by weaving po~ypropylene
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~ fibers of suitable diameter and suitable mesh. If necessary
or desirable, the filter ma~erial can be glazed and singed
so as to bind the fibers into the pack~ or filter, and
prevent the fibers from working loose.
Figure 4 illustrates another location where it is
desirable to provide a filter which will prevent the passage
of contaminating particles but will allow the passage of
sulfur hexafluoride gas9 which filter must be impervious to
the effects of sulfur hexafluoride or the arc products
resulting therefrom. In this figure, ~he support means 1
comprises a barrier insulator 40, illustrated as being of
conical cross section) which is secured to the inner con~
ductor 14 and extends to a support ring 42 which is disposed :
.~ adjacent to, and secured to, the outer sheath 12. A more
detailed description of this type o~ barrier insulator 1~0
. and the support ring 42 may be found in the referenced
:~ U. S. Patent 4~161,621. The purpose of this barrler
insulator 40, is to substantially compar~mentalize ~he
;~ sections of the transmission line 10 on opposing long1tu-
. 20 dinal sections 44, ~6 of the barrler ~nsulator 400 B~ such
-. compartmentalizing, any fault which occurs in one section9
.~ for example 44, will not transmit its contamination par- -
ticles across the support insula~or 40 into the other trans- :
missi.on line section 46~ However7 to facilitate the filling
~ of the transmission line 10 with sulfur hexafluoride gas9 it
~ is desirable to provide a means for allo~ng the passage of
the gas past the barrier insulator 40. This can be provided
by the filter ~. As with the preceding embodimentO this
filter should allow the passage of the sulfur hexafluoride
gas without permit~ing the passage of the contamination
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`: particles. The filter 48 may be disposed wlthin an opening
50 within the support ring 42,. and the filter 48 should
contact both the ring 42 and the outer sheath 12. The
filter 48 is of the polypropylene felt material previously
: described with respect to Figure 3.
Another location where it may be desired to util-
.. ize the propylene felt filter of this invention is illus-
.~. trated in Figure 5. This ~igure illustrates a plug-in joint
connection between electrically conducting members 56, 58,
. 10 which, for example, may be two sections of the inner con- ;
: ductor 14. The one electrically conducting member 56 would :
. have a plug member 60 at one end thereof, and the other
.; electrically conducting member 58 would hav.e a socket 62 at
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one end thereof. The plug member 60 would be disposed
within the socket 62 to provide electrical connection be- :
tween the conducting members 56 and 58. A plurality of
contacts 64 may be utilized to provide electrical contact
: between the plug member 60 and the conducting member 58. To
minimize corona and arcing at this connection, a shield 66
20 may be disposed about and encircle this ~oint connection. .:
The shield 66 would extend longitudinally outwardly to both
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the conducting members 56 and 58. A mounting rod 68, or a ~.
plurality of similar rods, would be utilized for securing
the shield 66 to the conducting member 58. A wiper 70 would
.. be disposed between the shield 66 and the conducting member ;
56 to prevent the escape of any conducting particles from
the area 72 between the shield 665 the conducting members 56
:~ and 58~ and the plug member 6~ to the insulating gas 16.
However9 it is desirable to.allow this insulating gas 16 to
~; 3o enter into this ~oint region 72. Thi.s can be accomplished,
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: without allowing the passage. of the contamination particles,
. which may be generated by the sliding action of the plug
member 60 in the socket 62, by utilizing a polypropylene
felt filter 74. This filter 74, of the polypropylene felt
: construction previously described, would be disposed wlthin
an opening 76 in the shield 66, and would contact both the
; shield 66 and the conducting member: 58. By being so dis-
; posed, the filter 74 would allow the passage of the insulat-
ing gas 16 into the region 72 of the joint, but would pre-
vent the passage of conducting particles from wlthin the
!~ j oint area 72 outwardly into khe insulating g2s 16 where it
may cause flashover and breakdown. Although described with
respect to the transmission line 10 of Figure 1, the plug-in
joint of Figure 5 ma~, for example, be within a disconnect
switch, a gas-insulated substation, or any other gas-lnsul-
ated electrical apparakus.
Another location wherein the polyethylene felt
~ilter may be utilized in i.llustrated in Figure 6~ In this
Figure, the insulating spacer 80 completely ~ills in the
cross-sectional area between the inner conductor 14 and khe
outer sheath 12. The spacer 80 has a central opening 82
therein through which khe inner conductor 14 extends, and
one or more openings 84 which extend longitudinally khrough
the spacer 80. In this opening 84 is disposed the poly-
propylene felt filter 86, which can be utilizeq tc stop the
migration o~ decomposition particles, dust, or dirt past the
insulaking spacer 80, but which permits the flow of the
insulating gas therethrough throughout the len~th of the
transmission line 10. A more detailed descripti:on of thi.s
type of insulaking spacer 80~ with.`its openings 84 therein,
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may be found ln the United States patent to Artbauer et al~U~ S. Patent No. 37996f~14 issued December 7, 1976. As
before~ the polypropylene felt fil~er ~6 can be made to the
desired velocity and filter size by weaving polypropylene
fibers o~ suitable diameter and suitable mesh, and may be
glazed and singed so as to bind the fibers in~o the filter
and prevent the fibers from working loose.
Thus, it can be seen that this invention provides
a filter which prevents the passa~e of contamination dust
.
but which allows the passage of the insulating gas in gas :~
insulated electrical apparatusO The polypropylene felt
filter can be utilized in ~hose numerous loca~ions in gas-
insulated electrical appara~us whère it is desired to pro-
vide such filteringg and provides such filtering without
being attacked by a sulfur hexaM uoride arc or the decompo-
sition products resulting from such arc,
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