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Патент USA US3083267

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March 26, 1963
ca. E. ANDREWS ETAL
3,083,257
LIQUID-INSULATED ELECTRIC CABLES
Filed Sept. 23. 1959
2FIG.
FIG.3
INVENTORS
GLENN E. ANDREWS
BY GEORGE FEICK III
71,“; W,M%M
* 44
ATTORNEYS
United States Patent ()??ce
1
3,083,257
Patented Mar. 26, 1963
2
result of the periodic power load fluctuations to which
virtually all cables are subjected during the course of
their daily operation. When the power load increases,
the conductors of the cable are heated and they raise the
temperature of the dielectric liquid within the enclosure
member. Conversely, a decrease in the power load cools
the conductors and they then lower the temperature of the
3,083,257
LIQUID-INSULATED ELECTRIC CABLES
Glenn E. Andrews and George Feiclr III, Needham, Mass,
assignors, ‘by mesne assignments, to Anaconda Wire
and Cable Company, Hastings on Hudson, N.Y., a
corporation of Delaware
Filed Sept. 23, 195?, Ser. No. 841,715
8 Claims. (Ci. 174-14)
surrounding dielectric liquid. Hence, a corresponding
cyclic contraction and expansion of the liquid occurs
This invention relates to electric power cables of the 10 within the cable during its operation. This cyclic expan
type which include an extended outer enclosure member
sion and contraction is used according to this invention
and an insulating liquid contained within the enclosure
to pump the liquid in through the inlet check valve and
member and, more particularly, to such a liquid~insulated
out through the outlet check valve.
electric power cable combined with a new self-pumping
When the dielectric liquid is pressurized, as it often is
system for circulating the insulating liquid through the 15 in electric power cables for very high voltage service, a
enclosure member.
preferred form of the invention provides correspondingly
Dielectric hydrocarbon oil which has been used as an
pressurized supply and discharge reservoirs from which
insulating ?uid in an electric power cable of the type
and into which the liquid may be delivered. The inven
described usually evidences a certain amount of chemical
tion also contemplates the use of a suitable recycling
deterioration after exposure to high voltages over pro 20 system between the supply and discharge reservoirs which
longed periods of time. Such deterioration appears to be
permits the used oil to be re-conditioned to its original
due to a progressive oxidative degradation of the oil which
insulating efficiency.
causes a reduction in its dielectric strength and a corre
These and other advantages of the invention are ap
sponding increase in its power factor.
Consequently,
parent in the following description of preferred embodi
sustained use of a given quantity of dielectric oil in a 25 ments thereof, wherein
power cable operating at high voltages impairs the di
electric e?iciency of the cable insulation. This effect is
particularly noticeable in conventional lead-sheathed and
FIG. 1 is a schematic illustration of a lead-sheathed
oil-?lled cable combined with the new circulating means;
FIG. 2 is a section taken along the line 2-2 of FIG. 1;
FIG. 3 is a schematic illustration of a pipe-type oil
pipe-type cables containing a’ hydrocarbon oil impregnant
since the oil is usually introduced into the cable as a 30 ?lled cable combined with the new circulating means; and
permanent insulating medium.
FIG. 4 is a section taken along the line 4-4 of FIG. 3.
Referring ?rst to FIGS. 1 and 2, a length of lead
sheathed electric power cable 10 is shown terminated at
its opposite ends with conventional potheads 11 and 12.
The cable 19 includes an inner multi-stand conductor 14,
Primarily, it is the purpose of this invention to provide
means for maintaining liquid-insulated electrical cables
of this type ‘at substantially their original insulating ef?~
ciency notwithstanding the degradation that the liquid
undergoes during operation of the cable. This broad
a layer of oil-permeable paper tape 15 helically wrapped
purpose is achieved by combining with the cable a novel
system for circulating the dielectric liquid through the
cable so that the used dielectric liquid is substantially
continuously displaced by newly-conditioned liquid. The
system contemplates employing the periodic power load
changes on the cable to achieve the pumping action re
40
about the conductor 14 throughout its length, and a close
?tting extended outer lead sheath 16. On the inside sur
face of the outer lead sheath 16 are formed a plurality
of longitudinally arranged channels 18 extending about
the periphery of the layer of paper tape 15 throughout
substantially its entire length. When the cable 10 is in
stalled, a dielectric hydrocarbon oil 19 is forced under
quired to effect the circulation.
In general, the new circulating means is provided in
pressure through'the channels 18 so that the oil com
combination with an electric power cable which includes 45 pletely impregnates the paper tape 15 to insulate the
an extended outer enclosure member and a dielectric
conductor 14.
Typical oil pressure in a lead-sheathed
liquid contained within the outer enclosure member. The
cable of this type is about 0 to 25 psi. above atmos
circulating means comprise an inlet conduit leading from
pheric.
a source of the liquid and communicating with the in
According to the invention, an inlet conduit 20 is
terior of the enclosure member. An inlet check valve is
connected to one end portion of the cable 10, for exam
provided in the inlet conduit to permit unidirectional flow
ple at the base of the pothead 11 as in the embodiment
of the liquid from this source into the enclosure member
shown. The inlet conduit 20 communicates with the
of the cable. Also, an outlet conduit is provided which
interior of the outer lead sheath 16 to provide access to
communicates with the interior of the enclosure member
the channels 18. Located in the inlet conduit 20 is an
at a point remote from the point where the inlet conduit 55 inlet check valve 22 of any suitable type which permits
communicates therewith. An outlet check valve is in
unidirectional ?ow only into the cable 10. At the end
cluded in the outlet conduit which permits unidirectional
of the inlet conduit 20 remote from the pothead 11 is
flow of the liquid out of the enclosure member. Hence,
an enclosed supply tank 24 containing a reservoir 25 of
variations in the temperature of the cable during opera
60 the cable oil 19 in its newly-conditioned state. The res
tion cause contraction and expansion of the liquid there
ervoir 25 is ‘at a pressure equal to that within‘the cable
within which alternately draws the liquid into and forces
10, so that under normal conditions there is no ?ow of
it out of the enclosure member through the inlet and out
oil through the inlet check valve 22. A valved inlet 26
let check valves respectively.
is provided in the supply tank 24 to permit the oil to be“
These variations in the temperature of the cable are a
introduced into the tank 24 when desired.
3,083,257
3
4
At the opposite end of the lead-sheathed cable 1%), an
outlet conduit 27 is connected to the base portion of the
pothead 12 in communication with the channels 18 in the
In this embodiment the new circulating means includes
an enclosed supply tank 49 containing a supply reservoir
50 for the cable oil 47 in its newly-conditioned state.
cable. Located in the outlet conduit 27 is an outlet check
The reservoir 50 is pressurized at a pressure equal to
valve 28 of any suitable type which permits ?ow only out
of the cable 10. At the end of the outlet conduit 27
remote from the pothead 12 is an enclosed discharge tank
30 which contains a discharge reservoir 31 of the cable
oil 19 in its used (slightly degraded) state. The res
ervoir 31 is also at a pressure equal to that within the 10
that within the cable 401. A valved inlet 51 extends from
the supply tank 49 to provide means for introducing the
oil into the tank 49 when desired. An inlet conduit
52 leads from the supply tank 49 into the base of the pot
head 41 so that the reservoir 50 communicates with the
interior of the pipe 45. Located in the inlet conduit 52
cable 10, so that under normal conditions there is no
is an inlet check valve 53 permitting unidirectional ?ow
flow of oil through the outlet check valve 28. A valved
of the oil 47 from the reservoir 50 into the pipe 45.
drain 32 is provided in the discharge tank ‘30' to with
To provide a depository for the oil 47 after its use as
draw oil from it as desired.
a dielectric in the cable, an enclosed discharge tank 55
During the operation of the cable 10, the conductor 15 is provided which contains a discharge reservoir 56 for
14 is cyclically heated and cooled by corresponding
the used cable oil 47. The reservoir 56 is also under
periodic increases and decreases in the amount of current
pressure equal to that within the cable 40 and a valved
carried thereby. Such variations in the power load on
drain 57 is provided in the tank 55 to empty it when
the cable 10 occur regularly in virtually all electrical
desired. Leading from the tank 55 to the base portion of
systems as the power demand ?uctuates during the course 20 the pothead 42 is an outlet conduit 58 which provides
of the cable’s daily operation. As a result, the tempera
communication between the reservoir 56 and the interior
ture of the oil 19 therewithin also rises and falls peri
of the pipe 45. An outlet check valve 59 is provided in
odically, thereby causing it to expand and contract corre
the outlet conduit 58 for permitting unidirectional ?ow
spondingly. When the oil 19 contracts, the internal
of the oil 47 out of the pipe 45 into the tank 55.
pressure within the cable 10, decreases and the inlet check 25
As in the previous embodiment, the temperature of the
valve 22 opens to admit the newly-conditioned oil from
conductor 43 varies cyclically during the operation of the
the reservoir 25 into the cable at the pothead 11. Con
cable 40 and causes contraction and expansion of the oil
versely, when the oil 19 expands, the internal pressure
7 therewithin. When the oil 47 contracts, newly-condi
within the cable 10 increases and forces the used oil at
tioned oil from the reservoir 50 is admitted into the cable
the pothead 12 through the outlet check valve 28 into 30 through the inlet check valve 53 and, conversely, when
the reservoir 31. Since the points at which the inlet and
the oil 19 expands, the used oil at the other end of the
outlet conduits 20 and 27 communicate with the interior
cable is forced out through the outlet check valve 28 into
of the lead sheath 16 are remote from one another, an
the reservoir 56. Since the inlet and outlet conduits ‘52
intermittent circulation of the oil 19 is effected from
and 58 respectively communicate with the interior of the
the pothead 11 to the pothead 12 through the entire length 35 pipe 45 at remotely spaced junctions, the oil 47 is inter
of the cable 10.
mittently circulated throughout substantially the entire
The particular construction of the cable 10 and pot
length of the cable 40.
heads 11 and 12 in FIGS. 1 and 2 are shown only for
Again, the particular construction of the cab-1e 40 and
purposes, of illustration. It should be clear that many
potheads 41 and 42 is shown only for purposes of illus
other types of lead-sheathed cables may be combined with 40 tration. Thus, the circulating means of the invention
the new circulating means. For example, there may be
may be combined with many other designs of pipe-type
three conductors 14 within the lead sheath 16, each
cables other than the single-conductor type shown in
insulated by its own layer of paper tape 15. Also, rather
the drawings.
'
than having grooves 18 on the inside surface of the lead
As shown in dotted lines in FIG. 3, a recycling system
sheath 16, there may be continuous oil passages formed 45 may be incorporated in the new circulating means. Such
or provided in the valley spaces between two or more
a system may include a discharge conduit 60 leading from
conductors or otherwise provided within the sheath.
the discharge tank 55 and a supply conduit 61 leading into.
It may also be advantageous to incorporate a recycling
the supply tank 49. A re-conditioning unit 62, may be
system in this new circulating, means, as shown in dotted
located between the discharge and supply conduits 60
lines in FIG. 1. This may include a discharge conduit 50 and 61 in communication therewith. The unit ‘62 may
34 leadingv from the discharge tank 30, or directly from
be of any suitable type which is capable of treating they
the outlet conduit 27, ‘and a supply conduit 35 leading into
used oil to return it to its original insulating e?iciency so
the supply tank 24, or directly into the inlet conduit 20.
that it is prepared for re-circulation back through the.
Between the ‘discharge and supply conduits 34 and 35,
cable 40.
‘
and in communication therewith, there may be provided a 55
We claim:
,
re-conditioni-ng unit 37 of any suitable type. In such a
1. In an electric power cable which includes an ex
unit 37, the degraded oil is treated to return it to its
tended outer enclosure member and a dielectric liquid
original insulating e?iciency, so that it is ready to be
contained within Said outer enclosure member, means for
recirculated back through the cable 10.
circulating said liquid through said enclosure member
Referring now to the embodiment shown in FIGS. 3 60 comprising an exterior source of said liquid, an inlet con
and 4, the new circulating means is there shown in com~
duit leading from said source and communicating with
bination with a pipeetype electric power cable 4t) termi
the interior of said enclosure member, an inlet check valve
nated at its opposite ends with conventional potheads 41
in said inlet conduit permitting unidirectional flow of said '
and 42. The cable 449 includes an inner multi-strand
liquid from said source into said enclosure member, an
conductor 43, an oil-permeable layer of paper tapes 44 65 outlet conduit communicating, with the interior of said
helically wrapped about the conductor 43 throughout its
enclosure member at a point remote from the point where.
length, and an extended outer steel pipe 45 enclosing
said inlet conduit communicates therewith, and an outlet
check valve in said outlet conduit permitting unidirec
able shielding tape and/or skid wires 46 may also be
tional ?ow of said liquid out of said enclosure member,
helically wrapped about the paper tape 15. When the 70 whereby variations in the temperature of said cable dur-.
cable 40 is installed, a dielectric oil 47 is forced under
ing operation cause contraction and expansion of the liq
pressure into the pipe 45 around the paper-covered
uid therewithin and alternately draw the liquid into and.
conductor 43 to impregnate the paper tape 15. The oil
force it out of said enclosure member through said inlet‘
pressure in a typical pipe-type cable of this, sort is ap
and outlet check valves respectively.
proximately 200‘ p.s.i. above atmospheric.
2. In an electric power cable which includes an ex
75
and spaced from the paper-covered conductor 43. Suit
8,083,257
5
6
tended outer enclosure member and a dielectric liquid
contained within said outer enclosure member, means for
lead sheath and a dielectric liquid impregnating porous
insulation within said sheath, means for circulating di
electric liquid through said sheath comprising an enclosed
supply reservoir providing a source of said liquid at a
pressure equal to that within said cable, an inlet conduit
circulating said liquid through said enclosure member
comprising a supply reservoir providing a source of said
liquid, an inlet conduit leading from said supply reservoir
and communicating with the interior of said enclosure
member, an inlet check valve in said inlet conduit permit
leading from said supply reservoir and communicating
with the interior of said lead sheath, an inlet check valve
in said inlet conduit permitting unidirectional ?ow of said
liquid from said supply reservoir into said lead sheath,
ting unidirectional ?ow of said liquid from said supply
reservoir into said enclosure member, an outlet conduit
communicating with ‘the interior of said enclosure member 10 an outlet conduit communicating with the interior of said
at a point remote from the point where said inlet conduit
lead sheath at a point remote from the point where said
communicates therewith and leading to said reservoir,
inlet conduit communicates therewith and leading into
and an outlet check valve in said outlet conduit permit
said reservoir, an outlet check valve in said outlet conduit
ting unidirectional flow of said liquid out of said enclosure
permitting unidirectional ?ow of said liquid out of said
member back to said reservoir, whereby variations in the 15 lead sheath into said reservoir, whereby variations in the
temperature of said cable during operation cause contrac
temperature of said cable during operation cause contrac»
tion and expansion of the liquid therewithin and alter
tion and expansion of the liquid therewithin and alter
nately draw the liquid into and force it out of said en
nately draw the liquid into and force it out of said en
closure member through said inlet and outlet check valves
closure member through said inlet and outlet check valves
respectively.
3. In an electric power cable which includes an ex
tended outer enclosure member and a pressurized dielec
tric liquid contained within said enclosure member, means
for circulating newly-conditioned dielectric liquid through
20
respectively.
6. In an electric cable which includes an outer lead
sheath closely covering at least one conductor insulated
with porous material and a dielectric oil impregnating said
porous material and contained in passages inside said
said enclosure member comprising an enclosed supply 25 sheath, means for circulating newly-conditioned dielec
reservoir providing a source of newly-conditioned liquid
tric oil through said sheath comprising an enclosed supply
reservoir providing a source of said newly-conditioned oil
under pressure equal to that within said cable, an inlet
conduit leading from said supply reservoir and communi
at a pressure equal to that within said cable, an inlet
conduit leading from said supply reservoir and communi
cating with the interior of said enclosure member, an inlet
check valve in said inlet conduit permitting unidirectional 30 cating with the interior of said sheath, an inlet check
valve in said inlet conduit permitting unidirectional How
flow of said liquid from said supply reservoir into said
enclosure member, an enclosed discharge reservoir under
of said oil from said supply reservoir into said sheath,
an enclosed discharge reservoir providing a depository for
pressure equal to that within said cable providing a de
pository for said liquid after its use as a dielectric in
said oil after its use as a dielectric in said cable, an out
said cable, an outlet conduit communicating with the in~ 35 let conduit communicating with the interior of said sheath
at a point remote froim the point where said inlet conduit
terior of said enclosure member at a point remote from
communicates therewith and leading to said discharge
the point where said inlet conduit communicates therewith
and leading into said discharge reservoir, an outlet check
reservoir, an outlet check valve in said outlet conduit per
mitting unidirectional ?ow of said oil out of said sheath
valve in said outlet conduit permitting unidirectional ?ow
of said liquid out of said enclosure member into said
into said discharge reservoir, and a recycling system com
prising means for withdrawing the used oil from said dis
discharge reservoir, whereby variations in the temperature
charge reservoir and reconditioning it and then returning
of said cable during operation cause contraction and ex
pansion of the liquid therewithin and alternately draw the
the reconditioned oil to said supply reservoir, whereby
variations in the temperature of said cable during opera
liquid into and force it out of said enclosure member
through said inlet and outlet check valves respectively.
45 tion cause contraction and expansion of the oil there
within and alternately draw the oil into and force it out
4. In an electric power cable which includes an ex
of said enclosure member through said inlet and outlet
tended outer enclosure member and a pressurized di
check valves respectively.
electric oil contained within said enclosure member,
means for circulating newly-conditioned dielectric oil
7. In an electric power cable which includes an outer
through said enclosure member comprising an enclosed 50 pipe, at least one conductor insulated with porous mate
supply reservoir providing a source of said newlyacondi
rial enclosed within said pipe, and a pressurized dielectric
tioned oil under pressure equal to that within said cable,
liquid contained within said pipe and impregnating said
an inlet conduit leading from said supply reservoir and
porous material, means for circulating dielectric liquid
communicating with the interior of said enclosure mem
through said pipe comprising an enclosed supply reservoir
ber, an inlet check valve in said inlet conduit permitting 55 providing a source of said liquid at a pressure equal to
unidirectional ?ow of said oil from said supply reservoir
that within said pipe, an inlet conduit leading from said
into said enclosure member, an enclosed discharge res
supply reservoir and communicating with the interior of
ervoir under pressure equal to that within said cable pro
said pipe, an inlet check valve in said inlet conduit per
viding a depository for said oil after its use as a dielectric
mitting unidirectional ?ow of said liquid from said sup
in said cable, an outlet conduit communicating with the 60 ply reservoir into said enclosure member, an outlet con
interior of said enclosure member at a point remote from
duit communicating with the interior of said pipe at a
the point where said inlet conduit communicates there
point remote from the point where said inlet conduit corn—
with and leading into said discharge reservoir, an outlet
municates therewith and leading into said reservoir, an
check valve in said outlet conduit permitting unidirec
outlet check valve in said conduit permitting unidirection
tional ?ow of said oil out of said enclosure member into 65 al How of said liquid out of said pipe into said reservoir,
said discharge reservoir, and a recycling system compris
whereby variations in the temperature of said cable dur
ing means for withdrawing the used oil from said dis
ing operation cause con-traction and expansion of the
charge reservoir and re-conditioning it and then introduc
liquid therewithin and alternately draw the liquid into
ing the re-conditioned oil into said supply reservoir,
and force it out of said enclosure member through said
whereby variations in the temperature of said cable dur 70 inlet and outlet check valves respectively.
ing operation cause contraction and expansion of the oil
8. In an electric power cable which includes an outer
therewithin and alternately draw the oil into and force it
pipe, at least one conductor insulated with porous mate
out of said enclosure member through said inlet and out
rial enclosed within said pipe, and a pressurized dielectric
let check valves respectively.
oil contained within said pipe and impregnating said
5. In an electric power cable which includes an outer 75 porous material, means for circulating newly-conditioned
3,083,257
7
8
dielectric oil through said pipe comprising an enclosed
supply reservoir providing a source of said newly
voir, whereby variations in the temperature of said cable
during operation cause contraction and expansion of the
conditioned oil at ‘a pressure equal to that Within said
oil therewithin and alternately draw the oil into and force
it out of said pipe through ‘said inlet and, outlet check
cable, an inlet conduit leading from said supply reservoir
and communicating with the interior of said pipe, an inlet 5 valves respectively.
check valve in said inlet conduit permitting unidirectional
References Cited in‘ the ?le of this patent
flow of said oil from said supply reservoir into said pipe,
UNITED STATES PATENTS
an enclosed discharge reservoir providing a depository
for said oil after its use as a dielectric in said cable, an
outlet conduit communicating with the interior of said 10
pipe at a point remote from the point where said inlet
conduit communicates therewith and leading into said
discharge reservoir, an outlet check valve in said outlet
conduit permitting unidirectional ?ow of said oil out of 15
said pipe into said discharge reservoir, and a recycling
system comprising means for withdrawing the used oil
from said discharge reservoir and re-conditioning it and
then returning the re-conditioned oil to said supply reser—
1,094,231
Mennesson _____, ______ __ Apr. 21, 1914
1,981,536
2,006,932
2,065,927
Zapf ________________ __ Nov. 20‘, 1934‘
Rosch ________________ __ July 2, 1935‘
Scott ________________ __ Dec. 29, 1936
2,095,090
2,423,482 '
Aime ______ _'__,________ __, Oct. 5, 1937“
Chochol ______________ __ July 8, ,1947‘
2,587,539
Seaman ________ __ ____ __ Feb. 26, 1952
2,590,679-
Callahan ____________ __ Mar. 25, 1952
491,200
Great Britain _________ __ Aug. 29-, 1938
FOREIGN PATENTS
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