Molecular sieve abstract
Molecular sieve material is placed in the main condensate return
in vaporization-cooled transformers. The sieve material can be removed
and replenished without de-energizing the transformer.
Molecular sieve claims
We claim:
1. In a vaporization-cooled transformer having a transformer tank,
a heat exchanger and an internal condensate return path for conveying
condensed dielectric coolant from the heat exchanger to the tank,
the combination comprising:
a container located in the condensate return path, said container
including an inlet communicating with the heat exchanger and an
outlet communicating with the transformer tank;
a quantity of molecular sieve material accommodated in said container;
separate valve means in said inlet and outlet for controlling the
flow of condensed dielectric coolant through said container;
a bypass conduit connected between the heat exchanger and the transformer
tank;
additional valve means in said conduit for controlling the flow
of condensed dielectric coolant therethrough; and
a valved opening in said container affording access from externally
of the transformer to said molecular sieve material for the replenishment
thereof while said container remains in situ and isolated from the
condensate return path by said valve means and said bypass conduit.
2. The apparatus of claim 1 wherein said molecular sieve material
includes a colorant for indicating when said molecular sieve material
is saturated with water.
3. The apparatus of claim 2 wherein said molecular sieve container
includes a transparent portion for providing visual access with
said molecular sieve material.
Molecular sieve description
BACKGROUND OF THE INVENTION
U.S. patent application, Ser. No. 110046 filed Jan. 7 1980 and
incorporated herein for purposes of reference, discloses the placement
of molecular sieve material both in the flow and return paths of
the condensable dielectric coolant used in vapor-cooled transformers.
The placement of the molecular sieve material in the path of the
vaporized coolant provides for the removal of a quantity of water
vapor from the coolant in vapor form. The molecular sieve material
in the liquid return path removes any water existing when the coolant
is in condensed form.
Since water is continuously evolved from the cellulosic insulation
material used within the transformer winding, a substantial quantity
of molecular sieve material must be employed within the vapor path
in order to insure that the molecular sieve material does not become
saturated and inoperative over the entire life of the transformer.
It has since been determined that the more efficient mechanism
for water adsorption is when the water is in a condensed state upon
contact with the molecular sieve-adsorbing surface. The proper placement
of molecular sieve material thereby allows a smaller quantity of
sieve material to be employed at a substantial saving both in transformer
size and in the quantity of molecular sieve material employed.
The purpose of this invention is to describe an arrangement for
using small quantities of molecular sieve material efficiently employed
for water adsorption and means for removing and replacing the molecular
sieve material upon saturation.
SUMMARY OF THE INVENTION
The invention comprises the imposition of a valved container of
molecular sieve material in the main condensate return path of a
vaporization-cooled transformer to adsorb any water existing within
the transformer in a condensed state. A valved condensate return
bypass line, in combination with the valved molecular sieve container,
allows the molecular sieve material to be removed and replenished
without interfering with the operation of the transformer. In one
embodiment the valved container comprises a transparent material
for observing any color change that occurs when the molecular sieve
material is water-saturated.
BRIEF DESCRIPTION OF THE DRAWING
The single FIGURE is a front sectional view of a vapor-cooled transformer
employing the molecular sieve arrangement according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The single FIGURE shows a vaporization-cooled transformer 10 of
the type employing a transformer tank 11 connected with a heat exchanger
assembly 12. A winding arrangement 13 and a transformer core 14
are included within tank 11 and a feed-through bushing 15 permits
electrical connections with winding arrangement 13. In order to
provide dielectric and cooling facility to both winding arrangement
13 and core 14 a quantity of condensable dielectric coolant 16
is included within tank 11. The condensable coolant comprises a
chlorinated fluorocarbon such as trichlorotrifluoroethane which
becomes heated during transformer operation and vaporizes. The vapor
flow path is indicated by arrows and proceeds through an opening
in tank cover 8 into an inlet 9 to an intake manifold 17. A plurality
of cooling tubes 18 interconnect between intake manifold 17 and
an exit manifold 19 whereby vaporized coolant 16' enters cooling
tubes 18 and condenses to form liquid droplets 16" before returning
to tank 11 by means of exit manifold 19. An expansion tank inlet
27 connects between intake manifold 17 and expansion tank 28 to
allow for the expansion of any noncondensable gasses remaining within
transformer tank 11 before transformer 10 becomes energized. A quantity
of molecular sieve material can be included within expansion tank
28 in order to adsorb any water vapor within the expansion tank
as described in the aforementioned U.S. patent application. Any
coolant 16 remaining within expansion tank 28 can return to tank
11 by means of an expansion tank outlet 28. In accordance with the
instant invention, a container 20 is incorporated between exit manifold
19 and tank 11 in order to receive condensed coolant 16" upon
return to tank 11. As described earlier, it was determined that
the efficiency of water adsorption on the surface of molecular sieve
material 29 is greatly improved if the coolant 16 is in liquid rather
than vapor form upon contact with the surface of molecular sieve
material 29. The imposition of molecular sieve material 29 in container
20 assures that any dielectric coolant 16 contacting molecular sieve
material 29 will be in liquid form as condensed droplets 16"
indicate. Further, the placement of molecular sieve material 29
in the condensate return path assures that the temperature of the
molecular sieve material will be at a low temperature to further
increase the adsorption efficiency. When the molecular sieve material
29 is a zeolite substance such as manufactured by the Linde Corporation,
suitable colorants can be added so that a color change occurs when
the molecular sieve material becomes saturated with water. In order
to continuously view the molecular sieve material, container 20
can be fabricated from plastic or glass material or can contain
a transparent sight glass to provide visual access to the condition
and color of molecular sieve material 29. When it is determined
that molecular sieve material 29 has become saturated, then the
molecular sieve material can be removed in the following manner.
Bypass valve 30 which is normally closed during transformer operation,
is opened in order to provide a path for condensed coolant 16"
through condensate return bypass line 21 back to tank 11. First
valve 31 which is normally open, and second valve 32 which is
normally open, are both closed in order to isolate container 20
from exit manifold 19 and tank 11. Container 20 is then bypassed
and molecular sieve material 29 is accessible through valved opening
33 for treatment in order to remove any water vapor adsorbed therein
by heating and/or vacuum treating. Alternatively, a fresh supply
of molecular sieve material 29 can be introduced within container
20. Bypass valve 30 is then closed and valves 31 and 32 are opened
to redirect the path of condensed coolant 16" through molecular
sieve material 29 within container 20 back to tank 11. The frequency
of replacement of molecular sieve material 29 depends to a large
extent upon the degree of loading employed for vaporization-cooled
transformer 10. When the transformer is operated above 100% of rated
load, the degree of outgassing from winding arrangement 13 is substantially
greater than when the transformer is operated, for example, at 50%
to 75% of rated load. It may be advantageous to operate vaporization-cooled
transformer 10 greater than 100% of rated voltage in order to drive
the water vapor out of the cellulosic materials within winding arrangement
13 for the first several hundred hours of operation. Molecular sieve
material 28 could then be removed and either regenerated or replaced.
The transformer could then be operated slightly lower than 100%
voltage rating and molecular sieve material 29 could then operate
for long periods of time before saturation occurs and replenishment
becomes necessary. In the event that molecular sieve material 29
is to be outgassed, rather than replaced, a simple heating and evacuation
procedure can be employed with container 20 remaining in place within
vaporization-cooled transformer 10. Bypass valve 30 connecting condensate
return bypass line 21 can be opened and valves 31 and 32 can be
closed. Valve 33 connecting with container 20 above the surface
of molecular sieve material 29 is now opened and connection is made
with a vacuum pump. The vacuum pump is operated until the adsorbed
moisture within molecular sieve material 29 is removed whereupon
valves 30 and 33 are closed. Valves 31 and 32 are reopened in order
to continue the flow of condensed coolant 16" through container
20 and in contact with molecular sieve material 29.
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