Note: Descriptions are shown in the official language in which they were submitted.
`` 10~8B94
GASEOUS DIELECTRIC MIXTURES
BACKGROUND OF THE INVENTION
I. Field of the Invention
This invention relates to a process for the production
of dielectric mixtures, useful for preventing or diminishing the
formation of carbon in dielectric fluids during electrical
discharges therein.
II. Description of the Prior Art
During the operation of electrical equipment, such as
switches, circuit breakers, transformers, and the like, arcing,
sparking or glow discharges usually or occasionally occur,
especially at higher voltages. Dielectric materials are common-
ly employed to reduce or prevent the possibility of such
arcing, sparking and glow discharges. For example, solid insu-
lators, such as ceramics or resins, may be used to support or
surround electrical conductors. Or, fluid dielectric materials,
such as oils or gases, may be used to insulate electrical con-
ductors.
A related problem involves the breakdown of carbon-
aceous dielectric materials. During arcing, these materials - -
tend to decompose and form carbon, which, being an electrical
conductor, not only shortens the gap between conductors,
but also eventually leads to carbon bridge short circuits, or
carbon tracking. This is a serious problem which has plagued
the electrical industry for years.
As used herein, arc interruption includes arc suppression
and arc quenching, and refers to preventing or reducing arcing
between electrodes. Carbon suppression refers to preventing the
formation of carbon during arcing.
Sulfur hexafluoride (SF6) is well-known as an excel-
lent gaseous dielectric. See, e.g., U.S. Patent 3,059,044,
.
lQ68894
issued to R. E. Friedrich et al., October 16, 1962. It is
unique in its electric arc interrupting properties. However,
SF6 does have a few inherent disadvantages: insufficient
vapor pressure at low temperatures, high freezing point, only
fair thermal stability compared with fluorocarbons and high cost.
For some years, it has been known that certain electro-
negatively substituted carbon compounds (halogenated alkanes) are
al ~ highly useful fluid insulators in electrical apparatus. Typical
examples are dichlorodifluoromethane (CC12F2), octafluorocyclo-
butane (c-C4F8), hexafluoroethane (C2F6), octofluoropropane (C3F8),
decafluorobutane (C4Flo), trichlorofluoromethane (CC13F), sym-
dichlorotetrafluoroethane (CClF2CClF2), tetrafluoromethane (CF4),
chloropentafluoroethane (CClF2CF3) and chlorotrifluoromethane
(CClF3). While all of the above have reasonably good dielectric
strengths, it is difficult to prevent spark-over or other electri-
cal discharge from occurring in apparatus containing these materials
when high voltage surges develop. The spark-over or other discharge
typically leads to carbon track formation.
A patent issued to J.A. Manion, et al., U.S. Patent
3,650,955, issued December 9, 1966, teaches the use of CC12F2
combined with c-C4F8 as an arc interrupter gas. However, this
combination has been observed to evidence extensive carbon
tracking properties.
Mixtures of SF6 and CO2 have been suggested as a
potential gaseous dielectric medium. See, e.g., U.S. Patent
3,059,044, issued to R. E. Friedrich et al., October 16, 1962.
However, no composition range having practical utility is dis-
closed.
Perhalogenated fluids, including SF6 and perhalogen-
ated alkanes, have been absorbed on molecular sieves (zeolites),
which are then incorporated as fillers in organic insulators; see
--2--
10~8894
U. S. Patent 3,305,656, issued to J. C. Devins, February 21,
1967. During high voltage operation, voids in the insulation are
filled by the perhalogenated fluid, which then serves as an arc
interrupter.
Attempts have been made to develop gaseous dielectric
compositions as carbon tracking suppressants. For example, B. J.
Eiseman, U.S. Patent 3,184,533, issued May 18, 1965, teaches
the use of an oxygen-containing oxidizing agent, such as SO2,
NO2 and N2O, to suppress carbon tracking of certain electro-
negatively substituted carbon compounds, such as saturated poly-
halohydrocarbon compounds, saturated perhalohydrocarbon compounds,
saturated perfluoroethers and the like. However, none of these
oxidizing agents is desirable because of their corrosive nature,
toxicity, and/or chemical reactivity.
There remains in the art a need for efficient gaseous
dielectric compositions that evidence superior carbon suppression
properties.
SUMMARY OF THE INVENTION
In accordance with the invention, carbon formation in
20 a dielectric fluid during an electrical discharge from an electri- -
cal conductor is suppressed by maintaining in contact with the
electrical conductor during operation a gaseous dielectric mixture
consisting essentially of (I) SF6 and CO2 or (II) at least one
halogenated alkane plus at least one gas selected from the group
consisting of SF6 and CO2, or (III) at least one perfluorinated
ether plus at least one gas selected from the group consisting of
SF6 and CO2.
Ratios of SF6 and CO2, of group I mixtures, useful in
substantially eliminating carbon formation consist essentially of
mixtures of SF6 and CO2 containing from about 1 to 50 mole percent
of CO2, preferably about 1 to 30 percent CO2 and most preferably
about 10 to 30 mole percent CO2.
-3-
10f~8894
Halogenated alkanes useful in the practice of the inven-
tion are those which contain from 1 to 4 carbon atoms and at most
one hydrogen atom, with the remaining hydrogen atoms replaced by
at least one halogen selected from the qroup consisting of fluorine,
chlorine and bromine. The halogenated alkanes desirably have a vapor
pressure of at least about 100 Torr at 20C. These compounds are
gaseous under operating conditions.
Perfluorinated ethers useful in the practice of the
invention are those which contain from 2 to 6 carbon atoms and
may be mono- or di-ethers, cyclic or acyclic. The perfluorinated
ethers have a vapor pressure of at least about 100 Torr at 20C
and are gaseous under operating conditions.
The amount of SF6 and/or CO2 required to suppress
carbon formation is unique to each mixture. In general, however,
in group II mixtures containing halogenated alkanes for a binary
mixtures and for multicomponent mixtures containing either SF6 or
CO2, gaseous mixtures containing at least about 10 mole percent of
SF6 or at least about 15 mole percent of CO2 are required to
suppress carbon tracking. For multicomponent mixtures (ternary and
higher) containing both SF6 and CO2, carbon formation is sup-
pressed for compositions lying in regions rich in SF6 and CO2 on a
ternary diagram defined by a line whose minimum extremities are
defined by
1 SF6 - 15 CO2 - 84 halogenated alkane
10 SF6 - 1 CO2 - 89 halogenated alkane
(the numbers are in mole percent).
Certain of these mixtures form novel compositions. Such
novel compositions consist essentially of at least one halogenated
alkane plus SF6 and CO2. The halogenated alkanes contain from 1 to 4
carbon atoms and at most one hydrogen atom, with the remaining
hydrogen atoms replaced by at least one halogen selected from the
-4-
-` 1068894
group consisting of fluorine, chlorine and bromine. The halo-
genated alkanes desirably have a vapor pressure of at least about
100 Torr at 20C. The amount of SF6 and CO2 in the compositions
is as given above.
Perfluorinated ethers useful in the practice of the
invention in group III mixtures are those which contain from 2 to
6 carbon atoms and may be mono- or di-ethers, cyclic or acyclic.
The perfluorinated ethers have a vapor pressure of at least about
100 Torr at 20C. Such a vapor pressure limitation permits the
use of certain perfluorinated ethers which are liquid at room
temperature but which evidence at sufficiently high vapor pressure
to be useful over a limited range of composition. Preferably,
the perfluorinated ethers have a vapor pressure of at least about
400 Torr at 20C and most preferably, are totally gaseous (760
Torr) at room temperature and have a boiling point of less than
about 5C.
Further in accordance with the invention, improved di-
electric breakdown voltages that are unusally high are obtained by
employing specific gaseous dielectric mixtures within the scope of -~ -
20 this invention in certain critical proportions set forth below. -~
BRIEF DESCRIPTION OF THE DRAWING
__ __ ~
FIG. 1, on coordinates of breakdown voltage in kv-rms and
concentration in mole percent, is a plot in a binary system A-B of
the dielectric strength of various mixtures of components A and B
wherein A is a halogenated alkane and B is SF6 and/or CO2.
FIG. 2, on coordinates of breakdown voltage in kv-rms and
concentration in mole percent, is a plot of various binary mixtures -
of haloalkanes with SF6;
FIG. 3, on coordinates of breakdown voltage in kv-rms and -
concentration in mole percent, is a plot of various binary mixtures
of haloalkanes with CO2;
-5-
. ~ ... . . . .
1068894
FIG. 4, on coordinates of concentration in mole percent,
is a ternary plot of the system SF6-CO2-CC12F2, showing useful
regions of carbon suppression and improved dielectric strength;
FIG. 5, on coordinates of concentration in mole percent,
is a ternary plot of the system SF6-CO2-CHClF2, showing useful regions
of carbon suppression and improved dielectric strength;
FIG. 6, on coordinates of concentration in mole percent,
is a ternary plot of the system SF6-CO2-CBrF3, showing useful regions
of carbon suppression and improved dielectric strength;
FIG. 7, on coordinates of concentration in mole percent,
is a ternary plot of the system SF6-CO2-CClF2CClF2, showing useful
regions of carbon suppression and improved dielectric strength;
FIG. 8, on coordinates of concentration in mole percent,
is a ternary plot of the system SF6-CO2-CClF2CF3, showing useful
regions of carbon suppression and improved dielectric strength; -
FIG. 9, on coordinates of concentration in mole percent,
is a ternary plot of the system SF6-CClF3-CHF3, showing useful
regions of carbon suppression, - -
FIG. 10, on coordinates of concentration in mole percent,
is a ternary plot of the system CO2-CF3CF3-c-C4F8, showing useful :
regions of carbon suppression and improved dielectric strength;
FIG. 11, on coordinates of breakdown voltage in kv-rms
and concentration in mole percent, is a plot of the binary system
SF6-X, where X is a perfluorinated ether, showing proportions
having improved dielectric strength;
FIG. 12, on coordinates of breakdown voltage in kv-rms
and concentration in mole percent, is a plot of the binary system
CO2-X, where X is a perfluorinated ether showing proportions having
improved dielectric strength; and
FIG. 13, on coordinates of breakdown voltage in kv-rms
and concentrations in mole percent and is a plot of the binary
--6--
10~;8894
system SF6-CO2 showing dielectric breakdown as a function of CO2
addition to SF6.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the invention, carbon formation in a
dielectric fluid during an electrial discharge from an electrical
conductor is suppressed by maintaining in contact with the electric
conductor during operation a gaseous dielectic mixture consisting
essentially of a mixture of SF6 and CO2 in specified mole ratios
(group I mixtures) or at least one of SF6 or CO2 in combination
with at least one halogenated alkane tgroup II mixtures) or at least
one of SF6 or CO2 in combination with at least one perfluorinated
ether (group III mixtures).
Halogenated alkanes useful in the practice of the inven-
tion for group II mixtures are those which contain from 1 to 4
carbon atoms, since compounds with a greater number of carbon atoms
tend to possess undesirably low vapor pressures at desired operat-
ing temperatures. ; ~
The halogenated alkanes contain at most one hydrogen ~ -
atom, with the remaining hydrogen atoms replaced by at least
one halogen selected from the group consisting of fluorine,
chlorine and bromine. More than one hydrogen atom per molecule
results in excessive carbon tracking.
The halogenated alkanes desirably have a vapor pressure -
of at least about 100 Torr at 20C. The vapor pressure limitation --
permits the use of certain halogenated alkanes, such as 1,1,2-tri-
chloro-1,2,2-trifluoroethane (CC12FCClF2), which are liquid at room
temperature but which evidence a sufficiently high vapor pressure
to be useful over a limited range of composition. Preferably,
the halogenated alkanes have a vapor pressure of at least ahout 400
Torr at 20C, and most preferably, are totally gaseous (760 Torr)
at room temperature and have a boiling point of less than about 5C.
--7--
10~t3894
Examples of halogenated alkanes useful in the practice of
the invention include chlorodifluoromethane (CHClF2), bromotri-
fluoromethane (CBrF3), hexafluoroethane (CF3CF3) and cycloocta-
fluorobutane (c-C~F8).
Unexpectedly, in many of these systems, improved break-
down voltage characteristics that are unusually high are obtained
by employing specific gaseous dielectric mixtures of this invention
within certain critical proportions set forth in examples below.
Preferably, perhalogenated alkanes find use in applications such as
high dielectric strength mixtures. Perhalogenated compounds are
totally halogenated and include no hydrogen. Examples include
chlorotrifluoromethane (CClF3), 1,2-dichloro 1,1,2,2-tetrafluoro-
ethane (CClF2CClF2), and chloropentafluoroethane (CClF2CF3).
I. Binary Compositions of Group II Mixtures
Binary compositions of group II mixtures consist
essentially of mixtures of two components, where one component is
selected from the group consisting of halogenated alkanes and the
second component is selected from the group consisting of SF6 and CO2.
Examples of binary systems preferred as carbon formation suppressants
include SF6-ccl2F2~ SF6-CHClF2~ SF6 CClF2CClF2~ SF6 3~
SF6-CClF2CF3, CO2-CC12F2 and CO2-CHClF2. While each combination
evidences a unique useful range for carbon suppression, in general,
at least about 10 mole percent of SF6 or at least about 15 mole
percent of CO2 is required to obtain suppression. Many combina-
tions may require somewhat more SF6 or CO2. Such a determination
is easily within the ability of one skilled in the art, however,
and in the Examples section below, details are set forth for
determining optimum composition ranges and preferred examples are
given; see also Table I below.
Gaseous dielectric mixtures which have a low tendency to
form carbon when su,bjected to repeated electrical sparking (break-
-8-
- , ,
106889~
down) are desired for use as carbon suppression. This objective
is attained by the addition of SF6 or CO2 diluent to halo-
genated alkanes in proper quantities.
Table I summarizes the data developed for group III
binary mixtures which include SF6 or CO2. In Table I are the
results of tests of various diluent compounds with potential carbon
suppression capability, i.e., SF6, CO2, SO2, NO and air. The
number listed in Table I in mole percent (suppression value), is
the minimum quantity of the diluent component which will prevent
carbon formation under the conditions of the tests described in
Example 2 below. The stable inert gases, CF4 and N2, which also
appear in Table I, serve as both diluents and blanks. Inspecting
Table I, it is evident that by comparing the suppression values
of SF6 and CO2 (and others) with those of N2 and CF4, the effective- ;
ness of carbon suppression gases and the tendency of various gaseous
dielectrics to form carbon can be evaluated. In cases where carbon -~
suppression is most effective, inert diluents generally require a
minimum of about 50 to 70 mole percent concentration to suppress
carbon, compared with a minimum of about 10 to 40 mole percent
concentration for suppression of diluents in accordance with the
invention. The amount of diluent (SF6 or CO2) needed for carbon
suppression varies, depending upon the particular halogenated
alkane.
1068894
TABL~3 I
CARBON FORMATION CONDITIONS
BINARY SYSTEMS
Compound SF6 CO2 N2 CF4 SO2 NO Air
CClF3 10
CBrF3 10 15 20 10
2 2 10 15 50 50
CC13F 30 - - -
CHClF2 35 45 75 75
CHF3 10 15 50 50
3 3 20 35 30 25
2 3 25 25 50 70
CClF2CClF2 45 45 70 70
c-C4F8 35 55 70 75 20 20 40
From Table I,it is apparent that SF6 and CO2 are most effective sup-
pressants with CClF3, CBrF3, CC12F2 and CHF3. Somewhat more sup-
pressant is required for CF3CF3 and CClF2CF3 and even more
suppressant is required for CC13F, CHClF2, c-C4F8 and CClF2CClF2.
In general, less diluent is required to suppress carbon formation
when SF6 or CO2 is employed than when N2 or CF4 is employed.
With c-C4F8, it is possible to compare the effectiveness of SF6
and CO2 with the suppressor gases of SO2 and NO of U.S. Patent
3,184,533 and with air. The accuracy of suppression values is + 5
percent. Thus, SF6 is only somewhat less effective than NO or SO2.
Carbon dioxide has about the same effect as air.
Without subscribing to any particular theory, it is poss-
ible that since SF6 is an inert diluent up to about 200C, and CO2
is an inert diluent up to about 300C, their action in carbon sup-
pression is probably the formation of fluorine or oxygen atoms under ~ ~-
arc conditions. These atoms then subsequently react with the -
carbon-containing fragments of the arced halogenated alkanes, there- -
1 0 - ' " '
1068894
by forming non-conducting decomposition products rather than
electrically conducting carbon.
Sulfur dioxide (SO2) is a toxic, corrosive gas and is
thus undesirable in a practical system. Nitric oxide (NO) in addi-
tion is chemically unstable. Nitrous oxide (N2O), also chemically
unstable, is an anesthetic. Air is undesirable since it tends to
attack equipment components such as metals and plastics, particu-
larly at the usual operating range of 120 to 250C.
Since halogenated alkanes vary in their carbon formation
tendencies, the desired composition ranges are conveniently based upon
the carbon suppression values of Table I. That is, for SF6 mixtures,
the broad range of compositions useful as dielectric gases varies from
the minimum diluent necessary to suppress carbon tracking up to about
99 mole percent of SF6. For CO2 mixtures, compositions having a -
breakdown voltage of greater than about 10 kv-rms (kilovolt-root
mean square) are considered useful, except in certain special appli-
cations. Generally, compositions containing at least the minimum
amount of CO2 necessary to suppress carbon tracking, but less than
about 65 to 80 mole percent of CO2, depending on the particular
gaseous mixture, are considered useful.
Of course, operating at voltages considerably less than
the breakdown voltage at which carbon formation appears would permit
use of a somewhat broader range of compositions. Preferred composi-
tions are those that retain about 90~ of the breakdown voltage of the
higher of the two components.
Within the broad range disclosed above, many combinations
of halogenated alkanes with SF6 and with CO2 evidence an unex- -
pected enhancement of dielectric strength, as measured by breakdown -
voltage, using a standard cell as described by ASTM D2477-66T. ~ -
Examples of such systems include SF6-CC12F2, SF6-CBrF3 and CO2-
CBrF3. It would be expected that for most binary compositions,
--11--
10~8894
breakdown voltage would vary linearly with composition. However,
for some compositions, an unexpected enhancement of breakdown vol-
tage is observed. This may take the form either of a moderate
positive deviation from linearity or of a significant positive
deviation from linearity to the extent that over some range of com-
position, the observed breakdown voltage is equal to or greater than
that of either of the two end members. The latter condition is
referred to herein as a synergistic effect. It is not possible to
indicate general composition ranges. However, such a determination
is easily within the ability of one skilled in the art. The Examples
section sets forth further details and lists preferred examples; see
also Tables IV and V, below.
An example of both carbon suppression and improved di-
electric strength in accordance with the invention is shown in
FIG. 1, which is a plot of breakdown voltage in kv-rms as a
function of composition in mole percent for a binary system of com-
ponents A and B. Carbon formation appears over the range indicated
by the dotted portions of the curves. In this example, component
B is chloropentafluoroethane (CClF2CF3). Component A is variously
SF6 (curve 10); CO2 (curve 11); and CF4 (curve 12). Where component
A is SF6 (curve 10), there is not only a positive deviation from
linearity (cf. line 13), but an actual enhancement such that a -
the mixture over a range of composition evidences a breakdown ~ ~ -
voltage greater than that of either of the two end members. Where
component A is CO2 (curve 11), there is a positive deviation from
linearity. Where component A is CF4 (curve 12), both extensive
carbon formation and little deviation from linearity are observed.
Line 13 depicts the expected linear behavior of breakdown voltage
with composition variation. Such results for binary mixtures are
typical of many of the mixtures of halogenated alkanes with SF6 and
C2 disclosed herein. Such mixtures tend to exhibit both low carbon
-12-
,
10~8894
formation and enhanced breakdown voltage characteristics.
FIGS. 2 and 3 depict preferred group II binary mixtureswith SF6 and CO2, respectively. In FIG. 2, the following curves
represent the breakdown voltages of the listed compositions with
SF6: curve 20, dichlorodifluoromethane (CCl2F2); curve 21, chloro-
difluoromethane (CHClF2); curve 22, 1,2-dichloro-1,1,2,2-tetra-
fluoroethane (CClF2CClF2); curve 23, chlorotrifluoromethane (CClF3);
and curve 24, chloropentafluoroethane (CClF2CF3). In FIG. 3, the
following curves represent the breakdown voltages of the listed
compositions with CO2: curve 30, CHClF2 and curve 31, CCl2F2.
II. Multi-Component Compositions of Group II Mixtures
Ternary compositions of group II mixtures consist
essentially of mixtures of three compounds, A, B and C, at least
one of which is selected from the group consisting of halogenated
alkanes and at least one of which is selected from the group con-
sisting of SF6 and CO2. Examples of ternary systems preferred as
carbon suppressants include SF6-CO2-CCl2F2, SF6-CO2-CHClF2,
2 2 6 C2 CClF2CF3, SF6-CO2-CBrF SF CCl
and CO2-CF3CF3-c-4F8. While each combination evidences a unique
useful range for carbon suppression, in general, for multicomponent
mixtures containing either SF~ or CO2, gaseous mixtures con-
taining at least about lO mole percent of SF6 or at least about 15
mole percent of C02 are required to suppress carbon formation.
For multicomponent mixtures containing both SF6 and C02, carbon
formation is suppressed for compositions lying in regions rich in
SF6 and C02 on a ternary diagram defined by a line whose minimum
extremities are defined by
1 SF6 - 15 CO2 - 84 halogenated alkane
10 SF6 - 1 CO2 - 89 halogenated alkane.
Many combinations may require somewhat more SF6 and/or CO2. As
before, such a determination is within the ability of one skilled
-13-
. , : .:
10~8894
in the art. The Examples section below sets forth the details fordetermining such ranges and lists preferred examples.
Within the broad range of compositions useful for carbon
suppression, many ternary mixtures evidence an unexpected enhance-
ment of dielectric strength. Preferred examples of these systems
6 2 2F2' SF6 C2-C~ClF2' SF6-CO2-CClF CClF
SF6-CO2-CClF2CF3, SF6-CO2-CBrF3, 5F6-CHF3-CHClF2 and CO2-CF3CF3-
c-C4F8. Mixtures possessing this property are also listed in the
Examples section.
An example of both carbon suppression and improved dielec-
tric strength in accordance with the invention is shown in FIG. 4,
which is a plot of breakdown voltage in kv-rms as a function of
composition in mole percent for the ternary system SF6-CO2-CC12F2.
Carbon formation appears for compositions rich in CC12F2, defined
by a line whose extremities are defined by
(b) 1 SF6 - 15 CO2 - 84 CC12F2
(c) 10 SF6 - 1 CO2 - 89 CC12F2.
This system evidences useful dielectric behavior within an area on
the ternary diagram defined by a polygon a-b-c-d-e-a having at its
20 corners the points defined by: -
(a) 1 SF6 - 65 CO2 - 34 CC12F2
(b) 1 SF6 - 15 CO2 - 84 CC12F2
(c) 10 SF6 - 1 CO2 89 CC12F2
(d) 98 SF6 - 1 CO2 - 1 CC12F2
(e) 24 SF6 - 75 CO2 - 1 CC12F2.
There is a synergistic BDV effect within an area on the ternary
diagram defined by a polygon f-g-d-h-f having at its corners the
points defined by
-14-
..
, . ~
10~894
(f) 30 SF6 ~ 25 CO2 45 CC12F2
(g) 30 SF6 - 1 CO2 - 69 CC12F2
(d) 98 SF~ - 1 CO2 - 1 CC12F2
(h) 74 SF6 - 25 CO2 - 1 CC12F2
See also Examples 2 and 21, below.
Other preferred examples are depicted in FIGS. 5 through
10. The figures are associated with the following systems, which
are explained in further detail in the Examples section below:
FIG. 5, SF6-CO2-CHClF2 (Example 22); FIG. 6, SF6-CO2-CBrF3 (Example
23); FIG. 7, SF6-CO2-CClF2CClF2 (Example 25); FIG. 8, SF6-CO2-
CClF2CF3 (Example 26); FIG. 9, SF6-CClF3-CHF3 (Example 27) and FIG.
10, CO2-CF3CF3-c-C4F8 (Example 34).
Quaternary and higher compositions within the above
definition may also be formulated in accordance with the
invention. One such example is SF6-CO2-CC12F2-CClF2CF3.
III. Group III Mixtures
Examples of perfluorinated ethers useful in the practice
of the invention for group III mixtures include perfluorodimethyl
ether, (CF3)2O, perfluorodiethyl ether, (C2F5)2O, perfluoro-1,4-
dioxane,
O
F2C fF2
F2C\ /CF2
perfluoro-1,2-dimethoxy ethane, CF3O(CF2)2OCF3, perfluoro-1,2- ;
epoxyethane, F2C-CF2, perfluoro-1,3-epoxypropane, F2C-CF2, and
F C-O
perfluoro-2,3-epoxy-2-methylbutane, (CF3)2-C-CFCF3.
Mixtures of the perfluorinated ethers with SF6 may
contain from about 1 to 99 mole percent of SF6. The presence of
-15-
. . .
1~6889~
SF6 serves to increase the vapor pressure of the mixture and reduce
its cost. An increased vapor pressure is desirable, since as
temperature is decreased, the gas density correspondingly is
decreased, with an accompanying decrease in breakdown voltage.
Increased vapor pressure serves to maintain a high breakdown
voltage.
Mixtures of the perfluorinated ethers with CO2 may con-
tain from about 1 to 75 mole percent of CO2. For CO2 mixtures,
only compositions having a breakdown voltage of greater than about
10 kv-rms are considered useful. Typically, use of greater than
about 75 mole percent of CO2 in these mixtures results in a break-
down vo~tage of less than about 10 kv-rms. The combination of CO2 ~-
with perfluorinated ethers serves the same function as SF6.
Mixtures of one or more of the perfluorinated ethers with ~ ~-
SF6 plus CO2 also result in further reduction in cost with little
sacrifice in the desirable properties described above. Examples of
such compositions include SF6-CO2-(CF3)2O and SF6-CO2-(C2F5)2O.
Preferred mixtures of the perfluorinated ethers with SF
and/or CO2 are those which retain 90% of the dielectric breakdown
voltage of the highest component. For example, employing the
methods described by ASTM D2477-66T, a mixture of SF6 and (C2F5)2O
over the range of about 1 to 60 mole percent of SF6 evidences a
dielectric breakdown voltage of at least 20.0 kv-rms (kilovolt-
root mean square), which is 90% of the dielectric breakdown voltage
of pure (C2F5)2O, the component having the higher dielectric break-
down voltage.
With some combinations of perfluorinated ethers and SF6
and/or CO2 for group III mixtures within the proportions disclosed
above we have unexpectedly found some evidence of enhancement of
dielectric strength, as measured by breakdown voltage. Examples
f ch systems include SF6-(CF3)2O, SF6 (C2 5)2 2 2
-16-
- , , , , , ~ . . . . . . .
106889~
It would be expected that for binary compositions, breakdown
voltage would vary linearly with composition. However, for some
compositions, an unexpected enhancement of breakdown voltage is
observed. This may take the form either of a moderate positive
deviation from linearity or of a significant positive deviation
from linearity to the extent that over some range of composition,
the observed breakdown voltage is equal to or greater than that
of either of the two end members. The latter condition is
referred to herein as a synergistic effect. Although it is not
10 possible to define general composition ranges, such a determi- -~
nation is easily within the ability of one skilled in the art.
For example, employing the methods described by ASTM D2477-66T,
a mixture of SF6 and (C2F5)2O over the range of about 1 to 55
mole percent of SF6 evidences a dielectric breakdown voltage of
at least 22.1 kv-rms (kilovolt-root mean square). At 40 mole ~-
percent of SF6, this value is observed to rise to 24.3 kv-rms.
The dielectric breakdown voltages of pure SF6 and pure (C2F5)2O
are 16.79 and 22.1 kv-rms, respectively. -~
Similarly, a mixture of CO2 and (CF3)2O over the range
of about 1 to 45 mole percent of CO2 and a mixture of CO2 and
(C2F4)2O over the range of about 1 to 50 mole percent of CO2 both
evidence a synergistic effect. In FIGS. 11 and 12 the breakdown
voltage of some perfluorinated ethers with SF6 and CO2, respec-
tively, are shown. It is apparent that there is deviation from
linearity, ranging from a slightly positive deviation for curve 10
to a substantial deviation for curves 11 and 21. The curves are
plotted from the data of Table II.
106889~
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106889~
IV. Group I Mixtures
Mixtures of SF6 and CO2 within the contemplation of
group I mixtures of the invention contain from about 1 to 50 mole
percent of CO2. The presence of CO2 serves to increase the vapor
pressure of the mixture, lower its freezing point below -50C,
and reduce its cost. An increased vapor pressure is particularly
desirable, since as temperature is decreased, the gas density
correspondingly is decreased due to condensation or solidification
of various components, with an accompanying decrease in breakdown
voltage. Thus, increased vapor pressure serves to maintain a high
breakdown voltage.
The effect of CO2 addition to SF6 on vapor pressure at
various temperatures is given in Table III below. There, it is
seen that addition of about 10 to 30 mole percent of CO2 results
in a substantial increase in vapor pressure over that of pure SF6
over the same temperature range. This increase is considerably
qreater than that predicted by Raoult's law. Such mixtures are
particularly useful in high voltage apparatus exposed to sub-
freezing temperatures. Also, the stability of CO2 at high tempera-
tures (200C and higher) indicates that these mixtures are alsouseful in high temperature applications.
--19-- ,.,
10~i889~
,, I . ~` ~ o ~
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-20-
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1068894
Unexpectedly, mixtures of SF6 and CO2 within the pro-
portions of about 1 to 50 mole percent of CO2 retain at least 90%
of the dielectric breakdown voltage of pure SF6, which is con-
sidered to be substantially equal to the breakdown voltage of SF6.
Over the range of about 1 to 30 mole percent of CO2, the observed
breakdown voltage is approximately equal to or greater than that
of SF6. The latter condition in these group I mixtures is referred
to herein as a synergistic effect. For example, employing the
methods described by ASTM D2477-66T and a gap of 0.1 inch between
electrodes, a mixture of SF6 and CO2 over the range of about 1 to
30 mole percent of CO2 evidenced dielectric breakdown voltages of
about 16.2 to 16.5 kv-rms (kilovolt-root mean square). The dielec-
tric breakdown voltages of pure SF6 and pure CO2 were 16.32 and
6./16 kv-rms, respectively.
An increase in pressure and an increase in gap distance
for compositions over the range of about 10 to 30 mole percent of
C2 results in breakdown voltages that are still within 90% of
that of pure SF6. These results are listed in Table IV below.
'
-21-
106889~
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u7
-22-
,, , , , , :
10~8894
FIG. 13 depicts the breakdown voltage of mixtures of
SF6 and CO2 in group I mixtures at room temperature. It is
apparent that there is significant deviation from linearity.
These results, together with the effects of temperature and
pressure given above and the lack of carbon formation observed
for these mixtures, indicate that mixtures of SF6 and C02 within
the proportions disclosed form excellent gaseous dielectric com-
positions suitable for use over a wide range of temperatures and
pressures.
The breakdown voltage data for mixtures of SF6 and CO2
are listed in Table V below. From the data given, the useful range
for gaseous dielectric behavior may be determined. The mixtures
over the range of about 1 to 50 mole percent of CO2 evidenced
breakdown voltage values at least about 90% of that of SF6. Mix-
tures over the range of about 1 to 30 mole percent of C02 evidenced
unusually high breakdown voltage values compared with the SF6.
Since the normal expected behavior is a linear dependence with com-
position, such unusual behavior is considered to be a synergistic -
effect, and such mixtures are preferred.
No carbon formation was observed within the limits of -
the test.
~BLE V
Breakdown Voltage, kv-rms, as a Function of CO2 Addition
(mole ~ercent) to SF
_ _ 6
0 10 20 30 40 50 60 70 80 90 100
16.32 16.47 16.36 16.19 15.78 15.24 13.28 11.33 9.83 8.08 6.16
All compositions disclosed herein have utility as gaseous
dielectric mixtures for carbon suppression. As such, they have
application in electrical apparatus, especially high voltage power --
30 equipment, such as transformers, capacitors, coaxial lines and
minisubstations, having a chamber in which electrical arcing
--23--
.. , .. : : ~
10~8894
occasionally occurs and which includes the gaseous dielectric mix-
ture. Some of the mixtures are particularly useful in certain
specific areas, such as for extreme temperature conditions, when
high dielectric strength is required, which are indicated in
examples set forth below.
The considerations in choosing a particular system in-
clude the cost of the components, the temperature performance
desired (low or high), the electrical properties desired, and the
relative safety of the total mixture.
EXAMPLES
I. Description of Test Procedure
Breakdown voltage (BDV) was measured by equipment which
included a glass breakdown voltage cell as described by ASTM D2477-
66T, a 50 kv-rms (kilovolt-root mean square), 60 Hz, 5 kva trans-
former and suitable accessory circuits. A vacuum manifold with
Bourdon Tube type manometer, solenoid valves and controls was also
used.
The cell had an 0.75 inch sphere and a 1.5 inch plane elec-
trodes. The breakdown cell filling manifold, using solenoid valves,
furnished connections to the cell, the manometer, various gas inlets
and the vacuum pump. The manometer was a Wallace and Tiernan model
62A-4D-0800, ranging in two rotations of the indicator needle be-
tween 0 and 800 Torr absolute. A simple control panel governed the
solenoid valves used to admit the various gases of the mixtures in
the BDV cell. The BDV measurement conditions were 60 Hz, 0.100 inch
gap, 760 Torr total pressure and ambient room temperature. Compo-
sitions were prepared in terms of partial pressure, accurate to
+ 0.5 Torr, and converted to mole percent assuming ideal gas law
behavior. -
The electrodes had to be polished prior to taking BVD data.
They were polished with E5 emery grit, soaked in xylene for 30 min,
-24-
~: ' '
.: .
~0~8894
rinsed with petroleum ether and dried at 100C for 15 min. A few
preliminary breakdown voltage shots were necessary prior to taking
data to condition the electrodes. Even so, the BDV of pure compo-
nents, such as SF6, was observed to vary slightly from one experi-
ment to the next.
For measuring carbon suppression, there were two levels
of testing. In the first, any carbon appearing after 5 BDV shots
was monitored as a "go-no go" test. For a more severe exposure
test, 50 successive BDV shots were taken in the same manner.
Carbon tetrafluoride, CF4, the most stable fluorocarbon
known, and nitrogen, N2 served as inert diluents and blanks. In
the test for carbon formation, the measurements started at high SF6
or CO2 concentrati~ns. These were gradually reduced until carbon
appeared. Carbon was usually observed to form on the grounded plane
electrode.
Example 1. - Procedure for Measurement of Breakdown Voltage
This Example demonstrates the breakdown voltage measure-
ment by the ASTM D2477-66T method, using various dielectric mix-
tures. The equipment included a vacuum manifold, the glass
breakdown voltage cell, 0 to 50 kv test set rated at 5 kva and
40,000 ohms of 250 watt current limiting resistors. The manifold
had valved connections to air, to the vacuum pump, to the manometer
and to three cylinders which contained components A, B or C. -
An air gap of two 12.5 cm diameter brass spheres served -
for a peak voltage calibration standard. Prior to measurements,
the transformers voltmeters were calibrated with this gap using the
BDV methods of ASTM D2477-66T, i.e., averaging 5 successive
spark breakdowns at set gap distances. The meters were accurate
to 0.5 kv, or within calibration.
In preparing a test sample, the ideal gas law was used
and pressure percent was assumed equal to mole percent. The desired
-25-
, . , , , - ,
10~889~
mole percent of each component was calculated as the number of Torr
compared to 760 Torr (1 atmosphere), which yielded the desiréd mole
percent. Prior to make up of the composition the test cell was
evacuated to less than 1 Torr. During make up of the composition
the component to be present in the smallest amount was admitted
first, until it attained the desired partial pressure. This was
followed by the component with the next highest percentage and
finally by the component present in the largest mole fraction.
Table VI below presents the pressures used for some SF6-CC12F2
mixtures, together with the breakdown voltage of each composition
and its standard deviation (SD).
TABLE VI
BREAKDOWN VOLTAGE OF SF6-CC12F2 MIXTURES i-~
SF6C12F2
P, P, BDV + SD,
Mole %Torr Mole % Torr kv-rms* kv-rms*
100 760 0 0 17.43 0.33
608 20 152 17.74 0.51
456 40 304 18.53 0.29 -~
20 40 304 60 456 18.46 0.51
152 80 608 17.90 0.43
0 0 100 760 17.28 0.32
*rms = root mean square value, i.e. BDV rms = 0.707 BDV peak.
Synergism is indicated in the magnitude of about 1 kv-rms greater
than the breakdown voltage of SF6 over the range of about 40 to
60 mole percent of SF6; see also FIG. 2 and Example 4, below.
Example 2 - Process for Measurement of Carbon Formation Suppression
This Example describes the method of measuring carbon suppres- -
sion, using SF6, CO2 and CC12F2. The equipment of Example 1
was used for the tests. The compositions were again made up using
pressure percent (mole percent) at one atmosphere total pressure.
-26-
10~889~
To evaluate carbon formation, a given sample of definite composi-
tion was repeatedly sparked, as in Example 1, and BDV observéd.
There were two levels of exposure, 10 sparks and 50 sparks, all
applied successively to the same gas sample. If carbon appeared,
the BDV cell was disassembled and the electrodes cleaned and condi-
tioned again.
Table VII presents the pressures and compositions of the
samples, the observed breakdown voltages and the number of shots
which did, or did not, produce carbon. With these mixtures, a 5 per-
cent change in composition caused a large increase in carbon forma-
tion suppression: at 90 CC12F2 - 10 CO2, carbon formed after 20
sparks, whereas at 85 CC12F2 - 15 CO2, no carbon appeared after 50
sparks. Similarly, pure CF2C12 formed carbon after 10 sparks, while
at 95 CC12F2 - 5 SF6, no carbon appeared after 50 sparks. A detailed
study of this system is shown in FIG. 4 and is discussed below in
further detail in Example 21. In FIG. 4, the breakdown voltages of
compositions in the system SF6-CO2-CC12F2 are depicted on a ternary -
plot as a function of mole percent.
-27-
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1068894
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106885~4
II. Binary Group II Mixtures
A. SF Binary Mixtures
The breakdown voltage data for binary group II mixtures
which included SF6 is listed in Table VIII. From the data given,
both the minimum amount of SF6 useful in suppressing carbon
formation and the useful range for gaseous dielectric behavior
may be determined. Many binary mixtures evidenced breakdown
voltage values within about 90~ of that of the higher end member
over a range of compositions; such mixtures are preferred.
Certain binary mixtures evidenced unusually high breakdown vol-
tage values compared with the values of either end member. Since
the normal expected behavior is a linear dependence with compo-
sition, such unusual behavior is termed a synergistic effect, and
such mixtures are also preferred. Following Table VIII is a
discussion of some of the binary mixtures including SF6 and their
utility.
-29-
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-30
~06889~
Example 3. System SF -CCl F
6 3-
A BDV of 23.7 kv was observed for CC13F, compared with a
value of 18.1 kv for SF6. The system evidenced useful dielectric
behavior over the range of about 30 to 99 mole percent of SF6. The
BDV was at least 90% that of CC13F over the range of about 30
to 70 mole percent of SF6. At least about 30 mole percent of
SF6 was required to suppress carbon formation in CC13F.
The combination of SF6 and CC13F is an inexpensive
dielectric mixture. The preferred operating temperature range is
greater than ambient but less than 150C.
Example 4. System SF6-CC12F2 (FIG. 2, curve 20)
This system evidenced useful dielectric behavior over the
range of about 10 to 99 mole percent of SF6. There was a synergistic
BDV effect over the range of about 40 to 80 mole percent of SF6. At
least about 10 mole percent of SF6 was required to suppress carbon
formation in CC12F2.
The combination of SF6 and CC12F2 is an inexpensive
dielectric mixture for use in units such as underg~ound or underwater
high voltage coaxial lines, capacitors and in gas filled transformers.
Example 5. System SF -CClF3 (FIG. 2, curve 23)
This system evidenced useful dielectric behavior over the
range of about 15 to 99 mole percent of SF6. The BDV was at
least 90~ that of SF6 over the range of is about 60 to 99
mole percent of SF6. There was a synergistic BDV effect over -~
a narrow range of about 75 to 85 mole percent of SF6. At
least about 15 mole percent of SF6 was required to suppress
carbon formation in CClF3.
This system is useful in raising the vapor pressure of SF
without substantially decreasing the BDV. Hence, it is suitable for
low temperature use in transformers and capacitors.
Example 6. System SF -CBrF
6 3
This system evidenced useful dielectric behavior over the
-31-
.. ... . . . . .
.. .. .. ..
..
,, . ., , ~ , . .
10~8894
range of about 10 to 99 mole percent of SF6. The BDV was at least
90% that of SF6 over the range of about 20 to 99 mole percent of
SF6. There was a synergistic BDV effect over the range of about
60 to 85 mole percent of SF6. At least about 10 mole percent of
SF6 was required to suppress carbon formation in CBrF3.
Example 7. System SF -CHClF (FIG. 2, curve 21)
6 2 - ---
An SF6-CHClF2 azeotrope existed at 90 mole percent of SF6.
This system evidenced useful dielectric behavior over the range of
about 35 to 99 mole percent SF6. A synergistic effect was observed
over a narrow range of about 40 to 50 mole percent of SF6. At
least about 35 mole percent of SF6 was required to suppress carbon ..
formation in CHClF2.
The combination of SF6 and CHClF2 is an inexpensive
dielectric mixture with only a slight compromise in SF6 BDV and
vapor pressure.
Example 8. System SF6 CHF3
This system evidenced useful dielectric behavior over the
range of about 15 to 99 mole percent of SF6. The BDV was at least
90% that of SF6 over the range of about 65 to 99 mole percent of
SF6. At least about 15 mole percent of SF6 was required to suppress
carbon formation in CHF3.
The use of CHF3 can increase the vapor pressure of SF6 -
without substantial SF6 BDV decrease, either alone or together with
an azeotropic mixture of CClF3. These gaseous dielectric mixtures
are useful in low temperature applications, such as gas filled trans- -.
formers which are exposed to winter conditions.
Bxample 9. System SF -CClF CClF (FIG. 2, curve 22)
6 2 - 2 -
A BDV of 21.8 kv was observed for CClF2CClF2, compared :
with a value of 16.6 kv for SF6. The system evidenced useful di- ~ -
30 electric behavior over the range of about 45 to 99 mole percent of :
SF6. The BDV was at least 90% that of CClF2CClF2 over the range
-32-
: . .
1068894
of about 45 to 85 mole percent of SF6. At least about 45 mole per-
cent of SF6 was required to suppress carbon formation in CClF2CClF2.
This system evidenced a substantial BDV improvement over SF6 alone.
The relatively high boiling point of CClF2CCLF2 (3.6C)
limits low temperature uses of this system, but at ambient room temp-
erature or above, it is a satisfactory dielectric mixture at only
moderate cost.
Example 10. System SF -CClF CF (FIGS. 1, curve 10 and 2, curve 24)
~ 2- 3
This system evidenced useful dielectric behavior over the
range of about 25 to 99 mole percent of SF6. There was a synergistic
effect over the range of about 25 to 90 mole percent of SF6, and a
substantial synergistic effect (greater than about 1 kv) over the range
of about 30 to 60 mole percent of SF6. At least about 25 mole percent
of SF6 was required to suppress carbon formation in CClF2CF3.
The combination of SF6 and CClF2CF3 is an inexpensive
gaseous dielectric mixture having the same or higher dielectric
strength than SF6 alone.
Example 11. System SF -CF CF
6 - 3 - 3
This system evidenced useful dielectric behavior over the
range of about 20 to 99 mole percent of SF6. At least about 20 - ~ -
mole percent of SF6 was required to suppress carbon formation in
3 3
The low boiling point of CF3CF3 (-78C) and its good
thermal stability make it a desirable diluent for SF6 for low
temperature applications. Also, since CF3CF3 is a very ther-
mally stable gas, the addition of sufficient SF6 to suppress car-
bon formation (about 20 mole percent) should lead to a more desirable
high temperature gaseous dielectric mixture for use in transformers~
Example 12. System SF6-c-C4F8
A BDV of 19.9 kv was observed for c-C4F8, compared
with a value of 17.7 kv for SF6. The system evidenced useful
-33-
.
10~8894
dielectric behavior over the range of about 35 to 99 mole percent
of SF~. At least about 35 mole percent of SF6 was required for
carbon suppression.
The SF6-c-C4F8 system has a higher BDV than SF6 alone.
It is not suitable for use below 0C due to the high boiling point
of c-C4F8 (-6C). On the other hand, c-C4F8 can be a component
in high temperature gaseous dielectric mixtures; see also its use
with CO2 in Example 20, below.
B. CO2 Binary Mixtures
The breakdown voltage data for binary group II mixtures
which included CO2 are listed in Table IX. From the data given,
both the minimum amount of CO2 useful in suppressing carbon forma-
tion and the useful range for gaseous dielectric behavior may be
determined. As before, mixtures evidencing at least 90% of the
breakdown voltage of the higher of the two components are preferred,
as are synergistic compositions. Following Table IX is a discussion
of some of the binary mixtures including CO2 and their utility. -
In general, while CO2 binary mixtures tended to evidence
less BDV synergism than did the SF6 binary mixtures, they evidenced
good carbon suppression properties. Except in special applica-
tions, such as low voltage use, mixtures evidencing breakdown
voltages of less than about 10 kv-rms are not considered to be as
useful as those greater than about 10 kv-rms.
-34-
1~688~34
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I ~ o ~o
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8 ~ o _, ~ o ,~ o ~
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.:
-35-
106889~
Example 13. System CO -CCl F (FIG. 3, curve 31)
2 2-2
This system evidenced useful dielectric behavior over
the range of about 15 to 65 mole peecent of CO2. The BDV was at
least 90% that of CC12F2 over the range of about 15 to 35 mole per-
cent of CO2. At least about 15 mole percent of CO2 was required to
suppress carbon formation in CC12F2.
At about 20 mole percent of CO2, this system has a BDV
of 14.9 kv, compared with a BDV of 16.1 kv for pure SF6. This
system is an inexpensive gaseous dielectric mixture suitable for
operation in the range of about -20C to 150C.
Example 14. System CO -CBrF
2 3
This system evidenced useful dielectric behavior over
the range of about 15 to 65 mole percent of CO2. At least about -
15 mole percent of CO2 was required to suppress carbon formation
in CBrF3.
This binary system is useful in high temperature applica-
tions.
Example 15. System CO -CHClF (FIG. 3, curve 30)
2 2
This system evidenced useful dielectric behavior over
the range of about 45 to 70 mole percent of CO2. There was a
synergistic effect over this entire range. At least about 45 mole
percent of CO2 was required to suppress carbon formation in CHClF2.
This system is an inexpensive dielectric mixture for low
voltage uses when SF6 is not economically practical.
Example 16. System CO2-CHF3
This system evidenced useful dielectric behavior over the
range of about 15 to 99 mole percent of CO2. There was a synergistic
effect over a narrow range of about 15 to 25 mole percent of CO2.
At least about 15 mole percent of CO2 was required to suppress
carbon formation in CHF3.
-36-
. .
10~889~
Example 17. System CO2-CClF2CClF2
This system evidenced useful dielectric behavior over
the range of about 45 to 85 mole percent of CO2. At least about
45 mole percent of CO2 was required to suppress carbon formation
2 2
Example 18. System CO2-CClF2CF3 (FIG. 1, curve_ll)
This system evidenced useful dielectric behavior over
the range of about 25 to 70 mole percent of CO2. The BDV was at
least 90~ that of CClF2CF3 over the range of about 25 to 35 mole
percent of CO2. At least about 25 mole percent of CO2 was required
to suppress carbon formation in CClF2CF3.
This system is suitable for dry type transformers up to
about 250C and is relatively inexpensive compared with SF6.
Example 19. System CO -CF CF
2 - 3 - 3
This system evidenced useful dielectric behavior over
the range of about 35 to 50 mole percent of CO2. At least about
35 mole percent of CO2 was required to suppress carbon formation
3 3'
Example 20. System CO -c-C F
2 4-8
This system evidenced useful dielectric behavior over .
the range of about 55 to 75 mole percent of CO2. At least about
55 mole percent CO2 was reqùired to suppress carbon formation
c C4F8- -
This system can be used in formulating multi-component
mixtures which do not contain SF6 and which are suitable for ~ -
operating temperatures up to about 300C.
III. Multicomponent Group II Mixtures
Data for these group II mixtures are most conveniently
represented on ternary diagrams expressed in mole percent.
-37-
' '
,. ' : ,. - . ', ' ~ ,
10~889~
Example 21. System SF -CO -CCl F ( FIG . 4 )
6- 2 2-2
This system evidenced useful dielectric behavior with-
in an area on a ternary diagram defined by a polygon a-b-c-d-e-a
having at its corners the points defined by:
(a) 1 SF6 - 65 CO2 - 34 CC12F2
(b) 1 SF6 - 15 CO2 - 84 CC12F2
( c ) 10 SF6 - 1 C2 - 89 CCl 2F2
(d) 9~ SF6 - 1 CO2 - 1 CC12F2
(e) 24 SF6 - 75 CO2 - 1 CC12F2.
There was a synergistic BDV effect within an area on the
ternary diagram defined by a polygon f-g-d-h-f having at its corners
the points defined by
(f) 30 SF6 - 25 CO2 - 45 CC12F2
(g) 30 SF6 - 1 CO2 - 69 Ccl2F2
(d) 98 SF6 - 1 C2 - 1 CC12F2
(h) 74 SF6 - 25 CO2 - 1 CC12F2
Carbon formation was suppressed for compositions lying in -:~
regions rich in SF6 and CO2 defined by a line b-c whose extremities ~.
are defined by
(b) 1 SF6 - 15 CO2 - 84 CC12F2
(c) 10 SF6 - 1 C2 - 89 CC12F2.
This system is an inexpensive gaseous dielectric mixture
suitable for coaxial lines exposed to temperatures down to -30C.
Example 22. System SF6 CO2-CHClF2 ( FIG 5 )
This system evidenced useful dielectric behavior within
an area on a ternary diagram defined by a polygon a-b-c-d-e-a having
at its corners the points defined by
(a) 1 SF6 - 70 CO2 - 29 CHClF2
(b) 1 SF6 - S0 CO2 - 49 CHClF2
IC) 35 SP6 - 1 C2 - 64 CHClF2
(d) 98 SF6 - 1 CO2 - 1 CHClF2
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1068894
(e) 24 SF6 - 75 CO2 - lCHClF2.
There was the synergistic BDV effect within an area on
the ternary diagram defined by a polygon c-d-f-c having at its
corners the points defined by
(c) 35 SF6 - 1 CO2 - 64 CHClF2
(d) 98 SF6 - 1 CO2 - 1 CHClF2
(f) 64 SF6 - 35 CO2 - 1 CHClF2.
Carbon formation was suppressed for compositions lying
in regions rich in SF6 and CO2 defined by a line b-c whose ex-
tremities are defined by(b) 1 SF6 - 50 CO2 - 49 CHClF2
(c) 35 SF6 - 1 CO2 - 64 CHClF2.
Example 23. System SF -CO -CBrF (FIG 6)
6 - 2 3-
This system evidenced useful dielectric behavior within
an area on a ternary diagram defined by a polygon a-b-c-d-e-a having
at its corners the points defined by -
(a) 1 SF6 - 65 CO2 - 34 CBrF3 -
(b) 1 SF6 - 15 CO2 - 84 CBrF3
(c) 10 SF6 - 1 CO2 - 89 CBrF3
Id) 98 SF6 - 1 CO2 1 CBrF3
(e) 24 SF6 - 75 CO2 - 1 CBrF3.
There was a synergistic BDV effect within an area on the
ternary diagram defined by a polygon f-g-h-d-f having at its corners
the points defined by
(f) 50 SF6 - 49 CO2 - 1 CBrF3
(g) 50 SF6 - 5 CO2 - 45 CBrF~ -
(h) 54 SF6 - 1 CO2 - 45 CBrF3 ~ :
(d) 98 SF6 - 1 CO2 - 1 CBrF3~
Carbon formation was suppressed for compositions lying :~.
in regions rich in SF6 and CO2 defined by a line b-c whose ex-
tremities are defined by
-39- :
.
1068894
(b) 1 SF6 - 14 CO2 - 85 CsrF3
(c) 14 SF6 - 1 CO2 - 85 CBrF3.
Example 24. System SF -CO -CC1 FCClF
6 2 2 2
This system evidenced useful dielectric behavior with-
in an area on a ternary diagram defined by a polygon having at
its corners the points defined by
1 SF6 - 74 C02 - 25 CC12FCClF2
25 SF6 - 50 CO2 - 25 CC12FCClF2
38 SF6 - 1 C02 - 61 CC12FCClF2
98 SF6 - 1 CO2 - 1 CC12FCClF2
25 SF - 74 CO - 1 CC1 FCClF
Carbon formation was suppressed for compositions lying
in regions rich in SF6 and C02 defined by two lines whose
extremities are defined by
1. 1 SF6 - 74 C02 - 25 CC12FCClF2
25 SF6 - 50 CO2 - 25 CC12FCClF2
2- 25 SF6 ~ 50 CO2 ~ 25 CCl FCClF
38 SF6 - 1 CO2 - 61 CC12FCClF2.
Example 25. System SF6 CO2-CClF2CClF2 (FIG. 7)
This system evidenced useful dielectric behavior within
an area on a ternary diagram defined by a polygon a-b-c-d-e-a hav-
ing at its corners the points defined by
(a) 1 SF6 - 85 CO2 - 14 CClF2CClF2
(b) 1 SF6 - 45 CO2 - 54 CClF2CClF2
(c) 45 SF6 - 1 CO2 - 54 CClF2CClF2
(d) 98 SF6 - 1 C02 - 1 CClF2CClF2
(e) 24 SF6 - 75 CO2 - 1 CClF2CClF2
There was a synergistic BDV effect within an area on
the ternary diagram defined by a polygon f-c-d-g-f having at
its corners the.points defined by
(f) 11 SF6 - 35 CO2 - 54 CClF2CClF2
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~068894
(c) 45 SF6 - 1 CO2 - 54 CClF2CClF2
(d) 98 SF6 - 1 CO2 - 1 CClF2CClF2
(g) 64 SF6 - 35 CO2 - 1 CClF2CClF2.
Carbon formation was suppressed for compositions lying
in regions rich in SF6 and CO2 defined by a line whose extremi-
ties are defined by
(b) 1 SF6 - 45 CO2 - 54 CClF2CClF2
(c) 45 SF6 - 1 CO2 - 54 CClF2CClF2.
Exam~le 26. System SF -CO -CClF CF (FIG. 8)
6 2 2 ~ 3
This system evidenced useful dielectric behavior within
an area on a ternary diagram defined by a polygon a-b-c-d-e-a having
at its corners the points defined by :~
(a) 1 SF6 - 70 CO2 - 29 CClF2CF3
(b) 1 SF6 - 25 CO2 - 74 CClF2CF3
(c) 25 SF6 - 1 CO2 - 74 CClF2CF3
(d) 98 SF6 - 1 CO2 - 1 CClF2CF3
(e) 24 SF6 - 75 CO2 - 1 CClF2CF3.
There was a synergistic effect within an area on the
ternary diagram defined by a polygon f-c-d-g-f having at its
corners the points defined by
(f) 35 SF6 - 20 CO2 - 45 CClF2CF3
(c) 25 SF6 - 1 CO2 - 74 CClF2CF3
(d) 98 SF6 - 1 CO2 - 1 CClF2CF
(g) 79 SF6 - 20 CO2 - 1 CClF2CF3.
Carbon formation was suppressed for compositions lying .
in regions rich in SF6 and CO2 defined by a line b-c whose ex- ~ ~:
tremities are defined by
(b) 1 SF6 - 25 CO2 - 74 CClF2CF3
(c) 25 SP6 - 1 CO2 - 74 CClF2CF3. ,:- -
Example 27. System SF6-CClF3-CHF3 (FIG. 9)
The system evidenced useful dielectric behavior within
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106~894
an area on a ternary diagram defined by a polygon a-b-c-d-a having
at its corners the points defined by
(a) 10 SF6 - 89 CClF3 - 1 CHF3
(b) 25 SF6 - 37.5 CClF3 - 37.5 CHF3
(c) 10 SF6 - 1 CClF3 - 89 CHF3
(d) 98 SF6 - 1 CClF3 - 1 CHF3.
Carbon formation was suppressed for compositions lying
in regions rich in SF6 defined by two lines, a-b and b-c, whose
extremities are defined by
1. (a) 10 SF6 - 89 CClF3 - 1 CHF3
(b) 25 SF6 - 37.5 CClF3 - 37.5 CHF3
2- (b) 25 SF6 - 37.5 CClF3 - 37.5 CHF3
(c) 10 SF6 - 1 CClF3 - 89 CHF3.
This system is useful in gas filled transformers
operating under winter conditions and in circuit breaker controls.
Example 28. System SF6 CHF3-C~ClF2
This system evidenced useful dielectric behavior within
an area on a ternary diagram defined by a polygon having at its
corners the points defined by
20 SF6 - 79 CHF3 - 1 CHClF2
44 SF6 ~ 1 CHF3 - 60 CHClF2
98 SF - 1 CHF - 1 CHClF .
6 3 2
There was a synergistic BDV effect within an area on ~:
the ternary diagram defined by a polygon having at its corners
the points defined by
45 SF6 ~ 5 CHF3 - 50 CHClF2
49 SF6 ~ 1 CHF3 - 50 CHClF2
98 SF6 ~ 1 CHF3 - 1 CHClF2
S 6 5 CHF3 1 CHClF2.
Carbon formation was suppressed for compositions lying
in regions rich in SF6 defined by a line whose extremities are
defined by
-42-
~ . . , :
10f~889~
20 SF6 - 79 CHF3 - 1 CHClF2
44 SF6 ~ 1 CHF3 - 60 CHClF2
Example 29. System SF -CCl F -CClF CClF
6- 2-2 2 2
This system evidenced useful dielectric behavior within
an area on a ternary diagram defined by a polygonal having at
its corners the points defined by
6 89 CC12F2 - 1 CClF2CClF2
47 SF6 - 1 CCl F - 52 CClF CClF
6 2 2 1 2CClF2.
Carbon formation was suppressed for compositions lying
in regions rich in SF6 defined by a line whose extremities are
defined by
6 2 2 2CClF2
47 SF6 - 1 CC12F2 - 52 CClF2CClF2.
Example 30. System SF6-CC12F2-CClF2CF
This system evidenced useful dielectric behavior within
an area on a ternary diagram defined by a polygon having at its -~
corners the points defined by : -
11 SF6 - 88 CC12F2 - 1 CClF2CF3
26 SF6 - 1 CC12F2 - 73 CClF2CF3 -~ -
98 SF6 - 1 CC12F2 ~ 1 CClF2CF3
There was a synergistic BDV effect within an area on
the ternary diagram defined by a polygon having at its corners ...
the points defined by
30 SF6 ~ 55 CC12F2 ~ 15 CClF2CF3
30 SF6 - 1 CC12F2 - 69 CClF2CF
98 SF6 - 1 CC12F2 - 1 CClF2CF
44 SF6 - 55 CC12F2 - 1 CClF2CF3.
Carbon formation was suppressed for compositions lying
30 in regions rich in SF6 defined by a line whose extremities are ~-~
defined by
-43-
~.
. .
10~8894
11 SF6 - 88 CC12F2 - 1 CClF2CF3
26 SF6 - 1 CCl F2 ~ 73 CClF CF
Example 31. System SF6-CClF3-CClF2CF3
This system evidenced useful dielectric behavior within
an area on a ternary diagram defined by a polygon having at its
corners the points defined by
6 3 C 2 F3
6 3 2CF3
98 SF6 ~ 1 CClF3 - 1 CClF2CF3
14 SF6 - 85 CClF3 - 1 CClF2CF3
There was a synergistic BDV effect within an area on the
ternary diagram defined by a polygon having at its corners the
points defined by
30 SF6 ~ 15 CClF3 - 55 CClF2CF3
S 6 CClF3 69 CClF2CF3
98 SF6 - 1 CClF - 1 CClF2CF
84 SF6 - 15 CClF3 - 1 CClF2CF3.
Carbon formation was suppressed for compositions lying
in regions rich in SF6 defined by a line whose extremities
are defined by
1 SF - 95 CClF - 4 CClF CF
27 SF6 - 1 CClF3 - 74 CClF2CF3
Example 32. System SF -CBrF -CClF CClF
6 3 ~ -2 2
This system evidenced useful dielectric behavior within
an area on a ternary diagram defined by a polygon having at its
corners the points defined by ~
14 SF6 - 85 CBrF3 - 1 CClF2CClF2 -
45 SF6 - 1 CBrF3 - 54 CClF CClF
98 SF6 - 1 CBrF3 - 1 CClF2CClF2.
Carbon formation was suppressed for compositions lying
in regions rich in SF6 defined by a line whose extremitiès are
-44-
~0~j889~
defined by
14 SF6 - 85 CBrF - 1 CClF CClF
45 SF - 1 CBrF - 54 CClF CClF
Example 33. System CO2-CBrF3-CClF2CClF2
This system evidenced useful dielectric behavior within
an area on a ternary diagram defined by a polygon having at its
corners the points defined by
2 3 2CClF2
45 C2 ~ 1 CBrF3 - 54 CClF CClF
85 CO2 - 1 CBrF3 - 14 CClF2CClF2
50 C2 ~ 49 CBrF3 - 1 CClF2CClF2.
Carbon formation was suppressed for compositions lying
in regions rich in CO2 and defined by a line whose extremities
are defined by
15 CO2 - 84 CBrF3 - 1 CClF2CClF2
45 C2 ~ 1 CBrF3 - 54 CClF2CClF2.
Example 34. System CO2 CF3CF3 c C4_8 (
This system evidenced useful dielectric behavior within
an area on a ternary diagram defined by a polygon a-b-c-d-e-f-g-a
having at its corners the points defined by
(a) 35 CO2 - 64 CF3CF3 - 1 c-C4F8 ~
(b) 15 CO2 - 70 CF3CF3 - 15 c-C4F8 . :
(c) 15 CO2 - 50 CF3CF3 - 35 c-C4F8
(d) 55 CO2 - 1 CF3CF3 - 44 c-C4F8 :~
(e) 75 CO2 - 1 CF3CF3 - 24 c-C4F8 .
(f) 75 C2 ~ 15 CF3CF3 10 c C4F8
2 49 CF3CF3 - 1 c-C4F8.
There was a synergistic BDV effect with an area on the
ternary diagram defined by a polygon h-c-d-j-i-h having at its ~.
corners the points defined by
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10~8894
( 2 3 3 4 8
(c) 15 CO2 - 50 CF3CF3 - 35 c-C4F8
( ) 2 3 3 c C4 8
(j) S8 CO2 - 1 cF3cF3 - 41 C-C4F8
( ) 2 3 3 4 8-
Carbon formation was suppressed for compositions lying
in regions rich in C02 defined by three lines, a-b, b-c and c-d,
whose extremities are defined by
1. (a) 35 CO2 - 64 CF3CF3 - 1 c-C4F8
(b) 15 CO2 - 70 CF3CF3 - 15 c-C4F8
2. (b) 15 CO2 - 70 CF3CF3 - 15 c-C4F8
(c) 15 CO2 50 cF3cF3 35 c C4F8
3. (c) 15 CO2 - 50 CF3CF3 - 35 c-C4F8
(d) 55 CO2 - 1 CF3CF3 - 44 c-C4F8.
Example 35. System 90 SF6-10 CO2-CC12F2 CClF2CF3
This quaternary system, in which SF6 and CO2 were held
in a constant ratio of 90/10, evidenced useful dielectric behavior
within an area on a ternary diagram of SF6-CO2, CC12F2 and
CClF2CF3 defined by a polygon having at its corners the points
defined by
10 SF6-C02 ~ 89 CC12F2 ~ 1 CClF2CF3
6 2 2 2 2 3
98 SF6-CO2 - 1 CC12F~ - 1 CClF2CF3-
There was a synergistic BDV effect within an area on the
ternary diagram defined by a polygon having at its corners the
points defined by
40 SP6-CO2 - 30 CC12F2 - 30 CClF2CF3
30 SF6-C2 ~ 1 CC12F2 ~ 69 CClF2CF3 -
6 2 C12 2 1 CClF2CF3
69 SF6-CO2 - 30 CC12F2 - 1 CClF2CF3.
Carbon formation was suppressed for compositions lying in
-46-
10f~889~
regions rich in SF6-CO2 defined by a line whose extremities
are defined by
10 SF6-CO2 - 89 CC12F2 - 1 CClF2CF3
6 C2 1 CC12F2 69 CClF2CF3.
The following examples are illustrative of perfluori-
nated ether (group III) systems.
Example 36._ System SF6-(CF3)2O (FIG. 11, curve 10)
Both pure (CF3)2O and mixtures with SF6 over the entire
range of SF6 addition (about 1 to 99 mole percent of SF6) evidenced
useful dielectric behavior. The BDV was at least 90% that of SF6
over the range of about 10 to 99 mole percent of SF6.
Example 37. System SF6 (C2F5)2O (FIG. 11, curve 11)
Both pure (C2F5)2O and mixtures with SF6 over the entire
range of SF6 addition (about 1 to 99 mole percent of SF6) evidenced
useful dielectric behavior. The BDV was at least 90% that of
(C2F5)2O over the range of about 1 to 60 mole percent of SF6. ~
There was a synergistic BDV effect from about 1 to 55 mole percent ~ -
of SF6
Example 38. System CO2-(CF3)2O (FIG. 12, curve 20)
Both pure (CF3)2O and mixtures with CO2 over the range
of about 1 to 65 mole percent of CO2 addition evidenced useful
dielectric behavior. The BDV was at least 90% that of (CF3)2O
over the range of about 1 to 50 mole percent of CO2. There was a -
slight synergistic BDV effect from about 1 to 45 mole percent of
CO2 ' '
Example 39. System CO2 (C2F5)2O (FIG. 12, curve 21)
Both pure (C2F5)2O and mixtures with CO2 over the range
of about 1 to 75 mole percent of CO2 evidenced useful dielectric
behavior. The BDV was at least 90~ that of (C2F5)2O over the range
of about 1 to 45 mole percent of CO2. There was a synergistic BDV
effect over the range of about 1 to 50 mole percent of CO2.
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... . . ..
. "
