FIELD OF INVENTION
[001] The present invention in general relates to medium voltage electrical bushing
for electric traction application. The present invention more particularly relates to
medium voltage electrical bushing used in electric traction application to be used in
most extreme environmental condition like dusty and deserted areas where the dust
concentration in air reaching high value of 1.6 mg/m3, coastal areas where humid and
salt laden atmosphere with pH value of 8.5, sulphase of 7 mg/liter, concentration of
chlorine 6mg/liter and maximum conductivity 130µ siemens/cm. The medium voltage
electrical bushing having the provision of withstanding high fault currents with
optimized insulation creepage distance. The invention is specifically related to the
medium voltage electrical bushing for electric traction application and method of
manufacturing thereof.
BACKGROUND OF THE INVENTION
[002] A medium voltage bushing is conventionally used for passing an electrical
conductor through a locomotive or electric traction system to transmit electrical
current and voltage from an overhead line to an electrical bus transmission system in
the locomotive. Existing medium voltage bushings for electrical locomotive or electric
traction system uses inorganic based ceramic material as main insulation. These
bushings are fragile in nature and need careful handling. Their mechanical strength is
weak and while assembling on the loco of traction systems, chances of breakage are
more. Process cycle for making these insulators takes long duration because it involves
various steps like moulding, firing at temperatures of about 850 degree centigrade,
pre-stage machining, sintering and final machining to the required dimensions.
Dimensional tolerance is poor and there is high shrinkage while manufacturing.
Density of ceramic insulator is.3.69 gm/cm3.The length of the bushing on either side
of the system is commensurate with the medium (air or gas). The bushing will have

suitable flange assembly for mounting the same to the locomotive or electric traction
system body.
[003] The reliability of the medium voltage bushings is governed by following
parameters:
• Quality of the metal conductor and connectors during service.
• Void free preparation of the epoxy insulation.
• Heat conduction and thermal expansion based incompatibilities.
• Prevention of gas or rainy water leakage
• Prevention of leakage current
[004] In order to hold the high voltage conductor firmly to the electrically grounded
metal enclosure of locomotive or electric traction system, in a position sufficiently far
away from the grounded enclosure to avoid dielectric breakdown, bushing is provided
with metal fittings or metal flange to the enclosure.
[005] The bushing should satisfy required insulation requirement and should have
proper mechanical strength enough and for this purpose the insulators are processed
with aluminum filled or silica filled epoxy resin system. A material, such as epoxy, is
usually selected which has a coefficient of expansion similar to the metal/copper
conductor so as to minimize the possibility of voids being formed at the critical
interface where the insulator meets the metal/copper conductor. This is because such
voids are subjected to high electrical fields at the critical bushing conductor interface
region, which can lead to ionization within the voids, flashover and a reduced life
expectancy for the bushing. This high electrical field at this critical region approaches
a value equal to the product of the field at the inner conductor in the gas and the
dielectric constant of the bushing.

[006] US patent publication US 2005/0199418 discloses a dielectric bushing in
particular a high voltage bushing for a high-voltage apparatus. According to this
invention, in order to realize the field control in the field-stressed zone (7; 7a, 7b), at
least one screening electrode (6; 6a, 6b) arranged in the interior (20) of the insulator
part (2; 2a, 2b; 2c) is eliminated and replaced with a non-linear electric and/or
dielectric field control element (9; 9a, 9b; 9i, 9o; 9s) on the insulator part (2; 2a, 2b;
2c) in the region of the first installation flange (4; 8). Among other things,
embodiments refer to: design criteria for the geometric arrangement and for the
specific materials of the field control element (9; 9a, 9b; 9i, 9o; 9s), in particular
various axial and radial arrangements of field control elements (9; 9a, 9b; 9i, 9o; 9s),
as well as the realization of the field control element (9; 9a, 9b; 9i, 9o; 9s) in the form
of a coating or of a massive element that absorbs mechanical forces.
[007] According to US patent US7795541B1 which relates to an insulating device
for medium or high voltage electrical equipment in the shape of a disc inside an
enclosure acting as a support for an electrical conductor. The disc is made of
thermoplastic polyester. The disc can be worked starting from a thick board using
conventional machining tools and it can be provided with particular arrangements, for
example to facilitate its assembly or connection of conductors supported on it.
[008] Another prior art US Pat. 3,318,995 discloses cast electrical bushing
construction having controlled and shielded shrinkage voids. In this patent cast resin
bushings are disclosed, which remain electrically reliable even with differential
thermal expansion or shrinkage due to cavitation between metal and cast resin. For
this purpose, regions with increased cracking tendency are electrically shielded by
partially conductive or semi conductive field shielding layers. The layers are either
arranged on the high-voltage inner conductor or electrically connected to this end; or
they are arranged on shielding electrodes and electrically connected to these end,
wherein the shielding electrodes in turn are electrically connected to the grounded

housing of the connected apparatus. The field shielding layers create a field-free space
between themselves and the inner conductor or themselves and the shielding electrode
and effectively shield cavities in the casting resin.
[009] Still there exists requirement for an insulator which accommodates the high
voltage conductors in a common electrically insulated enclosure and the need also
exists for the less expensive insulator with medium voltage conductors and which
replaces the common metallic conductor or metal fitting or metallic flange with bushes
to reduce the final weight and cost of the insulator.
[0010] The need exists for less expensive insulator systems and manufacturing
process for the manufacture of medium voltage insulating products such as cast epoxy
insulator and other medium voltage insulating products, which are void free and which
meet the depicted medium voltage insulation requirements.
[0011] The present invention is directed to address the above problems and focus on
medium voltage electrical bushing for insulating medium voltage conductor from
electrically grounded metal enclosure/fitting of locomotive or electric traction system.
OBJECTS OF THE INVENTION
[0012] It is an object of the invention to provide a medium voltage electrical bushing
for insulating medium voltage conductor through metal enclosure of locomotive or
electric traction system.
[0013] Yet another object of the invention is to provide the medium voltage electrical
bushing used for electrical systems operated at 1 KV and up to 36 KV.

[0014] Another objective of the present invention is to provide improved elastomeric
composition having good weathering and tracking resistance for withstanding most
extreme environmental condition like dusty, deserted as well as coastal areas and
suitable for the manufacture of protective weather sheds for the medium voltage
electrical bushing.
[0015] Another objective of the present invention is to provide the medium voltage
electrical bushing for electric traction application at lesser weight and lesser cost.
[0016] These and other objects and advantages of the present subject matter will be
apparent to a person skilled in the art after consideration of the following detailed
description taken into consideration with accompanying drawings in which preferred
embodiments of the present subject matter are illustrated.
SUMMARY OF THE INVENTION
[0017] The present invention provides a method of manufacturing medium voltage
electrical bushing for insulating medium voltage conductor for electric traction
application comprising the steps of configuring a mold having a first half and a second
half interacting along a parting plane. Configuring a cavity corresponding to the
medium voltage electrical bushing, the cavity is encompassed by the first half of the
mold and the second half of the mold. Positioning a nozzle at the first half of the mold
for discharging liquefied material into the cavity. Closing the mold by relative
movement of the first half of the mold with respect to the second half of the mold until
the cavity is closed. Injecting polymer composite dough and liquefied material through
the nozzle. Opening the mold by relative movement of the first half of the mold with
respect to the second half of the mold and removing the bushing from the mold cavity.

[0018] In an aspect of the invention, a method for manufacturing the medium voltage
electrical bushing for electric traction application by epoxy resin composition
comprising of formulating the additive mix polymer dough, molding it to required
geometry in a mold and gelling the polymer filled mold.
[0019] In an aspect of the invention, the epoxy resin composition for high voltage
insulation comprising of inorganic additive system having a polymer of Bisphenol–A
epoxy resin of 90-100 parts by weight wherein the additive comprises of a micro
structured alumina or silica powder of 40-70 parts by weight.
[0020] In an aspect of the invention, micro structured alumina or silica filler / additive
content of 40%-70% parts by weight is easily filled up the intra-molecular voids
thereby improving the electrical, mechanical, thermal properties. Due to the
availability of more surface area for these fillers, suitable filler composition improves
the properties of the molded epoxy bushing.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0021] It is to be noted, however, that the appended drawings illustrate only typical
embodiments of the present subject matter and are therefore not to be considered for
limiting of its scope, for the invention may admit to other equally effective
embodiments. The detailed description is described with reference to the
accompanying figures. In the figures, a reference number identifies the figure in which
the reference number first appears. The same numbers are used throughout the figures
to reference like features and components. Some embodiments of system or methods
or structure in accordance with embodiments of the present subject matter are now
described, by way of example, and with reference to the accompanying figures, in
which:

[0022] FIG. 1 shows a cross sectional view of a medium voltage electrical bushing for
insulating medium voltage conductor for electric traction application according to the
present invention;
[0023] FIG.2a shows circular shaped aluminium metal insert or flange in accordance
with the present invention;
[0024] FIG.2b shows an aluminium metal insert or bushes in accordance with the
present invention;
[0025] FIG.3 shows a method of manufacturing medium voltage electrical bushing for
insulating high voltage conductor for electric traction application according to one
embodiment of the present invention.
[0026] The figures depict embodiments of the present subject matter for the purposes
of illustration only. A person skilled in the art will easily recognize from the following
description that alternative embodiments of the structures and methods illustrated
herein may be employed without departing from the principles of the disclosure
described herein.
DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE
PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING
DRAWINGS
[0027] It should be appreciated by those skilled in the art that any block diagrams
herein represent conceptual views of illustrative systems embodying the principles of
the present subject matter. Similarly, it will be appreciated that any flow charts, flow
diagrams, state transition diagrams, pseudo code, and the like represent various
processes which may be substantially represented in computer readable medium and
executed by a computer or processor, whether or not such computer or processor is
explicitly shown.

[0028] In the present disclosure, the word "exemplary" is used herein to mean
"serving as an example, instance, or illustration." Any embodiment or implementation
of the present subject matter described herein as "exemplary" is not necessarily to be
construed as preferred or advantageous over other embodiments.
[0029] While the present disclosure is susceptible to various modifications and
alternative forms, specific embodiment thereof has been shown by way of example in
the drawings and will be described in detail below. It should be understood, however
that it is not intended to limit the present disclosure to the particular forms disclosed,
but on the contrary, the present disclosure is to cover all modifications, equivalents,
and alternative falling within the spirit and the scope of the present disclosure.
[0030] The terms “comprises”, “comprising”, or any other variations thereof, are
intended to cover a non-exclusive inclusion, such that a setup, device or method that
comprises a list of components or steps does not include only those components or
steps but may include other components or steps not expressly listed or inherent to
such setup or device or method. In other words, one or more elements in a system or
apparatus proceeded by “comprises… a” does not, without more constraints, preclude
the existence of other elements or additional elements in the system or apparatus.
[0031] In the following detailed description of the embodiments of the disclosure,
reference is made to the accompanying drawings that form a part hereof, and in which
are shown by way of illustration specific embodiments in which the disclosure may be
practiced. These embodiments are described in sufficient detail to enable those skilled
in the art to practice the disclosure, and it is to be understood that other embodiments
may be utilized and that changes may be made without departing from the scope of
the present disclosure. The following description is, therefore, not to be taken in a
limiting sense.

[0032] The present invention relates to a medium voltage electrical bushing for
medium voltage applications which has enhanced dielectric properties such as
capacitance, tan delta value, partial discharge with optimized insulation. The medium
voltage electrical bushing used in electric traction application to be used in most
extreme environmental condition with protective weather sheds.
[0033] Also, the present invention further describes a method of producing medium
voltage electrical bushing for medium voltage applications using epoxy resin
composition (the epoxy resin composition filled with micro structured alumina or
silica filler / additive content) which will enhance the electrical properties.
[0034] In one embodiment a medium voltage electrical bushing for insulating high
voltage conductor (1) for electric traction application with high voltage conductor (1)
supported by for example circular shaped aluminium metal insert/aluminium or
metallic flange (4) which is connected to electrically grounded enclosure are
manufactured as per the chemical composition mentioned in Table.1 below, by
injection compression molding in which the inorganic additive system comprising i)
micro structured alumina or silica (40-70 part by weight), ii) white or brown pigment
(0.5 – 2.0 part by weight), iii) accelerator (0.5 – 2.0 part by weight) and in the desired
proportion are to be mixed homogeneously with the epoxy resin Biphenyl ‘A’ (90 –
100 parts) along with the carboxylic acid anhydride hardener (90 – 100 parts) in a
mixing chamber for a period of 6 – 10 hours using a homogenizer by maintaining a
temperature of the mixing chamber in the range of 60-650C with counter vacuum level
in the range of 4-5 Torr in order to get an additive-mixed polymer dough. The range
of formulations comprising inorganic additive and the polymer along with its counter
hardener is furnished in the Table 1. The so-derived additive-mixed polymer mix is
now poured into an alloy steel mold with required geometry and dimension depending
on the dimension and geometry/profile of the composite body to be fabricated. The
same bushing is tested electrical properties as mentioned in Table.2. Test results

confirm that the developed bushing as in FIG.1 complies with the international
standards.
[0035] In one embodiment for the fabrication of the epoxy insulator (3), the inorganic
additive system comprising i) micro structured silca (40-70 part by weight), ii) brown
pigment (0.5 – 2.0 part by weight), iii) accelerator (0.5 – 2.0 part by weight) and in the
desired proportion are to be mixed homogeneously with the epoxy resin Bisphenol ‘A’
(90 – 100 parts) along with the carboxylic acid anhydride hardener (90 – 100 parts) in
a mixing chamber for a period of 6 – 10 hours using a homogenizer by maintaining a
temperature of the mixing chamber in the range of 60-650C with counter vacuum level
in the range of 4-5 Torr in order to get an additive-mixed polymer dough. The range
of formulations comprising inorganic additive and the polymer along with its counter
hardener is furnished in the Table 1.
Table 1: Composition of the Composite Body
Micro structured Pigment Accelerator Bisphenol Carboxylic acid
Silica or alumina white or (part by ‘A’ (parts be anhydride as
Powder (part by brown color weight) weight) hardener (parts
weight) (part by by weight)
weight)
40-70 0.5 – 2.0 0.5 – 2.0 90 – 100 90 – 100
[0036] In a preferred embodiment as shown in FIG. 1 the cross sectional view of the
medium voltage electrical bushing for insulating medium voltage conductor (1) for
electric traction application. With the configuration of medium voltage electrical

bushing for insulating medium voltage conductor (1) for electric traction application
shows an insulator (3) coupled with a medium voltage conductor (1). The brass bush
(2) is connected to medium voltage conductor (1) for keeping the medium voltage
conductor (1) firmly in position to act as mechanical stopper and support for the
fasteners during connecting to other conductor coming from overhead line. The
bushing is connected firmly to the grounded metal enclosure of locomotive or electric
traction system by aluminum or metallic flange (4). In order to reduce the weight of
the final developed bushing, the circular shaped (as shown in FIG 2a) aluminum flange
(4) is replaced either with the Stainless Steel (S.S) or aluminum bushes (4) as shown
in FIG 2b.
[0037] In a preferred embodiment the method for manufacturing the medium voltage
electrical bushing for electric traction application by epoxy resin composition
comprising of formulating the additive mix polymer dough, molding it to required
geometry in a mold and gelling the polymer filled mold.
[0038] In a preferred embodiment, the epoxy resin composition for high voltage
insulation comprising of inorganic additive having a polymer of Bisphenol–A epoxy
resin of 90-100 parts by weight wherein the additive comprises of a micro structured
silica or alumina powder of 40-70 parts by weight.
[0039] In a preferred embodiment, the micro structured silica or alumina filler or
additive content of 40%-70% parts by weight is easily filled up the intra-molecular
voids thereby improving the electrical, mechanical, thermal properties. Due to the
availability of more surface area for these fillers, suitable filler composition improves
the properties of the molded epoxy bushing.
THE POLYMERIC SYSTEM

[0040] In a preferred embodiment the Bisphenol ‘A’ epoxy resin is a reaction product
of Bisphenol ‘A’ with epichlorohydrin or the like, which is known in the art. The
Bisphenol ‘A’ epoxy resin used in the medium voltage electrical bushing for insulating
high voltage conductor (1) for electric traction application usually has an epoxy
equivalent of 170 or more. Such a Bisphenol ‘A’ epoxy resin is commercially available
as EPIKOTE series from Yuka Shell, Japan, ARALDITE series from Huntsman,
Germany, Lapox series from Atul Limited, India and other similar sources. Suitable
heat curing hardeners of carboxylic acid anhydride type matching with the epoxy
resins are selected based on the requirement.
[0041] In a preferred embodiment the identified polymers are of Bisphenol ‘A’ epoxy
resin, which is a reaction product of Bisphenol ‘A’ with epichlorohydrin or the like
that normally has an epoxy equivalent of 170 or more. However, the additive system
along with the process mentioned is also applicable to similar group of polymers.
[0042] In a preferred embodiment the selected polymer is Bisphenol ‘A’, a hardener,
carboxylic acid anhydride is also to be used along with the polymer for accelerating
the setting and hardening process of the polymer. The hardener is selected on the basis
of compatibility of mixing and hardening process to that of its base polymer. In one
embodiment, other hardener are also used with base polymer which is available from
a number of commercial sources.
[0043] In a preferred embodiment a silica or alumina filled epoxy resin formulation is
used for improved capacitance, Tan delta, partial discharge extinction voltage level
and breakdown voltage level. The silica or alumina filled epoxy resin formulation is
with protective weather sheds for protection against severe environmental conditions.

[0044] In a preferred embodiment the silica or alumina filled epoxy resin formulation
with protective weather sheds with optimized creepage distance and withstanding high
fault currents.
FABRICATION / MANUFACTURING OF THE BUSHING
[0045] In a preferred embodiment a mold for making of medium voltage electrical
bushing for insulating medium voltage conductor (1) for electric traction application
in comprises: two-part mold in which, a second half of the mold interacting with the
first half of the mold along a parting plane, at least one cavity corresponding to bushing
encompassed by the first and the second half of the mold. The mold further comprises
at least one adapter suitable to receive and temporarily hold a conductor during
injection molding of the bushing, one injection nozzle arranged at the first half and
second half of the mold discharging directly or indirectly into the cavity. The injection
mold comprises the at least one adapter which form part of one of the mold halves. In
a preferred embodiment the at least one adapter is selected in cylindrical shape. The at
least one adapter having a clamping means to temporarily receive and hold the
conductor. The one or more adapter is arranged displaceable independent of a
movement of the mold halves.
[0046] In one embodiment the injection nozzle discharges into the cavity through a
gap designed to act as a thin film gate, and this gap is interconnected to a mould cavity
of required geometry/dimensions into which the material is to be discharged. The gap
is a variable geometry in circumferential direction and/or have several segments. The
material is injected by one distribution channel arranged at a circumferential position
with respect to the bushing geometry. The distribution channel partially encompasses
the bushing. In a preferred embodiment the distribution channel is separated in
segments.

[0047] FIG.3 shows a method (100) for medium voltage electrical bushing for
insulating medium voltage conductor (1) for electric traction application as described
above in general comprises the following method / steps:
Step 102: Providing an injection mold using automatic pressure gelation
(APG) technique first half of the mold, second half of the mold interacting with the
first half of the mold along a parting plane, cavity corresponding to the medium voltage
electrical bushing for insulating medium voltage conductor (1) for electric traction
application encompassed by the first and the second half of the mold, injection nozzle
arranged at the first half of the mold suitable to discharge liquefied material into the
cavity directly or indirectly.
Step 104: Closing the mold by relative movement of the first half of the mold
with respect to the second half of the mold until the cavity is closed.
Step 106: Injecting liquefied material through the injection nozzle.
Step 108: Opening the mold by relative movement of the first with respect to
the second half of the mold.
Step 110: Removing the bushing from the mold cavity
[0048] In one embodiment the injection compression molding process increases the
advantages of the injection molding process, which helps to reduce residual stress in
the part through the evenly distributed pressure throughout the mold cavity during the
compression step. The pressure distribution which leads to a superior surface quality,
when used in combination with a mirror polished mold cavity surface. Also, the
bushing surface having a surface roughness that is as low as possible resides in that
electric field is locally less intensified at the insulator surface compared to bushing
surface having a higher roughness.

[0049] In a preferred embodiment the so-derived additive-mixed polymer mix is now
poured into an alloy steel mold with required geometry and dimension depending on
the dimension and geometry/profile of the composite body is fabricated.
[0050] In one embodiment, to fabricate the bushing which is a composite body by
molding with the homogenous resin mix prepared according to the former one by
providing alloy steel die fabricated to the required dimension of the bushing and letting
into the mold the homogenous resin mix which is in low viscosity liquid state under a
pressure of 2-4 atmospheres. In a preferred embodiment, another way to fabricate the
composite body by maintaining the temperature of the mold at about 130-150 deg. C,
thereby keeping the epoxy mix under these conditions in the mold for a period of 30-
50 minutes for gelling and then post curing the insulator (3) in an air-circulating oven
for a period of 8-12 hours at 130-140 deg. C to help in cohesive bonding of the resin
and the hardener system.
[0051] The derived composite body / bushing are subjected to the requisite dielectric
tests like proof voltage, dissipation factor, and breakdown voltage as per the specified
test procedures to obtain the properties enlisted in Table 2.
Table 2. Properties of a bushing composite body
AC high voltage Dissipation factor Partial discharge test
withstand test (one
minute)
More than 100 kV 0.00010 – 0.00012 PD less than 1pC

[0052] In a preferred embodiment the silica filled epoxy resin formulation reduces
weight and size of the insulator (3). The insulator (3) having reduced weight as enlisted
in Table 3.
Table.3 Weight of the insulator composite Body
Weight of the bushing Body with ceramic Weight of the bushing Body
insulation system In Kgs composite insulation system In Kgs
40-50 25-30
[0053] The invention would be more understood in terms of taking various examples,
which are explained in the following:
Example1:
[0054] The medium voltage electrical bushing for insulating high voltage conductor
(1) for electric traction application with medium voltage conductor (1) supported by
circular shaped aluminium metal insert/aluminium flange (4) which is connected to
electrically grounded enclosure are manufactured as per the chemical composition
mentioned in Table.1 above, by injection compression molding in which the inorganic
additive system comprising i) micro structured alumina or silica (40-70 part by
weight), ii) white pigment (0.5 – 2.0 part by weight), iii) accelerator (0.5 – 2.0 part by
weight) and in the desired proportion are to be mixed homogeneously with the epoxy
resin Biphenyl ‘A’ (90 – 100 parts) along with the carboxylic acid anhydride hardener
(90 – 100 parts) in a mixing chamber for a period of 6 – 10 hours using a homogenizer
by maintaining a temperature of the mixing chamber in the range of 60-650C with
counter vacuum level in the range of 4-5 Torr in order to get an additive-mixed
polymer dough. The range of formulations comprising inorganic additive and the
polymer along with its counter hardener is furnished in the Table 1. The so-derived

additive-mixed polymer mix is now poured into an alloy steel mold with required
geometry and dimension depending on the dimension and geometry/profile of the
composite body to be fabricated. The same bushing is tested electrical properties as
mentioned in Table.2. Test results confirm that the developed bushing as in Fig.1
complies with the international standards.
Example 2:
[0055] A medium voltage electrical bushing for insulating high voltage conductor (1)
for electric traction application with medium voltage conductor (1) supported by
circular shaped aluminium metal /aluminium bushes (fig 2b) instead of circular shaped
aluminium metal insert/aluminium flange (4) (fig 2a) as mentioned in Example 1
which are interposed at specified locations in circular shape manner connected to
electrically grounded enclosure are manufactured as per the chemical composition
mentioned in Table.1 above, according to steps mentioned in
Fabrication/Manufacturing of the bushes (2) mentioned bushing is tested for electrical
properties as mentioned in Table.2. Test results confirm that the developed bushing
as in Fig.1 complies with the international standards.
Example 3:
[0056] A medium voltage electrical bushing for insulating high voltage conductor (1)
for electric traction application with high voltage conductor (1) supported by Stainless
Steel (S.S) metal bushes (fig 2b) instead of circular shaped aluminium metal
insert/aluminium flange (4) (fig 2a) as mentioned in Example 1 which are interposed
at specified locations in circular shape manner connected to electrically grounded
enclosure are manufactured as per the chemical composition mentioned in Table.1
above, according to steps mentioned in Fabrication/Manufacturing of the bushes (2)
mentioned in example 1. The same bushing is tested electrical properties as mentioned

in Table.2. Test results confirm that the developed bushing as in Fig.1 complies with
the international standards.
[0057] It should be noted that the description and figures merely illustrate the
principles of the present subject matter. It should be appreciated by those skilled in the
art that conception and specific embodiment disclosed may be readily utilized as a
basis for modifying or designing other structures for carrying out the same purposes
of the present subject matter. It should also be appreciated by those skilled in the art
that by devising various assembly that, although not explicitly described or shown
herein, embody the principles of the present subject matter and are included within its
spirit and scope. Furthermore, all examples recited herein are principally intended
expressly to be for pedagogical purposes to aid the reader in understanding the
principles of the present subject matter and the concepts contributed by the inventor(s)
to furthering the art and are to be construed as being without limitation to such
specifically recited examples and conditions. The novel features which are believed to
be characteristic of the present subject matter, both as to its organization and method
of operation, together with further objects and advantages will be better understood
from the description when considered in connection with the accompanying figures.
[0058] These and other advantages of the present subject matter would be described
in greater detail with reference to the following figures. It should be noted that the
description merely illustrates the principles of the present subject matter. It will thus
be appreciated that those skilled in the art will be able to devise various arrangements
that, although not explicitly described herein, embody the principles of the present
subject matter and are included within its scope.
[0059] It will be further appreciated that functions or structures of a plurality of
components or steps may be combined into a single component or step, or the
functions or structures of one-step or component may be split among plural steps or

components. The present invention contemplates all of these combinations. Unless
stated otherwise, dimensions and geometries of the various structures depicted herein
are not intended to be restrictive of the invention, and other dimensions or geometries
are possible. In addition, while a feature of the present invention may have been
described in the context of only one of the illustrated embodiments, such feature may
be combined with one or more other features of other embodiments, for any given
application. It will also be appreciated from the above that the fabrication of the unique
structures herein and the operation thereof also constitute methods in accordance with
the present invention. The present invention also encompasses intermediate and end
products resulting from the practice of the methods herein. The use of “comprising”
or “including” also contemplates embodiments that “consist essentially of” or “consist
of” the recited feature.
[0060] Although embodiments for the present subject matter have been described in
language specific to structural features, it is to be understood that the present subject
matter is not necessarily limited to the specific features described. Rather, the specific
features and methods are disclosed as embodiments for the present subject matter.
Numerous modifications and adaptations of the system/component of the present
invention will be apparent to those skilled in the art, and thus it is intended by the
appended claims to cover all such modifications and adaptations which fall within the
scope of the present subject matter
[0061] It should be noted that the description and figures merely illustrate the
principles of the present subject matter. It should be appreciated by those skilled in the
art that conception and specific embodiment disclosed may be readily utilized as a
basis for modifying or designing other structures for carrying out the same purposes
of the present subject matter. It should also be appreciated by those skilled in the art
that by devising various arrangements that, although not explicitly described or shown
herein, embody the principles of the present subject matter. Furthermore, all examples

recited herein are principally intended expressly to be for pedagogical purposes to aid
the reader in understanding the principles of the present subject matter and the
concepts contributed by the inventor(s) to furthering the art and are to be construed as
being without limitation to such specifically recited examples and conditions. The
novel features which are believed to be characteristic of the present subject matter,
both as to its organization and method of operation, together with further objects and
advantages will be better understood from the following description when considered
in connection with the accompanying figures.
[0062] These and other advantages of the present subject matter would be described
in greater detail with reference to the following figures. It should be noted that the
description merely illustrates the principles of the present subject matter. It will thus
be appreciated that those skilled in the art will be able to devise various arrangements
that, although not explicitly described herein, embody the principles of the present
subject matter and are included within its scope. The present invention will now be
described more specifically with reference to the following specification.
[0063] It should be noted that the description and figures merely illustrate the
principles of the present subject matter. It should be appreciated by those skilled in the
art that conception and specific embodiment disclosed may be readily utilized as a
basis for modifying or designing other structures for carrying out the same purposes
of the present subject matter. It should also be appreciated by those skilled in the art
that by devising various arrangements that, although not explicitly described or shown
herein, embody the principles of the present subject matter and are included within its
spirit and scope. Furthermore, all examples recited herein are principally intended
expressly to be for pedagogical purposes to aid the reader in understanding the
principles of the present subject matter and the concepts contributed by the inventor(s)
to furthering the art and are to be construed as being without limitation to such
specifically recited examples and conditions. The novel features which are believed to

be characteristic of the present subject matter, both as to its organization and method
of operation, together with further objects and advantages will be better understood
from the following description when considered in connection with the accompanying
figures.
[0064] Although embodiments for the present subject matter have been described in
language specific to package features, it is to be understood that the present subject
matter is not necessarily limited to the specific features described. Rather, the specific
features and methods are disclosed as embodiments for the present subject matter.
Numerous modifications and adaptations of the system/device of the present invention
will be apparent to those skilled in the art, and thus it is intended by the appended
claims to cover all such modifications and adaptations which fall within the scope of
the present subject matter.

WE CLAIM:
1. A method (100) of manufacturing medium voltage electrical bushing for
insulating high voltage conductor (1) for electric traction application
comprising the steps of:
configuring a mold having a first half and a second half interacting along a
parting plane;
configuring a cavity corresponding to the me dium voltage electrical bushing,
wherein the cavity is encompassed by the first half of the mold and the second
half of the mold;
positioning a nozzle at the first half of the mold for discharging liquefied
material into the cavity;
closing the mold by relative movement of the first half of the mold with respect
to the second half of the mold until the cavity is closed;
injecting polymer composite dough and liquefied material through the nozzle;
opening the mold by relative movement of the first half of the mold with
respect to the second half of the mold; and
removing the bushing from the mold cavity.
2. The method as claimed in claim 1, wherein the mold is an injection mold, using
automatic pressure gelation (APG) technique in the first half of the mold and
the nozzle is an injection nozzle arranged at the first half and second half of
the mold for discharging liquefied material into the cavity.
3. The method as claimed in claim 1, wherein the injection mold comprises at
least one adapter which forms part of one of the mold halves.
4. The method as claimed in claim1, wherein the at least one adapter has a
cylindrical shape.

5. The method as claimed in claim 1, wherein the at least one adapter comprises
of clamping means to temporarily receive and hold the conductor (1).
6. The method as claimed in claim 1, wherein the nozzle discharges into the
cavity through a gap configured to act as a film gate wherein the gap is
interconnected to a chamber into which the material is to be discharged.
7. The method as claimed in claim 1, wherein the mold comprises at least one
adapter to receive and temporarily hold the bush (2), the conductor (1) during
the molding and wherein the bush (2) is made up of metal which includes brass.
8. The method as claimed in claim 1 or 7, wherein the high voltage conductor (1)
is coupled with an insulator (3), in which the brass bush (2) being connected
to the section of the insulator (3) using a plurality of fasteners, and the
aluminum metallic bushes or stainless steel metallic bushes are interposed
between flanges (4) of the metal container for enabling the flanges (4) which
are coupled by the fasteners.
9. The method as claimed in claim 1, wherein the medium voltage electrical
bushing for insulating high voltage conductor (1) is supported by flange (4)
including circular shaped Aluminium flange (4) which is connected to
electrically grounded enclosure.
10. The method as claimed in claim 1, wherein the medium voltage electrical
bushing is fabricated using an inorganic additive system comprising a micro
structured silca or alumina which is 40-70 part by weight, a white or brown
pigment which is 0.5 – 2.0 part by weight, accelerator which is 0.5 – 2.0 part

by weight and mixed homogeneously with the epoxy resin Bisphenol ‘A’
which is 90 – 100 parts along with the carboxylic acid anhydride hardener
which is 90 – 100 parts in a mixing chamber for a period of 6 – 10 hours using
a homogenizer by maintaining a temperature of the mixing chamber in the
range of 60-650C with counter vacuum level in the range of 4-5 Torr in order
to attain an additive-mixed polymer dough.