FIELD OF THE INVENTION
The present invention generally relates to bus ducts or gas insulated bus
ducts particularly a support insulator device to support HT conductors during
storage, transportation without expensive insulators. More particularly, the
invention relates to an improved support insulation for three phase or single
phase gas insulated bus ducts.
BACKGROUND OF THE INVENTION
Long-distance gas insulated bus duct for high voltage and high power
transmission with grounded enclosure and an inner conductor is known in the
art and sometimes nomenclatured as bus bar and with plurality of support
insulators. The long-distance transmission line is usually for air insulated and
gas insulated bus ducts. The mounting insulators allow simple assembly and
installation of the bus bar.
Although a long-distance gas insulated transmission line/bus duct is costlier
than an overhead line, it requires considerably less maintenance effort, as the
inner conductor /bus bar is not subject to any external dirt and weather
influences. The long-distance transmission line according to the present
publication is filled in the interior for insulation purposes with an inert gas like
pure SF6 or N2—SF6 gas mixture.
The gas insulated bus duct can be laid underground or overhead. The inner
conductor, which is in the form of a tubular conductor, in the long-distance
transmission line carries an AC voltage. Gas insulated bus duct generally
installed in power station at a length of few hundreds of meters to kilometers.
Assembly of these bus ducts at site is really a challenging task without
affecting performance. Hence, method/mode of transportation of the bus
duct units from manufacturing units to power station play an important role
in successful commissioning of such bus ducts.

While the present invention relates to gas insulated switchgear, particularly
support insulators of gas insulated bus ducts, prior Pat. Nos. US2784012 and
US2396131 teach support insulator of post type at four locations located
radially from the bus bar. With reference to prior Pat. No. US8759684, the
bus bar is supported by plurality of post insulators. In these conventional
arrangements, even though the insulators are inside the bus duct,
performance of bus duct is affected by reliability of the insulators. Most of
these known arrangements are installed only at sites with restricted
cleanliness. Following are some of the drawbacks with these known
arrangements:
1. Requirement of more number of insulators per unit length of bus duct.
2. Conventional arrangement is not cost effective solution.
3. Assembly time required at site is very high.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an improved support
insulation for three phase or single phase gas insulated bus ducts.
Another object of the invention is to propose an improved insulated support
for gas insulated bus bar extending out of bus duct enclosure.
A still another object of the invention is to propose an improved insulated
support to support high voltage buses during transportation, storage at site
and for installation.
Yet another object of the invention is to propose an improved insulated
support for gas insulated bus bar suitable for indoor and outdoor switchgear
applications.

Another object of the invention is to propose an improved support insulation
for three phase or single phase gas insulated bus ducts which has a provision
to guide a bus bar current transfer contact.
A still another object of the invention is to propose an improved support
insulation for three phase or single phase gas insulated bus ducts which is
enabled to protect the gas insulated bus duct from environment, dust and
foreign particles.
Yet another object of the invention is to propose an improved support
insulation for three phase or single phase gas insulated bus ducts which has
insulation to prevent the support from high voltage bus bar and allows to
hold positive gas pressure.
A further object of the invention is to propose an improved support insulation
for three phase or single phase gas insulated bus ducts, which provides
sealing of gas insulated bus duct from external environment.
A still further object of the invention is to propose an improved support
insulation for three phase or single phase gas insulated bus ducts which
substantially correspond to other bus ducts at site for connection without
dismantling bus bars.
Yet further object of the invention is to propose an improved support
insulation for three phase or single phase gas insulated bus ducts which is
capable of guiding the bus bar as well as the housing current transfer contact
of bus bar housing.
A further object of the invention is to propose an improved insulated support
for three phase common enclosure bus duct.

SUMMARY OF THE INVENTION
Accordingly, there is provided an improved insulated support for gas insulated
bus duct.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention is described with the help of Figures 1 to 7, where:
Figure 1: Conventional support insulators of gas insulated system.
Figure 2: Configuration of Gas insulated bus duct.
Figure 3: Insulated support for single phase Gas insulated bus duct
Figure 4: Insulated support with support cover for single phase Gas insulated
bus duct.
Figure 5: Configuration of gas insulated bus duct with insulated support
assembly.
Figure 6: Insulated support Assembly for three phase compact gas insulated
bus duct.
Figure 7: Configuration of three phase compact gas insulated bus duct with
insulated support assembly.
DETAILED DESCRIPTION OF THE INVENTION
The gas insulated bus duct comprises a bus bar or high voltage conductor
[01] in grounded metallic enclosure [02]. The Bus bar [01] is made of high
electrical conductivity material to enable efficient current flow with minimal
power loss and is insulated from the grounded metallic enclosure [02] with
designed SF6 gas or SF6 – N2 mixture density and an epoxy support insulator
[03] made of SF6 gas compatible filled epoxy material. A socket/HT integrator
[04] is made of high electrical conductivity material makes the electrical
connection between the epoxy insulator [03] and bus bar [01].

The grounded metallic enclosure [02] which encloses the bus bar [01]
consists of a plurality of angularly disposed ports [05]. These ports [05] are
used either as gas port covers, molecular sieve cover, man holes etc. The
epoxy support insulator [03] consists of three parts. First one is a HT insert
[06] with an integrated shield [07]. Second one is a low tension (LT) insert or
metallic studs. The third one is a casted epoxy body [08]. The HT integrated
shield [07] has a cylindrical / spherical profile and its profile / radius depend
on the operating voltage under which insulator [03] is used. The HT
integrated shield [07] is fastened electrically to the high voltage (HV)
conductor / bus bar [01]. The HT integrator cum shield [07] provides low
contact resistance current transfer from a HT insert [06] to the bus bar [01].
In a gas insulated bus duct, the epoxy support insulator [03] can be
projected out of the bus duct enclosure (02) depending on bus duct
configuration. Fig. 2 shows the bus duct configuration. In such situations, the
bus ducts with support insulator cannot be transported on either side of bus
duct due to requirement of more insulators than it is required to be installed
at site. Alternatively, the bus duct can be transported with this outwardly
projected insulator, however, it is essential to assemble the continuation bus
ducts at site. This may not be reliable and accurate enough for successful
operation. To overcome this problem, an innovative support insulator [09] is
proposed. Figure 3 shows Insulated support for single phase Gas insulated
bus duct. This insulator [09] shall be used in place of said outwardly
projected insulator during transportation and storage. This special insulator
[09] is made of low cost insulating material and has less moisture absorption.
This special support insulator [09] has provision to hold a cover [10] which
guides a bus bar current transfer contact [11]. The support cover [10] is
made from metallic tube and provides weather protection to the bus bar
current transfer contact [11]. The cover [10] is fastened to the support
insulator [09] through a sealing arrangement [12]. Figure 4 shows an

Insulated support [09] with support cover for single phase Gas insulated bus
duct. The support insulator is fastened to a Bus duct enclosure [02] through a
modified sealing arrangement [13]. This arrangement helps in keeping bus
duct assembly under positive pressure, and provides support to the bus bar
including guiding of current transfer contact of bus bar etc. Figure 5 shows
Configuration of gas insulated bus duct with insulated support assembly.
The epoxy support insulator [03] holds the bus bar [01] through a socket/HT
Integrator [04]. This arrangement can be extended to three phase bus duct
also. In three phase bus duct, the support insulator [14] holds the bus bars
[15] through sockets/HT Integrator [16] in such a configuration where each
bus bar [15] is placed at the vertices of an equilateral triangle or right angled
or any arbitrary angle in a grounded metallic enclosure [17] filled with SF6
gas or SF6-Na2 mixture at designed density. Figure 6 shows Insulated
support for three phase compact Gas insulated bus duct. This special support
insulator [14] has provision to hold a cover [18] which guides bus bar current
transfer contact [19]. The three phase support insulator has cylindrical profile
and can be fastened to the tubular grounded enclosure [17]. Figure 7 shows
the configuration of three phase compact gas insulated bus duct with
insulated support assembly.

ADVANTAGES OF THE INVENTION
1) The support insulator is capable to support the high voltage gas
insulated bus during transportation, storage at site and for future use.
2) The insulated support suitable for indoor and outdoor switchgear
applications.
3) The insulated support has a provision of guiding bus bar as well as
housing current transfer contact of bus bar. The support cover is
made from metallic tube and provides weather protection to the bus
bar current transfer contact.
4) The insulated support has a provision to protect the gas insulated bus
duct from environment, dust and foreign particles.
5) The insulated support is configured to correspond with other bus ducts
at site for fabrication without dismantling the bus bars.

WE CLAIM :
1. An improved support insulation for three phase or single phase gas
insulated bus ducts, the gas insulated bus duct comprises at least one
bus bar or high voltage conductor (01,15) having a plurality of gas
port covers (05,10,18) and insulated from a grounded metallic
enclosure (02,17) filled with SF6 gas or SF6-Na2 mixture at designed
density and enclosing the bus bar; an epoxy support insulator
(03,09,14) holding the bus bar (01,15) through HT-integrators (04,16)
and making an electrical connection between the epoxy insulator and
the bus bar, the support insulator (03,09,14) formed of low-cost
insulating material with low-moisture absorption property, and having
means for holding the cover (05,10,18) guiding a bus bar current
transfer contact (11,19), wherein the cover (05,10,18) is attached to
the support insulator through a sealing arrangement (12,13) which in
turn fastened to the bus duct enclosure (02,17) to maintain the bus
duct assembly under positive pressure including supporting the bus bar
(01,15) as well as guiding the current transfer contact (11,19) to the
bus bar (01,15).
2. The support insulator as claimed in claim 1, wherein the support
insulator (03) is configured to hold the bus bar (01) through the HT
integrator (04).

3. The support insulator as claimed in claim 1, wherein the support
insulator (14) holds the bus bars (15) through the HT Integrator (16)
such that each of the bus bars (15) is placed at the vertices of an
imaginary equilateral triangle or right angle or an arbitrary angle in
the grounded metallic enclosure (17).