FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2005
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION A heat sink for a lightning arrester
APPLICANT (S)
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR (S)
Devraj John Yesuraj, of Crompton Greaves Limited, Switchgear (SI & S4) R&D Division, Switchgear Complex, Crompton Greaves Limited, A3, Ambad, Nashik, Maharashtra, India; Awkale Ramesh Ramkrishna, of Crompton Greaves Limited, SI-R&D Division, Switchgear Complex, Crompton Greaves Limited, A3, Ambad, Nashik, Maharashtra, India; and Jha Nitin, of Crompton Greaves Limited, S4 R&D Division, Switchgear Complex, Crompton Greaves Limited, A3, Ambad, Nashik, Maharashtra, India, all Indian Nationals.
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION:
This invention relates to the field of switchgear equipment.
Particularly, this invention relates to Lightning Arrester equipment.
More particularly, this invention relates to a heat sink for a lightning arrester.
BACKGROUND OF THE INVENTION:
A lightning arrester is a device used on electrical power systems to protect the insulation on the system from the damaging effect of lightning, switching surges etc. Lightning arrestors are designed to divert / bypass over voltage to ground in terms of energy i.e. V*I*T. They are used for Insulation coordination purpose.
Environmental conditions and proper maintenance and monitoring plays an important role in governing their life and health status. If Lightning Arrester is not installed in parallel with the equipment then the equipment gets damaged permanently when it experiences an over voltage surge. Hence, Lightning arresters plays an important role in insulation coordination.
For use in a High Voltage line, a lightning arrestor or a plurality of lightning arrestors are placed at pre-defined locations through the line, and near the equipment in substations, at line entrance etc.
Surge arrester is designed to dissipate or divert surges within itself in the form of energy V*I*T. During this process lot of heat is generated inside the arrester which

is to be dissipated as soon as possible. In order to address this problem heat sink is designed which is capable of absorbing maximum amount of heat energy to the atmosphere. A typical lightning arrestor consists of a ZnO blocks stacked one over the other to form a column. The ZnO block has non-linear behavior i.e. it offers low resistance to high voltage and high resistance to low voltage. The ZnO column is supported by aluminum connectors which give mechanical strength as well as electrical conductivity to ZnO column. When the arrester ZnO columns dissipate energy in the form if energy i.e. V*I*T, lot of heat is generated. The upper and the lower part of ZnO column dissipate heat faster due to conduction phenomenon. Heat dissipation in the central column is only radially which is very slow.
In order to dissipate this heat from central part of ZnO column, solid aluminum heat sinks are used at different positions. The dimension of heat sink is same that of ZnO blocks. The drawback of these sink is that they don't have sufficient area to dissipate heat. Hence, there is a need for a better heat sink, especially at the intermediary positions.
PRIOR ART:
US4335417 discloses a Heat sink thermal transfer system for zinc oxide varistors. EP0233022 discloses an Electrical surge arrester/dive. JP2271501 discloses an electric surge arrester. GB2322487 discloses a Surge arrester. CA1162978 discloses a heat sink thermal transfer system for zinc oxide varistors.
However, there is scope for an improved design with better and increased heat dissipation characteristics to enhance the life of the lightning arrester.

OBJECTS OF THE INVENTION:
An object of the invention is to increase heat dissipation characteristics of a lightning arrester.
Another object of the invention is to provide casted heat sinks to fit in line with the blocks of the lightning arrester.
Yet another object of the invention is to maintain the performance of a lightning arrester.
Still another object of the invention is to provide a heat sink and lightning arrester with better reliability.
An additional object of the invention is to provide a lightning arrester and heat sink which is easily assembled on to the lightning arrester.
SUMMARY OF THE INVENTION:
According to this invention, there is provided a heat sink for a lightning arrester being a substantially annular heat sink with a stepped circumference, in that, said heat sink resembles a wheel rim with a stepped circumference including a dual symmetric flange portion and a dual symmetric bead portion.
According to another embodiment of this invention, there is provided a lightning arrester composed of a plurality of conductor blocks stacked coaxially about a

central FRP tube and within insulator tubing, with heat sink blocks intermittently coaxially disposed, therebetween, said heat sink being a substantially annular heat sink with a stepped circumference, in that, said heat sink resembles a wheel rim with a stepped circumference including a dual symmetric flange portion and a dual symmetric bead portion.
Typically, said conductor blocks are ZnO blocks.
Typically, said heat sink is an Aluminum heat sink.
Typically, said heat sink includes a plurality of radially displaced holes about the stepped circumference of the heat sink, from inner circumference to outer circumference.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates a schematic of the lightning arrester with heat sink of the prior art.
The invention will now be described in relation to the accompanying drawings, in
which:
Figure 2 illustrates a schematic of the lightning arrester with heat sink;
Figure 3 illustrates a side view of the heat sink;
Figure 4 illustrates an isometric view of the heat sink;

Figure 5 illustrates a top view of the heat sink;
Figure 6 illustrates a sectional isometric view of the lightning arrester with the heat sink; and
Figure 7 illustrates a front sectional enlarged view of the lightning arrester with the heat sink.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
According to this invention, there is provided a heat sink (100) for a lightning arrester (10).
The lightning arrester is a plurality of blocks (13) as shown in Figure 1 of the accompanying drawings. There are intermediary heat sinks (11) of the prior art shown in Figure 1 of the accompanying drawings. The top and bottom zones of the lightning arrester are shown by dotted circles, and the direction (radial and axial) dissipation of heat at that top and bottom zones are shown by the dashed arrow lines. In the intermediary zone, however, heat dissipation, even in the presence of heat sinks is radial only.
Figure 2 illustrates a schematic of the lightning arrester with heat sink. Figure 6 illustrates a sectional isometric view of the lightning arrester with the heat sink. Figure 7 illustrates a front sectional enlarged view of the lightning arrester with the heat sink.

In accordance with an embodiment of this invention, there is provided a heat sink (100) adapted to be co-axially fitted with blocks (13) of the lightning arrester. The construction of heat sink is a substantially annular heat sink with a stepped circumference (12), in that, it resembles a wheel rim. The stepped circumference includes a dual symmetric flange portion (14) and a dual symmetric bead portion (16).
Figure 3 illustrates a side view of the heat sink (100). Figure 4 illustrates an isometric view of the heat sink (100). Figure 5 illustrates a top view of the heat sink (100).
The stepped design of the heat sink provides relatively more surface area for heat dissipation without compromising on its strength or on the geometry of the lightning arrester. ,
In accordance with another embodiment of this invention, there is provided a plurality of radially displaced holes (18) about the stepped circumference of the heat sink, from inner circumference to outer circumference. Holes are provided in the sink to allow the air flow/movement from inside to outside because ZnO blocks are doughnut in shape so hot air can move from bottom or from top when the blocks are assembled. With this heat sink design, holes provide space for the hot air to flow radially; hence helping in cooling.
Reference numeral 15 (Figure 6) refers to central FRP tube.
Reference numeral 17 (Figure 6) refers to insulator.

While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim,
1.A heat sink for a lightning arrester being a substantially annular heat sink with a stepped circumference, in that, said heat sink resembles a wheel rim with a stepped circumference including a dual symmetric flange portion and a dual symmetric bead portion.
2.A heat sink as claimed in claim 1 wherein, said heat sink includes a plurality of radially displaced holes about the stepped circumference of the heat sink, from inner circumference to outer circumference.
3.A heat sink as claimed in claim 1 wherein, said heat sink is an Aluminum heat sink.
4.A lightning arrester composed of a plurality of conductor blocks stacked coaxially about a central FRP tube and within insulator tubing, with heat sink blocks intermittently coaxially disposed, there between, said heat sink being a substantially annular heat sink with a stepped circumference, in that, said heat sink resembles a wheel rim with a stepped circumference including a dual symmetric flange portion and a dual symmetric bead portion.
5.A lightning arrester as claimed in claim 1 wherein, said conductor blocks are ZnO blocks.
6.A lightning arrester as claimed in claim 1 wherein, said heat sink is an Aluminum heat sink.
7. A lightning arrester as claimed in claim 1 wherein, said heat sink includes a plurality of radially displaced holes about the stepped circumference of the heat sink, from inner circumference to outer circumference.