, Description:FIELD OF THE INVENTION

[001] The present invention relates to fabrication of high voltage electrical insulators, in particular to composite long-rod insulators (CLR) for sub-station applications having 400kV of voltage ratings, 120kN of electromechanical strength with preferably 5mm of insulation sheath thickness of the derived composite insulators.

BACKGROUND/PRIOR ART OF THE INVENTION

[002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[003] Composite insulators have been witnessing increased popularity primarily because of significant advantages, i.e., shorter string length under pollution, less weight, easy manufacturing, lower price and no requirement for periodic cleaning etc. With the advancement of new materials for interface, high-strength FRP support structures, HTV silicone compounds etc., and also availability of new generation fabrication equipments that facilitate manufacturing of composite insulators with precision with advanced quality control in the course of manufacturing, its popularity has increased in recent years.

[004] Composite insulator is normally fabricated by an injection molding method by using an appropriate insulating polymeric material, such as, silicone rubber, ethylene propylene copolymer (EPM), ethylene-propylene-diene copolymer (EPDM), and or polyurethane, etc. structure of which is generated in the form of sheds on the surface of an elongated core rod of fiber-reinforced plastics (FRP).

[005] Now, reference may be made to the following publications:-

[006] An insulator, concretely relates to an insulator for high voltage transmission lines belongs to transmission line accessory technical field, constitute including insulator post, last ring flange, lower flange dish and full skirt, last ring flange and lower flange dish fixed cup jointing in the upper and lower both ends of insulator post respectively, the full skirt cup joint the insulator post surface between last ring flange and lower flange dish, the full skirt constitute by big full skirt and umbellule skirt that a plurality of intervals set up, the tip cross -section of full skirt be the toper, being located and being provided with a striking cover between full skirt and the last ring flange of the superiors, this striking is sheathe in and is provided with a plurality of lightning rods, still is connected with an earth connection.

[007] A method for producing a composite insulator, the insulator, which is constituted by a rod, surrounded by an insulating layer, and its ends respectively two metal end fittings. The method comprises the steps of: the two metal interfaces fixed to both ends of the rod, the interface between the metal end fitting for fixing the insulator; the insulating layer mounted around the rod and the metal interface, while each metal interface leaving a portion of the end portion is not covered by the insulating layer, so as to then be fixed to the metal end fitting thereon.

[008] Composite insulators for UHV transmission lines, in which the composite insulator comprising a core rod, fittings, and equalizing rings, sheds the sheath, the sheath covering the core Sheds the rod surface, the sheath and the sheds connection fittings. The fittings are attached to the equalizing ring, the sheath is above 110-2 sheds methyl vinyl silicone rubber as the base, in which fumed silica is added as a reinforcing agent, a flame retardant aluminum hydroxide powder, an appropriate amount of a vulcanizing agent and additives etc.

[009] An outside insulation cover of synthetic insulator and high-pressure synthetic insulator is umbrella skirt-shaped, the concave of umbrella skirt faces a down, a plurality of annular strengthening ribs are arranged at the brim and middle of the concave. The technology parting line of the outside insulation cover adopts transverse setup; the parting line of the high-pressure synthetic insulator is arranged at the strengthening ribs which are arranged at the fringe of the umbrella skirt. More than three supporting points used for fixing the core rod, which are in the fillet of the outside insulation cover, are evenly arranged at each segment of each umbrella set.

[010] A composite insulator by injection molding once, and relates to an insulator for power transmission lines. The composite insulator comprises a mandrel bar, a hardware fitting with tubular joints, an umbrella-shaped insulator, and sheaths arranged at the two ends of the umbrella-shaped insulator, wherein the sheaths are positioned on the surface of the mandrel bar and connected with the mandrel bar fixedly, and the two ends of each of the sheaths are respectively fixedly connected with pipe orifices of the hardware fitting of which the two ends are provided with the tubular joints; the pipe orifices of the tubular joints of the hardware fitting towards the umbrella-shaped insulator are provided with stepped circles; and the sheaths at the two ends of the umbrella-shaped insulator at least coat the stepped circles at the pipe orifices of the hardware fitting and are fixedly connected with the stepped circles in a water sealing manner. The insulator not only improves the connection strength of the sheaths, the mandrel bar and the hardware fitting, but also greatly improves the water sealing effect due to the addition of a plurality of junction surfaces. In order to further improve the water sealing effect, at least one circle of groove is arranged on the outer revolution surfaces of the stepped circles, and the number of the junction surfaces is increased, so the sealing effect is further improved. Finally, the umbrella-shaped insulator is combined according to the size of the umbrella shape so as to effectively overcome creepage.

[011] An electrical insulator that is produced by coating a molded part of the insulator with a hydrophobic plasma-polymer coating. The plasma-polymer coating is produced by igniting a plasma in a non-polar working gas or a working gas having non-polar groups at a working pressure of between 0.001 Pa (1·10-5 mbar) and 50 Pa (5·10-1 mbar). The electrical power input per chamber volume lies between 0.5 and 5 kW/m3, the gas flow per chamber volume lies between 10 and 1000 sccm/m3. A durable, hard and hydrophobic plasma-polymer coating is created, the quality of which is independent of the material of the molded part.

[012] A ceramic composite long-rod insulator comprising a body, the body sheds outside the outer insulating sheath, at both end portions of the body are respectively provided with adhesive attachment fittings, each of said attachment fittings the mounting hole is jagged, with the outlet end of the attachment end portion of each metal circular arc and provided with a rectangular groove on the outside of the end portion. By rational design, using high-quality raw materials, selected advanced production technology, have excellent mechanical and electrical properties. Using a high temperature vulcanized silicone rubber as the outer insulating jacket sheds to a high strength ceramic for insulation, vibration process variable using the high-strength Portland with plastic end fitting made of composite insulators of porcelain.

[013] Fabrication of composite insulator that include a FRP core rod and a sheath which is formed by integrally moulding an insulating polymeric material to cover the core rod over substantially the entire length thereof. The sheath is composed of a plurality of moulded portions which are aligned with each other in the axial direction of the core rod. Adjacent moulded portions of the sheath are arranged relative to each other so that a gap is left between the opposite ends of the moulded portions. The gap is filled by a joint insulating material which is integrally united to the polymeric material of the adjacent moulded portions.

[014] The method and apparatus for manufacturing composite insulators which include a FRP core rod covered by a sheath and provided with a plurality of sheds which are made of an electrically insulating polymeric material. The sheds are set on a support member arranged on a downstream side of an extruder. The extruder is fed with a core rod and extrudes a polymeric material to form a sheath on the core rod. The core rod with the sheath is moved toward the downstream side through an opening in the support member. The sheds are sequentially moved along the support member toward the downstream side and transferred onto predetermined locations on the sheath that have passed through the opening and have reached the downstream side. An assembly is thus formed which includes the core rod, sheath formed on the core rod, and sheds transferred onto the sheath. The assembly is then heated to vulcanize the sheath and adhere it to the core rod and the sheds.

[015] A composite insulator containing means for providing early warning of impending failure due to stress corrosion cracking, flash-under, or destruction of the rod by discharge activity conditions. In this invention, a composite insulator comprising a fiberglass rod surrounded by a polymer housing and fitted with metal end fittings on either end of the rod is doped with a dye-based chemical dopant. The dopant is located around the vicinity of the outer surface of the fiberglass rod. The dopant is formulated to possess migration and diffusion characteristics correlating to those of water, and to be inert in dry conditions and compatible with the insulator components. The dopant is placed within the insulator such that upon the penetration of moisture through the housing to the rod through a permeation pathway in the outer surface of the insulator, the dopant will become activated and will leach out of the same permeation pathway. The activated dopant then creates a deposit or stain on the outer surface of the insulator housing. The dopant comprises a dye that is sensitive to radiation at one or more specific wavelengths or is visually identifiable. Deposits of activated dopant on the outer surface of the insulator can be detected upon imaging of the outer surface of the insulator by appropriate imaging instruments or the naked eye.

[016] US patent number 20050120975A1 dated June 09, 2005 by Takanori Kondo, NGK Insulators Ltd., Japan described how to prevent breakage of a cover member of a polymer insulator caused by pecking by a bird, through use of an avian repellent which is carried by the polymer insulator and an avian repellence maintained at least during construction of power transmission equipment, thereby inhibiting pecking of the polymer insulator by birds. The bird-pecking-preventive polymer insulator according to the invention includes an insulator body, and a holding metal piece is fitted on each end of the insulator body, the insulator body being composed of a core member is formed of a reinforced plastic material and a cover member is formed of a rubber material and covering the periphery of the core member, wherein the cover member carries an avian repellent such as capsaicin.

[017] A method for manufacturing a composite high-voltage insulators in which a plurality of skirts are manufactured and joined to a rod, and more particularly to a method for manufacturing a composite high-voltage insulator in which an expanding pipe is inserted into a plurality of skirts arranged in a line by a skirt holder to expand the inner diameters of the skirts, so that the skirts are mounted on precise positions of the rod, and an adhesive agent is easily applied, so that an interface between different materials is not formed in order to improve reliability of insulator products.

[018] The manufacturing of composite insulators by utilizing specified materials, process parameters along with designs for specified applications is a continued interest. The applications of composite insulators are constantly being monitored by the End Users depending on what kind of circumstances and difficulties they come across while these composite insulators on the job and hence invention in this field have been taking place to address new challenges and technical necessities. Further, as the environmental pollution have witnessed to increase substantially in many parts across the globe, the composite insulators are selected depending on the pollution level/type in the geographical regions of the transmission line/s and hence composite insulators must be complied with specific pollution norms depending on the geographical location of the transmission lines.

[019] In this context, this invention discloses the manufacturing process of 400kV 120kN ‘composite long-rod’ (CLR) insulators for sub-station applications in which the thickness of HTV silicone rubber insulation shed is kept preferably at 5mm and fabricated by an injection moulding process, by using additive-modified high temperature vulcanized (HTV) silicone rubber material (chemically known as methyl vinyl silicone rubber). The insulator has a core structure which is an elongated ‘fibre reinforced polymer (FRP)’ rod, while the hardware of the said insulators are forged steel materials, and the interface bonding/reinforcing material is silane-based catalyst-modified adhesive material respectively. The specific aspects of this invention is more disclosed in the subsequent sections.

OBJECTS OF THE INVENTION

[020] The principal objective of this invention is to provide a process for manufacturing of 400kV 120kN long-rod composite insulators with variable insulation sheath thickness.

[021] Another object of the invention is to provide a process for manufacturing of 400kV 120kN long-rod composite insulators with variable insulation sheath thickness which is simple.

[022] A further object of this invention is to provide a process for manufacturing of 400kV 120kN long-rod composite insulators with variable insulation sheath thickness which serves the purpose efficiently.

[023] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.

SUMMARY OF THE INVENTION

[024] One or more drawbacks of conventional systems and process are overcome, and additional advantages are provided through the apparatus and a method as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be part of the claimed disclosure.

[025] The present invention is devised to provide a fabrication method for manufacturing of 400kV 120kN ‘composite long-rod’ (CLR) insulators preferably with insulation shed thickness of 5mm for sub-station applications by utilizing an injection moulding process, wherein the plurality of insulation sheds of the said CLR insulator is an additive-modified high temperature vulcanized (HTV) silicone rubber material (chemically known as methyl vinyl silicone rubber), core structure of said insulator is an elongated ‘fibre reinforced polymer (FRP)’ rod, metallic hardware of the said insulators are forged-steel materials, while the interface bonding/reinforcing material is a commercial adhesive material respectively.
[026] According to this invention, there is provided a process for manufacturing of 400kV 120kN long-rod composite insulators with variable insulation sheath thickness comprising steps of:-
a. moulding of a plurality of insulation sheds,
b. holding the insulation sheds by a core structure of fibre reinforced polymer rod,
c. fixing of metallic hardware at the terminal ends of the core rod,
d. application of interface bonding/reinforcing agent between the insulation sheds and the FRP rod for interface bonding.
[027] The plurality of insulation sheds in the 400kV 120kN CLR insulators with variable insulation sheath thickness is an additive-modified high temperature vulcanized (HTV) silicone rubber material (methyl vinyl silicone rubber).
[028] The plurality of insulation sheds is moulded by using the said additive-modified HTV silicone rubber material in a die in an injection moulding machine at temperature range of 165-175oC with curing time in the range of 650-750 seconds and counter injection pressure level in the range of 200-220 Bar.
[029] The core structure is an elongated ‘fibre reinforced polymer (FRP)’ rod upto a length of 3.5 meter with core diameter of 24 mm that holds the insulation sheds.
[030] The surface treatment of the FRP rod is carried out by a chemical treatment process followed by using a silane-based catalyst-modified adhesive material in xylene solvent, followed by a heat-treatment process at any temperature in the range of 100-130oC for a period of 20-30 minutes, prior to the injection moulding process, which is done for strengthening the bonding between the interface region of silicone rubber insulation sheds and FRP rod in the composite insulator structure.
[031] The fabrication process allows the plurality of insulation sheds to get aligned continuously throughout the FRP rod structure with nearly uniform thickness of about 5mm by maintaining equal distance (pitch) from one shed to another of about 50mm across the axial direction of the rod that varies in diameter in alternate sheds repeatedly about 155mm to about 125 mm on the entire length of FRP core rod, sheath of which has a tapered angle of about 10o at the top and about 5o at the bottom of each sheath.
[032] The metallic hardware are forged steel materials, wherein one end of the rod that is fitted is EN19 grade forged steel known as ‘ball fitting’, and at another end of the rod, which is known as ‘socket fitting’ is EN8 grade forged steel.
[033] Prior to the injection moulding for generating the insulation sheds on the core FRP rod structure, metallic hardware conductors are fitted over the terminal-ends of the FRP rod by using an appropriate metallic jaw and also by applying a crimping pressure level in the range of 150-170 Bar with holding time in the range of 5-10 seconds that the metallic hardware fixes at the terminal ends of the FRP rod.
[034] The metallic hardware conductor-fitted FRP rod structure is placed in the mould for generating the plurality of insulation sheds by injection moulding process with prior cleaning the said hardware ultrasonically by using a non-aqueous solvent, including trichloro-ethelene in order to remove dirt/greasy matter from the surface.

[035] The interface bonding/reinforcing agent is a silane-based catalyst-modified adhesive in xylene-solvent and is used for strengthening interface bonding between silicone rubber and FRP rod.

[036] The total length including the hardware fittings of the 400kV 120kN CLR insulators is for example 3625 + 50 mm, wherein the creepage distance of the 400kV 120kN CLR insulators is for example 10500 + 50mm, wherein the torsion load of the 400kV 120kN CLR insulators is for example 50+2 Nm, wherein electromechanical strength of the 400kV 120kN CLR insulators is atleast 120kN and upto 150kN.

[037] The 400kV 120kN CLR insulators have the following properties.

Sl. No. Description/Parameter Unit Value
1 Mechanical strength (Tensile) kN 120
2 Total length mm 3625±50
3 Creepage distance mm 10500
4 Coupling designation mm 20
5 Core diameter mm 24
6 Torsion Load Nm 50
7 Individual units/insulator No. 1
8 Corona rings/Insulator No. 2
9 Insulation Sheath - Big (Diameter) mm 136
10 Insulation Sheath – Small (Diameter) mm 116
11 Pitch (Big Sheath to Big Sheath) mm 60
12 Insulation Sheath Thickness mm 06+0.5
13 Sheath (tapered) angle Degree 7(at the top); 3.5 (at the bottom)
14 Shore Hardness of the Silicone Rubber Sheath (Post-curing) 65
15 AC Voltage rating kV 400

[038] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

[039] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.

[040] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS OF INVENTION:

[041] While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.

[042] The present invention provides a fabrication method for the manufacturing of 400kV 120kN composite long-rod (CLR) insulators. The structure of said composite insulator comprises a core rod, plurality of insulation sheds of which are continuously aligned towards the axial direction of the entire core rod and the metallic hardware, which are fitted at the terminal ends of the insulator structure for ohmic contacts respectively.

[043] As per the basic design of materials of construction for the said 400kV 120kN CLR insulator, the core rod is an elongated fiber-reinforced polymer (FRP) material, the plurality of insulation sheds is an additive-modified high-temperature vulcanized (HTV) silicone rubber material and the metallic hardware parts are made of forged-steel EN8 grade material for ‘socket fittings’ at one terminal end and EN19 grade of forged steel as ‘ball-fittings’ at the other terminal end of the CLR insulator structure.

[044] As per the invention, the insulation sheds which cover the entire length of core elongated FRP rod surface, in which a plurality of sheds are formed by integrally molding an insulating material, i.e., additive-modified silicone high-temperature vulcanized (HTV) rubber by an injection molding machine at definite temperature/s with a definite period of curing time of the HTV rubber material, prior surface treatment of the FRP rod. During the molding process, the insulation sheds get aligned to one another in the axial direction of the core FRP rod. The surface treatment of the FRP rod is carried out in order to strengthen the bonding between the interface region of silicone rubber insulation material & FRP rod in the composite insulator structure. Hardware fittings, which are cleaned ultrasonically by using non-aqueous solvent, are manually inserted over the terminal-ends of the FRP rod and fixing of the hardware at the terminal ends of the FRP rod is carried out by a so-called ‘crimping technique’ using appropriate metallic jaws and also by applying sufficient pressure in a manner that the metallic hardware fixes at the terminal ends of the FRP rod. Hence, hardware-fitted FRP rod structure is placed in the mould for generating the plurality of insulation sheds by injection moulding process at an elevated temperature and pressure.

[045] Further, each shed in the composite insulator structure is aligned axially to the adjacent shed by maintaining a pre-determined and equi-distance gap, all the area of FRP rod of which is continuously molded with the same insulating material, i.e., additive-modified silicone HTV rubber in a monolithic manner. The diameter of each adjacent molded shed is also varied so that the diameter of each repeated insulation shed becomes the same across the length of the FRP rod, which is integrally united throughout the length of the FRP rod in the composite insulator body structure.

[046] It is also possible that the same HTV silicone rubber insulation material in the form of thin fibrous structure gets also formed on the surfaces of the insulation sheds during the injection moulding process. These extra fibrous materials on the surface of moulded insulation sheds is termed as ‘flashes’, which were removed, after which the fabricated CLR insulators are preliminary tested by NDT method for correctness of interfaces.

[047] The fabricated insulators are then subjected to routine visual checks and the next level of testing comprising various type tests, electrical tests, mechanical tests, vibration tests and pollution tests respectively by following validated testing procedures in accredited laboratories.

[048] The fabricated insulators need to essentially pass all the type of tests depending on the application criteria after which it is confirmed for the desired quality with reliable performance of the 400kV 120kN composite long-rod (CLR) insulators.

[049] The following examples will bring more detailed explanation about the fabrication process for ensuring desired quality of the insulators with reliable performance for applications.
Example 1:
[050] In this example, composite long-rod’ (CLR) HVDC insulators having a total length (including hardware fittings) about 3625+50mm mm with counter i) creepage distance about 10,500 mm, ii) torsion load about 50 Nm, iii) coupling designation about 20 mm, iv) voltage ratings of 400kV and v) minimum electromechanical strength of about 120kN is fabricated by following an injection moulding technique.

[051] The said 400kV 120kN ‘composite long-rod’ (CLR) insulators structurally comprise primarily, i) plurality of insulation sheds, which is moulded by using an additive-modified high temperature vulcanized (HTV) silicone rubber material (chemically known as methyl vinyl silicone rubber), ii) a core structure, which is an elongated ‘fibre reinforced polymer (FRP)’ rod upto a maximum length of 3.675 meter with counter diameter of about 24 mm that holds the insulation sheds, iii) metallic hardware, which are forged steel materials, fixed at the terminal ends of the core rod and another iv) interface bonding/reinforcing agent which is used for strengthening interface bonding between silicone rubber and FRP rod respectively.

[052] The surface treatment of the FRP rod was carried out in order to strengthen the bonding between the interface region of silicone rubber insulation sheds & FRP rod in the composite insulator structure. Hence, the surface of the FRP rod was modified by a chemical treatment process, followed by using a silane-based catalyst-modified adhesive material in xylene solvent followed by a heat-treatment process at a temperature of 120oC for a period of 20 minutes prior to the injection moulding process. Prior conducting the surface treatment of the FRP rods, the rods were also cleaned with a non-aqueous solvent, i.e., iso-propyl alcohol.

[053] Further, prior to the injection moulding for generating the insulation sheds on the core FRP rod structure, metallic hardware fittings were manually inserted over the terminal-ends of the FRP rod, which was carried out by a so-called ‘crimping technique’ using an appropriate metallic jaw and also by applying a crimping pressure of 150 Bar with holding time of 5 seconds during crimping, so that the metallic hardware fixes at the terminal ends of the FRP rod. The metallic hardware were cleaned ultrasonically by using a non-aqueous solvent, trichloro-ethelene in order to remove any dirt/greasy matter from the surface. However, similar other non-aqueous solvents can also be used for this purpose. Therefore, hardware-fitted FRP rod structure was placed in the mould for generating the plurality of insulation sheds by injection moulding process. The hardware material for ‘ball fitting’ at one end of the rod is EN19, while at another end of the rod, which is known as ‘socket fitting’ is EN8 respectively. The total length including the hardware fittings of the aforesaid 400kV 120kN CLR insulators is 3625+50mm.

[054] In this example, the aforesaid 400kV 120kN composite long-rod insulator was fabricated by placing the surface-modified core FRP rod by a chemical treatment process in a stainless steel die in the injection moulding machine, wherein the said additive-modified HTV silicone rubber material is moulded in the form of round sheds at a temperature of 170oC with counter injection pressure of 210 Bar on the surface of core FRP rod having curing time of 650 seconds.

[055] The insulation sheds which cover the entire length of core elongated FRP rod surface, in which a plurality of sheds are formed by integrally molding the said additive-modified silicone high-temperature vulcanized (HTV) rubber material by the injection molding machine, prior surface treatment of the FRP rod. During the molding process, the insulation sheds got aligned to one another in the axial direction of the core FRP rod.

[056] The injection moulding process that allowed the plurality of insulation sheds to get aligned continuously throughout the FRP rod structure with nearly uniform thickness of 5mm by maintaining equal distance (pitch) of 50mm from one shed to another across the axial direction of the rod that vary in diameter from 155mm in alternate shed to 125mm repeatedly on the entire length of FRP core rod, sheath of which has a tapered angle of about 10o at the top and about 5o at the bottom of each sheath. The shore hardness of sheath HTV rubber material (post-curing) resulted in the range of 65-68.

[057] The creepage distance of the aforesaid 400kV 120kN CLR insulators is 10500mm, while the torsion load of the aforesaid 400kV 120kN CLR insulators is 50Nm.

[058] After the injection moulding process, HTV silicone rubber insulation material in the form of thin fibers got deposited on the surface of the insulation sheds, which are termed as ‘flashes’, were removed from the surface. Therefore, the flash-free surfaces of the CLR insulators are then subjected to routine visual checks & other routine tests, primarily, mechanical test (tensile load) by NDT method (ultrasonically) for correctness of interfaces.

[059] The fabricated insulators after the preliminary routine tests were then subjected to the next level of testing, comprising various type tests, electrical tests, mechanical tests, vibration tests and pollution tests respectively by following validated testing procedures in accredited laboratories.
[060] The fabricated insulator i.e., 400kV 120kN long-rod composite insulator has passed through all the desired testing, i.e., mechanical, electrical, vibration and pollution testing, therefore confirms its reliable performance as an insulator in sub-station applications with 400kV voltage rating having a counter electro-mechanical strength upto 120kN of the CLR insulators.

[061] The following 400kV 120kN composite long-rod (CLR) insulator fabricated in this example, showed the following properties, as per Table A:

Table A: Technical properties of the fabricated 400kV 120kN composite long-rod (CLR) insulator under Example 1:

Sl. No. Description/Parameter Unit Value
1 Mechanical strength (Tensile) kN 120
2 Total length mm 3625±50
3 Creepage distance mm 10500
4 Coupling designation mm 20
5 Core diameter mm 24
6 Torsion Load Nm 50
7 Individual units/insulator No. 1
8 Corona rings/Insulator No. 2
9 Insulation Sheath - Big (Diameter) mm 136
10 Insulation Sheath – Small (Diameter) mm 116
11 Pitch (Big Sheath to Big Sheath) mm 60
12 Insulation Sheath Thickness mm 06+0.5
13 Sheath (tapered) angle Degree 7(at the top); 3.5 (at the bottom)
14 Shore Hardness of the Silicone Rubber Sheath (Post-curing) 65
15 AC Voltage rating kV 400

Example 2:

[062] In this example, all other conditions remained the same to that of the Example 1, the only difference is that the following parameters were varied during the injection moulding process in order to get 400kV 120kN composite long-rod (CLR) insulators.

• Crimping pressure of the metallic hardware: 160Bar
• Injection moulding temperature: 165oC
• Curing time of the HT Silicone Rubber: 700 Sec

[063] The following 400kV 120kN composite long-rod (CLR) insulator fabricated in this example, showed the following properties, as per Table B.

Table B: Technical properties of the fabricated 400kV 120kN composite long-rod (CLR) insulator under Example 2:

Sl. No. Description/Parameter Unit Value
1 Mechanical strength (Tensile) kN 120
2 Total length mm 3625±50
3 Creepage distance mm 10500
4 Coupling designation mm 20
5 Core diameter mm 24
6 Torsion Load Nm 50
7 Individual units/insulator No. 1
8 Corona rings/Insulator No. 2
9 Insulation Sheath - Big (Diameter) mm 136
10 Insulation Sheath – Small (Diameter) mm 116
11 Pitch (Big Sheath to Big Sheath) mm 60
12 Insulation Sheath Thickness mm 06+0.5
13 Sheath (tapered) angle Degree 7(at the top); 3.5 (at the bottom)
14 Shore Hardness of the Silicone Rubber Sheath (Post-curing) 65
15 AC Voltage rating kV 400

Example 3:

[064] In this example, all other conditions remained the same to that of the Example 1, the only difference is that the following parameters were varied during the injection moulding process in order to get 400kV 120kN composite long-rod (CLR) insulators.

• Crimping pressure: 170Bar
• Injection moulding temperature: 175oC
• Curing time of the HT Silicone Rubber: 750 Seconds

[065] The following 400kV 120kN composite long-rod (CLR) insulator fabricated in this example, showed the following properties, as per Table C

Table C: Technical properties of the fabricated 400kV 120kN composite long-rod (CLR) insulator under Example 3:

Sl. No. Description/Parameter Unit Value
1 Mechanical strength (Tensile) kN 120
2 Total length mm 3625±50
3 Creepage distance mm 10500
4 Coupling designation mm 20
5 Core diameter mm 24
6 Torsion Load Nm 50
7 Individual units/insulator No. 1
8 Corona rings/Insulator No. 2
9 Insulation Sheath - Big (Diameter) mm 136
10 Insulation Sheath – Small (Diameter) mm 116
11 Pitch (Big Sheath to Big Sheath) mm 60
12 Insulation Sheath Thickness mm 06+0.5
13 Sheath (tapered) angle Degree 7(at the top); 3.5 (at the bottom)
14 Shore Hardness of the Silicone Rubber Sheath (Post-curing) 65
15 AC Voltage rating kV 400

[066] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.

[067] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.

[068] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particulars claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances, where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B”.

[069] The above description does not provide specific details of manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art are capable of choosing suitable manufacturing and design details.

[070] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.

[071] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.

[072] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims:1. A process for manufacturing of 400kV 120kN long-rod composite insulators with variable insulation sheath thickness comprising steps of:-
- moulding of a plurality of insulation sheds,
- holding the insulation sheds by a core structure of fibre reinforced polymer rod,
- fixing of metallic hardware at the terminal ends of the core rod,
- application of interface bonding/reinforcing agent between the insulation sheds and the FRP rod for interface bonding.
2. The process as claimed in claim 1, wherein the plurality of insulation sheds in the 400kV 120kN CLR insulators with variable insulation sheath thickness is an additive-modified high temperature vulcanized (HTV) silicone rubber material (methyl vinyl silicone rubber).
3. The process as claimed in claim 1 or 2, wherein the plurality of insulation sheds is moulded by using the said additive-modified HTV silicone rubber material in a die in an injection moulding machine at temperature range of 165-175oC with curing time in the range of 650-750 seconds and counter injection pressure level in the range of 200-220 Bar.
4. The process as claimed in the claims 1-3, wherein the core structure is an elongated ‘fibre reinforced polymer (FRP)’ rod upto a length of 3.5 meter with core diameter of 24 mm that holds the insulation sheds.
5. The process as claimed in the claims 1-4, wherein the surface treatment of the FRP rod is carried out by a chemical treatment process followed by using a silane-based catalyst-modified adhesive material in xylene solvent, followed by a heat-treatment process at any temperature in the range of 100-130oC for a period of 20-30 minutes, prior to the injection moulding process, which is done for strengthening the bonding between the interface region of silicone rubber insulation sheds and FRP rod in the composite insulator structure.
6. The process as claimed in the claims 1-5, wherein the fabrication process allows the plurality of insulation sheds to get aligned continuously throughout the FRP rod structure with nearly uniform thickness of about 5mm by maintaining equal distance (pitch) from one shed to another of about 50mm across the axial direction of the rod that varies in diameter in alternate sheds repeatedly about 155mm to about 125 mm on the entire length of FRP core rod, sheath of which has a tapered angle of about 10o at the top and about 5o at the bottom of each sheath.
7. The process as claimed in the claims 1-6, wherein the metallic hardware are forged steel materials, wherein one end of the rod that is fitted is EN19 grade forged steel known as ‘ball fitting’, and at another end of the rod, which is known as ‘socket fitting’ is EN8 grade forged steel.
8. The process as claimed in the claims 1-7, wherein prior to the injection moulding for generating the insulation sheds on the core FRP rod structure, metallic hardware conductors are fitted over the terminal-ends of the FRP rod by using an appropriate metallic jaw and also by applying a crimping pressure level in the range of 150-170 Bar with holding time in the range of 5-10 seconds that the metallic hardware fixes at the terminal ends of the FRP rod.
9. The process as claimed in the claims 1-8, wherein the metallic hardware conductor-fitted FRP rod structure is placed in the mould for generating the plurality of insulation sheds by injection moulding process with prior cleaning the said hardware ultrasonically by using a non-aqueous solvent, including trichloro-ethelene in order to remove dirt/greasy matter from the surface.
10. The process as claimed in the claims 1-9, wherein the interface bonding/reinforcing agent is a silane-based catalyst-modified adhesive in xylene-solvent and is used for strengthening interface bonding between silicone rubber and FRP rod.
11. The process as claimed in the claims 1-10, wherein the total length including the hardware fittings of the 400kV 120kN CLR insulators is for example 3625 + 50 mm, wherein the creepage distance of the 400kV 120kN CLR insulators is for example 10500 + 50mm, wherein the torsion load of the 400kV 120kN CLR insulators is for example 50+2 Nm, wherein electromechanical strength of the 400kV 120kN CLR insulators is atleast 120kN and upto 150kN.
12. The process as claimed in the claims 1-11, wherein the 400kV 120kN CLR insulators have the following properties:-
Sl. No. Description/Parameter Unit Value
1 Mechanical strength (Tensile) kN 120
2 Total length mm 3625±50
3 Creepage distance mm 10500
4 Coupling designation mm 20
5 Core diameter mm 24
6 Torsion Load Nm 50
7 Individual units/insulator No. 1
8 Corona rings/Insulator No. 2
9 Insulation Sheath - Big (Diameter) mm 136
10 Insulation Sheath – Small (Diameter) mm 116
11 Pitch (Big Sheath to Big Sheath) mm 60
12 Insulation Sheath Thickness mm 06+0.5
13 Sheath (tapered) angle Degree 7(at the top); 3.5 (at the bottom)
14 Shore Hardness of the Silicone Rubber Sheath (Post-curing) 65
15 AC Voltage rating kV 400