Epoxy insulators and bushings Wiki
Everything you always wanted to know about epoxy insulators and epoxy bushings, their most important properties, the technical background and the manufacturing process.
- What is Aliphatic epoxy resin?
Aliphatic epoxy resins are typically formed by glycidylation of aliphatic alcohols or polyols. The resulting resins may be monofunctional (e.g. dodecanol glycidyl ether), difunctional (butanediol diglycidyl ether), or higher functionality (e.g. trimethylolpropane triglycidyl ether). These resins typically display low viscosity at room temperature and are often referred to as reactive diluents. They are rarely used alone, but are rather employed to modify (reduce) the viscosity of other epoxy resins. This has led to the term ‘modified epoxy resin’ to denote those containing viscosity-lowering reactive diluents. A related class is cycloaliphatic epoxy resin, which contains one or more cycloaliphatic rings in the molecule. This class also displays low viscosity at room temperature, but offers significantly higher temperature resistance than the aliphatic epoxy diluents. However, reactivity is rather low compared to other classes of epoxy resin, and high temperature curing using suitable accelerators is normally required.
- What is APG - Automatic Pressure Gelation process?
After preparing and mixing, the cast resin compound is cast under pressure into the mould that is fixed on a clamping unit according to the automatic pressure gelation process.
Processing under pressure is important in this case, since shrinkage of the casting during the curing process should be avoided. Most modern epoxy insulators are cast with this process. For insulators or bushings with complex geometries the vacuum casting process could be used.
- What are ASTM Fire & Smoke standards?
For certain applications like railways, trams and third rail it is crucial to have insulators and materials certified by ASTM standards like ASTM E662 (Standard Test Method for Specific Optical Density of Smoke Generated by Solid Materials), ASTM E162 (Standard Test Method for Surface Flammability of Materials Using a Radiant Heat Energy Source) or ASTM D635 (Standard Test Method for Rate of Burning and/or Extent and Time of Burning of Plastics in a Horizontal Position). GIPRO Insulator outdoor epoxy resins are certified according the ASTM standards. Please have a look at pantograph insulators or powerrail insulators.
- What is a back plug insulator?
Back plug is another term for a termination plug, which is used as insulation end for medium voltage cable connectors or so-called separable connectors of outer cone connections. GIPRO is one of world leaders in termination plug manufacturing with a yearly produced amount of several hundred thousand termination plugs and back plugs.
- What is Breakdown voltage or breakdown strength?
When subjected to a high enough voltage, insulators suffer from the phenomenon of electrical breakdown. Epoxy resins offer a very high electrical breakdown strength. This strength varies for indoor epoxy resins from 30 to 40 kV/mm and for outdoor epoxy resins from 20 to 35 kV/mm. Epoxy insulators therefore feature a very good insulation ability even with low insulation thickness - subject to the condition that it was manufactured properly.
- What are Bushing plates?
Medium voltage bushing plates and high voltage bushing plates are used in different electrical devices like instrument transformers, oil-filled transformers and other medium voltage equipment.
- What is cast resin?
Cast-resin formulations are important in the electronics industry, and are employed in motors, generators, transformers, switchgear, bushings, and insulators. Cast resins are excellent electrical insulators and protect electrical components from short circuiting, dust and moisture. In the electronics industry epoxy resins are the primary resin used in overmolding integrated circuits, transistors and hybrid circuits, and making printed circuit boards.
- What are Cycloaliphatic epoxy resins?
Cycloaliphatic epoxy resins (CEP) are high performance products for use in adhesive, civil engineering, electrical, composite and many other applications where improved outdoor resistance, as compared to standard Bisphenol A or Bisphenol F diglycidyl ether epoxies, is needed.
- What are EN Fire & Smoke standards?
For certain applications like railways, trams and third rail it is crucial to have insulators and materials certified by EN standards like EN 45545-2: fire testing of materials and components for trains (the standard defines a classification system that specifies requirements for fire behaviour of materials and products used in trains). GIPRO Insulator outdoor epoxy resins are certified according the EN 45545-2 standard. Please have a look at pantograph insulators or powerrail insulators.
- What is an Epoxy insulator?
An electrical insulator casted with epoxy resin and hardener. Insulators could be made from an indoor epoxy resin system like a Bisphenol A-epichlorohydrin resin and an anhydride hardener of from an UV and wheaterproof outdoor epoxy system like a cycloaliphatic epoxy resin and hardener.
- What are Epoxy housings used for?
What is an epoxy housing needed for: Epoxy cast-resin is a duroplastic polymer which has a high electrical insulation ability. The electrical breakdown strength of GIPRO's resins is between 20 kV/mm up to 40 kV/mm, depending on the kind of system. Due to the high insulation resistance cast-resin housings are used for switches in medium-voltage applications and are to find in a lot of electrical substations / transformer stations. Epoxy housings can be cast in nearly every required shape and dimension and are therefore ideal for customer specific insulation solutions. Some say also pole-housing as alternative term.
- What is Epoxy resin?
Epoxy resin formulations are important in the electronics industry, and are employed in motors, generators, transformers, switchgear, bushings, and insulators. Epoxy resins are excellent electrical insulators and protect electrical components from short circuiting, dust and moisture. In the electronics industry epoxy resins are the primary resin used in overmolding integrated circuits, transistors and hybrid circuits, and making printed circuit boards.
- What are Epoxy Terminals?
Epoxy terminals or epoxy terminal bushings are round or squre-shaped plates cast of epoxy resin, with different small bolts or cables going through the bushing.
These bushing plates are used for different types of transformers like instrument transformers or oil filled transformers. Sometime these goods are also called terminal blocks. Learn more about epoxy terminals.
- What is High voltage?
For voltage categories exist different scales. GIPRO considers values from 72.000 V (72 kV) and above as belonging to High Voltage Level.
- What is an Insulator?
An electrical insulator is a material whose internal electric charges do not flow freely, and therefore make it nearly impossible to conduct an electric current under the influence of an electric field. Usable materials are glass, porcelain, glass-fibre, silicones and epoxy resins. The insulation ability depends on the used material, the distance between current and earth and the applied voltage. It is characterized as breakdown strength or breakdown voltage.
- What is low voltage?
For voltage categories exist different scales. GIPRO considers values from 0 to 1000 V (1 kV) as belonging to Low Voltage Level.
- What are low voltage post insulators?
These insulators can be made from epoxy resin or polyester and are used mainly in low voltage switchgear for support of bus bars.
- What is medium voltage?
For voltage categories exist different scales. GIPRO considers values from 1000 V (1 kV) to 72.000 V (72 kV) as belonging to Medium Voltage Level.
- Medium voltage bushings design
In order to develop a safe and efficient new mv bushing from epoxy resin, you should have know-how about the electric requirements due to valid standards of your area of application, but as well you should know in detail about abilities and behaviour of epoxy resin and the special processes of epoxy casting. GIPRO has longtime experience on manufacturing safe and gas-thight medium voltage bushings with very low partial discharge levels, to be used in oil-insulated or gas-insulated switchgear.
Our technical sales people and engineers can offer you quick and easy consulting on how to design your medium voltage bushing.
- Medium voltage insulators design
In order to develop a safe and efficient new medium voltage epoxy insulator, you should have know-how about the electric requirements due to valid standards of the area of application, but as well you should know in detail about abilities and behaviour of epoxy resin and the special processes of epoxy casting.
GIPRO's technical sales people and engineers can offer you quick and easy consulting on how to design your insulator.
- What is a Medium Voltage Spout?
A spout is a housing for a medium-voltage switch or an isolated housing for contacting copper-bars within a switch-gear.
- What are NF F Fire & Smoke standards?
For certain applications like railways, trams and third rail it is crucial to have insulators and materials certified by NF F standards like NF F 16-101 and NF F 16-102 fire test to railway components. GIPRO Insulator outdoor epoxy resins are certified according the NF F standards. Please have a look at pantograph insulators or powerrail insulators.
- What are Pantograph insulators?
Pantographs are devices to collect current from overhead lines. Pantographs are used for tramways and other light rail vehicles which normally run between 750 V and 3 kV, some also up to 6 kV and for heavy rail vehicles which run mainly between 15 kV and 25 kV. The pantograph insulators protect the railcar roof from the electric current which runs through the pantograph. Pantograph insulators exist for up to 3 kV, 6 kV and up to 25 kV in different heights and shapes.
Important is the definition of minimum clearance distance and minimum creepage distance which is taken according to railway standards like the EN 50124. The technical requirements are given due to the pollution degree and the overvoltage category of the railnet.
- What is Partial discharge in insulators or bushings?
In electrical engineering, partial discharge (PD) is a localized dielectric breakdown (DB) of a small portion of a solid or fluid electrical insulation (EI) system under high voltage (HV) stress, which does not bridge the space between two conductors. While a corona discharge (CD) is usually revealed by a relatively steady glow or brush discharge (BD) in air, partial discharges within solid insulation system are not visible [wikipedia.org].
The testing of partial discharge in manufactured cast-resin insulators or bushings is crucial for the lifetime of these electric insulation products. If there are problems within the insulation a total break-down could be not far away. If you have need of testing the partial discharge of a product that let you feel insecure, please contact our Sales team. We support you with your questions.
- What are Powerrail insulators?
Powerrail systems are a means of providing electric traction power to trains, and they use an additional rail (called a "conductor rail") for the purpose. On most systems, the conductor rail is placed on the sleeper ends outside the running rails. The conductor rail is supported on ceramic insulators, epoxy insulators or insulated brackets, typically at intervals of around 3-6 metres. In recent years the outdated ceramic pot insulators are more and more replaced by epoxy powerrail insulators. The advantage of epoxy insulators are the possibility to use the mounting situation of the existing powerrail. No bigger construction change is necessary. Epoxy powerrail insulators can be cast in nearly every required geometry and design and are therefore very flexible.
- What are Railway insulators?
Railway insulators is a very general term, which is used for all kind of insulators, that are used in the electrification of rail systems. It includes insulators for catenary wires, as well as third-rail insulators and insulators for rolling-stock (which is described in the following). At GIPRO you can find epoxy insulators for rolling stock as well as for third rail / powerrail insulation. Insulators for catenary wires are not part of the GIPRO delivery program.
- What is a rolling stock insulator?
Rolling stock means in a technical jargon railcars, locomotives, metro or tramways.
Insulators for rolling stock are therefore used for technical insulation of electrical applications on rail roofs, like pantograph support insulators, pin-insulators, roof-line insulators or insulators for third rail current collectors. Find more about GIPRO's railway insulators.
- What are roof-line insulators?
On electric locomotives there could be an electric roof-line connection between the several pantographs (current collectors). To protect the locomotive from the current roof-line insulators are used for insulation. Another term for them is pin-insulators. All terms together with pantograph insulator belong to the category of locomotive insulators.
- What are termination plugs?
Cable terminating plugs are used in medium voltage cable connectors. There are two widely-accepted and standardized bushing designs – outer and inner cone – each having its own advantages. For example, the inner cone system normally provides higher mechanical stability whereas the outer cone system offers greater flexibility for installation on different cable constructions. Plug-in type bushings are used for liquid filled transformers and all other types of medium voltage systems with the relevant standards for these applications being EN 50180 and EN 50181. In recent years, the Type C outer-cone bushing has become the most common connection on distribution networks. Increasing energy density on such network has required some modification to extend the range of this type of bushing from 630 A to 1250 A rated current. As a result, the separable connector must be designed to cope with this new requirement so as to avoid becoming the ‘bottleneck’ of the connection between cable, bushing and separable connector. (> More about plug solutions)
- What are third-rail insulators?
Third-rail systems are a means of providing electric traction power to trains, and they use an additional rail (called a "conductor rail") for the purpose. On most systems, the conductor rail is placed on the sleeper ends outside the running rails. The conductor rail is supported on ceramic pot insulators, epoxy insulators or insulated brackets, typically at intervals of around 3-6 metres.
In recent years the outdated ceramic insulators are more and more replaced by epoxy third-rail insulators. The advantage of epoxy insulators are the possibility to use the mounting situation of the existing third rail. No bigger construction change is necessary. Epoxy third-rail insulators can be cast in nearly every required geometry and design and are therefore very flexible.
- What is a tramway insulator?
The current collector of tramways (pantograph) needs to be insulated from the railcar's roof. Therefore tramway insulators are used in different height, shapes and creepage distance with voltage levels between 750 V and 6 kV. The used support insulators are made from UV resistant cycloaliphatic epoxy resin (CEP).
- What is vacuum epoxy casting?
The cast resin compounds are prepared under vacuum, mixed and then cast under vacuum in the casting tank. With this technology also epoxy insulators and epoxy bushings can be cast, that have complex geometries or that are bigger than normal clamping machines surfaces. GIPRO also casts one of the biggest epoxy recloser poles in the vacuum chamber.