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La Granja Glass Insulators

30 Sep, 2022

La Granja Glass Insulators
More than 100 million installed - In over 100 countries - On all Continents

Toughened Glass Insulator - The technical advantages

High thermal and mechanical resistance
Many Utilities report unacceptable numbers of polymer failures while expressing concerns for long term reliability. Toughened glass insulators, due to the thermal treatment received, offer great resistance to both the mechanical and thermal stress, which is normal for suspension insulators, as well as accidental impacts which may occur during transport, handling, and installation. They are also highly resistant to sudden changes in temperature.

Reduced ageing
This is true even when insulators are subjected to large mechanical loads. LGI has insulators in service in high voltage transmission grids for over 85 years.

High dielectric resistance and homogeneous potential distribution
Dielectric strength is high due to the homogeneity of the glass, which makes them practically impossible to puncture. The insulator has high electrical capacitance and achieves homogeneous potential distribution in strings, thereby helping to improve the phenomenon of radio interference and the corona effect.

Easy inspection and mechanical reliability
Toughened glass insulators offer a very important advantage: an intact glass insulator is always a “healthy” insulator. If the glass were to break for any reason, it would break up into small pieces, whilst the mechanical resistance of the insulator “stub “remains practically the same as that of the intact insulator. This provides confidence for asset managers and power line inspection crews, simplifying inspection as it can be carried out using the naked eye from the ground or from a helicopter. The insulator string practically maintains its original mechanical properties until maintenance work can be scheduled. Furthermore, thanks to the homogeneity of the glass, the annual spontaneous shattering rate for installed LGI insulators (measured empirically by the world’s main electricity operators) has been shown to be below the 0.02% that is normally required by customers, thereby significantly reducing maintenance costs and providing a lower cost of ownership.

For these reasons, glass insulators are becoming the cost-effective solution for new construction and for the replacement of aging porcelain or polymer insulators


La Granja Glass Insulators - Made of Glass and Passion

La Granja Insulators (LGI) is a member of the VERESCENCE Group.
The VERESCENCE Group has facilities throughout the world (total of 7 plants including France, Spain and United States) with over 2,340 employees. It is now the world leader in speciality glass products (Power Line Insulators, Perfumery and cosmetics, & Spirits Bottles) with an annual turnover of around 321 million euros.

A major player in the insulator market for nearly 90 years (previously known as ESA, Saint-Gobain La Granja, Vicasa and SGD) LGI has built up its reputation for reliability, professionalism and innovation based on the following:

  • La-Granja Insulator production is at the forefront of Quality and Technology and has benefitted from regular investment throughout its existence.
  • Ongoing innovation policy: Pin-type insulators, toughened glass suspension insulators, RTV silicone coated insulators (SILGLASS®).
  • Over 85 years’ collaboration with the main electricity network operators throughout the world.
  • Over 100 million insulators installed in electricity distribution and transport networks for medium to high voltages of up to 765 kV in over 100 countries in all continents
  • Quality, environmental and health and safety management systems, certified according to the highest international standards: ISO 9001, ISO 14001, OHSAS 18001, ISO 17025 and ISO 22716.

La-Granja Toughened Glass Insulators (TGI)

Suspension insulator components
Suspension insulators consist of the following elements:

  • A dielectric profile made of toughened glass with the suitable properties and shape for the environmental conditions it was designed for.
  • Hot-dipped galvanised ductile or malleable cast iron cap, marked with our brand name “ESA” and engraved and stamped as per the applicable standards for the correct identification and individual traceability.
  • Hot-dipped galvanized forged steel pin.
  • The cap and pin are assembled on the glass piece using aluminous cement to withstand the thermomechanical efforts.
  • Lastly, the insulator cap includes a stainless steel or phosphor bronze locking device (split pin) which secures the coupling of the units.

Also, on request, the pins can be supplied protected using an anti-corrosion zinc sleeve (sacrificial anode). This zinc sleeve is strongly recommended for insulators that may be installed in heavily polluted environments.

On clevis and tongue type insulators, the caps are equipped with a forged steel bolt and a pin.

The range of suspension insulators produced at La-Granja complies with the main international and national standards: IEC, ANSI, CSA, BS, NF, UTE, UNE & DIN..

For each standard, there is a wide variety of mechanical resistances ranging from 40 kN up to 400 kN, covering a variety of power lines and substations.

Within each standard and for each mechanical load, the suspension insulators are divided into groups depending on the glass profile.

The groups are as follows:

Standard profile insulators
These are the most common and most frequently used insulators for lines in low pollution environments, where they perform well due to their small, well-spaced ribs and a creepage distance which exceeds the requirements of the IEC 60305 and ANSI C29.2 standards

Anti-pollution or Anti-fog profile insulators
LGI offer two different shapes which are recommended for areas with medium to heavy pollution. Their longer creepage distance, which exceeds the requirements of the IEC 60305 standard, is achieved due to deeper ribs, and reduces the effects of pollution without increasing the length of the string.

Aerodynamic profile insulators
Due to the flat dielectric profile, this type of insulator is highly recommended for desert areas because the absence of ribs, which helps to reduce the accumulation of residues, particularly on the inner surface of the dielectric. At the same time, its shape permits regular and constant airflow which enables the wind to perform a self-cleaning process. These can also be used in areas of critical industrial or mixed pollution (desert and industrial pollution).

SILGLASS®: Silicone-coated insulators (RVT)

Silicone-coated insulators offer an excellent alternative which guarantees optimum performance for high voltage overhead lines in areas with heavy pollution. They minimise leakage current and thereby reduce operation and maintenance costs.

The product used to coat the insulators is Room Temperature Vulcanization (RTV) silicone which contains mineral fillers embedded in the silicone itself.

This silicone increases the hydrophobic nature of the insulator’s surface, with a Lotus leaf effect, thereby improving its performance in polluted areas. Furthermore, the fillers absorb the energy of any possible electric arcs and serve to protect the integrity of the coating.

Silicone-coated insulators are an economical solution because they eliminate the need to regularly clean, whilst still maintaining the mechanical reliability that glass suspension insulators have demonstrated over the years.

Silicone-coated insulators are the result of bringing together high-quality insulator technology and high-performance silicone, combined by the most advanced application technology. It has the heritage of mechanical reliability together with excellent pollution resistance.

This is a fantastic solution utilised more and more on a large scale throughout the world’s main Distribution & Transport Networks.

Mechanical, electrical, and dimensional data
The guaranteed mechanical and electrical values for each insulator is recommended by the IEC, BS, ANSI and CSA standards. Similarly, the dimensional data (spacing, diameter, coupling standard, creepage distance) also comply to these standards.


Manufacturing process

1.- Glass melting and composition
The glass manufactured by La-Granja is obtained through a very specific melting process, using a modern furnace and control technology which have been specially designed by the company. This guarantees excellent quality glass in terms of homogeneity and chemical composition.

2.- Forming
Our expertise and technology in the pressing process, together with recent investments, enables LGI to produce the most demanding insulator profiles and sizes, going above & beyond the requirements of international standards.

3.- Tempering and thermal shocks
Tempering is the thermal treatment applied to the glass immediately after forming. The first stage is thermal balancing, to homogenize the temperature throughout the entire depth of the piece. The second stage is the hardening itself, which is achieved by cooling the outer areas to create residual compressive stress on the surface and tensile stress on the inside. This provides improved mechanical, thermal and electrical properties, as well as guaranteeing unbeatable resistance to ageing.

After hardening, all the pieces are subjected to thermal shocks, above & beyond the gradients established by international standards. This shock guarantees the elimination of faulty pieces.

4.- Assembly
The process for assembling the glass and metal parts is carried out in the same industrial plant as the rest of the manufacturing process, in a highly automated workshop using technology designed by LGI. It is based on the hot curing of high resistance, low expansion coefficient aluminous cement, to achieve excellent mechanical stability over time and high residual mechanical resistance, close to that of an intact insulator.

5.- Testing and trials
100% of the insulators are subjected to demanding quality checks carried out by automatic systems, including routine mechanical test.

Maximum quality levels are guaranteed by means of an exhaustive process monitoring system which constantly measures and checks all the variables using automatic data capture systems. At the end of the whole process, statistical quality checks are carried out for all manufactured batches.

Research and development
The desire to research and develop new technological solutions has formed part of LGI’s DNA, ever since VERESCENCE La Granja was founded in 1932.

La Granja Insulators have an insulator laboratory accredited under the ISO 17025 Standard (General requirements for the competence of testing and calibration laboratories).

For this purpose, the plant has different facilities:

High Voltage Facility: With a power frequency generator and an impulse generator

Mechanical Testing Facility: With two tensile machines with a capacity of up to 100T and 30T, respectively

Thermal Facility: Consisting of a special room for performing thermal and thermal-mechanical tests

Pollution Chamber: To test performance of RTV silicone coated insulators under polluted conditions and to carry out “tracking and erosion” tests

Type tests and special tests in external laboratories
Type test and special test reports are available for all insulators produced by LGI, in accordance with applicable standards, carried out by independent, accredited and internationally reputed laboratories.

These reports serve to demonstrate, once again, the quality and reliability of the LGI product. They are regularly updated and available to any client who wishes to consult them.

LGI’s IT system enables the gathering of real-time information regarding the availability and location of their products, including traceability. The information for each individual insulator is entirely computerised. Making it possible for LGI to achieve full traceability, in a fast and simple way, for both the components used in insulator manufacturing and the results obtained in each control process:

This ensures constant monitoring and traceability, from manufacturing right through to customer delivery.

TEN Group is the exclusive distributor for La Granja Insulators.

La-Granja Insulators, a member of the VERESCENCE Group -

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