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Comparison of ceramic and composite insulators

Comparison of ceramic and composite insulators shows that SIR insulators offer more advantages than porcelain insulator, ceramic insulator, glass insulator, EPDM polymer insulator, and other type insulators.

composite insulator

Comparison of ceramic and composite insulators:
Polymeric insulators are increasingly being used in both the distribution and transmission voltage ranges and are steadily capturing a wider share of the market. The primary impetus for their increased acceptance by the usually cautions electric power utilities is their substantial advantage compared to inorganic insulators which have primarily been porcelain and glass. One of their major advantages is their low surface energy and thereby maintaining a good hydrophobic surface property in the presence of wet conditions such as fog, dew and rain. Other advantages include:

Light weight which results in a more economic design of the towers or alternatively enabling to upgrade the voltage of existing systems without changing the tower dimensions. The light weight of the composite insulator strings also permits an increase in the clearance distance between the conductor to ground and an increase in the phase-to-phase distance in order to reduce the electric and magnetic fields which are becoming a growing concern to some members of the general public. The light weight of the composite insulators also obviates the need to use heavy cranes for their handling and installation and this saves on cost

A higher mechanical strength to weight ratio which enables the construction of longer spans of towers

Line post insulators are less prone to serious damage from vandalism such as gunshots which cause the ceramic insulators to shatter and drop the conductor to the ground

Much better performance than ceramic insulators in outdoor service in the presence of heavy pollution as well as in short term tests when done according to the method outlined in

Comparable or better withstand voltage than porcelain and glass insulators

Easy installation thus saving on labor cost

The use of composite insulators reduces the maintenance costs such as of insulator washing which is often required for ceramic and glass insulators in heavily contaminated environment.

Comparative general capabilities of insulators:
Porcelain ceramic: resists weather, resists UV
EPDM polymer: light weight, resists weather, lower cost installation / breakage, resists UV
SIR: hydrophobic recovery, light weight, contamination resistant, leakage current control, resists weather, lower cost installation / breakage, resists UV

Comparative general properties of different insulators are given above, compared with a competitive insulator, such as a porcelain insulator, ceramic insulator, glass insulator and EPDM polymer insulator, SIR insulators offer many advantages, including:
Superior long-term insulation
Strong yet light weight
Less susceptible to damage caused by shipment, installation or vandalism
Reduced maintenance costs
Sustained hydrophobicity, resulting in lower leakage currents, reduced dry band arcing, and less risk of flashover
Resistance to atmospheric and chemical degradation
Outstanding UV resistance compared with EPDM
Good property and color retention under all weathering conditions.

When it comes to selecting the best material for HV insulators used in power transmission and distribution applications, there’s really only one choice. For overall performance and long-term value, SIR is the clear winner. Insulators made with silicone are easy to install, reduce maintenance costs, are more resistant to vandalism, and offer superior long-term insulating properties.

Compared with porcelain, insulators made with SIR are far easier to install. That’s because silicone insulators require no assembly and generally weigh less than 25 percent of their ceramic counterparts. That can mean a weight saving of up to 180 kilograms per insulator, depending on the application a difference installation crews really appreciate when working on a transmission line high above the ground. In addition, power loss through leakage currents across the insulator is also minimized using SIR.

Porcelain insulators are frequently vandalized simply because they shatter dramatically when struck. Even when struck by bullets, SIR insulators are better equipped to go on doing their job with almost no performance loss. And since there is no dramatic visual loss of insulator integrity, vandals quickly lose interest in shooting at them. This can significantly reduce maintenance costs.

Silicone polymers have inherently good electrical insulating qualities. They are nonconductive because of their chemical nature and, when compounded with the proper tillers and additives, are used to produce rubber for a wide range of electrical insulating applications.

A comparison of life cycle costs (LCC) for ceramic discs (incl. washing), silicone coated ceramic discs and SIR insulators was carried out. The annual LCC for a coated ceramic disc are about 60- 67%, the LCC for a silicone insulator are only 30-34% referring to the LCC for a ceramic discs string.

Traditionally, insulator failure rate (FR) is defined as the number of insulator failures per 10.000 insulators per year. In accordance with international practice, the failure rate acceptable to the electric utilities worldwide is less than one. Failure is defined as the loss of ability of a device to perform any of its intended functions. Therefore, actual insulator failures or flashovers, even if the insulation is self restored, will be counted as insulator failures.

The following equation was developed to calculate the reliability index (RI) from the failure rate of used SIR insulators as well as other used insulators:
RI = 1/(1+FR) (1)
where RI = 1
FR : Number of failed insulators per 10.000 insulators per year
The LCCs of the insulators are shown in Table 2 and calculated as follows using a 30 year life for porcelain desert long rod (DLR) insulators and a predicted life for SIR insulators of 25 year:
LCC =purchase cost+replacement cost+lifetime wash cost (2)
Also, each cost component as a percentage of LCC and LCC saving given by use of SIR insulators, are shown along with LCC comparison in Table 2.

The above calculations show that the LCC of DLR insulators is about 1.5 times that of SIR insulators. This means that the saving is the result of the difference in purchase cost (89% of LCC for DLR insulators and 85% of LCC for SIR insulator). Nevertheless, other significant advantages of SIR insulators include easier installation, transportation and improved power-system reliability.

Because of the technology of SIR insulators is relatively new, this development could still have greater advantages over porcelain insulators as the benefits from improvements in materials and design and the economies of mass production materialize. These potential benefits seem likely to make SIR insulators the most cost-effective type of insulator in future, even for applications in desert environments.


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