In the event of a flashover, the intense localized energy causes an abrupt temperature elevation. If the arc is severe enough, a ceramic or glass insulator will fracture. During a less severe incident, the leakage currents frequently dry into pathways that later lead to dry-band arcing, which can be severe enough to damage the housing material. 

Utilities have developed a number of other techniques for coping with contamination. High-pressure washing, silicone dielectric greases and RTV silicone coatings have all been applied to ceramic and glass insulators with some success. Each method has its drawbacks, however. 

Washing of insulators is labor-intensive, and can be dangerous to workers, since it is generally impractical to shut down service. Results are sometimes inadequate – no amount of cleaning would have removed contamination fast enough to prevent the 1991 FP&L outages, for example. When insulators are grouped together, such as in a substation, pressure washing or hand cleaning can be very difficult to accomplish while the station is energized, due to the clearances that must be maintained. Washing can be economical on easily accessed lines, but can be very impractical in remote areas or difficult access locations. Silicone greases offer a longer-lasting solution, as silicone fluid within the grease formulation encapsulates contaminants, rendering them nonconductive and retaining a hydrophobic surface. However, the grease will eventually be overwhelmed by contamination, at which time it must be removed and replaced (generally from three months to five years, depending on the severity of the conditions). 

Sprayable RTV silicone elastomers have proven more effective, offering much better long-term resistance to contamination and moisture. Developed from the same product family as construction sealants, the coatings are formulated with arc resistant additives and dispersed in solvent. This solution offers longer remedial relief from contamination and associated problems, but utilities and OEMs continued to seek a more permanent solution, especially for new installations. 

This need has led to the continued development of polymer housings for insulator and arrester designs. In particular, silicone rubber seems to be emerging as a material of choice among insulator specifiers. In fact, nearly every major insulator manufacturer now offers a design with a silicone housing. The increased demand for silicone rubber can be attributed to a general upsurge in composite design use, as well as a growing preference for silicone over other elastomers.

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