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The Economics of Substation Maintenance

Because power dissipation in a substation is not nearly as great as that across a transmission/distribution line, the economics of leakage current suppression is not explored. However, Si-COAT offers tremendous benefits in the reduction of maintenance in substations.

Coastal environments are notoriously difficult in terms of substation maintenance and reliability. However modern industrial environments can have even greater degrading effects on maintenance expenditures.

In coastal environments, salt laden air and fog have a devastating effect on insulators and other electrical equipment. The resulting conductive medium that they form on insulator surfaces lead to heavy losses in the form of leakage current. If the condition goes undetected it can worsen until a flashover occurs. In most cases the station is taken off line resulting in a blackout with significant equipment damage and economic losses for the utility and its customers.

Traditionally, the insulators on coastal substations are regularly washed with high pressure water to remove the salt deposits before they build up to the danger point. This is an expensive procedure and seldom completely eliminates the problem. Albeit rather outdated technology, another common practice for the suppression of leakage current is greasing of insulators, typically with silicone grease. Again, this is a labor intensive and costly exercise that is a short term solution at best. Insulators that have been greased need to be cleaned and re-greased frequently.

In industrial environments much the same conditions exist. Although the contaminants are different and may take longer to build up, they are usually much more adherent to unprotected insulators. It is not uncommon to have to resort to mild abrasive blasting to remove them in order to maintain system reliability.

In virtually all cases, regular washing of insulators can be eliminated or dramatically reduced when Si-COAT RTV Silicone High Voltage Insulator Coating is employed. In cases where greasing is employed, that practice is totally eliminated with the use of Si-COAT.

Consider a typical coastal station where water washing was used to keep the station operating. This client owned a coastal 230kV Switchyard at a 2000 MW thermal generating station on the Western coast of the United States. The station housed 72 insulators that had to be washed every month.

A local maintenance contractor charged USD 5,010 to wash the station. This took three days, during which the station had to be de-energized. Neglecting the cost of the station downtime, the annual cost to wash the insulators amounted to USD 60,120 and the station still experienced frequent, unplanned power outages! Clearly, washing alone wasn't doing the job and a long term, reliable solution had to be found.

Si-COAT was chosen not because it was clearly the most economic solution, but because its use resulted in substantial long term operational savings.

The costs associated with coating the insulators with Si-COAT 570 were:

ItemCost (USD)Water washing (surface preparation) of Insulators to be Coated5,010Material Costs18,720Labor to Apply the Coating6,600Total Cost of Coating 72 Insulators30,330

Considering that each water washing was costing the utility $60,120, the net savings of $29,760 by using Si-COAT represents a payback period of approximately 6 months justifying the project.

However, even after coating the insulators, the utility prudently decided to wash the insulators once a year as a precautionary measure. Consequently, over the 10 year warranty period, the utility was expecting to save, additionally:

Savings (USD)First Year29,760Annual ($60,120 - $5010 over the remainder warranty period)55,110Total over the 10 Year Warranty Period525,750

For more details on either of the studies above, please contact CSL Silicones Inc.