Salt water spray canal contamination of overhead transmission lines

Installation of this country's first salt water spray cooling canal 200 feet (61 meters) from the transmission lines of a power station, created an insulator contamination problem several orders of magnitude greater than that possible from natural seaside salt contamination. A unique insulator contamination monitoring program is described, together with the data obtained for twelve months prior to operation of the spray cooling canal, and eight months with the canal in operation. An early warning device was developed and tested for alarming when a dangerous amount of insulator contamination is detected. Several methods of improving line performance are described including the use of resistance graded (RG) insulators. The reason for the failure of the RG insulators to perform satisfactorily is explained. A relationship between insulator contamination level as a function of distance from the salt water spray cooling canal is developed which will be helpful in determining adequate separation between a salt water cooling canal and adjacent overhead transmission lines. This paper will be of considerable aid in the planning of future salt water spray cooling canals and the design of insulator contamination monitoring programs.