Having decided the voltage that are required to be created at any substation it is necessary to establish a common insulation level for all items of equipment of each system voltage.
It is to be ensured that the breakdown or flashover strength of all insulation (particular voltage) in the station will exceed the selected level.
After the development of station type lightning arresters the B.I.L’S have been determined on the basis of the protective characteristics of the lighting arresters.
These levels help us in the selection of proper equipment.
The protective devices are then so selected that their flashover values are considerably lower than the B.I.L of the apparatus, thereby leaving sufficient margin of protection.
Saturday, March 14, 2015
BASIC INSULATION LEVELS BIL
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