This thesis reviews the line insulation coordination practices of Turkish Electricity Transmission Company with special focus on E.H.V. transmission line towers&rsquo / top geometry and ground clearances. In respect of this, the national regulation, &ldquo / Elektrik Kuvvetli Akim Tesisleri Y&ouml / netmeligi&rdquo / , is critically evaluated.The national regulation lags behind the modern world practice and the provisions of the regulation lead to uneconomical designs. The possible benefits of the modern practices are shown by application examples.