An alternative transmission line design method is proposed that reduces the required conductor-to-ground clearance. In this method, third harmonic voltage is injected to the line, such that the peak amplitude of phase voltages is reduced while the fundamental component remains intact. The injected voltage does not influence the load or generation sides. The objective is to utilize the insulating strength of the conductor-to-ground clearance almost continuously rather than only during the crest voltage, as opposed to conventional ac lines. With this approach, for the same fundamental voltage level, the proposed line requires lower conductor to ground clearance. This could reduce the line construction capital investment by using shorter transmission towers. Furthermore, the existing ac lines could be upgraded with this method to increase their ground clearance, if desired. Injection of third harmonic voltage can also increase the loadability of existing ac lines, if the new phase-to-phase clearance is met. In this webinar, the operation of a power transmission line with injected third harmonic voltage is presented.