حفاظت از خطوط انتقال هوایی در برابر صاعقه با استفاده از سیم های زمین

• An external lightning protection system of OH lines is analyzed.• Dimensioning is performed by using both EMTP-ATP and rolling sphere method.• Experimental verification from the aspect of shielding failures is performed.• Possible applications of the analyzed protection system are noticed.• Disadvantages of the analyzed protection system are noticed.In this paper, a new kind of overhead transmission line (OHL) lightning protection system based on external ground wires is analyzed. Instead of a standard ground wire, two ground wires placed at the top of separate external towers located at both sides of the protected line are used. This type of protection should be applied in specific circumstances for protection of short OHL sections which are highly endangered by lightning. The distance between external protection system and OHL is calculated by using EMTP-ATP. Calculations are performed in order to avoid flashovers from the point where lightning strikes the external protection system to the protected OHL. A rolling sphere method is used to calculate the height of external ground wires above OHL phase conductors to avoid shielding failures. An experiment in a high voltage laboratory is performed to verify the dimensions of the external protection system from the aspect of shielding failures. According to the results of simulation and experiment, the optimal dimensions of the external protection system are determined.