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An experimental investigation was performed on a UHV tower model for the EMTP multiconductor calculation of lightning overvoltage at substations associated with backflashover at an adjacent transmission tower. The various lightning surge response characteristics were measured on an actual UHV tower, and parameters of a multistory transmission tower model that can reproduce voltages across the insulator strings, voltages of the crossarms, and voltages of the power lines were determined. A value of 120 R was determined as the surge impedance at each section of the multistory tower model, which closely agreed with the tower surge impedance measured for the UHV tower alone.

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A control device for point-on-wave closing or autoreclosing of shunt reactor compensated transmission lines for reduction of closing overvoltages is presented. The device is the first of its kind. It was put into field service successfully more than a year ago. Development aspects and basic investigations on the relevant transient switching phenomena are presented. The algorithm employed works independently of the shape of the voltage signal to be synchronized on by means of pattern recognition. Peculiarities of the hardware are high redundancy and a system to bypass the controller at any malfunction of the electronic circuits. The efficiency of the controller was verified by a combination of transient network analyser tests and EMTP simulations showing the ability of the device to suppress overvoltages. This procedure is generally recommended for future application o f control devices as a type test procedure.