Varecki - state University "Lviv PC, politechnica" UKRAINE
Jurahosk - state University "Lviv PC, politechnica" UKRAINE
Kens - state University "Lviv PC, politechnica" UKRAINE

LvivEnergo System ha; bees; commissioned a Multipurpose Static Thyrstor Compensator (STC) to provide automatic , continuous voltage control on a substation buses, re duct. i on of power losses and heating of icy wire; of outgoing ail Iines in mountain region of i of western ukraine. This paper descibes engineering studies which were conducted to ._elect the design and relay protection, determine Harmonic filtering requirements and to simulate transient. overvoltage due to ground fault, The studies have shown that. the STC at such conditions meets the specified requirements Field tests were confirmed the design requiremens hi oh must. be taken into acount.