Within the framework of implementation of the annual repair program and preparation for 2015-2016 autumn-winter season, power engineers of Ulyanovsk branch of IDGC of Volga, JSC (a member of Rosseti Group) replace insulators at 0.4-110 kV overhead power transmission lines. All in all, during the year, the power engineers plan to replace 18,846 insulators at power transmission lines of various voltage categories. In case of long-term operation insulators lose their insulating properties which may result in their damage and, consequently, technological failures in operation of electric equipment and interruptions in power supply to consumers. Worn out and defective elements of equipment are replaced with more modern analogs, environment resistant and more efficient in operation. So, at 110 kV power transmission lines insulators will be replaced with new ones made from tempered glass. The advantage of this insulation is that its damage may be detected upon visual examination without use of special diagnostic procedures which, in its turn, makes it possible to timely replace defective parts. Replacement of insulation as an integral part of the repair program will ensure improvement of reliability of power supply to consumers of the Ulyanovsk region, reduction of risk of technological failures and preparedness of the regional electric grid facilities for smooth and continuous operation of upcoming period of maximum loads.