Apparatus for finding faults in overhead power transmission lines, containing; a helicopter-type aircraft, a control system and an apparatus (2, 3) for inspecting overhead power transmission lines, all connected to a battery which is attached to the outside of a case of the apparatus for finding faults, wherein the apparatus (2, 3) for inspecting overhead transmission lines is attached to the outside of the case, wherein the control system is configured to acquire, process and analyse data collected by controlling the operation of the apparatus (2, 3) for inspecting overhead transmission lines, wherein the apparatus for finding faults further contains a drive system located in the case and connected to a motor, which is powered by the battery and which is attached to the battery, the drive system is configured to lock the position of the apparatus for finding faults relative to a lightning-protector cable or a power conductor and to move the apparatus for finding faults along the overhead power transmission lines, wherein the apparatus for finding faults contains the case, the battery and the motor, characterized in that the case is additionally outfitted with guides configured to set the trajectory of the lightning-protector cable or power conductor inside the apparatus for finding faults in overhead power transmission lines to a position permitting locking of the apparatus for finding faults on the lightning-protector cable or power conductor, in that the drive system consists of two traveling rollers, which are configured to be rotated by the motor for moving the apparatus for finding faults, and of a clamping roller, which is configured to move relative to the lightning-protector cable or the power conductor, in a vertical plane with respect to a vertical position of the helicopter-type aircraft and to clamp the lightning-protector cable or the power conductor to the traveling rollers, wherein the guides are configured that, when the drive system has lowered the clamping roller, the lightning-protector cable or a power conductor is able to fall between them, is able with the aid of the guides to bypass the clamping roller and is able to fall between the clamping roller and the travelling rollers in order to clamp the lightning-protector cable or the power conductor to the traveling rollers by lifting the clamping roller. a helicopter-type aircraft, a control system and an apparatus (2, 3) for inspecting overhead power transmission lines, all connected to a battery which is attached to the outside of a case of the apparatus for finding faults, wherein the apparatus (2, 3) for inspecting overhead transmission lines is attached to the outside of the case, wherein the control system is configured to acquire, process and analyse data collected by controlling the operation of the apparatus (2, 3) for inspecting overhead transmission lines, wherein the apparatus for finding faults further contains a drive system located in the case and connected to a motor, which is powered by the battery and which is attached to the battery, the drive system is configured to lock the position of the apparatus for finding faults relative to a lightning-protector cable or a power conductor and to move the apparatus for finding faults along the overhead power transmission lines, wherein the apparatus for finding faults contains the case, the battery and the motor, characterized in that the case is additionally outfitted with guides configured to set the trajectory of the lightning-protector cable or power conductor inside the apparatus for finding faults in overhead power transmission lines to a position permitting locking of the apparatus for finding faults on the lightning-protector cable or power conductor, in that the drive system consists of two traveling rollers, which are configured to be rotated by the motor for moving the apparatus for finding faults, and of a clamping roller, which is configured to move relative to the lightning-protector cable or the power conductor, in a vertical plane with respect to a vertical position of the helicopter-type aircraft and to clamp the lightning-protector cable or the power conductor to the traveling rollers, wherein the guides are configured that, when the drive system has lowered the clamping roller, the lightning-protector cable or a power conductor is able to fall between them, is able with the aid of the guides to bypass the clamping roller and is able to fall between the clamping roller and the travelling rollers in order to clamp the lightning-protector cable or the power conductor to the traveling rollers by lifting the clamping roller.