The majority of medium-voltage overhead lines are currently operated with AlFe conductors which have a simple construction and which rank among the cheapest versions of overhead lines from the point of view of initial investments. These overhead lines can be susceptible, however, to faults primarily in mountain and wooded areas, with an ensuing decrease in safety and operations reliability, as well as with limitations to the electric power supply. This draws attention to outdoor overhead lines with covered conductors, which are relied upon for use for connecting "defined" systems (SMART GRIDS) with an external electric power system. These conductors, with mostly XLPE and PE basic insulation, are able to resist both mechanical and electric strain caused by falling trees or branches and consequently their total number of faults is significantly lower. Massive usage of overhead lines with covered conductors is currently contradicted by prevailing difficulties in detecting faults. This article describes the possibility of detecting covered conductor faults and verifying the methodology under both laboratory and real conditions.

Presentation of partial-discharge (PD) signals is one of the most conclusive indicators of defects and the ongoing degradation process in electric insulating systems [3], [7],
[8]. Methods using PD detection consequently rank among the most effective diagnostic methods to directly estimate the condition of the insulation system [5], [9]. Continuous monitoring of electric device conditions has particular importance for industrial distribution of electric power in terms of safety and reliability. Detection and subsequent processing of PD signals constitute the main principle of the new method to determine mediumvoltage (MV)-covered conductor faults. The primary aim of this proposed methodology is automatic online detection of covered conductor faults such as:
• trees falling onto a covered conductor;
• branches falling onto a covered conductor;
• covered conductors falling onto the ground.

Please, see full paper lenght here