Assessing the remaining life time of 220 kV and 400 kV OHTL and the required measures for the coordination of remaining life times of the various constructive elements of lines

The paper makes an analysis of the eighteen 220 and 400 kV overhead electric lines belonging to C.N. Transelectrica - Sibiu Branch (TSO) on the basis of a unitary methodology for assessing their technical state and taking into consideration the different types of expertise conducted until now, including the multispectral analysis from the helicopter of seven lines. Performance criteria for insulators, risk analysis of special route area and maintenance strategies to extend the normal life time have been established. Considering that different constructive elements of the line, located in a certain area, have different life times, concrete measures of lines alignment to obtain convergence of the partial remaining times have been established. Special attention was given to lines with major importance in the national electric system, proposing measures to increase their reliability based on detailed expertise methodology.