A method is provided for protection in a mixed power transmission line by controlling a switching device connected thereto through an Intelligent Electronic Device (IED). The mixed line has two or more sections with at least one overhead section (10A) and at least one underground section (10B), wherein every two consecutive sections are connected at a junction (10C). The method is implemented by the IED (14), which receives a signal from a measurement equipment. The IED detects a travelling wave from the signal, and determines a first peak of the travelling wave and at least one a peak width, a rise time and a discharge time of the first peak. The IED identifies the section with the fault based on a comparison of at least one of the peak width, the rise time and the discharge time with a corresponding threshold value of each junction, and controls the switching device based on the comparison.