Detection of partial discharge in covered conductor medium voltage distribution lines

This paper presents a method for detecting the location of partial discharge in medium voltage covered conductor (CC) lines. The use of CCs is increasing day by day due to higher reliability, less susceptibility to climate change, and fewer short circuit faults than overhead lines.  CCs are commonly used in forests.  The lack of rapid failure detection of protection relays when the tree falls on the CC is one of its most important disadvantages. Scratching of CC insulation due to a tree falling on it usually leads to partial discharge (PD), which can lead to short circuit faults in the long run. Because the CC may be installed in an impassable path, it is difficult to detect a tree falling on the CC or the growing foliage colliding with the CC, and if not done promptly, it can lead to a short circuit fault. In this paper, for the first time, while obtaining a three-phase CC model, the falling of a tree on CC is simulated by applying a PD pulse source at the desired location. The proposed method is that first the PD signal is applied at the location of the electrical posts and the waveform obtained at the end of the line is stored and then their FFT is calculated as reference signals. To find the location of an unknown location PD, the signal obtained at the end of the line is saved after eliminating its main component of frequency and noise. Afterward, its FFT is calculated. Then, using the method of maximum correlation of signals, the nearest electric pole to the location of PD is determined. The proposed method was applied in different cases in a sample system, and satisfactory results were obtained.