Identification Method of Lightning Stroke and Short-circuit Faults Using S-transformed Characteristics

The ultra-high-speed protection of the power transmission system may be interfered by lightning strokes on lines. It is limited to distinguish the lightning stroke and the common short circuit fault based on the current traveling-waves. We proposed a new method to distinguish the lightning strikes and common short-circuit faults on the basis of the characteristic of the bus voltage signals using S-transform. Through extracting the feature of the voltage signal using time-frequency contour and amplitude envelope vectors by S-transform, an idiographic method for identification of the three types of transient processes was proposed. If there is high frequency component in the voltage signal, the transient process is caused by lightning stroke. If the modified first order central moment BF 0, there is fault, and if BF 0 there is not fault. According to the S-transformed characteristic of bus voltage the different transient type can be identified exactly. The methods of both feature extracting and recognition algorithm were proposed also. The IEEE RBTS-6 as the standard testing system was used to illuminate the run-of-mill principle through the PSCAD/EMTDC. The simulation results indicate that the proposed method is effective with reasonable accuracy and its accuracy is not affected by fault types, transient resistance condition and fault location. The instrument of the power quality can be equipped on the system to evaluate the wave of the bus voltage, this paper provide the basic theory to distinguish the lightning strikes and the short-circuit fault through the voltage wave observed from the power quality instrument.