An algorithm based on traveling waves for transmission line protection in a TCSC environment

• New protection algorithm for transmission lines in a TCSC environment.
• Algorithm based on traveling waves, wavelets and probabilistic neural network (PNN).
• The TCSC harmonic frequencies and its interaction with traveling waves is analyzed.
• Algorithm accurate and fast to detect, locate and classify faults at any point in the line.
• Wavelets and PNN are reliable to discriminate and classify faults in complex power systems.

This paper describes a new relaying algorithm for the protection of transmission lines with a Thyristor Controlled Series Compensator (TCSC). The algorithm is based on the pattern of traveling waves generated during a fault event. Several tools like modal analysis, the discrete wavelet transform and a probabilistic neural network trained to work with the energy contained in the wavelet transform coefficients are applied to analyze the high frequency pattern generated during the fault. The proposed algorithm is capable of detecting, locating and classifying faults in a reliable way. The impact of harmonic frequencies generated by the TCSC in the protection algorithm was also analyzed. Several studies were carried out in order to validate and to assess the effect of several fault parameters on the algorithm accuracy. The obtained results show that for a sampling rate of 100 kHz, the algorithm error in calculating the distance to the fault is less than one percent of the total transmission line length. A higher sampling rate improves the algorithm accuracy.