Contents lists available at ScienceDirect Electrical Power and Energy Systems journal homepage: www.elsevier.com/locate/ijepes An enhanced fault detection and location estimation method for TCSC compensated line connecting wind farm Biswajit Sahoo ⁎ , Subhransu Ranjan Samantaray Schools of Electrical Sciences, Indian Institute of Technology, Bhubaneswar, India ARTICLE INFO Keywords: TCSC compensated line Travelling wave Fast discrete S-transform Fault location Real-time digital simulator (RTDS) Doubly-fed induction generator (DFIG) windfarm Wide area protection (WAP) Phasor measurement unit (PMU) ABSTRACT The paper presents a new approach to enhance the fault detection, and location determination based on tra- velling waves using Fast Discrete S-transform (FDST) for TCSC compensated lines connecting to wind farm. The FDST is applied to the modal components of measured currents at each terminal to detect the arrival time of the first travelling wave (transient) produced by the fault. The proposed method includes detecting the terminal with fastest arrival time of wave to identify the faulted section and estimate the fault location by using proper distance index. The simulation results have demonstrated good performance of the proposed scheme under different fault locations, fault resistances, fault inception angles, fault types, faulted sections, variations in TCSC parameters and changing wind speeds. The performance validation on the real-time digital simulator (RTDS) platform en- hances the applicability of the proposed protection scheme for the TCSC based compensated line integrated with wind farm. The performance comparison with the conventional travelling wave fault location algorithms using Continuous Wavelet Transform (CWT) shows potential ability of the proposed method. 1. Introduction In modern era, the development of electric power transmission fa- cilities has been confined, because of energy, environmental, and reg- ulatory issues [1]. Among the FACTS devices, Thyristor Controlled Series Capacitors (TCSC) is one of the most effective tools to provide compensation to transmission systems that enhance system stability, power transfer capability, reduce power system oscillations and trans- mission losses [2]. However, the introduction of series compensation raises several concerns for the protection relays using traditional methods because of the sudden changes initiated by the corresponding TCSC control mechanisms in system parameters such as load currents and line impedances. There are several operating modes of TCSC in normal and faulted conditions namely bypass mode, blocked mode, capacitive boost mode and inductive boost mode. During system dis- turbances, basically when TCSC operation switches between different modes, TCSC dynamics have a notable effect on the power system protection causing problems like overreaching, loss of security and hence mal-operation of relay [3]. In recent times, wind-farms are also growingly unified to the grids at different levels of voltage. Integration of such wind-farms has a sig- nificant advantage as it enhances the reliability of the system. The trouble that appears in unifying wind farms is basically because of uncontrollable wind speed which continually changes throughout a day leading to fluctuation in wind-farm output power which has a nonlinear relationship with the wind speed. When such a farm is connected to the grid through a transmission line, the transmitted power and the relay end voltage fluctuates continually. Furthermore, wind-farm generation capacity also significantly influences the tripping boundary of the dis- tance relay. So the protection task becomes more complex and chal- lenging [4]. Thus, when both TCSC and wind-farms are integrated to- gether in the transmission line the system becomes more complicated and the conventional relaying scheme is greatly affected. Various fault location algorithms have been devised in past decades such as extracting fundamental frequency current and voltage phasors [5], using differential equations of transmission line for calculation of line parameters [6] or artificial intelligence techniques like neural network [7]. Among these, impedance-based schemes are the most used by researchers and utilities because of their simplicity and low com- putational complexities [8]. However, these fault-location methods are normally sensitive to power system load flow, high fault resistance, and series compensation [9]. To mitigate this issue, the travelling-wave- based fault locators (FLs) have been growingly used as an substitute, as their precision depends primarily on time synchronization and the data- acquisition system sampling rates [10]. Apart from the conventional ones, a differential relaying scheme based on the transient energy extracted using the discrete wavelet transform (DWT) in the current signals is proposed for transmission line http://dx.doi.org/10.1016/j.ijepes.2017.10.022 Received 5 July 2017; Received in revised form 9 October 2017; Accepted 16 October 2017 ⁎ Corresponding author. E-mail address: bs15@iitbbs.ac.in (B. Sahoo). Electrical Power and Energy Systems 96 (2018) 432–441 0142-0615/ © 2017 Elsevier Ltd. All rights reserved. MARK