Advances in Electrical and Computer Engineering Volume 15, Number 3, 2015 Fault Detection and Localization in Transmission Lines with a Static Synchronous Series Compensator Enrique REYES-ARCHUNDIA, José Leonardo GUARDADO, Edgar Lenymirko MORENO- GOYTIA, José Antonio GUTIERREZ-GNECCHI, Fernando MARTÍNEZ-CÁRDENAS Instituto Tecnológico de Morelia, Ave. Tecnológico 1500, 58120, Morelia, México ereyes@itmorelia.edu.mx 1 Abstract—This paper proposes a fault detection and localization method for power transmission lines with a Static Synchronous Series Compensator (SSSC). The algorithm is based on applying a modal transformation to the current and voltage signals sampled at high frequencies. Then, the wavelet transform is used for calculating the current and voltage traveling waves, avoiding low frequency interference generated by the system and the SSSC. Finally, by using reflectometry principles, straightforward expressions for fault detection and localization in the transmission line are derived. The algorithm performance was tested considering several study cases, where some relevant parameters such as voltage compensation level, fault resistance and fault inception angle are varied. The results indicate that the algorithm can be successfully be used for fault detection and localization in transmission lines compensated with a SSSC. The estimated error in calculating the distance to the fault is smaller than 1% of the transmission line length. The test system is simulated in PSCAD platform and the algorithm is implemented in MATLAB software. Index Terms— fault location, flexible AC transmission systems, transmission lines, wavelet transform, waves propagation. I. INTRODUCTION The introduction of power electronics in transmission networks has increased significantly over the last two decades. Some examples of these new developments are the extensive use of power converters and Flexible AC Transmission Systems (FACTS) under the framework of the smart grid concept. These developments also represent new challenges to other electrical engineering areas. For example, in power system protection is of great interest to assess the impact that dynamic compensators may have on conventional protection schemes. This is because FACTS controllers, like the Thyristor Controlled Series Compensator (TCSC), can modify the impedance measured by conventional distance relays [1-2]. This is also true for the case of Static Compensators (STATCOM); for example, in [3-4] the authors demonstrate that these devices have an impact in the tripping characteristic of protective relays. On the other hand, in [5-6] the authors have demonstrated that the SSSC also affects the tripping characteristics of distance relays. From the above, power electronic devices can have an impact in the characteristics of modern protection schemes. 1 This work was supported by CONACYT, DSA and the Tecnológico Nacional de México. The development of new protection algorithms for power transmission networks with power electronic devices in service is a need. In [7], Ghorbani et al proposed a method for protecting power transmission lines with a SSSC in service. This approach is based on compensating the zero sequence voltage injected by the SSSC. Although this method was proposed initially for fault detection and localization, its main drawback is the long times required (≈ 60 ms) for fault localization, as shown in [8]. In [9], Zonkoly and Desouky used optimization techniques and the wavelet transform based in entropy in order to discriminate whether the fault is before or after the SSSC in a series compensated transmission line. It should be mentioned that this approach was not capable to pin point the precise distance to the fault in order to facilitate repairs and service restoration. In general, fault detection and localization in transmission lines with a SSSC device in service is a great challenge, because this device injects voltage and current to the transmission network which may lead to over-reach in conventional distance relay and therefore malfunctioning. In order to overcome these difficulties, new alternative techniques are being continuously explored. A trend of development is based on sampling at high frequencies the faulted signals for further analysis and processing. Thus, after fault inception two electromagnetic waves are produced which travel in both directions along the transmission line. Relays at both ends of the line measure these high frequency pulses (traveling waves), and by using reflectometry principles and digital signal processing techniques, the exact distance to the fault can be calculated. This approach requires high frequency sampling rates (>20 kHz). In addition, the Wavelet Transform (WT) is used quite frequently to discriminate the high frequency components due to the transient fault period from the low frequency components generated by power electronic devices, since both signals are superimposed to the power frequency signal (50-60 Hz). The WT has been successfully applied for fault detection and localization in overhead transmission lines [10], cables [11], distribution lines [12], STATCOM and TCSC compensated transmission lines [13-14]. As far as the authors know, never before this approach has been applied successfully to transmission lines with a SSSC in service. This paper proposes a fault detection and localization 17 1582-7445 © 2015 AECE Digital Object Identifier 10.4316/AECE.2015.03003 [Downloaded from www.aece.ro on Monday, August 31, 2015 at 15:53:41 (UTC) by 200.33.171.57. Redistribution subject to AECE license or copyright.]