Abstract
The conventional distance protection scheme malfunctions sometimes in case of a fixed series capacitor compensated transmission line due to the change in relaying impedance of the protected line during faulty conditions. In order to mitigate this problem, a combined discrete Fourier transform and fuzzy (CDFTF) based algorithm has been proposed in this paper. This method has been tested on a 400 km, 735 kV series compensated transmission line network and WSCC 3-machine 9-bus system for all fault types using MATLAB/Simulink and PSCAD platforms, respectively. A fixed series capacitor is located at the middle of the protected line. The fundamental components of phase currents, phase voltages, and zero-sequence current are fed as inputs to the proposed scheme. The fault detection, faulty phase selection, and fault classification are achieved within 1/2–1 cycle of power frequency. The proposed CDFTF-based scheme is less complex and is better than other data mining techniques which require huge training and testing time. Test results corroborate the proposed scheme reliability with wide variations in fault location, fault resistance, fault inception angle, evolving faults, compensation level, and heavy load interconnection. The results discussed in this work indicate that the proposed technique is resilient to wide variations in fault and system conditions.
Highlights
Various schemes have been proposed earlier for fault classification in uncompensated and compensated transmission lines. ese algorithms usually require measurements at one end or two ends of lines
In [5], decision tree-based fault classification is proposed for a transmission line compensated by a fixed series capacitor
In [15,16,17,18], fault classification schemes based on fuzzy logic have been presented with different feature extraction techniques such as discrete Fourier transform [15], wavelet transform [16], higher order statistics [17], and angular differences among the sequence components of the fundamental currents [18]
Summary
In this work, combined DFT and fuzzy logic technique based on the fault classification scheme has been proposed for a series compensated transmission system. For knowledge of the ground involvement in the fault, a sequence analyzer is used to calculate the magnitude of zero-sequence current. The fundamental component magnitude of 3-phase currents and voltage signals are applied to the proposed fuzzy-based fault classification algorithm. E fuzzy based fault classifier (FFC) is designed separately for each phase and for ground identification. For identification and classification of faulty phase(s), the fundamental component of voltage and current using DFT is considered as input. If a fault occurs in the protected zone, three-phase voltage and current signals are acquired at the relay point which will be further preprocessed by fullcycle DFT for the feature extraction process. Erefore, a total of 129600 fault cases has been generated [(FL ∗ 20) ∗ (FR ∗ 9) ∗ (FIA ∗ 9) ∗ (FT ∗10) ∗ (% Xc ∗ 8)]
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