An intelligent protection scheme for series-compensated transmission lines connecting large-scale wind farms

Abstract

Series-compensated transmission lines (SCTLs) are increasingly preferred for transmitting bulk amounts of electricity generated from the present-day large-scale wind farm to the utility grid due to several technical and economic benefits. However, when a fault occurs in such a wind farm-integrated SCTL, the impedance across the metal oxide varistor (MOV)-protected series capacitor varies non-linearly. Also, the fault current contributed from the wind farm side is quite different compared to the grid side. Consequently, the widely used fixed impedance-based distance relaying schemes showed limitations when used for protecting such crucial TLs. In this paper, the impacts of series compensation and wind farm integration on distance relay are investigated, and this paper proposes an intelligent relaying scheme using only the current measurements. In the proposed scheme, the fault detection task is performed using the signs of the half-cycle magnitude differences of the line end positive-sequence currents, and the fault classification task is performed using only the local current measurements processed through the Fourier–Bessel series expansion (FBSE) bagging ensemble (BE) classifier. The non-stationary components present in the current signal at the initiation of a fault are captured by calculating FBSE coefficients, and the singular value decomposition is applied for dimensionality reduction of the feature set. Finally, the extracted features are used by the BE classifier for fault classification. The method is evaluated in MATLAB/Simulink® on numerous fault and non-fault data simulated in two-bus systems and also validated through the OPAL-RT (OP4510) manufactured real-time digital simulation platform. The obtained results (response time for fault detection and classification <10 ms), including the comparative assessment results (fault detection accuracy =100% and fault classification accuracy =99.37%), justify the effectiveness of the proposed relaying scheme in protecting the wind farm-integrated SCTLs.

Advanced Protection for the Smart Grid

“…The step size is similar to the selection of the field of view, which needs to be selected adaptively according to the fish population and concentration distribution. Therefore, as shown in (15), this paper introduces the step size adjustment factor, which enables the step size to be adjusted depending on the change in the field of view. Meanwhile, the step of redefining the step size is eliminated, and the algorithm becomes more concise.…”

“…The value for the current amplitude of phase A and I 2 /I 1 , I 0 /I 1 ratios at the sending end provide a maloperation for the device. Furthermore, the current amplitude of phase A gives (10)(11)(12)(13)(14)(15) % of its values at normal operation.…”

“…In addition, the behavior of the traditional protective relay under these simulated faults was examined, as shown in Figure 4, by computing the DFT-based amplitude for threephase currents and ratios (I 2 /I 1 , I 0 /I 1 ) at both ends. The value of the current amplitude of phase A gives (140-160) % from its value at normal operation at the sending end, which is considered a shunt fault, but the value of the same phase A gives (10)(11)(12)(13)(14)(15) % from its values at normal operation at the receiving end, which is considered a series fault. Moreover, the values of both ratios (I 2 /I 1 , I 0 /I 1 ) at both ends resulted in a malfunction for both protection devices.…”

“…The recorded amplitude for phase A at the sending end gives (10)(11)(12)(13)(14)(15) % of its values at normal operation, demonstrating that its devices cannot detect this fault condition. However, at the receiving end, the recorded amplitude for the same phase gives (140-160) % of its value at normal operation, which is considered a shunt fault.…”

“…The presented scheme is embedded in the PFD unit on both ends to detect and identify these faults when one or two conditions are verified. In the sending end PFD unit, the first condition is proving if the obtained sending end current for phase a at fault is equal to or less than (10)(11)(12)(13)(14)(15) % of the sending end current for phase A at normal operation. The second condition is verifying if the obtained receiving end current for phase A at fault is equal to or more than (140-160) % of the receiving end current for phase A at normal operation.…”