Abstract
This paper discusses a critical study of fault detection and fault time analysis in a Unified Power Flow Controller (UPFC) transmission line. Here the Discrete Wavelet Transform (DWT) and Discrete Fourier Transform (DFT) approach are used for processing the faulty current signal to obtain fundamental current signal. The extracted fault current signals from the current transformer are fed to DWT and DFT approach for computing spectral energy (SE). The differential spectral energy (DSE) of phase currents are evaluated by taking the difference of SE obtained at sending and receiving end. The DSE is the key factor for deciding the fault in any of the phase or not. The Daubechy mother wavelet (db4) is used here because of its high accuracy of detection with less processing time. The novelty of the scheme is that it can accurately detect the critical fault variation of the line. Number of simulations are validated at the extreme condition of the line and compared to other conventional existing scheme. Multi-phase fault in double circuit line, CT saturation, UPFC operating condition (series voltage and angle), UPFC location and wind speed variation including wind farm simulation are validated to verify the performance of the scheme. The advantages of the scheme is that it works effectively to detect the fault at any stage of critical condition of the line and fault detection time remains within 20 msec (less than one cycle period). This scheme protects both internal and external zone including parameter variation of the line.
Highlights
Protection of Transmission line including flexible AC transmission system (FACTS) controller [1] is a major challenging task for the researchers a days
It is always preferred to install middle of the transmission line. As you know it can actively control the voltage and frequency by compensating reactive and active power of the line uniformly. For this reason the optimal location we have considered the Unified Power Flow Controller (UPFC) at the middle of the transmission line
The scheme operates satisfactory under different line parameters such as Rf (1 Ω -100 Ω) which is relatively high, SI (0–30% increase of Normal SI), FIA (0–90 degree), reverse power flow, effect of UPFC operating condition, effect of CT saturation, multiphase fault and effect of UPFC location which is the extreme side parameter variation case of strong and weak system of UPFC integrated transmission line
Summary
Protection of Transmission line including flexible AC transmission system (FACTS) controller [1] is a major challenging task for the researchers a days. The process is not easy to filter out the high frequency signal from noisy signal Another approach of ANN and fuzzy logic are proposed [5, 6] but this scheme fails to provide accurate results because of inaccurate phasor input data and large numbers of neurons. The strong inspiration for developing an algorithm which detects fast response time to detect all shunt types fault including the variation of UPFC parameter and entire line protection. The section-1 discusses the introduction, section-2 signal processing DWT and DFT algorithm, Section-3 the methodology for fault detection and response time, Section-4 simulation results and Section-5 describes the conclusion part of the paper. Modified wavelet is expressed as qffiffiffiffiffiffiffiffiÀffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiÁffiffi φk;lðtÞ 1⁄4 1= ak0φ t−lb0ak0=ak0
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