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Fault Analysis
Published in Ramesh Bansal, Power System Protection in Smart Grid Environment, 2019
In the per unit system the actual values of quantities are expressed as fractions of reference quantities, such as rated or full-load values. The per unit (p.u.) value is defined as: () per unit(p.u.)value=theactualvalue(inanyunit)thebaseorreferencevalueinthesameunit
Static Electric Network Models
Published in James A. Momoh, Mohamed E. El-Hawary, Electric Systems, Dynamics, and Stability with Artificial Intelligence Applications, 2018
James A. Momoh, Mohamed E. El-Hawary
It is usually convenient to use a per unit system to normalize system variables, to offer computational simplicity by eliminating units and expressing system quantities as dimensionless ratios. Thus X¯(in per unit)=X(actual quantity)X(base value of equation)
Elements of Transmission Networks
Published in George Kusic, Computer-Aided Power Systems Analysis, 2018
Engineering units of kilovolts (kV), kiloamps (kA), ohms (Ω), megavolt-amperes reactive (Mvar), and so on, are descriptive of the electrical aspects of equipment, but very often it is necessary to compare the operating point of equipment with its rated value, or to compare one piece of equipment with another. For example, a power transmission network contains interconnected voltage levels, 220 kV, 110 kV, 69 kV, and others, that are coupled by transformers, so if each voltage were compared to nominal or percent of rated voltage, it is possible to determine quickly which are within standard acceptable limits of ±5%. The per-unit system is applied to power systems to aid in comparing magnitudes and accommodating various voltages.
Fuzzy-Based Relaying Scheme for Transmission Line Based on Unsynchronized Voltage Measurement
Published in IETE Journal of Research, 2022
Biswapriya Chatterjee, Sudipta Debnath
In this work, an integrated approach for the protection of a transmission line has been proposed using voltage signal only. The detection and classification of faults has been done using a threshold-based FI scheme, which is evaluated using the DFT technique. DFT has widely been used to estimate the fundamental component of faulty signals. Also, the DFT algorithm is easy to implement due to its simplicity and accuracy [25]. The presence of ddc in the current signal deteriorates the performance of fault detection schemes based on current signals [25]. As this paper uses voltage signal only, DFT has been effectively used to develop a robust protection scheme for transmission line. Simulation results reveal that different faults can be easily detected without any complex mathematical computation to remove the ddc content from the voltage signal. Location estimation has been done using positive sequence voltage magnitude and FIS. Positive sequence components are widely used in fault analysis. Faulty zone has been identified by comparing the voltage magnitudes of the two ends. Proper fuzzy engine has been applied to locate the fault. Fuzzy logic system provides flexible mathematical framework for processing imperfect and imprecise information. The machine learning tools, viz. ANN, ANFIS, DT, and SVM require heavy training and/or optimal tuning of its parameters. FIS requires no training [19], which is a major advantage of using this technique. This algorithm is developed in per unit system; hence, the location accuracy is insensitive to the voltage level variation of transmission system. At the same time, it is also capable of estimating the precise value of fault location, as the mean percentage error is 0.63% under wide variations in system and fault parameters.