Sensitivity analysis of a fault impedance measurement algorithm applied in protection of parallel transmission lines

Global Sensitivity Analysis (GSA) of fault impedance measurement algorithms that are used in Intelligent Electronic Devices (IEDs) is presented in this seminar. The proposed methodology is useful when evaluating the characteristic of the algorithm for distance protection of a transmission line as affected by additional parallel line. The methodology is useful when parameters are uncertain. The computation in GSA relies on Quasi-Monte Carlo (QMC) technique to calculate variance of the measurement error as well as parts of this variance that are contributed by uncertainty of individual parameters. Different conditions will affect variation of parameters in this problem, e.g. load flow angles, geometry of towers, non-homogeneous system, transmission line parameters, error in relay setting as well as fault resistance which cannot be measured. Pre-screening process using Morris method is required in this experiment to remove non-influential parameters, and reducing the factor space, before applying the variance based sensitivity analysis using QMC. Fault impedance as function of uncertain parameters (i.e. factors), which are represented with specific distribution functions, is calculated during the fault simulated in DIgSILENT PowerFactory. Samples in the factor space are generated using the Sobol quasi-random sequence in SIMLAB software tool. The simulation of the transmission line faults and the calculation of the performance index of the algorithm are automated using the program developed in DIgSILENT Programming Language (DPL). Calculation of sensitivity measures has been done in SIMLAB. This technique is applied to study the fault impedance measurement of SEL-421.http://apscom2012.org