Sampling Rate Impact on Estimation of Untransposed Transmission Line Parameters Based on Fault Records
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Sampling Rate Impact on Estimation of Untransposed Transmission Line Parameters Based on Fault Records Eduardo C. M. da Costa1 · Sergio Kurokawa2 · Renato M. Monaro1 · Silvio G. Di Santo1 Received: 6 June 2016 / Revised: 10 November 2017 / Accepted: 19 February 2018 © Brazilian Society for Automatics–SBA 2018
Abstract This paper highlights the sampling rate impact over an estimation method based on modal analysis techniques applied on untransposed three-phase transmission line. The analysed method represents a transmission system in the modal domain as three independent propagation modes that are modelled as three single-phase transmission lines using a suitable π equivalent. The estimation procedure is carried out in the modal domain, without the explicit modelling of the phase mutual parameters, which means a significant simplification on the calculation process using the least-square solution method. Since the modal parameters are identified, the self- and mutual parameters can be calculated using the same modal transformation matrix during the line decoupling. The method estimation accuracy is evaluated for a range of sampling rate associated with the relays records. Keywords Sampling rate · Parameter estimation · Line parameters · Synchronized measurements · Fault records
1 Introduction The knowledge of the electrical parameters of power transmission lines is fundamental for reliable operation of power grids. The accurate parameter identification of transmission lines is directly associated with various issues in power system analysis, such as fault detection/location in overhead transmission lines and underground cables; correct parametrization of protection systems; determination of the insulation coordination; setting of the surge protection against lightning and other impulsive electromagnetic transients. The electrical parameters of transmission lines can be calculated based on the geometrical and physical characteristics of the line (line height, geometry of the tower/phases, soil characteristics, conductor properties, etc.) and taken into account the soil and skin effects. The conventional method for calculation of the line parameters is based on the approach using the Bessel function and the correction term of Car-
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Renato M. Monaro [email protected]
1
Escola Politécnica, Universidade de São Paulo, São Paulo, SP, Brazil
2
Faculdade de Engenharia de Ilha Solteira, Universidade Estadual Paulista, Ilha Solteira, SP, Brazil
son. However, the calculation of the earth-return impedance using the trigonometric series of Carson results in some inaccuracies resulting from approximations in the variable environmental conditions, non-homogeneous soil conductivity and in line geometrical structure (Hofmann 2003; Rachidi and Tkachenko 2008). Another way for identification of the line parameters is to estimate them based on current and voltage measurements at the line ends. These measurements are usually obtained using phasor measurements units—PMUs—and global position system—GPS—or by means of fault records of
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