Abstract
This paper proposes a new regression-based method to estimate resistance, reactance, and susceptance parameters of a 3-phase cable segment using phasor measurement unit (PMU) data. The novelty of this method is that it gives accurate parameter estimates in the presence of unknown bias errors in the measurements. Bias errors are fixed errors present in the measurement equipment and have been neglected in previous such attempts of estimating parameters of a 3-phase line or cable segment. In power system networks, the sensors used for current and voltage measurements have inherent magnitude and phase errors whose measurements need to be corrected using calibrated correction coefficients. Neglecting or using wrong error correction coefficients causes fixed bias errors in the measured current and voltage signals. Measured current and voltage signals at different time instances are the variables in the regression model used to estimate the cable parameters. Thus, the bias errors in the sensors become fixed errors in the variables. This error in variables leads to inaccuracy in the estimated parameters. To avoid this, the proposed method uses a new regression model using extra parameters which facilitate the modeling of present but unknown bias errors in the measurement system. These added parameters account for the errors present in the non- or wrongly calibrated sensors. Apart from the measurement bias, random measurement errors also contribute to the total uncertainty of the estimated parameters. This paper also presents and compares methods to estimate the total uncertainty in the estimated parameters caused by the bias and random errors present in the measurement system. Results from simulation-based and laboratory experiments are presented to show the efficacy of the proposed method. A discussion about analyzing the obtained results is also presented.
Highlights
Accurate estimates of line parameters are useful in improving the performance of power system monitoring and protection applications like accurate relay settings and fault location [1]
To facilitate the first step of temperature based dynamic line rating (DLR), this paper proposes a method to estimate the resistance of 3-phase cable system utilizing real-time phasor measurement unit (PMU) measurements
If the residual vector seemed to satisfactorily pass the tests to check the assumptions a − d, the uncertainty of the parameters was calculated considering the presence of random errors and bias errors in modeling caused by exclusion of the correction coefficients K2, K3 and K5
Summary
Accurate estimates of line parameters are useful in improving the performance of power system monitoring and protection applications like accurate relay settings and fault location [1]. Distance relays have reach zone settings based on the known positive sequence impedance of the protected line segment. High accuracy impedance estimates of the protected line would assist in a more accurate setting of the impedance in the distance relay which protects the line. It is known that accurate pre-fault line impedance and knowledge about impedance of loads on the line could be utilized to calculate the location of the faults more precisely [2]. A novel idea of utilizing real-time resistance estimates to monitor the temperature of an overhead line or a cable and facilitate dynamic line rating (DLR) was first mentioned in [3]. It was presented that the relationship between the conductor resistance and Energies 2019, 12, 4573; doi:10.3390/en12234573 www.mdpi.com/journal/energies
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