No 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.

DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:

Incorrect values of cable harmonic impedance can lead to wrong conclusions when assessing an impact of current distortion on the power network. A theoretical derivation of resistance and reactance for harmonic frequencies is not sufficient as it neglects operating conditions of cables as well as their configuration and actual installation pattern. In this paper, a noninvasive procedure for estimating parameters of the low-voltage cable is proposed. On contrary to invasive methods, the proposed technique does not require any external sources of harmonic excitation, and consequently, it does not introduce additional disturbances to the system. A disconnection of the cable is not required as the procedure meant to be performed online. The methodology employs natural variations of harmonic currents and voltages; however, the impedance angle is preserved due to the utilization of synchronized measurement samples. The developed signal processing algorithm provides noise reduction capabilities and smoothing of the output in presence of fluctuating harmonics. In addition, an attention is given to the metrological characterization of the measurement system and evaluation of uncertainty of impedance values. The results of the laboratory experiment indicate that for selective harmonics the variations of impedance estimates are no more than 10 m , which is in the range of calculated uncertainty values. The practical applicability of the method is discussed together with its limitations.

This paper presents a method to estimate parameters of a 3-phase line segment using PMU data. The novelty of this method is that it is capable of giving accurate estimates even in the presence of non-calibrated instrument transformers at both ends of the line whose ratio and phase correction coefficients are unknown. To do so, this method adds extra parameters in the regression model. These added parameters account for the errors present in the non-calibrated instrument transformers. In case the instrument transformers are calibrated at one end of the line, then the correction coefficients at the other end could also be estimated. The presented method does not require reversal of current flow direction in the line as a necessary condition. Results from simulated and laboratory experiments are presented to show the efficacy of the method. A discussion about analyzing the obtained results is also presented.

No abstract

DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:

We demonstrate high power direct diode-pumped femtosecond laser based on a commercially available configuration and pumped by multi-diode laser modules delivering high brightness and average power. The multi-diode modules employ beam-combining scheme preserving linear polarization and focusing properties of individual laser diodes. Stable passive Kerr lens modelocked (KLM) laser operation was demonstrated, producing 30 fs pulses at ∼300 mW average output power. A simple approach to numerical modelling of KLM laser operation in cases when longitudinal pump beam exhibits strong astigmatism is also discussed.