In Nordic Countries, distribution networks are traditionally unearthed and increasingly compensated. For such networks, switching their neutral point to the earth is practically applied through a resistor for better selectivity functions of earth faults. In this paper, the neutral switching and consequently an arrival time of the aerial mode traveling wave reflected from the fault point are utilized to accurately determine the earth fault distance. A concept to create traveling waves is implemented by earthing the neutral via a controlled-thyristor that provides a short period of high fault current and produces traveling waves to estimate the fault distance. Much higher transient signals are generated by earthing through an opposite charged capacitor. A capacitor-resistor divider is utilized to measure the reflected surge over a heterogeneous distribution feeder. An adaptive setting is proposed for stamping the arrival surge. The results provide evidence of the efficacy of the proposed fault distance estimation. Index Terms-Unearthed and compensated MV networks, earth faults, fault distance estimation, traveling waves. 0885-8977 (c)
In this paper, an accurate model for computing dielectric constant of dielectric nanocomposites is presented. The effect of interaction zone between the nanofiller and the resin material is calculated and taken into consideration in the developed model for polymer and ceramic resins. Also, the effect of filler volume fraction, filler dielectric constant and particle shape is studied through the proposed model. Finally, the validity of the proposed model for evaluating the dielectric constant of a uniform composite system of discrete particles dispersed within a matrix is achieved by comparison with experimental results. The proposed model shows simplicity and gives accurate results as compared to the other theoretical models.
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