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Calculation of geomagnetically induced current (GIC) flowing through power system during the geomagnetic storm has attracted more attention recently. However, for high voltage power systems with transmission lines over hundreds or even thousands of kilometers, the earth model and geomagnetical field generally vary significantly. So, it is essential to take them into consideration using limited earth survey sites and geomagnetic observatories. To address this problem, a Kriging method is introduced in this paper to make earth model and geomagnetical field interpolations. It has the characteristic of spatial autocorrelation by considering not only the distances between predicted points and training points but also the distances between training points themselves. Finally, a case study of the Central China 1000 kV ultra-high voltage (UHV) grid is carried out to illustrate the applicability and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The multi-terminal hybrid LCC/MMC HVDC has been applied to overcome the simultaneous commutation failure problem caused by the multi-infeed LCC-HVDCs in the East China. The high-speed and selectivity line protection method is required for the multi-terminal hybrid HVDC system. In this paper, the reflection and refraction of the fault traveling waves at different kinds of line terminals are characterized by transfer functions. Then the fault voltage as well as its first peak time at different line terminals when different internal and external faults occur are derived respectively. The conclusion proves that the first peak time of line-mode fault component voltage (FPTV) for internal faults is smaller than that for external faults, which is independent of fault impedance and fault type as well. Therefore, a FPTV-based non-unit ultra-high-speed dc line protection method is proposed. The algorithm is implemented in the developed protection prototype and validated in the Kun-Liu-Long three-terminal hybrid HVDC RTDS test system. The test results show that the proposed method can fast and correctly identify line faults in the multi-terminal hybrid HVDC system, even with 500 Ω fault impedance. Comparing with the traveling wave protection method of ABB, the proposed method improves the sensitivity when high-impedance faults occur. [ABSTRACT FROM AUTHOR]

High-frequency harmonic resonance has occurred frequently in the traction power-supply system (TPSS) when high-speed trains that are equipped with pulsewidth-modulation converters were serviced in the China High-Speed Railway (HSR). This phenomenon can result in serious voltage distortion, overheating of electrical components, and electromagnetic interference (EMI) of communication circuits. In order to address this issue, a complete mathematical model of the 2\,\times\,27.5-kV ac railway system, by means of the nodal admittance matrix, is presented to attain equal modeling of TPSS and modern train for harmonic studies in this paper. The impact of the train on resonance behavior of TPSS by employing resonance-mode assessment and modal sensitivity analysis are investigated. Finally, numerical simulation results using the presented model are compared to measurements results of the China HSR to verify the accuracy of the TPSS model and Norton model of the train, and proved that the method of resonance frequency shifts described is doable. The comparison results illustrate that the proposed model and harmonic resonance assessment can be useful for determining and mitigating the harmonic resonance problems in TPSS as well as the power system. [ABSTRACT FROM AUTHOR]