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The stator ground fault location of large generators can guide rapid maintenance. In this paper, a location criterion without fault transition resistance is constructed by using the fundamental potential and the third harmonic potential of the faulty winding simultaneously. The above potentials of the faulty winding are corresponding to the fault position. To precisely locate the grounding fault, it is necessary to clarify the analytical relationship between the faulty winding potential and the fault position. However, the existing methods often take the coil potential as the unit to analyze the winding potential, which has theoretical errors for the generators with short-pitch winding. Aiming at this problem, a more precise analysis method for winding potential is established by taking the slot conductor potential as the unit. To solve the location criterion, the optimization model for each slot conductor of the faulty phase is constructed. The slot conductor with the smallest optimal objective function value is judged as the faulty slot conductor, and the corresponding decision variable is judged as the fault position. Simulation and experiments verify the effectiveness of the proposed method, which can still meet the needs of engineering applications under multiple adverse conditions. [ABSTRACT FROM AUTHOR]

This paper presents a novel time-domain fault location algorithm on HVDC transmission lines. The Bergeron line model is adopted to construct a time-domain fault location equation, considering unsynchronized two-end measurement and uncertain line parameters. The zero time reference point is set to the sample point of arrival at each end for the traveling wave-head. Time-tags of all sample points change with the zero time reference. So the time difference of two-end measurements has changed also, and equals the time difference between arrivals at two ends for the traveling wave-head. That makes it possible to mix the traveling wave theory with the Bergeron time-domain fault location method. Besides, the ratio coefficient of wave velocities between different frequencies and digital band-pass filter are presented for better performance of the proposed method. Simulations and tests demonstrate that the proposed method can locate faults accurately on the HVDC lines even in the case of loss of signals from GPS. [ABSTRACT FROM AUTHOR]

Conservation voltage reduction (CVR) and distributed-generation (DG) integration are popular strategies implemented by utilities to improve energy efficiency. This paper investigates the interactions between CVR and DG placement to minimize load consumption in distribution networks, while keeping the lowest voltage level within the predefined range. The optimal placement of DG units is formulated as a stochastic optimization problem considering the uncertainty of DG outputs and load consumptions. A sample average approximation algorithm-based technique is developed to solve the formulated problem effectively. A multiple replications procedure is developed to test the stability of the solution and calculate the confidence interval of the gap between the candidate solution and optimal solution. The proposed method has been applied to the IEEE 37-bus distribution test system with different scenarios. The numerical results indicate that the implementations of CVR and DG, if combined, can achieve significant energy savings. [ABSTRACT FROM AUTHOR]

With the development of HVdc transmission technology, the isolation of dc faults is becoming increasingly important. As the most effective solution, hybrid HVdc circuit breaker (CB) is not mature enough, which has restricted its engineering application. Accordingly, this paper proposes an auxiliary dc CB scheme suitable for HVdc grid. In this scheme, the traditional half-bridge modular multilevel converter (MMC) is partially innovated to have the ability of auxiliary breaking operation. With the effect of the MMC auxiliary breaking (MAB) operation at both ends of the fault line, the dc fault current can be easily interrupted and isolated by low-cost CB unit installed in the dc transmission line. The equivalent circuit under MAB process is analyzed, and the fault isolation sequences are designed. Furthermore, the economic comparative analysis among three schemes is performed. Finally, a four-terminal bipolar HVdc grid test model is built in PSCAD/EMTDC; in addition, an MMC prototype with proposed scheme is also developed. The simulation and experimental results validate the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

Harmonic amplification and interaction of the PV plant which contains multiple parallel inverters influence the renewable power generation and operation seriously. In this article, the resonance mechanism and characteristics of a real large-scale PV plant are explored based on its plant-level circuit model. The component and system models are established first. The distribution rules of wideband resonance frequency from the perspective of the point of common coupling (PCC) and the inverter are respectively determined. Two different resonance bands excited by LCL filter and underground cable are further identified. At last, the practical case of harmonic resonance in the studied PV plant is investigated. Both the measured data and the simulation results support the analytical conclusions. This article combines the theoretical study with the engineering practice, which provides beneficial guidance on the resonance prevention. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including microgrids, system analysis and protection engineering.