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Small-scale synchronous generators (SSSGs) are widely utilized as distributed generators in power systems. A large fault current due to the SSSG phase-to-ground short circuit may result in excessive damages to the stator core and windings, in a way that major repairs, such as core disassembling and rewindings, become necessary. Thus, the fault current should be properly restricted to prevent such damages and reduce the required capital and time for SSSG repairs. In this research work, a model to calculate the SSSG internal fault current is developed. Meanwhile, an appropriate index to quantify the damages to the faulty SSSG is presented. Afterward, influencing parameters on reduction of the damages are investigated when either frequently used TT or TN grounding systems are applied for SSSGs. Studies show that the stator damages are mainly caused by the SSSG fault current rather than that of the system. Accordingly, to reduce the SSSG vulnerability to the stator earth fault, not only some applicable strategies are proposed for the both grounding systems, but also the favorable grounding system is determined. [ABSTRACT FROM AUTHOR]

While in many applications, multiterminal dc (MTDC) systems are potentially appropriate substitutes for their ac counterparts, their protection problems still require more attention. This paper proposes a novel traveling-wave-based methodology for fault location in MTDC systems. The traveling-wave principle, along with two graph theory-based lemmas, is deployed to locate the fault by sectionalizing the graph representation of the MTDC system. Accordingly, the system of equations relating the fault inception time, fault point, and first arrival time at different converter locations would be derived and solved. The method merely needs the first surge arrival times, thereby eliminating the practical problems in relation to identifying subsequent traveling waves. More important, it successfully determines the fault location, regardless of the network topology complexity, that is, the number of its meshes and radial lines. To demonstrate the effectiveness of the method, it is applied to some complicated MTDC systems containing meshes and radial lines. Numerous simulation studies carried out for different conditions verify high accuracy, robustness against fault impedance, and noise immunity of the proposed method. [ABSTRACT FROM AUTHOR]