In railway power supply systems using AC frequencies lower than the public grids of 50/60 Hz, high voltage AC overhead transmission lines in railway grid frequency are used as one measure of strengthening the systems. An increased resistance to overhead high voltage AC transmission lines, may motivate cables for future railway power systems. With the frequency of 50/60 Hz, reactive power produc...

Convex relaxations of the power flow equations and, in particular, the Semi-Definite Programming (SDP), Second-Order Cone (SOC), and Convex DistFlow (CDF) relaxations, have attracted significant interest in recent years. Thus far, studies of the CDF model and its connection to the other relaxations have been limited to power distribution systems, which omit several parameters necessary for mode...

The fast development of power electronics based on new and powerful semiconductor devices has led to innovative technologies, such as HVDC, which can be applied to transmission and distribution systems. The distribution voltage level is smaller than the transmission one, thus the power electronics are less expensive in distribution. The technical and economical benefits of this technology repre...

We describe theoretically the acoustoconductance (AC) of quantum contacts. One characteristic of a contact which distinguishes it from a long, uniform wire is a strong, energy-dependent transmission probability. This has several consequences for AC. Electrons which are forward scattered by phonons can contribute to AC and, furthermore, AC can have positive sign (i.e. a conductance-increase unde...

AC servo-driven precision transmission system is mainly composed of AC servo motor, mechanical transmission parts and control parts. Because of mutual coupling between various parts, particularly transmission system in mechanical coupling vibration in non-smooth transition, it will be of great harm to safe operation of the system. This paper made some overview and built the model of AC servo-dr...

We compare two superconducting transmission lines for use in a He dilution refrigerator using a NbTi wire inner conductor with NbTi foil and CuNi tubing outer conductors. The heat transfer is calculated using the Wiedermann-Franz Law, and the impedance and power loss are measured using a network analyzer at room temperature and at 4K. The transmission line with CuNi tubing is easy to construct,...

We never loaded a long extra high voltage to their thermal limits in order to keep sufficient margin against transient instability. With this scheme proposed in this paper, it is possible to load these lines very near to their thermal limits. Here we inject dc power in to dc transmission line to carry usual ac along with dc superimposed on it. The added power flow does not cause any transient i...

Deregulation and privatization as well as the increase use of renewable energy are posing new challenges on high voltage transmission systems. Environmental constraints, such as energy saving, loss minimization and CO2 reduction, will also play an important role. The loading of existing power systems will further increase, leading to bottlenecks and reliability problems. High voltage power elec...

Large offshore wind farms are recently emerging as promising alternative power sources. Long distances between offshore generation and onshore distribution grid demand new solutions for their connection to the AC network. HVDC systems based on voltage source converters (VSC) are a promising alternative to conventional AC transmission above a certain cable length. This paper presents a new VSC t...