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Existing security and reliability based EMS applications (e.g. Online Dispatcher Power Flow, Online Contingency Evaluation, Online Short Circuit Calculation, etc.) normally take real time snapshot of the system and perform necessary studies to evaluate the security and reliability of the network. As these applications do not provide any information about the security level of the system for the near future, the operator in control center may not get enough time to effectively arrange for proper corrective actions in case of security criteria violation. This paper presents an online early warning system based on steady state and dynamic security assessment which looks ahead and generate proper alarm for operators in case security criteria is expected to violate in near future. The proposed system can easily be integrated with SCADA/EMS system for transmission control room application to give operator a wide view of the entire network and help him in better control and monitoring of the power grid. [ABSTRACT FROM AUTHOR]

Fuel cells are the most appropriate power suppliers for mobile and portable minute electronic devices, yet they provide intrinsically low power source in practice. As a consequence, influential equipment which can improve output voltage of fuel cells is synchronous DC-DC boost converter. However, voltage collapse is the major drawback in this type of converters, and it occurs when load power increases substantially. Increase of current throughout the region of Mass Transport polarization of fuel cells appears as a dramatic voltage drop in the both fuel cell and converter, and this current yields a low output voltage. Accordingly, MOSFET switches of the converters would not be driven by the low output voltage, and voltage collapse appears. In this paper, it is devised that use of superconductor technology can limit the increased current and alleviate voltage collapse in synchronous converters. Hence it is introduced as a novel potential concept of superconductor application. To satisfy the Authors' aim, the superconductor is installed in series with the load after the node in which output voltage is sampled in order to derive MOSFETs by the controller circuit. By tuning the operation current of the superconductor in the value corresponding with the beginning point of the Mass Transport region of polarization curve, superconductor would be able to halt the current and cease voltage collapse. [ABSTRACT FROM AUTHOR]

In this paper allocating of DGs and optimal number, locations and size of solid State Fault Current Limiters (SSFCLs) is performed for a case study contains modern protective devices. Genetic algorithm (GA) is employed for optimal allocating of DGs and SSFCLs. The distribution system contains remote controllable switches in addition to conventional tools such as fuses, relays and circuit breakers. The results demonstrate that minimization of distribution protection system cost, is still valid for a distribution system, which contains modern protective devices. [ABSTRACT FROM AUTHOR]

There are several definitions for reactive power in non sinusoidal networks. However, there is still no unique definition that is accepted by the electrical communities. In this study seven of the most common power decompositions, are simulated and compared in AC electric arc furnace (EAF) plants. For this purpose a large amount of data was collected for a considerable number of melting processes, including currents and voltages of eight ac EAFs installed in Mobarakeh steel company (MSC), Isfahan, Iran. The reactive power definitions are compared to each other utilizing different methods and some statistic indices. By calculating the average of each definition over all recorded data the definitions that are beneficial to customers and those that are beneficial to the utilities are obtained. The problem encountered here is that the ideal definition for reactive power is unknown and there is no criterion to evaluate and compare the different definitions. So here the mean of the seven most common definitions is considered as the criterion and the distances of various definitions from it are calculated. Also, the capacitance that completely compensates the EAF reactive power is calculated according to each of the discussed definitions. [ABSTRACT FROM AUTHOR]