Blackout

About: Blackout is a research topic. Over the lifetime, 2088 publications have been published within this topic receiving 30433 citations.

Reducing RF blackout during re-entry of the reusable launch vehicle

Abstract: The Aerospace Corporation was tasked to assess radio frequency (RF) blackout phenomena caused by plasma generation around vehicles during reentry and presently known methodologies for mitigation of this condition inhibiting communications. The purpose was to understand these phenomena and mitigation approaches applicable to reusable launch vehicles (RLVs) used for commercial space. The viability and limitations of selecting frequency bands amenable to continuous communication in presence of plasma sheaths were assessed and mitigation recommendations provided. The ability to predict the ionized flow field for classes of vehicles most likely to emerge as hypersonic space transportation systems, with sufficient accuracy to identify the altitudes of blackout onset and recovery within reasonable bounds, has been demonstrated for altitudes greater than approximately 100 kft. This high-altitude regime is the most likely for future space transportation due to low g forces and low heat loads. For the lower, suborbital altitudes, many commercial RLVs will not be subjected to RF blackout because their relatively low velocities will not create conditions that generate plasma. Determination of the interaction of RF with a known ionized layer, including reflection, attenuation, refraction, high-power breakdown limits, and also effects of the plasma on the antenna characteristics, have been demonstrated successfully. Analytic codes are available to evaluate these phenomena. Approaches for mitigating the interruption of communications due to interactions of plasma electrons with RF signals are reviewed. The most promising are: aerodynamic shaping, injection of quenchants, use of magnetic windows, and use of high frequencies.

Geographically diverse on-screen displays for blackouts

Abstract: Blackout messages are provided that are specific to geographic areas. Blackout event data is received that includes location codes representing geographic areas affected by a blackout event. A determination is made whether a user is subject to the blackout event. If the user is subject to the blackout event, one or more blackout messages are selected and for presentation to the user. Selection of the blackout messages is based on a user location code for the user.

Multi-agent-based urban power grid isolated island black-start system and method

Abstract: A multi-agent-based urban power grid isolated island black-start system and method belongs to the field of operation control of power system field. A plurality of units which can achieve splitting isolated island operation are configured in main power plants in advance, the units are required to be capable of supplying first-class and second-class loads or providing start capacity of other power plants after undertaking auxiliary power load and can guarantee stable operation of auxiliary powers after emergency load shedding; when a power grid system suffers from large disturbance or has a major fault, transformer substation monitoring agents of an affected area and power plant monitoring agents can actively split into isolated island operation states, when the fault is finally evolved into a blackout, all the stable-operation power plant stage and transformer station stage isolated islands in the power grid report respective isolated island operation conditions to a power grid monitoring center agents. The multi-agent-based urban power grid isolated island black-start system and method can greatly shorten power grid black-start time and reduces economic losses and social influences caused by the blackout.

Communication-system blackout during reentry of large vehicles

Abstract: Much of the theoretical research on reentry blackout is in a format difficult for the communications design engineer to use in his system analysis. This paper derives simplified equations for the average sheath power loss that may be added (in dB) to the usual space loss to obtain an approximate total propagation loss. The plasma and sheath properties are discussed in detail but largely without supporting mathematics, in order to give the design engineer a better understanding of the overall problem. For the same reason and to provide insight into the final results, the average radiated power is found, using both intuitive and rigorous techniques. Several graphs of plasma properties are included in the development as an aid to numerical computations, and results are compared with the work of other authors.

When to Island for Blackout Prevention

Abstract: Cascading outages leading to large-area blackouts can be mitigated using intentional controlled islanding (ICI). An ICI scheme must define the most suitable time to split the system after a severe contingency (i.e., when to island), as well as to quickly determine the set of branches to be disconnected to create stable islands (i.e., where to island). Most of the works in the literature, however, focus on the latter and little has been done to address the “ when to island ” problem. To fill this gap, this paper proposes a unified methodology to determine the most suitable moment for islanding. First, the proposed methodology uses real-time information to estimate the rotor angles of generators, which, in turn, serve to define the suitable number of coherent generators and the actual coherent groups. It then adopts the concept of area-based center of inertia-referred rotor angle index to determine the actual time of islanding. The unified methodology for determining the number of islands to be created, the coherent generators, and the time for islanding is tested using the IEEE 39- and 118-bus test systems. Multiple case studies are presented to demonstrate the adaptability and effectiveness of the proposed unified methodology to different system conditions.