Showing papers on "Blackout published in 1993"

Electromagnetic pulse research on electric power systems: Program summary and recommendations

Abstract: A single nuclear detonation several hundred kilometers above the central United States will subject much of the nation to a high-altitude electromagnetic pulse (BENT). This pulse consists of an intense steep-front, short-duration transient electromagnetic field, followed by a geomagnetic disturbance with tens of seconds duration. This latter environment is referred to as the magnetohydrodynamic electromagnetic pulse (NMENT). Both the early-time transient and the geomagnetic disturbance could impact the operation of the nation's power systems. Since 1983, the US Department of Energy has been actively pursuing a research program to assess the potential impacts of one or more BENT events on the nation's electric energy supply. This report summarizes the results of that program and provides recommendations for enhancing power system reliability under HENT conditions. A nominal HENP environment suitable for assessing geographically large systems was developed during the program and is briefly described in this report. This environment was used to provide a realistic indication of BEMP impacts on electric power systems. It was found that a single high-altitude burst, which could significantly disturb the geomagnetic field, may cause the interconnected power network to break up into utility islands with massive power failures in some areas. However, permanent damage would more » be isolated, and restoration should be possible within a few hours. Multiple bursts would likely increase the blackout areas, component failures, and restoration time. However, a long-term blackout of many months is unlikely because major power system components, such as transformers, are not likely to be damaged by the nominal HEND environment. Moreover, power system reliability, under both HENT and normal operating conditions, can be enhanced by simple, and often low cost, modifications to current utility practices. « less

On monitoring nuclear power plant emergency diesel generator reliability

Abstract: If offsite power is interrupted, the availability of onsite alternating current power supplies is a major factor in assuring acceptable safety at commercial light-water-cooled nuclear power plants. To control the risk of severe care damage during station blackout accidents at a given plant, the reliability of the emergency diesel generators (EDGS) to start and load-run upon demand must be maintained at a sufficiently high level. The minimum EDG reliability, which we denote by RT, is targeted at either 0.95 or 0.975 per nuclear unit consistent with the reliability level that the plant operator assumed in the coping analysis for station blackout. In 1992 the US Nuclear Regulatory Commission (NRC) considered an amendment that would require licensees to test and monitor EDG reliability against performance-based criteria that indicate possible degradation from the EDG target reliability levels. They originally proposed the following set of fixed sample-size triggers for use in monitoring EDG reliability. The purpose of this report is to compare the performance of the proposed triggers with corresponding alternative sequential variable sample-size triggers which potentially permit earlier detection of EDG reliability degradation without significantly increasing the false alarm rate. The comparison is to be done in a simulated use environment bymore » means of Monte Carlo simulation. We are also interested in the inverse conditional probabilities of reliability degradation given that a trigger has occurred.« less

The postreinforcement pause and the blackout procedure: Are blackouts neutral stimuli?

Abstract: Three pigeons were trained to respond on a fixed-interval 300-sec schedule. Blackouts were introduced following each unreinforced response during either the first 180 sec or the last 120 sec of the interval. Blackouts reduced responding, with the greatest reduction occurring when they occurred during the last 120 sec of the interval. Only blackouts during the last 120 sec of the interval resulted in consistent decreases in pause length. These results are not consistent with the view that blackouts are neutral stimuli that simply function to reduce the number of interreinforcement responses.

Automatic Selection of Dispatching Command in Restoration of EHV Power System after Complete Blackout

Abstract: In this paper, an expert system is developed for re-energizing an EHV power system after a complete blackout. In order to restore the blackout areas which are not restored by operations based on the prescribed operation manual, we newly supplement several operations. These operations are selected to realize three restorative scenarios. The operations are executed at dispatch commands. We introduce several conditions so that the expert system can select appropriate commands as the restoration proceeds. The dispatch commands are classified into several groups, and their data are described in several objects. Those objects are controlled under one object, where such information as names of command groups, priority among the groups, etc., is written. By editing the contents of the objects, we can easily modify dispatch commands and restoration process. The operator checks the selected commands. If he judges them appropriate, then he issue them. If not he can reject, reserve, or replace them. The expert system is tested under various conditions to verify that it functions as designed.

Fuzzy Inference Application to Planning of Distribution Network Switching

Abstract: Optimal switching pattern planning is the main subject of distribution network reconfiguration to recover from a blackout or to avoid a blackout due to maintenance and construction. This is a combinatorial optimization problem, and an enumerative check of every pattern is necessary to obtain the optimal solution. In practice, successive heuristic search methods are adopted to obtain the quasi-optimal solution within a limited computation time. However, a very long computing time is still required when the problem size becomes slightly larger. The step-by-step nature of the methods results in many iterations, although it ensures satisfaction of the constraints. Reduction of the iterations is considered to be necessary to enhance processing speed. In this paper, “supply adequacy” is introduced as a new criteria index to guess the solution, which is obtained by fuzzy inference for each possible pair of source and load zone. The reconfiguration pattern is obtained at once or in a few processing steps by assigning to each zone the source with the highest adequacy. Numerical examples show that the proposed method can obtain the solution faster than the ordinary method, more remarkably with the increase of problem size.