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Visual sensitivity and body pigmentation are often shaped by both natural selection from the environment and sexual selection from mate choice. One way of quantifying the impact of the environment is by measuring how traits have changed after colonization of a novel habitat. To do this, we studied Poecilia mexicana populations that have repeatedly adapted to extreme sulphidic (H2S‐containing) environments...
The concentration of electric power at system buses adds to both the need for high-speed tripping in case of faults and the need to avoid false tripping in case of external faults. This combined need for both superior dependability and security has led to many enhancements and system modifications in bus protection. Bus configurations with multiple zones are particularly difficult to provide with...
This paper presents collected events to demonstrate the use of synchrophasor data to update and improve system models and system operation. Examples are given of responses to events captured using wide-area synchrophasor measurements. Phase angle, frequency, and voltage responses are displayed with discussion of the events, synchrophasor data views, and insights to be gained from the different data...
For decades, various versions of the Takagi algorithm have been used by microprocessor-based relays for fault location. This system provides accurate fault location, limited by nonhomogeneous infeed, load flow, fault resistance, and series-compensated or parallel lines. With the emphasis placed on reliability in today's power system, the need for improved accuracy in fault location has increased....
Distributed generation (DG), such as solar-energy-based photovoltaic (PV) systems, wind generation, and other renewable resources, is a quickly growing source of energy for today's power system. These assets pose challenges to grid reliability and power quality. One critical challenge is islanding (inadvertent system separation) detection, separation, and eventual resynchronizing. Research is underway...
The telecommunications revolution has increased the options and capabilities available for communications-based protection of transmission lines. To improve tripping speeds on long and short lines, protection engineers can select from a host of media, protocols, and logic schemes. The question to address is what communications scheme is best for which circumstances. This paper begins by establishing...
The telecommunications revolution has increased the options and capabilities available for communications-based protection of transmission lines. To improve tripping speeds on long and short lines, protection engineers can select from a host of media, protocols, and logic schemes. The question to address is what communications scheme is best for which circumstances. This paper begins by establishing...
Today's protection engineer is not at a loss for things to do. New and retrofit projects along with added system requirements have increased the workload for designing, setting, installing, and maintaining protection systems. It is not uncommon for engineers to look back at the "good old days" with nostalgia. This paper performs a component-by-component and line-by-line comparison of protection...
Modern production processes require very reliable service. A loss of electric power, even for a few seconds, causes a large loss of income to electricity users with time-critical and uninterruptible processes. To raise power system reliability to a higher level, multiple sources are used in combination with an automatic load transfer scheme. This paper examines several different load transfer schemes...
History has repeatedly demonstrated the need to start generating units without access to the external power grid. This "black start" ability speeds power system recovery from both system instabilities and natural disasters. Readiness for an actual black start condition can be demonstrated by bringing a generator up to speed and synchronizing it to the electric system without using any grid...
Numerous problems in power system protection have led to ongoing work for protection engineers to properly configure relays and other devices. These problems include power swing blocking, power swing tripping, and islanding detection. Traditional detection of these conditions using voltage and current have led to complex algorithms and setting guidelines. Distributed generation has complicated issues...
Growth in electric load, without a corresponding growth in service infrastructure, results in systems operating closer to voltage and frequency instability. While rotor angle stability, or real power stability, can be determined by balancing load and generation, until recent advances in technology, it was difficult to quantify or predict voltage stability. Synchronized phasor measurements (synchrophasors)...
This "Black Start" ability speeds power system recovery from both system instabilities and natural disasters. Salt River Project, based in Phoenix, Arizona, conducted an exercise using a number of hydroelectric generating stations and a thermal-generating station. This was a legitimate "Black Start" exercise because every part of the system connecting the hydro and thermal generation...
This paper describes the actual and possible applications of synchronized phasor measurements, or synchrophasors, which provides a method for comparing phase and sequence values from anywhere on a power system. It offers the optimal power system control. The degree to which it can be made useful depends on how far and how fast the data can be moved to the location were the information is processed,...
Communications assisted protective schemes in transmission applications have been in service for decades. With more emphasis being placed on distribution system reliability there is a need to establish protection methods for the varying communications being used on these systems. This paper examines different communication paths for protection signals, such as spread-spectrum radio, fiber-optic cable,...
Duchenne Muscular Dystrophy (DMD) is one of the most common lethal genetic disorders in humans. DMD is due to dystrophin gene mutations resulting in abnormal rates of muscle dystrophin expression. Thus, patients with this disorder suffer progressive loss of muscle strength and muscle weakness, resulting in inability to ambulate and eventual death. While intellectual impairment and behavioral...
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