Local Electric System Research Articles

Compatibility Study of Fuel-Cell Protective Relaying and the Local Distribution System

The goal of this study was to characterize the compatibility between the protective relaying system of a fully commercialized, 200-kW fuel cell and the local electric power system. This study was motivated by the fact that for several reasons, distribution utility engineers are uncomfortable with the synthesized protective relaying and hardware that is generally provided in distributed-generation (DG) systems. This study collected power grid disturbance electrical data and event-related, building-load electrical data over a period of six months. The study dealt with a larger-than-expected number of interruptions to grid-connect power generation. Problems relating primarily to load tracking and also to low power factor, complex load balance dynamics, and possible harmonic-distortion-induced instrumentation error produced some valuable conclusions and several recommendations that would be useful for companies interested in installing a grid-connected DG system.

Heating detached houses in urban areas

District heating systems using cogeneration, as well as local fuel-based and electric heating systems for detached houses, are analysed. The analysis includes the whole energy system, from the natural resource to the end user, with respect to primary energy use, emission and cost. The end-use technologies studied are heat pumps, resistance heaters and boilers. It was assumed that the base-load electricity, except for the cogenerated electricity, was produced in stand-alone power plants using wood chips or natural gas, while peak-load electricity and fuel used for transportation were produced from crude oil. The heat pump and district heating systems are found to be most energy efficient, followed by the local fuel-based systems. The wood-fuel-based systems emit about one tenth of the greenhouse gases emitted by the natural-gas-based systems. The sulphur and nitrogen oxide emission, however, is higher for wood-fuel-based systems. Systems based on natural gas are less expensive than the corresponding wood-fuel-based systems. Decarbonization and carbon dioxide sequestration, however, do not reduce the carbon dioxide emission to the low level of the wood-fuel-based systems and, in addition, make the natural-gas-based systems more expensive than the wood-fuel-based systems.

Fusion power deployment

Fusion power plants could be part of a future portfolio of non-carbon dioxide producing energy supplies such as wind, solar, biomass, advanced fission power and fossil energy with carbon dioxide sequestration. In this paper we discuss key issues, for other sources of energy, that could impact fusion energy deployment during the last half of this century. These include geographic issues such as resource availability, scale issues, energy storage requirements and waste issues. The resource needs and waste production associated with fusion deployment in the US should not pose serious problems (Fusion Technology 39 (2001) 513). One important feature of fusion power is the fact that a fusion power plant should be locatable within most local or regional electrical distribution systems. For this reason fusion power plants should not increase the burden of long distance power transmission to our distribution system. In contrast to fusion power, regional factors could play an important role in the deployment of renewable resources such as wind, solar and biomass or fossil energy with CO 2 sequestration. We examine the role of these regional factors and their implications for the deployment of these renewables, fossil, and fusion.

Description of a new computer wire coding method and its application to evaluate potential control selection bias in the Savitz et al. childhood cancer study

We developed a new computer wire coding method and then applied it to investigate the suggestion that control selection bias might explain the observed association between wire codes and childhood cancer made in the study conducted by Savitz et al. in the Denver area. The computer wire coding method used a geographic information system approach with data on the local distribution electric system and from tax assessor records. Individual residences were represented as a circle scaled to the ground floor area of the residence and centered on the lot centroid. The wire code of the residence was determined from the distance between the circle and the relevant power line, and from the current carrying capacity of that line. Using this method, wire codes were generated for 238 290 residences built before 1986, the time of the Savitz et al. study, in the Denver metropolitan area. We then attempted to reconstruct the 1985 population of hypothetically eligible control children in the Denver metropolitan area by using 1980 census data. Since data were not available to locate the children in each residence within a census block, uniform, Poisson, and negative binomial distributions were used to randomly assign children to residences. To evaluate the likelihood of the wire code distribution of the controls selected by Savitz et al., 100 random trials were conducted for each distribution, matching two controls to each case. The odds ratios between childhood cancer and very high current configuration (VHCC) wire codes were reduced when the assigned controls were used, suggesting control selection bias may have been present. However, control selection bias is unlikely to account for all the reported association between childhood cancer and wire codes in the Savitz et al. study. Bioelectromagnetics 21:346–353, 2000. © 2000 Wiley-Liss, Inc.

Description of a new computer wire coding method and its application to evaluate potential control selection bias in the Savitz et al. childhood cancer study

We developed a new computer wire coding method and then applied it to investigate the suggestion that control selection bias might explain the observed association between wire codes and childhood cancer made in the study conducted by Savitz et al. in the Denver area. The computer wire coding method used a geographic information system approach with data on the local distribution electric system and from tax assessor records. Individual residences were represented as a circle scaled to the ground floor area of the residence and centered on the lot centroid. The wire code of the residence was determined from the distance between the circle and the relevant power line, and from the current carrying capacity of that line. Using this method, wire codes were generated for 238 290 residences built before 1986, the time of the Savitz et al. study, in the Denver metropolitan area. We then attempted to reconstruct the 1985 population of hypothetically eligible control children in the Denver metropolitan area by using 1980 census data. Since data were not available to locate the children in each residence within a census block, uniform, Poisson, and negative binomial distributions were used to randomly assign children to residences. To evaluate the likelihood of the wire code distribution of the controls selected by Savitz et al., 100 random trials were conducted for each distribution, matching two controls to each case. The odds ratios between childhood cancer and very high current configuration (VHCC) wire codes were reduced when the assigned controls were used, suggesting control selection bias may have been present. However, control selection bias is unlikely to account for all the reported association between childhood cancer and wire codes in the Savitz et al. study.

The natural background levels of 50/60 Hz radio noise

Measurements of the natural background levels of 50- and 60-Hz radio noise by ELF/VLF (extremely low frequency/very low frequency) radiometers located at various sites around the world are reported. The measurements are made on the magnetic fields of the noise using loop antennas, and they cover the first three harmonics of the power line frequencies (frequencies in the range 50-180 Hz). Due to the likelihood of contamination from local electrical power systems, or even from nonlocal systems, the measurements at each power line frequency were made at adjacent frequencies and the desired noise amplitudes obtained by interpolation. It is shown that the magnetic spectral densities of the natural noise typically lie in the range 20-600 fT/ square root Hz or, taking the 50/60-Hz frequencies specifically, in the range 150-600 fT/ square root Hz. These ranges should be typical for most locations on the Earth's surface and for most seasons. >

The Hausdorff dimension as a tool of step-by-step prediction

Forecasts of the random processes occurring in power systems should be characterized by very high accuracy—inaccurate forecasts always cause serious economic losses for electrical energy producers and distributors. The processes of power demand, electrical energy demand, and development of power networks exhibit self-similar features. This peculiarity enables the Hausdorff dimension to be applied to formulate prediction models of the above-mentioned quantities. The models are characterized by simplicity and high accuracy. This work deals with models of step prediction of random linear and periodic functions characterized by self-similarity. The definition of the Hausdorff dimension and the principles of generating self-similar geometrical forms and formulating the prediction models for self-similar processes are presented. Examples of prediction models and their application in electrical power engineering are given. The problem of predicting power demands in state and local electrical power systems is described in detail. The reader is also provided with an annotated list of English-language papers issued in 1918–1980 concerning the prediction of power demands, as well as the most important American and Polish works of the last few years.

The role of a ‘local electrical conduction system’ during feeding in the Devonshire cup coralCaryophyllia smithiiStokes and Broderip

The electrical conduction systems underlying the control of feeding behaviour are described for the solitary cup coralCaryophyllia smithii. A nerve net and a slow conduction system were found to conduct non-decrementally to all parts of the animal and to control symmetrical parts of the feeding behaviour such as polyp expansion. The slow system was activated by receptors on the tentacles and oral disc. Of particular interest was the presence of a ‘local conduction system’ in the tentacles and oral disc. This system was shown to be important in the control of local, asymmetrical parts of the feeding behaviour such as the movements of single tentacles. The local conduction system consisted of radially conducting units each of which consisted of a single tentacle and its associated sector of oral disc. This allowed the radial spread of excitation (at less than 2 cm s-1) from tentacle to mouth or mouth to tentacle but did not allow excitation to spread around the oral disc. The threshold for excitation of the local conduction system was above that of the nerve net or slow conduction system. The cellular basis for local conduction is unknown but may involve the oral disc radial muscles and the tentacle longitudinal muscles. By appropriate electrical stimulation of the nerve net, slow system and local conduction system, a complete sequence of feeding behaviour could be evoked. This closely resembled the behaviour shown during normal feeding and included polyp expansion, local pharynx movements and local tentacle bending. It is concluded that ‘local conduction’ is an important element to include in models purporting to explain the control of anthozoan behaviour, particularly that in which local movements are important.

Electricity Supply Engineering

IT is at first sight surprising that anyone should write a treatise on power-frequency electrical engineering since comparatively little of a novel nature has been added to either theory or practice of electrical machines in the past twenty years. Within the last few years, however, the electricity supply systems of many countries have been integrated into a well-defined unit in which all the generating stations operate in conjunction with one another on a large, common high-voltage network. This practice has resulted in the development of much larger generators, transformers and other equipment than were used when individual power authorities operated comparatively small local electrical systems. Many problems involving stability of operation, short-circuit stresses, surge voltages and load control have thereby become accentuated. Great numbers of people have also become intimately interested in large-scale electricity supply ; in Great Britain, for example, the British electricity supply industry employs about 150,000 people, most of whom should aspire to attain a good level of technical knowledge regarding the equipment used in providing the public with electrical energy. Etude electromagnetique generale des machines electriques Par Prof. R. Langlois-Berthelot. Pp. 284. (Paris: Editions Eyrolles, 1949.) 1,600 francs. Etude industrielle generale des machines electro-magnetiques Par Prof. R. Langlois-Berthelot. Pp. 300. (Paris: Editions Eyrolles, 1949.) 1,700 francs.

Analysis of Costs of Variable-Load and Multiple Power Supply

Abstract This study is based upon the actual performance of a plant in operation and includes a classification of costs designed to facilitate the calculation of the influence made thereon by a load of variable demand. Also it attempts to simplify the consideration of load characteristics and to determine the value of constants relating to certain factors of operation. Reference is made to the application of the results to a study for determining the economics of a power supply for the local electric railway system.