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Electrical Injury: Electrical Engineer's Perspective and an Historical Review
Author(s) -
BERNSTEIN THEODORE
Publication year - 1994
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1111/j.1749-6632.1994.tb30430.x
Subject(s) - perspective (graphical) , engineering , computer science , artificial intelligence
Prior to 1880, the primary form of electrical injury was caused by lightning. Batteries and electrostatic machines were the major sources for electricity at that time. Generators and motors were being developed prior to 1880, but there was little general use for this equipment. There was tremendous growth in the use of electrical power and equipment following Thomas A. Edison’s demonstration of his electric light in 1879. By 1900, there were power-lines for the transmission and distribution of power throughout the country. Electric motors, transformers, lights, streetcars, power-lines, and other electrical equipment were in general use. With all of this electrical equipment available, it became possible for people to be electrically injured or electrocuted. Edison’s system for power delivery and utilization in the 1880s used direct current (dc). Motors, generators, meters, and a form of electrochemical watt-hour meter were used for his dc system. Direct current was fine for utilization, but it was not satisfactory for transmission of power over a distance. The voltage of a dc system could not be readily changed, so it had to be used at the same value at which it was generated. The power delivered over a power-line is proportional to the product of the voltage of the line and the current in the line. It is more efficient to use high voltage for power transmission so that the currents will be lower for a given power transmission. The lower currents make it possible to use smaller size conductors for power transmission over a distance. Greater insulation is necessary because of the high voltage, but this is usually not a problem for outdoor transmission lines where there is room for the insulators that support the bare lines. The bare lines are sometimes referred to as being air-insulated. Power cannot be utilized in factories or homes at the high voltage because of insulation problems. Due to the fact that the voltage of direct current systems had to be generated at the voltage at which it was utilized, long transmission lines could not be used to transmit high power because of the large size conductors that would be required to carry the large currents. If direct current systems were used, generating plants would be required every few miles. Transformers are used in alternating current (ac) systems to increase the voltage from the generators for transmission and distribution and to reduce the voltage for utilization. Alternating current systems were developed during the 1880s. Alternat-