The Principles of Electric Power Transmission by Alternating Currents |
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Common terms and phrases
alternating current aluminium amperes angle apparatus arrestor break-down breaker C. P. Steinmetz calculated capacitance capacitance current centimetre charging current choking coils circuit circuit-breaker coil condenser conductor material connected corona cost current flowing curve diagram diameter disc discharge ductors earth effect electrical electrodes electrostatic fault flash-over voltage flux formula frequency Hence high-frequency hyperbolic functions impedance increase inductance installed kilovolts lagging lead sheath leakage length lightning lightning arrestor line conductors line voltage load loge maximum method mile normal obtained occurs ohms open-circuited operating oscillation overhead lines overload relays porcelain potential power factor pressure rises protection reactance reactor receiving end receiving-end voltage sending end sending-end voltage short-circuit current shown in Fig sinh skin effect stress surface synchronous phase modifiers temperature thermal resistance three-core cable trans transmission line transmission systems trip vector voltage and current voltage to neutral volts wires zero
Popular passages
Page 247 - THE most economical size of the copper conductor for the electric transmission of energy, whether for the electric light or for the performance of mechanical work, would be found by comparing the annual interest of the money value of the copper with the money value of the energy lost in it annually in the heat generated in it by the electric current.
Page 247 - He remarked that (contrary to a very prevalent impression and belief) the gauge to be chosen for the conductor does not depend on the length of it through which the energy is to be transmitted. It depends solely on the strength of the current to be used, supposing the cost of the metal and of a unit of energy to be determined.
Page 214 - ... kV. In a cable of homogeneous insulation, the voltage which may be safely applied is limited by the maximum electric stress at the conductor, but if the dielectric is strong enough at that point it is excessive electrically (and therefore needlessly expensive) further away. If, however, the stress can be so distributed that its value in the outer layers of the dielectric is increased without increasing the stress at the conductor, the insulation thickness, for a given voltage, will be reduced....
Page 212 - A small conductor will allow a greater thickness of insulation, but on the other hand, the smaller radius of curvature tends to increase the stress; the effect of too large a radius of conductor is to cause an increase of stress through reduction of the total thickness of insulation. The maximum stress at the conductor surface is (by formula 1...
Page 309 - This table was prepared after a conference between the leading switchgear manufacturers in America, and was given in a paper, " Rating and Selection of Oil Circuit-breakers ", by EM Hewlett, JN Mahoney, and GA Burnham, read before the American IEE in 1918. The numbers given are factors by which the normal full-load current must be multiplied to get the short-circuit current at any given instant. The percentage reactance figures represent the total reactance in the circuit, including that of the generator,...
Page 39 - This maximum value is equal to O'O or BD. For still greater angles of lag the regulation diminishes again. With leading currents the regulation diminishes as the angle of lead increases, and becomes zero when <£., = / AOF.
Page 124 - To avoid a direct contact between the porcelain and the metal pin, a soft metal (generally lead) thimble is used. An adequate length of leakage path is obtained by providing the insulator with two or three petticoats or rain sheds. These are so designed that even when the outer surface of the insulator is wet due to rain, sufficient leakage resistance is still given by the inner dry surfaces.
Page 7 - ... the power dissipated in the form of heat, in overcoming the ohmic resistance, is proportional to the square of the current. A definite amount of power can therefore be transmitted with less loss when the voltage is high than when it is low; but, on each particular transmission, there is a limit to the pressure beyond which there is nothing to be gained in the matter of economy. This limit is determined by the cost of generating and transforming apparatus (which will be greater for the higher...
Page 20 - JO and the inductance per centimetre length due to the flux inside the conductor is cgs units, . (7) which is the internal inductance of the conductor. The total inductance of each wire per centimetre is therefore...
Page 146 - The corona extends until the increase in the effective diameter of the conductor is sufficient to bring the potential gradient at the edge of the corona down to the disruptive gradient of air, and the corona can then spread no farther at the particular voltage under consideration.