Showing papers in "Transactions of The American Institute of Electrical Engineers in 1933"
TL;DR: In this article, the analysis presented in a previous paper is extended to include a consideration of synchronizing and damping torque during continuous and transient oscillations, the description of an equivalent circuit which has been found useful in calculating the decrement of the short circuit current of interconnected machines, and the derivation of simple approximate formulas for the roots of the equation determining the wave shape of the current on three-phase short circuit.
Abstract: The analysis presented in a previous paper is extended to include a consideration of synchronizing and damping torque during continuous and transient oscillations, the description of an equivalent circuit which has been found useful in calculating the decrement of the short circuit current of interconnected machines, and the derivation of simple approximate formulas for the roots of the equation determining the wave shape of the current on three-phase short circuit.
320 citations
TL;DR: The field data for 1931 and 1932 are reviewed in this article, with especial reference to lightning stroke currents, showing that tripouts correlate almost exclusively with high tower leg currents of negative polarity, that is, the tower top is negative with respect to the base.
Abstract: The field data for 1931 and 1932 are reviewed, with especial reference to lightning stroke currents. When direct strokes take place to towers or ground wires, flashover occurs if the product of current and tower footing resistance is higher than the fiashover strength of the insulators. Flashover seldom occurs if ground wires are present and the towers have low footing resistance. Three years' records on four systems indicate tower currents varying from 1,000 to 150,000 amperes. Tripouts correlate almost exclusively with high tower leg currents of negative polarity, that is, the tower top is negative with respect to the base. This indicates that the severe lightning strokes come from negatively charged clouds. A great amount of experimental data, relating to flashover between electrodes of dissimilar shapes, are shown to be in accord with these field observations.
64 citations
TL;DR: In this article, the single-phase and poly-phase definitions of reactive power are considered and the polyphase definition is the better but requires the independent recognition of the effects of distortion and, in the case of four or more wires, mesh distribution.
Abstract: In this paper the single-phase and polyphase definitions of reactive power are considered. The single-phase definition is unsatisfactory when the current and voltage wave forms are complex. The polyphase definition is the better but requires the independent recognition of the effects of distortion and, in the case of four or more wires, mesh distribution. The geometric difference between the apparent power and the power may be called the fictitious power to distinguish it from the reactive power which is only part of the fictitious power.
62 citations
TL;DR: In this paper, the authors show the practical work done in the laboratory at Sharon to calibrate the measuring devices, and study the more interesting fundamental relationships that affect the operation and accuracy of these measuring devices.
Abstract: With the application of surge tests to high voltage electrical apparatus, the question of the measurement of high-surge voltages has become a subject of prime importance. It is accordingly desired in Part I to show the practical work done in the laboratory at Sharon to calibrate the measuring devices, and in Part II to study the more interesting fundamental relationships that affect the operation and accuracy of these measuring devices. The methods of voltage measurement used are the resistance potentiometer, capacity potentiometer, and sphere gap. The potentiometers serve as dividers of the high-surge voltages for measurement at the cathode-ray oscillograph. The resistance potentiometer is a fundamental standard but requires consideration of its limitations for very rapid phenomena. In cases where these can be compensated for or are negligible, the resistance potentiometer method is very desirable. The capacity potentiometer is a secondary standard which can be calibrated. If corona and oscillations can be eliminated, it is a very desirable method of measurement, inasmuch as it is less subject to distorting the wave shape of the surge. The sphere gap is useful as a secondary standard for occasional check measurements, and it is of interest that formulas derived from smaller gaps still hold, as indicated by the check between the calculated curve for the 200-cm sphere gap and the calibration points with the resistance potentiometer.
36 citations
TL;DR: In this paper, a new method for starting an arc cathode is described, which is of the separating contact type, but to a considerable degree is free from the inertia difficulty of ordinary separating contacts.
Abstract: AFTER presenting various theories of the cathode of an electric arc and describing numerous methods for initiating an arc cathode, a new method of starting the arc cathode is described. It is of the separating contact type, but to a considerable degree is free from the inertia difficulty of ordinary separating contacts. One form of this starter consists of a small section pointed tungsten rod placed in a mercury arc tube so that it dipped slightly to a depth of about one mm below the mercury surface. On sending sufficient current through the rod, the cathode of an arc was promptly started at the rod and mercury junction, and this starting could be regularly repeated 60 times per sec.
31 citations
TL;DR: To assist in clarifying the present concepts of reactive power, the following introduction to the subject has been prepared.
Abstract: To assist in clarifying the present concepts of reactive power, the following introduction to the subject has been prepared. An analysis of the reactive conventions made by Doctor Silsbee, a member of the subcommittee, is included.
28 citations
TL;DR: In this paper, the product of conductivity by viscosity is proposed as a measure of the electrical purity of an oil used for impregnation of wood pulp paper, and the paper when impregnated with each of the oils.
Abstract: Accurate measurements have been made of the electrical and other physical properties of 10 insulating oils, of a single grade of wood pulp paper, and of the paper when impregnated with each of the oils. Short time charge and discharge curves under continuous potential have thrown further light on the anomalous conduction as found in oils, and permit the separation of the total dielectric loss into two components. Of the total increase of the loss found in impregnated paper, over the separate losses in oil and in dry paper, one component is proportional to the effective conductivity of the oil. The other component, due to reversible absorption, is, for a given paper, a definite function of the free ion content of the oil as indicated by the product of the conductivity by the viscosity. These relations hold over the entire ranges of type of oil and temperature under study. The product of conductivity by viscosity is proposed as a measure of the ``electrical purity'' of an oil used for impregnation. The simplicity of the relations shown suggests that an extension of these studies to other grades of paper should make it possible to predict accurately, from the separate properties of paper and oil, the electrical behavior of any grade as impregnated with any type of oil.
24 citations
TL;DR: In this paper, the steady state stability characteristics of power systems were investigated under various operating conditions, and a simple method of determining the safe and dangerous regions of steady state operation was proposed.
Abstract: Composite loads and induction machines are included in the study of steady state stability characteristics of power systems reported in this paper. Reactive power characteristics must be considered when induction machines are involved, in addition to the real power characteristics which are considered for synchronous machine groups. A determination of the synchronizing power coefficients under various operating conditions, as described herein, provides a comparatively simple method of determining the safe and dangerous regions of steady state operation.
22 citations
TL;DR: In this article, loss measurements were obtained on conductors of three different diameters; namely, 1.125 in., 1.49 in., and 2.0 in. Voltages up to 600kv.
Abstract: Corona loss measurements were obtained on conductors of three different diameters; namely, 1.125 in., 1.49 in. and 2.0 in. Voltages up to 600-kv. line voltage were used in these measurements. Various surface conditions of the 1.125-in. cable were studied. These measurements include tests on the new cable as received, the cable as washed, scratch brushed, buffed and dragged. The aging of the dragged cable was observed for seven months. Data were obtained on the daily variation of loss. The effects of configuration and transposition were studied on No. 22 wire. A description of the modifications in the high-voltage wattmeter for these high-voltage measurements is reported.
22 citations
TL;DR: The transformer subcommittee of the A.I.E. electrical machinery committee presented a progress report covering its work to date on the impulse voltage testing of commercial electric power transformers as mentioned in this paper.
Abstract: The transformer subcommittee of the A.I.E.E. electrical machinery committee presents herewith a progress report covering its work to date on the impulse voltage testing of commercial electric power transformers. A tentative test procedure has been agreed upon, although complete agreement has not yet been reached on all details. It is hoped that this report will stimulate among members of the Institute discussion that will be helpful to the committee in completing a formal test code during the coming year.
21 citations
TL;DR: In this article, the problem of providing protection for rotating a-c machines against lightning overvoltages has two parts: 1. The protection of insulation to ground, which is mainly a question of the magnitude of the overvoltage, and 2.
Abstract: The problem of providing protection for rotating a-c machines against lightning overvoltages has two parts: 1. The protection of insulation to ground, which is mainly a question of the magnitude of the overvoltage, and 2. The protection of turn insulation, which is primarily a matter of wave front. To meet the first requirement, the overvoltage to ground must be limited to a safe value. This is assumed to be approximately equal to the crest value of the 60-cycle high potential test. To fulfill the second requirement, the turn voltage gradient must be limited to conform to the turn insulation. To secure these results, a protective scheme is proposed, which includes arresters 2,000 feet and 500 feet out on the line, or other means, to limit the incoming voltage to 2.5 times the crest value of the terminal arrester rating, a special arrester at the machine terminal to limit the voltage to the crest value of the machine high potential test, and a capacitor at the machine terminal to slope the wave front, thus limiting the turn-to-turn stresses. The capacitor also serves to limit internal overvoltages due to reflection at the neutral. For neutral grounded solidly or through resistance equal to or less than the combined surge impedance of the machine windings 0.1, ?f capacitance is sufficient; while for isolated neutral, capacitance up to 0.5 ?f may be necessary. Ground wires over the line for the initial 2,000 feet are recommended to protect against direct strokes.
TL;DR: In this article, a medium-speed cathode-ray oscillograph with a rotating film has been built for the study of circuit breaker transients, which can record complete story of the formation of arc, subsequent reignitions, and final extinction.
Abstract: A medium-speed cathode-ray oscillograph with a rotating film has been built for the study of circuit breaker transients. The film is wrapped around a drum and rotated in the vacuum at high speed. Each film shows in a continuous trace a complete story of the formation of arc, subsequent reignitions, and final extinction. More than 15 complete cycles may be recorded without excessive blurring. Each film is self-calibrated. A stutdy of several types of circuit breakers with this instrument shows that the nature of the transients at time of arc extinction varies with the type of breaker on test. Different types of breakers tested on the same circuit have different rates of rise of recovery voltage. The deionizing efficiency of a breaker influences not only the arcing time, but the transient oscillation at current zero. The influence of the deionizing efficiency of the breaker upon the stability of the decreasing arc current near current zero is studied and interesting conclusions made.
TL;DR: In this article, a brief description of impulse generators and discharge circuit constants involved in obtaining impulse voltages of desired wave shapes is given, and the relative influences of these constants are recognized.
Abstract: A brief description is given of impulse generators and the discharge circuit constants involved in obtaining impulse voltages of the desired wave shapes. The relative influences of these constants are recognized and simplified discharge circuits are given. The variations in the wave shape and the reasons for the differences in sparkover values obtained with the three test waves, ?/5, 1/10 and 1?/40, are discussed. The degree of accuracy of the sphere gap for use in measuring impulse voltages is outlined. The resistance-capacitance and the resistance-cable voltage dividers for the connection of the cathode ray oscillograph are described and their operation analyzed in detail. Both dividers are shown to be satisfactory when properly arranged. Data are given showing that the same kilovolts per millimeter on the oscillogram for widely different wave shapes can be obtained. A specimen table for recording of complete test data is suggested which, it is thought, will tend to eliminate a lack of uniformity and completeness in data previously reported.
TL;DR: In this paper, the voltage and current wave shape of rectifiers on both the d-c and a-c side of a mercury arc rectifier is studied. But the results of tests on rectifiers are given and are in reasonable agreement with the theoretical values which, for convenience in use, are plotted in the form of curves.
Abstract: This paper gives data on the voltage and current wave shape of mercury arc rectifiers on both the d-c and a-c side. The values of the harmonics at light load are considered first and the modifications of the harmonics under load due to impedance then are studied. The results of tests on rectifiers are given and are in reasonable agreement with the theoretical values which, for convenience in use, are plotted in the form of curves. The relation between the harmonics in rectifiers with different transformer connections is shown and consideration also is given to modifications introduced when the a-c voltage contains harmonics or has a phase unbalance. A brief discussion is given of some methods of modifying the harmonic voltages in this type of apparatus.
TL;DR: In the early days of the electrical industry, surges were relatively mysterious as to their origin, magnitude, and behavior as discussed by the authors, and the ordinary factory tests now required by the A.I.E. rules were the reflection of experience and judgment rather than the analysis which has been made possible in the last few years.
Abstract: IN THE early days of the electrical industry, surges were relatively mysterious as to their origin, magnitude, and behavior. The ordinary factory tests now required by the A.I.E.E. rules were the reflection of experience and judgment rather than the analysis which has been made possible in the last few years. From experience, it was found on the one hand that it was necessary to increase the insulation of some parts of the transformers far above the requirements of the A.I.E.E. rules (i. e., turn and coil insulation bushings) and, on the other hand, to limit the voltages transmitted to the transformer from the line, by the specification of line insulation and protective gaps. In the meanwhile, progress has been made in the laboratory study of the surge characteristics of the insulators, gaps, and insulation structures commonly used in transformers.
TL;DR: In this paper, the authors extended the analysis of the electrical torque on short circuit to cover the transient torques due to losses, which although not so large as the alternating torque may be the most serious factor in the effects of short-circuit torques.
Abstract: The calculation of the alternating torque developed on single-phase short circuit has been discussed by previous authors.1,7 This paper extends the analysis of the electrical torque on short circuit to cover the transient torques due to losses, which although not so large as the alternating torques may be the most serious factor in the effects of short-circuit torques. The resulting mechanical torques in the various parts of the machine are analyzed, and some important conclusions reached: (1) That a rigid stator transmits all the electrical torque developed; while the shaft and coupling of a coupled set, or the springs in a spring-mounted stator in general need transmit only a fraction of the alternating components. The greater part of the alternating components of the electrical torque are absorbed by the inertias involved, when the natural frequency of torsional oscillation is below the rated frequency. This is the case always for spring-mounted stators, and almost always the case for coupled rotors. (2) That the sudden increase in torque on short-circuit conditions determined by losses in the negative sequence resistance (mainly the rotor losses) or in the resistance of the external circuit, may produce higher mechanical torques in shafts and couplings than the alternating components of the electrical torque. (3) That there are other transient conditions which may produce more serious mechanical torques than sudden short circuit.
TL;DR: In this article, it is shown how an air gap of standardized construction can be used to advantage in expressing the impulse flashover of insulators and bushings, and various proposed schemes are shown to give protection to the transformer and against outages for both fast and slow waves.
Abstract: The general scheme of coordination is discussed. Average circuit insulation used in 1930 is shown. The relation that switching surges and arcing ground overvoltages bear on coordination is discussed giving the number and magnitude of such waves found in service. Levels of insulation in and around the station for outdoor and indoor apparatus are suggested. It is pointed out why a point gap offers the most reliable method of establishing the level for impulse testing of transformers. Also, reasons are given why bushings as made at present should not be used as the sole level for impulse testing. It is shown that on account of the similarity of the volt-time curves for insulations and sphere gaps for short impulse waves, the use of a sphere gap in parallel with a rod gap will give an added protection against direct strokes on or near the apparatus terminals. Also, various proposed schemes are shown to give protection to the transformer and against outages for both fast and slow waves. For potential and current transformers having voltage ratings differing from standard it is suggested that the coordination gaps be selected from the curve of gaps vs. rated circuit voltages. It is shown how an air gap of standardized construction can be used to advantage in expressing the impulse flashover of insulators and bushings. Curves are given showing the gap spacings that are the equivalent in flashover to suspension and pedestal insulators for the ?/5, 1/10 and 1 ?/40 positive and negative waves.
TL;DR: The results of the solution of the idealized non-linear differential equations of motion of synchronous motors which describe the pulling-into-step transients are presented to enable the determination of the performance of practically any machine.
Abstract: The Differential Analyzer at the Massachusetts Institute of Technology has made possible the rapid and accurate solution of the idealized non-linear differential equations of motion of synchronous motors which describe the pulling-into-step transients. The purpose of this paper is to present the results of these solutions in a useable form. These results give a rather complete analysis of the phenomena, and thus enable the determination of the performance of practically any machine. One of the factors which is considered in this paper is the time constant of the field circuit with the armature short-circuited. Curves are given showing the additional load which may be synchronized when the field switching is angularly controlled to the best angle. The influence of salient poles has been considered as well as non-uniformity of the amortisseur winding. The practical application of the study is indicated by a numerical example.
TL;DR: In this paper, the radial variation in electrical and chemical characteristics of cable insulation between conductor and sheath is investigated as a valuable means for throwing new light on cable deterioration in service, and an apparatus is described for the rapid accurate measurement of power factor of individual paper tapes taken from cable.
Abstract: Investigation of the radial variation in electrical and chemical characteristics of cable insulation between conductor and sheath is suggested as a valuable means for throwing new light on cable'deterioration in service. An apparatus is described for the rapid accurate measurement of power factor of individual paper tapes taken from cable. A method is given for determining the total oxidation products in the oil from the paper tapes, layer by layer, from sheath to conductor. The results obtained by applying these methods to several types of service aged cable are reported, together with the indications which they give of the relative importance of ionization and oxidation as aging factors.
TL;DR: In this article, it was shown that ordinary wood has considerable insulation strength for lightning voltages, and that wood can be used to advantage in combination with other measures for improving the lightning performance of lines.
Abstract: Operating experience with a large number of lines of various types, utilizing wood as lightning insulation, has demonstrated that ordinary woods have considerable insulation strength for lightning voltages, and that wood can be used to advantage in combination with other measures for improving the lightning performance of lines. The analyses have contributed materially to the present general conclusion that lightning strokes terminating on conductors and structures are responsible for the majority of lightning flashovers, at least on the higher-voltage lines; also that direct strokes must and can be coped with. The methods offering the greatest promise at present are; (1) diverting the lightning strokes from the conductors and conducting the lightning currents to earth without permitting flashover to the power conductors; (2) draining the lightning from the power conductors through fast operating dynamic follow current interrupting devices, thus avoiding insulator flashovers; and (3), a combination of these two methods. High lightning insulations alone are not generally effective in reducing the number of lightning tripouts of lines, though in the lower-voltage ranges, some decrease in the probability of dynamic current following the lightning arcs may be realized.
TL;DR: In this article, a continuation of a four-year operating record of an extensive 132-kv transmission system under lightning conditions, presents and discusses the record for 1930 and 1931.
Abstract: This paper, which is a continuation of a four-year operating record of an extensive 132-kv transmission system under lightning conditions, presents and discusses the record for 1930 and 1931. Operating experience is given on: 1. Yearly line outages due to lightning for all lines. 2. Severity and frequency of lightning storms over the system for a three-year period. 3. Frequency of double circuit outages. 4. Extent of line and station apparatus damage. 5. Effect of tower footing resistance in reducing lightning outages. 6. Reduction in tower footing resistances by the use of driven ground rods and counterpoises. 7. Effect on lightning outages by overinsulation. 8. Relative frequency of single-phase, two-phase and three-phase line faults. 9. Location of lightning flashovers on the line in reference to top, middle and bottom conductors. Conclusions are drawn from the results of the operating experience on these lines.
TL;DR: In this paper, the surge generator of 1,000 kv maximum and the cathode ray oscillograph used in these tests are described, showing the desirability of ultra-violet illumination of the sphere gaps, especially for the smaller gaps and shorter spacings.
Abstract: EQUIPMENT and methods used for the surge testing of distribution transformers at the engineering experiment station at Purdue University are described in this paper. The surge generator of 1,000 kv maximum and the cathode ray oscillograph used in these tests are described. Curves are presented to show the desirability of ultra-violet illumination of the sphere gaps, especially for the smaller gaps and shorter spacings.