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The calculation of a transformer's parasitics, such as its self capacitance, is fundamental for predicting the frequency behavior of the device, reducing this capacitance value and moreover for more advanced aims of capacitance integration and cancellation. This paper presents a comprehensive procedure for calculating all contributions to the self-capacitance of high-voltage transformers and provides a detailed analysis of the problem, based on a physical approach. The advantages of the analytical formulation of the problem rather than a finite element method analysis are discussed. The approach and formulas presented in this paper can also be used for other wound components rather than just step-up transformers. Finally, analytical and experimental results are presented for three different high-voltage transformer architectures.

Motor current signature analysis is the reference method for the diagnosis of induction machines. However, it features some drawbacks, as it is bound to steady-state conditions, and fault signatures may be created by different overlapping phenomena. This paper presents a full-time domain-based method for the quantitative evaluation of electrical faults in induction machines. It relies on stator current measurements; thus, it is compliant with switching power converter drives, provided that a proper current measurement technique is available. Moreover, it allows an accurate quantification of faults without requiring spectrum analysis; hence, it achieves high resolution even with a low time acquisition period. A fault index is computed as the energy of the signal in a suitable ldquofault bandwidth,rdquo thus reducing the effects of frequency variations. The aforementioned advantages are perfectly suited to time varying signals and to embedded drive diagnostic systems.

The paper deals with simulations of power line channel transfer functions in Network Simulator version 3. Firstly, an empirical model and calculation of the channel transfer function are given to reflect the necessity of channel transfer function for Power Line Communication system design. The framework for Power Line Communication in Network Simulator version 3 and then the necessary extension implementation are introduced. Other simulators are also mentioned. Secondly, various scenarios were implemented for the analysis and simulation of power line channel transfer functions. New scenarios for large topologies and for different approaches to calculate primary parameters were created. In the simulations, various kinds of topologies are considered for an analysis of the power line transfer function. The simulation part also focuses on the simulation of channel transfer function where the time- and frequency-selective impedances are considered. Finally, the last part focuses on measurements and a comparison of the simulation results with real measurements are given.

A methodis given in this paper for determining the wave forms of alternating currents which uses no highly specialized measuring apparatus. No contact maker is used, and it is generally appliable on polyphase circuits only. It is recommended as a method which may be used under many circumstances where the special contact maker apparatus is not available.

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The purpose of this paper is to present a system of design, not based upon the cut-and-try method associated with the use of an output constant, but directly upon general experimental data and the commercial guarantees of the machine; and to deal with the limitations imposed upon the development of large machines by the quality of brushes obtainable.

The division and arrangement of units and the system of electrical connections in a power station have much to do with the cost and successful operation of the plant. Conditions vary to an extent which prohibits the use of standard arrangements, but certain general principles are applicable to all layouts. For the purpose of this paper the factors to be considered are generators, transformers, lines, bus-bars, and switches with their relays. The kind of load, number of stations on system, lines in parallel, number of lines, size of generator and transformer units, and local conditions, govern the power house arrangements.

During the last few years there has been a gradually increasing tendency in this country toward the use of three-phase transformers on three-phase circuits instead of groups of three, or in some cases two, one-phase units. It is the purpose of this paper to outline briefly these two systems, and to point out as far as possible the important features of both, with their advantages and limitations.

In the summer of 1910 some tests were performed on the lines of the Great Western Power Company, which are operated at 100,000 volts, to obtain information on oscillations and rises of potential, due to switching operations. In these experiments the oscillograph was extensively used and this paper deals with some of the most important and representative records.

Detectors are classified as of the relay or of the transformer type. Relay detectors are arranged so that the energy for the indicator response comes from a local source of energy at the receiving station. Transformer detectors utilize the received energy for producing the indicator response. The need of an amplifying transformer type detector, which selectively neglects static, is mentioned. The basis of the heterodyne receiver, namely, the audible beats produced by the interference of two vibrations of inaudible (radio) frequency received on a nonpolarized receiver, is then fully considered. The development of the heterodyne receiver, its circuit arrangements, and the apparatus employed are described in detail. The use of the heterodyne in the Arlington‐Salem tests and the results obtained are given. Much interest has been shown in the heterodyne receiver since its use in the recent test between the Fessenden stations of the U.S. Navy at Arlington, Virginia, and aboard the cruiser, Salem. These trials mark the first public use of the heterodyne system, which has often been called the greatest of Professor Fessenden’s inventions; but, as a matter of fact, the method has been utilized in the National Electric Signaling Company’s plants for a number of years. It is the purpose of the present paper to explain the heterodyne principle, and to describe the apparatus by means of which it is put into practice. Since the invention involves a number of points which are quite outside the range of observation of the average worker in radio signaling, an introductory consideration of the fundamentals of receiving instruments in general is desirable. Every radio receiver is composed of two main parts; an energy absorber and an indicator. In some special forms of apparatus these two elements may be physically combined, but functionally they remain as distinct as before. The relation between the energy received and the response of the indicator, together with the process whereby the receipt of that energy effects the indication, probably serves as the best basis for classifying receivers in radio signaling. In the receiving instruments originally used (which were mainly various arrangements of coherers with auxiliary

Notwithstanding the now wide-spread use of the Audion as a detector in radio telegraph and telephone service few accounts of independent research into the nature of this instrument, or even cursory descriptions of its operation, seem to have been recorded, since the original paper presented before the American Institute of Electrical Engineers in 1906. At that time, pending patent applications prevented the presentation of a detailed description of certain forms and improvements which are to-day common knowledge among radio engineers. It is my purpose herein to outline briefly the subsequent development of the Audion, both as a radio detector and as an amplifier of minute electric impulses. The improved Audion, containing one hot and two independent cold electrodes, is described, and its action as a sensitive detector in radio telegraph and telephone work outlined. Its actiont is shown to be not that of a simple rectifier or valve, but that of a true relay device. The secondary circuit of a radio receiving transformer is connected in shunt between the "grid" electrode and the filament. The telephone receiver and dry battery are connected between the plate electrode and filament. There appears to be no known limit of sensitiveness below which the effect of minute received energy fails to be registered. The device is constant and reliable, requiring only initial adjustments of battery voltages. The Audion is incontestably a "potential operated" device.

The paper presents a very simple method for obtaining speed-time and distance-time curves, which avoids the usual step-by-step process with its tedious calculations. The method consists of plotting certain so-called ``service characteristics'' upon the diagram of motor characteristics with the speed-current and traction-current curves. The time and distance increments corresponding to assumed speed increments are found by simple divider operations.

The demand for testing dielectric media in terms of crest voltage has resulted in several schemes of measuring high voltage. The paper mentions and compares some of the methods of high-voltage measurement and describes in more detail the crest voltmeter which has been found to be more satisfactory in commercial testing than the spark gaps which have been adopted by the Institute in the Standardization Rules. The construction, operation, accuracy and applications of the crest voltmeter are briefly described. The present Standardization Rules for the measurement of high testing-voltages recommend spark-gap methods which under certain conditions are impractical, inconvenient, and dangerous. The summary states that the spark gaps should be only a calibrating standard and a more practical instrument, such as described, the preferred working standard.

It is generally agreed that a sine wave of electromotive force at generator terminals and on transmission lines is best. A sine wave is now specified as standard by the Standardization Rules of the Institute, but the present methods for prescribing allowable limits and for determining how near an actual wave is to a true sine wave are very unsatisfactory. The Standards Committee, through a sub-committee, is studying the subject in order to ascertain whether a standard can be specified that will be more suitable in its characteristics and more practical in its application. As a contribution to this study, the characteristics of a certain type of standard are here set forth. It is hoped that various points of view and much information may be brought out in discussion, which may be on the general subject and not limited to the particular phase discussed in the paper.

The purpose of the paper is to outline several methods by which single-phase power may be supplied from a polyphase system and to discuss their advantages and disadvantages. The unbalance in voltage when single-phase power is supplied direct from a polyphase circuit is explained. The law of distribution of load in the polyphase system is deduced, and the limitations of this method of supplying single-phase power are discussed. Single-phase generation is one solution of the problem, motor or steam drive may be used depending on the size of unit required. An outline of the theory of the single-phase generator is given from different points of view. The essential requirements for phase balancing are deduced from which an outline of the theory of phase balancing is developed. Attention is called to the requirements of the control apparatus. The behavior of the balancer under short circuit is given consideration. The merits of single-phase generation and phase balancing in the case of a single-phase load from one phase are discussed, with the conclusion that there is little difference in cost between the two schemes and there is much to be said in favor of single-phase generation for such a case.

The paper describes the conditions on the system in Toledo which was originally delta-connected. Serious trouble was experienced when a short circuit occurred especially with synchronous apparatus connected to the line which invariably failed due to the voltage drop occasioned by the severe short circuits on the delta system. This trouble was overcome by changing the transmission to a Y system with the neutral grounded. The effect of a short circuit with the new connection has been decidedly minimized.

This paper discusses the voltage changes, inherent in d-c. circuits, upon change of load. These variations are independent of i r drops or speed of prime movers. A simple means of mitigating their effect is given.

THE use of a number of different definitions of “power factor” as applied to unbalance polyphase system has led to much confusion. The present paper points out the mutual relations of a number of possible definitions and their relative merits for specific types of circuits.

THIS paper is a more complete presentation of the subject of power representation by means of symmetrical coordinates, which was briefly outlined in the author's paper on Symmetrical Co-ordinates presented at the 30th Annual Convention, 1918.

Owing to the advantages to be realized from the use of the star-star connection in interconnecting high-voltage transmission systems and from the fact that this connection requires the use of an auxiliary winding connected in delta to stabilize the neutral point or to decrease the inductance in the ground connection, a great majority of the transformers designed for interconnecting transmission lines are three-winding transformers. Another type of transformer which would be included in this general class would be that having an auxiliary winding for feeding a synchronous condenser used in controlling the voltage at the receiver end of the line. Many of the alternatives suchl as the choice between self-cooling or water-cooling, or between single-phase units and three-phase units, differ in no way from the same questions on transformers for ordinary service. However, there are a number of important features peculiar to three-winding transformers for these classes of service that complicate the design and operation to an extent that justifies special consideration of these problems. This paper will call attention to these special problems and indicate the way in which the design and performance of transformers for these classes of service are influenced by them.

This paper introduces adaptive decision-making logic to improve the performance of distance protection of transmission lines. The proposed approach incorporates the trajectory of the measured impedance into the relay final decision-making logic through a weighting procedure. Two criteria are used to weigh the impedance plane appropriately, where higher weights are assigned to the faults occurring at the interior areas of the relay protective zone and low resistance faults. The weights assigned to impedance samples are added together considering the amount of smoothness of the measured impedance trajectory. An adaptive neurofuzzy inference system (ANFIS) is used to implement the proposed decision logic. Meanwhile, the fault current amplitude is considered as the other input of the ANFIS network to accelerate the relay operation for close-in faults and to incorporate an index for the source-to-line impedance ratio into the final decision-making logic. Extensive simulation studies using PSCAD/EMTDC software indicate that the proposed approach provides a very reliable technique to make the distance protective scheme faster and smarter. It helps to achieve the optimal compromise between the protective relay operation time and security.

Relays have been used for many years in wire telegraphy and other electrical work. The practical operation of relays actuated by received radio signals is a comparatively recent development, and has been made possible by the development of the electron tube amplifier. This paper describes the development and the operating principles of a type of relay recorder which is designed to operate from the output terminals of a radio receiving set and which may also be operated by any other source of audio-frequency signal. By the use of special electron tube circuits the audio-frequency signal is caused to operate an ordinary telegraph relay. In order to avoid the necessity for using a very sensitive relay, designed to operate on currents of a milliampere or less, which would have delicate adjustments and light contacts and spring tension, advantage was taken of an electron tube amplifier, which has now become a reliable radio instrument, to increase the input voltage to the relay circuit thus making possible the use of a simple ordinary high-resistance telegraph relay. The relay device has therefore been developed to operate from the output circuit of any suitable amplifier in place of the ordinary telephone receivers. The operation of the relay may serve to work a sounder, buzzer, tape register or any mechanism for remote control by radio. Two types are described. One type is designed to be operated from batteries.

The process proposed in this paper is called ``Qualitative Analysis of Transmission Lines'' because of its similarity to chemical qualitative analysis. Based upon a previous presentation by Mr. Percy H. Thomas the ``critical load'' for transmission lines is introduced with a simple formula for determining it and various rules are given for the variation of power factor voltage, etc., of a line by relating the actual load to the critical load. The most important parts of Mr. Thomas's presentation are abstracted and presented showing the fundamental physical and mathematical basis for this method of analysis. The detail development of the formula for the critical load is then given and the effect of the various line constants upon it are briefly discussed. Working from the critical load a vector interpretation of the action of a long high-voltage transmission line is given. From this vector interpretation it is possible to predict certain essential operating characteristics of transmission lines. Based on the previous generalities practical examples of transmission lines operating at critical load are then given showing how it is possible by the qualitative analysis to predict desired conditions of operation. Two of these examples show the operation of a 3100 mile copper transmission line of 220 kv. nominal potential. Another shows a 3875-mile aluminum transmission line. In the conclusion an appeal is made for further work along these lines and it is pointed out particularly that this is not an approximate method but an exact method for ``Qualitative Analysis of Transmission Lines.''

There is great need for a better understanding on the part of transmission engineers of the traveling waves on lines. The complete analysis of such waves is inherently complicated, but there are certain approximate relations by which the progress of waves on our ordinary systems may be readily studied. Before any theory is accepted for practical use, however, it is necessary to check it carefully by experiment. This paper gives quantitative checks of the principal aspects of the theory of the traveling waves due to suddenly applied continuous potentials, as originally given by Heaviside. It is shown that this theory based on fixed line constants predicts accurately the progress of waves as far as magnitudes, speed of propagation, and shape of wave except at the wave front are concerned. The effect of steepness of wave front is discussed with relation to its practical aspects. It is proposed to follow this paper shortly with similar results on alternating-current transients. Tests on artificial lines and on an aerial line in the field are compared with computed results. Working rules for considering the progress of transients are discussed, together with certain results that may be obtained by their use. An extension of approximate analysis is given in an appendix, which is sufficiently accurate for transmission lines of the present length, and which is sometimes easier to handle than the complete theory. Reflections at apparatus, and at line junctures, is discussed qualitatively. There are several cases in which extreme potentials may arise.

This paper includes a brief description of the power circuits and radio equipment used in the carrier-current system; the method of calling employed, and use of this system as a trouble detector and recorder of switch operation.

This paper presents the theoretical basis for a theorem by which the practical analysis and visualization of short-circuit phenomena can be greatly simplified. The theorem follows from the approximation of neglecting resistance in the application of Kirchhoff's Law to closed circuits. Thus in any problem of short circuits in which the effect of resistance is negligible in the initial moment, and this includes many of them, the theorem applies. It is: If the resistance of a closed circuit is zero, then the algebraic sum of the magnetic linkages of the circuit must remain constant. Illustrative examples are given, including the transformer, the single-phase and polyphase alternator, and the induction motor.

Although this paper treats of the general case of floating neutral polyphase systems, one of its prime objects is to find the very simplest method of solving three-phase unbalanced star circuits. The method presented below is considered much simpler than the one in which the star circuit is replaced by an equivalent delta circuit; also simpler than the method of replacing one unbalanced circuit by two balanced circuits, one being subjected to direct phase rotation and the other to opposite phase rotation. Although these methods are fairly useful for the three-phase case, they become very unwieldy for a number of phases greater than three. Not only is this method more simple than any so far proposed, but it is a direct method, based on a straight forward application of Kirchhoff's Laws. A final and very important advantage of the method is that all the results are perfectly general, applying equally as well to a single-phase system as to any polyphase star system.

The use of so-called “artificial lines” — i.e. miniature models of electric circuits — for experimental laboratory studies of transmission-line phenomena is well known. The miniature models are commonly made so as to represent, in true proportion, the electrical constants of a real line. Thus there are artificial telephone lines, artificial submarine cables, artificial long-distance power-transmission lines, etc. A miniature line is a true model of a real line to the extent that the miniature circuit has, for any desired degree of approximation, the same electrical behavior as the full-size circuit. Such laboratory models frequently permit — far more conveniently than the full-size circuit — the study of actual circuit phenomena in a practical and efficient manner. When their limitations are properly understood, miniature circuits may be of great value to transmission-line and operating engineers. Miniature electric circuits may for the present purpose be divided into two general classes: (1) Miniature circuits intended for the study of problems on long lines, such as lines having continuously distributed circuit constants. (2) Miniature circuits for the solution of problems involving complete system networks, inclusive of generating-station and substation apparatus. The following paper deals with a three-phase miniature a-c. system of the network type. The circuit includes synchronous machines, transformers, adjustable resistors, reactors, and condensers, for complete representation of generating stations, substations, lines and loads. The circuit connections are variable, so that any system having not more than the available number of circuit elements may be represented for the correct experimental solution of low-frequency problems. This miniature system has so far given about three years of service in the experimental analysis of transmission system behavior, for existing systems and for systems to be constructed. The problems solved have been within the realms of both the designing and the operating engineers, and have been applied to power systems in this country as well as abroad. One of the by-products of the miniature system is the confirmation and extension of the theory of transmission-line phenomena. Several prominent engineers have expressed the belief, and made the prediction, that after a few years of proper use of the miniature system, the theory and calculation of the present transmission problems will have been so well established that experimental solutions will no longer be necessary. In this paper are given (1) a brief discussion of some of the present problems calling for solutions by the miniature experimental method, (2) a full description of the miniature equipment, (3) an outline of the operating procedure in the solution of problems, and (4) an example illustrating the application of the miniature equipment.

Carrier-current communication over transmission lines has been developed to a point where its practicability and value are thoroughly established. This paper discusses several recent developments in apparatus and methods of operation. Carrier-frequency energy flow along the line is discussed briefly to give a mental picture of the electromagnetic and electrostatic conditions existing. Standard 50 and 250-watt apparatus are shown in the illustrations and described briefly.

A great many uncoordinated researches and observations have been made of lightning on transmission lines both in the field and in the laboratory. It is the purpose of this paper to coordinate this work with a view of determining the various types and order of magnitude of predatory voltages to which transmission lines are subject. No claim is made for exact results. If it were possible to obtain such results, they could apply only to specific cases. A knowledge of the general types of disturbances and their order of magnitude should be of great value in determining the best means of providing against them. Failures of apparatus can be provided against in a number of ways, for instance, by excessive insulation; by less insulation but a design to prevent local high stresses; by prevention of high lightning voltages by placing the line under ground; by greatly limiting the possible voltage by a ground wire; by limiting the time of application of the high voltage by arresters; or by combinations of the above. Obviously, the matter of design and economics is also of importance in considering the problem of protection. The technical part of the discussion will not be limited to cloud lightning, but will cover other disturbances. Recent work of the author with his lightning generator and model transmission lines with and without ground wire will be included.

The need of infornmation at one point as to power conditions in large systems for load dispatching, billing, or other purposes has led to the development of various methods of transmitting power readings over long distances. The development of superpower emphasizes this need and the perfection of means of communicating complete information as to power and load conditions will hasten the development of superpower. We wish to discuss various automatic methods which may be employed for remote metering. Our paper will describe the following methods: 1. Frequency 2. Inverse Current 3. Potentiometer 4. Position 5. Voltage 6. Current 7. Impulse

Maintenance of the transmission efficiency of the telephone plant is conducted by a special force using methods and apparatus that have been developed for this purpose. This paper gives a brief description of the transmission characteristics of some of the common types of telephone circuits, outlines a general method for measuring their transmission efficiency and describes several of the most modern types of transmission measuring sets together with a brief mention of the oscillators which supply the power for testing.

In the sale of electric power especially in large amounts at high voltages, current transformers are universally used to operate the meters from the readings of which the bills are made out. While the secondary currents of such transformers reproduce fairly faithifully on a smaller scale the conditions of current strength and phase existing in their primary circuits, meter engineers are realizing more and more the importance of checking up the accuracy of this link in the chain of measurements. Many possible methods have been suggested for testing the accuracy of current transformers. Some are delightfully simple and inaccurate while others involve relatively intricate connections and sensitive apparatus, but give correspondingly more exact results. The present paper gives a critical discussion of the various possible methods with data as to the advantages and disadvantages of each, in order to serve as a guide to the meter engineer in selecting the method best suited to the particular working conditions of accuracy, speed, volume of testing, and intelligence of labor, existing in his plant. In all eleven distinct methods are described, and supplementary suggestions are made concerning various types of detecting instruments, etc.

Consideration is given to the method of determining and expressing the transmission efficiencies of telephone circuits and apparatus, and of the desirable qualifications for a unit in which to express these efficiencies. The ``transmission unit'' described in this paper has been selected as being much more suitable for this purpose under present conditions than the ``mile of standard cable'' which has been generally used in the past.

Referring to Dr. Carson's paper on "Static-to-Signal Ratio," the author discloses a system of twin side-band radiotelephonic transmission, wherein the carrier component is suppressed, but which differs from other carrierless transmitting systems in that a homodyne receiver is not required. This last peculiarity makes the system particularly suitable for short wavelength transmission and especially so in view of the fact that the disadvantage of broader wave-length spectrum inherent to twin side-band transmission vanishes as the wave-length decreases.

The paper deals firstly with the early forms of quadrodes or four-electrode tubes and leads up to a complete description of the Marconi type of quadrode or F. E. I. type and the attendant amplifier circuit. The amplifier described utilizes one F. E. I. tube and effects a one-stage radio frequency, a rectification, and a one-stage audio frequency. Information is detailed as to the practical experience obtained with this amplifier and quadrode, this particular combination now being a commercial issue to ships the radio installations of which are controlled by the Marconi International Marine Communication Company.

It is often necessary to use a series of consecutive tunablr circuits to cover a large range of wave lengths or frequencies. The papee describes a method of determining the constants of each circuit when the total wave length range and the accuracy of setting required in each intermediate range are given. Overlap between successive scales is provided for, and a method is indicated by which further conditions, such for instance as a limiting value of the damping of each circuit, may be introduced. The paper thus reduces the calculations of such circuits from an empirical problem to a straightforward engineering proposition.

This paper describes the development of the super-heterodyne receiver from a wartime invention into a commercial form of broadcast receiver apparatus now available to the general public. The success of the development is due to the low filament consumption vacuum tube and to the reduction in the number of tubes required by self-heterodyning, reflexing, and improvement in transformer design. Instances are cited of trans-Atlantic and trans-continental reception of broadcast stations by completely portable sets constructed in accordance with the methods described.

Current-limiting reactors are desirable only insofar as they are strictly reliable protective devices. In this paper general considerations of the factors affecting reliability are outlined, and some of the early weaknesses and the means taken to eliminate them are enumerated. Modern reactors are considered to be reliable and on large systems are considered practically indispensable. The thermal duty of a current-limiting reactor is a consideration affecting the reliability which has been the subject of considerable discussion. Various opinions have been expressed ranging from the idea that a reactor should fail first and open the circuit in the event of short circuit, to the idea that it should have enough thermal capacity to withstand short-circuit currents for long periods of time. A middle ground is suggested in this paper where recognition is given both to the protective function of the reactor and to the practical consideration of dimensions and cost.

The above paper describes briefly calculations required in the parallel wire system used by the Bureau of Standards for radio frequency standardization. Formulas involving a correction term are given by means of which the standard frequency can be calculated from the distance between two consecutive maximum settings along the parallel wire system. A numerical example is added, showing the magnitude of the correction term.

This paper presents a new adaptive hysteresis current control with unipolar pulse width modulation based on magnitude and time errors. Variable switching frequency due to fixed hysteresis bands is known as a drawback of hysteresis current control used in power system applications, which generates sub-harmonics and low order harmonics, and affects the quality of the power systems. Adaptive hysteresis band is a classical method to control the switching frequency. Several issues and solutions have been discussed and proposed in this paper to keep the switching frequency constant. Simulations have been carried out to verify the proposed adaptive hysteresis band controller and the results are discussed in this paper.

A device has been developed by the Bell System for suppressing ``echo'' effects which may be encountered under certain conditions in telephone circuits which are electrically very long. This device has been given the name ``echo suppressor'' and consists of relays in combination with vacuum tubes, which are operated by the voice currents so as to block the echoes without disturbing the main transmission. This paper gives a brief description of this device, together with a discussion of its possibilitie and limitations. A number of echo suppressors have been operated on commercial telephone circuits tor a considerable period so that their practicability has been demonstrated.

The paper discusses a method for determining the separate leakage reactances of transformer windings, originally suggested in 1921 by W. V. Lyon.2 The method is applicable only to three-phase banks of three identical transformers, and makes use of the third harmonic electromotive force and current which are introduced into the windings by the inherent magnetizing characteristics of the iron. Attempts made to determine the separate leakage reactances of a single transformer did not meet with success. The method may be used both with ``two-winding'' and ``multi-winding'' transformers. However, it is particularly convenient when the transformers have more than two windings. Laboratory tests have been made on small experimental, two-winding and three-winding transformers, and field tests on a bank of three-winding power transformers. The results in each case warrant the conclusion that the separate leakage reactances may be obtained with sufficient accuracy for engineering purposes.

The paper considers the performance of the stored mechanical energy in the moving masses connected synchronously to a transmission system during changes in load, changes in input, and changes of transmission capacity, The stored mechanical energy greatly affects the performance of a transmission system, during sudden changes in transmission line capacity occasioned by switching out or in a parallel circuit. Such switching operations lead to oscillations of input due to the interaction of stored mechanical energy and the altered difference in phase between generated and received voltages over a transmission line.

The purpose of this paper is to derive a practical method of design based upon the catenary formulas for spans whose supports are not at the same elevation. It is furthermore intended completely to formulate the method for applying it to any cable which is suspended freely or is uniformly loaded, as well as for obtaining its characteristics after the temperature or loading conditions of the cable have changed. After a brief survey of the present need for more accurate methods of mechanical design of transmission line cables, the several formulas which are adapted to spans with supports at unequal elevations are given, and the method of using them is fully explained. All such special formulas are fully derived in the appendix. The first method given depends somewhat upon interpolated values from the symmetrical span data. A second pure interpolation method is next described which has the advantage of being shorter than the first as well as more accurate, since it depends upon fewer interpolated values from mathematical tables. The use of these two methods is then fully illustrated by the solution of three typical spans. Data for the cable used in symmetrical spans are first given, and from these the solution for the span with supports at unequal elevation is obtained. For the purpose of comparison the computations used in obtaining the desired values by each method are given in full for one of the spans chosen.

At this time the power limit of transmission lines is a live subject and presents such complications as to require very careful analysis. The paper points out the essential features to be considered in a study of the problem, and calls attention to some out-standing results of an experimental investigation of the subject with a view to clarifying some of the points that have been under discussion in the past two years. It is shown that the problem of stability is not necessarily confined to long-distance, high-voltage transmission, but may be present in any system where the impedance of the transmitting circuit is high compared with the load to be carried. While the impedance of the transmission line and transformers plays an important part in establishing the breakdown point of a system, the characteristics of synchronous apparatus with the method of voltage regulation used are of equal importance. It is shown that the synchronizing power of synchronous apparatus is largely dependent upon the field excitation at the time excess load is applied, that field excitation is determined by the circuit conditions under steady load, and, in order to provide for increase of excitation with increasing loads of considerable magnitude, some automatic means of controlling the field is essential. The rate at which mechanical load in large quantities can be added to a system is limited on account of the necessity of change in angular displacement between the generators and receiving bus; this changing angle-requires relative speed change, which takes time.

This paper discusses series street lighting circuits from the point of view of their relations to nearby telephone circuits. These lighting circuits often have a much greater inductive influence in proportion to the amount of power transmitted than have most other types of power distribution or transmission circuits. This is due to the relatively large distortion in wave shape of voltage and current on certain types of these lighting circuits, and to the unbalanced voltages to ground which occur with series layoutts. Three general types of lighting circuits are discussed. These are a-c. arc circuits, d-c. arc circuits supplied by mercury arc rectifiers, and alternating-current incandescent circuits. Of these, the incandescent type of circuit, in which the lamps are equipped with individual series transformers or auto-transformers, is the most important in this respect. Measures for reducing interference from these circuits are discussed. It is hoped that the information given in the paper will be useful to power and telephone engineers in their cooperative efforts to solve these difficulties.

This paper is to discuss two forms of polarized telegraph relays which have been developed by the Bell System and applied originally to the metallic telegraph system. One of these relays was designed primarily for operation under severe and exacting circuit conditions and the other for application generally. Both relays are of the same general construction except that the former is more sensitive than the latter and is furnished with an auxiliary accelerating winding. Furthermore, this relay has incorporated in it certain refinements in construction and materials, which cause it to be extremely sensitive and to give reliable service for a comparatively long period without attention. The construction is of special interest in that the polarizing force of the permanent magnet is neutralized by the mechanical restraining force of the armature. A magnetic material having characteristics well suited to relay design and a new contact material are employed, which greatly improve the operating characteristics of the relay.

This paper describes in detail the equipment and circuit used in the production of the single sideband for trans-Atlantic radio telephony in the experiments at Rocky Point. The set consists of two oscillators, two sets of modulators, two filters, and a three-stage amplifier. The oscillators and modulators operate at power levels similar to those in high-frequency communication on land wires. The three-stage amplifier amplifies the sideband produced by these modulators to about a 500-watt level for delivery to the water-cooled tube amplifiers. The first oscillator operates at about 33,700 cycles. The modulator is balanced to eliminate the carrier; and the first filter selects the lower sideband. In these trans-Atlantic experiments the second oscillator operated at 89,200 cycles, but might operate anywhere between 74,000 and 102,000 cycles. The second modulator, which is also balanced, is supplied with a carrier by the second oscillator and with modulating currents by the first modulator and first filter. The second filter is built to transmit between 41,000 and 71,000 cycles, so that by varying the second oscillator, the resulting sideband, which is the lower sideband produced in the second modulating process, may be placed anywhere between these two figures. Transmission curves for the filters are given as well as some amplitude-frequency performance curves of the set.