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General remarks on the protective value of choke coils, their location and insulation, and on the use of extra insulation on the end turns of transformers, either with or without choke coils.

TESTS WITH ARCING GROUNDS AND CONNECTIONS Ernst J. Berg

Vol. xxvii—1908, pp. 741-751 Account of tests with arcing grounds on transformers with singlephase and polyphase connections to study the effect of such grounds under various conditions and indicate the best methods of protecting transformers.

Discussion, incorporated with paper by Percy H. Thomas on "Critical Study of Lightning Records on Taylor's Falls Transmission Line.”

A TRIGONOMETRIC METHOD FOR THE SOLUTION OF ALTERNATING

CURRENT PROBLEMS Harold Pender

Vol. xxvii-1908, pp. 1397-1424 Development of a short method for solving alternating-current problems with examples of its application to single-phase and three-phase transmission lines, transformer and induction motors. Tables of reactance capacity, resistance and drop factors for use in such calculations.

Discussion, pp. 1424-1427, by Messrs. Comfort A. Adams, W. A. Del Mar and L. W. Rosenthal.

Magnitude of errors involved by this method when applied to transmission line calculations.

HIGH-VOLTAGE TRANSFORMERS AND PROTECTIVE AND CONTROLLING

APPARATUS FOR OUTDOOR INSTALLATION K. C. Randall

Vol. xxviii-1909, pp. 189-207 Description of types of apparatus, with estimates of relative costs of outdoor and indoor installations. Operation of outdoor transformer stations.

Discussion, incorporated with that of A. B. Reynders' paper on “Condenser Type of Insulation for High-Tension Terminals."

CONDENSER TYPE OF INSULATION FOR HIGH-TENSION TERMINALS A. B. Reynders

Vol. xxviii-1909, pp. 209-220 Theory, construction and tests of special form of high-tension terminal bushing built with alternate layers of metal foil and insulation.

Discussion, pp. 221-268, including that of K. C. Randall's paper on "High-Tension Transformers and Protective and Controlling Apparatus for Outdoor Installation,” by Messrs. W. S. Moody, Percy H. Thomas, David B. Rushmore, Paul M. Lincoln, E. M. Hewlett, S. Piek, Guido Semenza, A. E. Kennelly, J. S. Peck, Ralph D. Mershon, W. S. Franklin, N. J. Neall, G. Faccioli, C. L. de Muralt, V. D. Moody, M. W. Franklin, A. B. Reynders, Ralph W. Pope, F. G. Baum, O. S. Lyford, Jr., Carl

Schwartz, J. B. Whitehead, John J. Frank, W. L. Waters, L. L. Perry, J. N. Kelman, August H. Kruesi, and D. Kos.

General discussion of the advisability of using outdoor transformer and switching stations. Experience with outdoor high-tension apparatus. Theory and calculation of condenser type bushings. Construction of oil and asphalt filled insulating bushings.

METHOD OF TESTING TRANSFORMER CORE LOSSES GIVING SINE WAVE

RESULTS ON COMMERCIAL CIRCUITS L. W. Chubb

Vol. xxviii – 1909, pp. 417-431 The use, construction and limits of accuracy of a special instrumentiron-loss voltmeter-consisting of a wattmeter connected in series by an exciting winding on a steel core and calibrated to read the impressed voltage of sine wave e. m. f. Also a description of a method of adjusting form factor in core-loss tests.

Discussion, pp. 432-438, by Messrs. Frederick Bedell, Charles P. Steinmetz, M. G. Lloyd, L. T. Robinson, Charles F. Scott and L. W. Chubb.

General discussion of the use and limitations of iron-loss voltmeter. Description of a method for obtaining sine wave from a commercial circuit.

THE TESTING OF TRANSFORMER STEEL M. G. Lloyd and J. V. S. Fisher

Vol. xxviii-1909, pp. 439-467 Conditions and requirements of the wattmeter method of core-loss testing, with description of Bureau of Standards modification of Epstein apparatus. Analysis of core losses and results of tests on large variety of transformer steels.

Discussion, pp. 468-473, by Messrs. L. T. Robinson, V. Karapetoff, C. E. Skinner, J. C. Lincoln, Clayton H. Sharp, Andrew Pinkerton, E. E. F. Creighton and M. G. Lloyd.

Discussion of the relative value of Bureau of Standards method and the Epstein method for commercial testing. Relation of magnetizing current to transformer regulation.

EVEN HARMONICS IN ALTERNATING-CURRENT CIRCUITS John B. Taylor

Vol. xxviii-1909, pp. 725-732 Description of conditions under which even harmonics may be produced in commercial circuits, with special reference to the effect of stray direct current on the performance of stationary transformers. Tests and oscillograms of transformer exciting current with stray direct current in the windings.

Discussion, pp. 733-736, by Messrs. Frederick Bedell, V. Karapetoff, Charles F. Scott, Charles P. Steinmetz and John B. Taylor.

Production of even harmonics in alternators and effect of direct current in the windings of a transformer upon the losses.

CORONA PHENOMENA IN AIR AND OIL AND THEIR RELATION TO

TRANSFORMER DESIGN W. S. Moody and G. Faccioli

Vol. xxviii-1909, pp. 769-798 Theoretical and experimental investigation of corona formation in apparatus of limited dimensions in air and in oil, showing the effect of character of surface, insulating masses, conductor masses, dimensions of conductor, etc.

Discussion, pp. 799-804, by Messrs. John B. Whitehead, J. C. Lincoln, Ralph D. Mershon, S. B. Charters, Jr., W. S. Moody and Harris J. Ryan.

Dielectric strength and conducting character of air. Mechanical strains due to corona under oil. Description of Ryan's corona voltmeter.

ELECTRICAL MEASUREMENTS ON CIRCUITS REQUIRING CURRENT AND

POTENTIAL TRANSFORMERS L. T. Robinson

Vol. xxviii-1909, pp. 1005-1039 Theoretical discussion of the effects of instrument transformers on the accuracy of ammeter and wattmeter measurements, together with tables of correction factors for phase angle error in power measurements. Theory of operation of series transformer showing effects of variation in frequency, secondary impedance, line current, power-factor and wave form. Description of methods of testing series and shunt instrument transformers with ratio and phase-angle performance curves from actual test.

Discussion, pp. 1040-1052, by Messrs. C. H. Sharp, M. G. Lloyd, L. W. Chubb, J. Dalemont, Albert F. Ganz and L. T. Robinson.

Methods of measuring ratio and phase angle of current transformers and correction factor for instrument transformers in polyphase measurements.

SOME PHASES OF TRANSFORMER REGULATION W. A. Hillebrand and S. B. Charters, Jr.

Vol. xxviii-1909, pp. 1253-1267 Experimental study of effect of phase and voltage unbalance on transformer regulation, using different systems of connection.

Discussion, pp. 1268-1278, by Messrs. F. E. Giebel, W. F. Lamme, B. G. Lamme, J. W. White, S. G. Gassaway, C. L. Gory, F. V. T. Lee, H. C. Holberton and W. A. Hillebrand.

General discussion of the effects of voltage unbalance on power apparatus and measuring instruments connected to transformers.

OBSERVATION OF HARMONICS IN CURRENT AND IN VOLTAGE WAVE

SHAPES OF TRANSFORMERS John J. Frank

Vol. xxix-1910, pp. 809-890 Experimental investigation and analysis of the wave form of transformer currents and e. m. f. for single-phase and polyphase connections, showing the practical signification of wave distortion in transformer

operation. Methods of wave analysis fully explained and 176 oscillograms shown.

Discussion, pp. 891-903, by Messrs. H. J. Ryan, G. Faccioli, W. A. Hillebrand, C. A. Copeland, L. B. Stillwell, C. L. Cory, Silvanus P. Thompson, Edmund C. Stone, C. Fortescue, C. A. Adams and J. J. Frank.

General remarks on the causes and effects of wave distortion in transformers. Analysis of hysteresis loops and additional explanations of the results of Mr. Frank's tests.

DISRUPTIVE STRENGTH WITH TRANSIENT VOLTAGES Joseph L. R. Hayden and Charles P. Steinmetz

Vol. xxix-1910, pp. 1125-1158 Account of experimental investigation of the effects of time and energy on the dielectric strength of air and oil. Full description of the method of testing and analysis of results. Characteristic curves of the dielectric strength of air and oil with different shaped electrodes, showing effect of duration of stress and of the energy behind the stress. Empirical equations.

Discussion, incorporated with that of H. W. Tobey's paper on “Dielectric Strength of Oil."

curves.

DIELECTRIC STRENGTH OF OIL H. W. Tobey

Vol. xxix-1910, pp. 1189-1207 Description of the properties of insulating oils and methods of testing and handling such oils. Tests showing effects of form of electrode, temperature, and moisture on dielectric strength of oils, with characteristic

Analytical and experimental study of methods of drying and filtering oil.

Discussion, pp. 1208-1232, including that of paper by Messrs. Joseph L. R. Hayden and Charles P. Steinmetz on “Disruptive Strength with Transient Voltages," and Mr. J. B. Whitehead's paper on “The Electric Strength of Air," by Messrs. D. B. Rushmore, V. Karapetoff, Percy H. Thomas, A. E. Kennelly, W. H. Pratt, E. E. F. Creighton, J. C. Lincoln, Charles F. Scott, Harris J. Ryan, R. D. Mershon, C. P. Steinmetz, John B. Whitehead and M. A. de Chatelain.

General comments on the results of the tests, with various suggested explanations of the phenomena of corona, and relation of diameter of the conductor and other factors to the apparent dielectric strength of air.

DETERMINATION OF TRANSFORMER REGULATION UNDER LOAD CONDITIONS AND

SOME RESULTING INVESTIGATIONS Adolph Shane

Vol. xxix-1910, pp. 1281-1294 Description of a method of measuring directly transformer regulation, also a method of direct determination of the transformer impedance triangle. Full account of tests made to establish the accuracy of the methods.

Discussion, pp. 1295-1302, by Messrs. Charles Fortescue, E. A. Wagner L. T. Robinson, Ralph W. Atkinson and Adolph Shane.

Objections to the author's methods. Modifications of the author's methods.

SOME RECENT DEVELOPMENTS IN EXACT ALTERNATING-CURRENT

MEASUREMENTS Clayton H. Sharp and William W. Crawford

Vol. xxix--1910, pp. 1517-1541 Description of design and construction of various precision devices, synchronous reversing key, adjustable mutual inductance, phase shifter and heavy current non-inductive shunt-showing their application in the accurate measurement of ratio and phase angle of series and shunt instrument transformers and in an alternating-current potentiometer.

Discussion, pp. 1542-1552, by Messrs. V. Karapetoff, L. T. Robinson, W. H. Pratt, C. P. Steinmetz, Clayton H. Sharp and William W. Crawford.

General remarks on precision measurements of alternating-current quantities. Description of a water-cooled electrodynamometer, also of a method of measuring very high frequency alternating current.

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