C. M. Foust

The Measurement of Surge Voltages on Transmission Lines Due to Lightning

This paper, after referring to the work of previous investigators in the application of the photographic Lichtenberg figures to the measurement of surge voltages, describes results of additional work in this field by the authors. Laboratory calibrations of photographic Lichtenberg figures, using the cathode ray oscillograph and the lightning generator, are shown. Data are presented relative to the accuracy obtainable with these figures as a means of measuring surge voltages. An extension of instrument design is described in which two recording elements are used to give greater certainty of result. Means for connecting a surge voltage recorder instrument to a transmission line by an insulator-string potentiometer are described, and calibration of the instrument with potentiometer is given up to 1400 kv. Specimen field records of surge voltages up to 2000 kv. are shown.

Direct Measurement of Surge Currents

A new instrument, called the surge crest ammeter, based upon the principle of magnetic retentivity has made available a direct and simple method of measuring surge currents. A study of the behavior of 2 magnetic links under the influence of oscillatory surge currents has made this instrument useful in measuring the per cent oscillation as well as crest values of surge currents. Specimen measurements included in this paper show briefly one application of this instrument.

Lightning Investigation at High Altitudes in Colorado

THE operation of transmission and distribution lines in the high altitudes of the Rocky Mountain region had indicated that lightning strokes were not so severe as at lower altitudes. Also glow discharges or corona currents from the earth have been observed at high altitudes from pointed objects and rocks. This investigation was made to determine the probable lightning current at altitudes from 6,000 feet to 13,500 feet and to measure corona current. It has been found that the probable stroke current decreases with increase of altitude from sea level to approximately 18,000 feet altitude at which point it appears that no current would be present. The highest mean temperatures at 18,000 feet do not exceed 32 degrees Fahrenheit, and comparison of temperatures in free air at altitudes up to 13,500 feet check temperatures on the earths surface and indicate that freezing temperatures may limit the formation of lightning.

Electric-Circuit Burning-Clear and Damage Phenomena on Aircraft Structures

Normal and continuous performance of electric circuits is a prerequisite to the effective use of airplanes. Electric short circuits which result in the loss of power for vital control operations or which cause fires are definite hazards. The extensive use of the 28.5-volt d-c aircraft systems, the proposed 120-volt d-c system, and the consideration being given a three-phase 120-208-volt a-c grounded neutral system for high-altitude planes necessitated an investigation into the burning-clear and damage phenomena on all circuits. Short circuits were applied on an aluminum-alloy section of an airplane, and oscillograms of short-circuit current and voltage taken. In both the a-c and d-c systems it was found that the fault-damage and burning-clear phenomena depended upon the energy level in the short-circuit area. When the contact area between the conductor and aircraft structure was small, the energy level was high, and the fault burned itself clear. In such cases the aircraft structure was perforated. Increase in contact area and a consequent reduction in energy concentration resulted in a sustained fault current. In some of these cases a definite welding of the conductor to the aircraft structure occurred, while in others no burning took place.

Measurements Pertaining to the Co-ordination of Radio Reception With Power Apparatus and Systems

EXPERIENCE has shown that electric-power apparatus and circuits may, under certain circumstances, influence radio reception. Groups representing electric-apparatus manufacturers, power companies, radio-apparatus manufacturers and service have been co-operating for several years on the control of this influence. Reports by these groups have summarized progress as this work proceeded. Standard measurement equipments and methods have been established. Papers have been presented also covering various aspects of the general problem. This paper gives the results of practical experience with standard equipments and methods for the measurement of radio influence factors. The various elements in the chain between measured characteristics of the power apparatus and the noise measured in the radio set are analyzed. Quantitative values for the various factors involved in average cases are given.

Some Impulse-Voltage Breakdown Tests on Oil-Treated Paper-Insulated Cables

Data are presented on impulse-voltage breakdown values obtained on oil-treated paper-insulated cables over the insulation thickness range from 0.187 inch to 0.600 inch. The average stress at breakdown approximates 1,600-1,700 volts per mil. High-density papers show some superiority over ordinary-density papers. Cathode-ray oscillograms of the testing wave (1½×40 impulse wave-positive polarity) before and at breakdown are included for a typical test.

Study of Driven Rods and Counterpoise Wires in High-Resistance Soil on Consumers Power Company 140-KV System

THE Consumers Power Company operates an extensive 140-kv system in eastern, southern, and western Michigan. In parts the top soil is sand, sometimes extending to a considerable depth, and tower footings in this soil have very high resistance compared with resistance encountered in other soils.

Some Recent Developments in Impulse-Voltage Testing

Impulse-voltage testing of electrical apparatus and circuits is a steadily growing practice and constant attention is therefore being given to improvements in testing methods. Accordingly, as progress is made it is necessary to describe recent changes. This paper presents a brief discussion of the present situation, describes some improvements in technique of surge analysis of apparatus and circuits, and in equipment for the generation and measurement of test surges.

Abridgment of lightning investigation on transmission lines

The surge voltage investigations, 1926 and 1927, are briefly reviewed, and data given for 1928 and 1929. The cathode ray oscillograph has played a prominent part in the last two years work, and about 115 oscillograms have been obtained. The following new instruments were introduced in 1929: Lightning stroke recorders; field intensity recorder; and rate of change of field intensity recorder. A vast amount of progress has been made in the solution of the lightning problem. Personnel, equipment, and technique are available for the complete solution of the problem by means of field and laboratory studies, carried on simultaneously and supplementing each other.