H. A. Peterson

Transformer magnetizing inrush currents and influence on system operation

When a transformer is energized, a transient current, known as magnetizing inrush current, generally flows for a short period of time until normal flux conditions are established. Under most practical system conditions, this current transient is of little consequence. However, in very rare cases a combination of circumstances may be obtained which results in this inrush being of such consequence as to impair momentarily the proper operation of the system. Because of the numerous faetors bearing upon this general problem, an investigation has been made to determine the effects of transformer inrush currents under a wide variety of system conditions. It is the purpose of this paper to discuss the mechanism by which inrush currents are produced, the results of tests and calculations, and studies made with the miniature-system analyzer. Factors that determine the significance, of inrush current from the standpoint of system operation and methods for reducing the inrush current or mitigating its effects are also discussed.

Overvoltages During Power-System Faults

OVERVOLTAGES may be produced by lightning, switching surges, faults, both solid and arcing, and the overspeeding of machines due to loss of load. The effect of circuit and machine characteristics on the duration and magnitude of these overvoltages has received considerable attention.1–10 Furthermore, field tests have been made in order to determine the effectiveness of different methods of grounding, and the accuracy of the methods used to calculate the magnitude of overvoltage during system faults.11–13

Switching Overvoltage Hazard Eliminated in High-Voltage Oil Circuit Breakers

High-voltage transmission lines, when de-energized by conventional oil circuit breakers, are often subjected to high-voltage surges which present a real hazard to terminal equipment. The mechanism of surge generation is initiated by circuit-breaker restriking phenomena which are encouraged by the interruption of the large leading currents required to charge moderate and high-voltage lines. By interposing suitable resistors across the interrupting elements during the opening stroke of the breaker, the switching overvoltages may be either eliminated by preventing restriking or so reduced in magnitude in the event of restriking that the system is relieved of their hazard. The development of this achievement is presented chronologically:

A New Differential Analyzer

TECHNICAL progress creates a need for tools which are capable of analyzing physical phenomena more accurately and rapidly. Electric calculating devices (d-c calculating boards, a-c network analyzers, and transient analyzers) represent significant attainments in fulfilling this growing need.

Power-System Voltage-Recovery Characteristics

WITH the increased use of protector tubes, a thorough knowledge of the recovery voltages to which they may be subjected has become highly desirable. The current range over which a tube can be expected to function successfully is necessarily dependent on the voltage recovery characteristics of the system in which the tube is applied. Since many systems have a large range of fault currents for the different fault and system conditions, it is essential that the corresponding voltage recovery characteristics be carefully considered. This paper presents the results of an investigation to determine and evaluate the importance of the factors which influence the voltage recovery characteristics of power systems. A very large number of tests were made on a specially designed miniature equivalent circuit representing a transmission line, connected apparatus, and the fault-clearing device. In that a miniature system was used, this investigation is similar to that made by Messrs. Evans and Monteith and presented in two recent papers.1,2 The results presented in this paper represent refinements and extensions to the understanding of the phenomena which will be of interest to both designers and users of protector tubes or other fault-clearing devices. Factors which have not been evaluated previously are shown to influence the phenomena considerably.

Arcing Faults in Power Systems

IT has for many years been recognized that voltage surges of considerable magnitude could be produced under certain system conditions by switching operations or by arcing faults. Such voltage surges have been studied in some detail in the past, and various theories have been developed to explain their occurrence and to predict their magnitude. The theories were in most cases sound, but the prediction of surge magnitude was on a rather insecure basis.

Abnormal Overvoltages Caused by Transformer Magnetizing Currents in Long Transmission Lines

As power-transmission distances have increased, new problems, both technical and economic have been encountered, analyzed, and taken into consideration in the design and operation of power systems. As transmission distances continue to increase it is logical to expect that in addition to the already exposed problems, new ones may arise which previously have not required consideration. It is the purpose of this paper to present an analysis of a technical problem which falls in the latter category.