David C. Prince

Ultrahigh-speed reclosing of high-voltage transmission lines

Reclosure of circuit breakers following a fault on a high-voltage transmission line with a minimum of delay in order that synchronous load will not fall out of step is described in this paper. Apparatus that performs a complete operation in approximately 20 cycles on a 60-cycle system may be used to obtain a high degree of service continuity from a single-circuit transmission line.

The Current-Limiting Power Fuse

1. Current-limiting fuses have been developed and tested which will interrupt a short circuit well before the current reaches the maximum value it would attain were the fuse not present. 2. These fuses have many desirable characteristics such as high interrupting capacity, silent operation, no discharge of any kind during interruption, and practically no pressure generation. 3. Such fuses have an ideal application in the protection of small-capacity circuits connected to high-power buses because the associated devices in the circuit are not subjected to the heavy momentary short-circuit current which would exist were the fuse not present.

Ultrahigh-Speed Reclosing or High-Voltage Transmission Lines

Reclosure of circuit breakers following a fault on a high-voltage transmission line with a minimum of delay in order that synchronous load will not fall out of step is described in this paper. Apparatus that performs a complete operation in approximately 20 cycles on a 60-cycle system may be used to obtain a high degree of service continuity from a single-circuit transmission line.

The Oil-Blast Circuit Breaker

A further development of the explosion-chamber principle avoids the mixing of arc and oil in the main gap, utilizing the high oil pressure together with smooth and controlled flow of oil from the chamber to sweep away the arc, replacing it with a stream of clean oil. With this design tests show that a voltage of 44 kv. per inch across the working gap actually is reached.

The Theory of Oil-Blast Circuit Breakers

Analyzing the oil-blast theory, data are presented to show effect of time and carbon on oil dielectric strength, correlation between voltage recovery rate and required oil velocity, lack of correlation between either current and voltage and necessary oil velocity, correlation between recovery rate and pressure in explosion chambers. Tests on various explosion chamber forms and photographs of the oil blast in action are presented.

Rectifier Voltage Control

Lack of voltage control is one of the objections which have been made to the use of rectifiers. The author describes a method of voltage control for rectifiers based on the use of a saturated core interphase transformer. Saturation of this device produces a gradual change from two three-phase rectifiers operating in parallel to one six-phase rectifier which has a higher inherent voltage ratio. The theory of operation is discussed and supporting oscillograms and observed regulation curves are shown.

Electronic Stabilizer for Power Transmission

An electronic stabilizer varies a reactive load electronically to maintain desired voltage and line current in a transmission line. The electronic stabilizer acts upon the transient reactance and therefore it has the fast response needed to increase the stability of long transmission lines.

European switchgear developments

AN electrical engineer visiting Europe is immediately struck by the wide differences in design of switch-gear compared to familiar practices in the United States. In England, metal-clad gear is nearly universal except for the highest voltages and even at 132 kv there are metal-clad gears. On the Continent there are almost no metal-clad gears. This does not result in any similarity between Continental stations and American open switching stations with their rows of tank-type circuit breakers. In France some tank-type oil circuit breakers still are being installed but a variety of different designs are appearing, while in Germany the tank-type circuit breaker may be said to be altogether obsolete.

A Compression Type Low Voltage Air Circuit Breaker

THE totally enclosed fuses employed to protect lowvoltage low-current distribution circuits perform their work so effectively and quietly that an analysis has been made to determine their principle of operation in order that this principle might be applied to a small circuit breaker.

Mercury Arc Rectifier Phenomena

Peter Cooper Hewitt invented the mercury arc rectifier in 1902, so that it can hardly be considered a new development. More than a half dozen different manufacturers are producing mercury arc rectifiers of various types and sizes and have been producing such rectifiers for years, so that commercial development is not new, yet technical literature is astonishingly bare of treatments going to the fundamentals of rectifier behavior. Many articles appear, describing this and that installation. Descriptions of structural details are not wanting. For specific glass rectifiers, performance curves are available which give the relation between current and voltage at which failures occur under standard conditions. Even this information does not seem to be published for the iron tank rectifiers. An engineer wishing to familiarize himself with the quantitative relations underlying rectifier design has thus practically nothing to go on. We cannot assume from this that manufacturers the world over have proceeded blindly for nearly a quarter of a century, but if they do know what happens in a mercury arc rectifier they at least have not told the public. The purpose of this paper is to present such information as is at present available to the author. This information does not include the knowledge of very important groups in the industry and would even seem to indicate that a very large aggregate capacity of rectifiers has been designed along incorrect lines. This offering is then made in a spirit of humility in the hope that those who know will point out wherein it is in error.