Showing papers on "Power-system protection published in 1973"
TL;DR: In this article, a rea1-time hybrid, analog-digital, computer technique for differential protection of generators is presented, where the fault/no fault decisions are based on the amplitude ratio of the "fault" and "average through" currents from a selected generator phase.
Abstract: This paper presents a rea1-time hybrid, analog-digital, computer technique for differential protection of generators. The fault/no fault decisions are based on the amplitude ratio of the "fault"' and "average through" currents from a selected generator phase. Analog input data pre-processor, fault monitor and soft-ware segments suitable for valid comparison during the transient period after the inception of a fault are described. Typical examples, from out of approximately 800 case studies, including internal and external faults using a three phase generator are presented.
24 citations
01 Jan 1973
7 citations
TL;DR: In this paper, an instrument was developed as part of a flux-tilt protective system for the light-water-cooled, heavy-water modulated power reactor (CANDU-BLW) at Gentilly, Quebec.
Abstract: An instrument has been developed as part of a flux-tilt protective system for the light-water-cooled, heavy-water-moderated power reactor (CANDU-BLW) at Gentilly, Quebec. This system is independent of the normal over-power protection instrumentation and is designed to prevent overheating of fuel that could result from spatial flux distortions (or tilts). Three identical instruments are used in the system, each comparing currents from ion chambers located at three positions around the reactor. If flux differences become greater than a preset level a trip signal is generated. The reactor is shut down by dumping heavy water if any two instruments generate simultaneous trip signals. Each instrument contains three linear-logarithmic amplifiers, comparators to sense high flux-tilt levels and logic circuits that combine the comparator signals to produce the final output in the form of relay contact closures. A mixed linear-logarithmic signal is developed from the measured ion chamber current to provide a fluxtilt signal that is non-linear with respect to reactor power.
4 citations
TL;DR: Several design features incorporated into a line of pulse-width modulated inverter drives include voltage and current protective circuits that provide SCR protection without fuses and a modified McMurray communication circuit is covered.
Abstract: Several design features incorporated into a line of pulse-width modulated inverter drives are described. They include voltage and current protective circuits that provide SCR protection without fuses. A modified McMurray communication circuit is covered. Design considerations for high-voltage (460 V) inverters and paralleling of inverters are discussed. Finally, a modular packaging system providing good maintainability is described.
4 citations
TL;DR: The first application of instantaneous trip circuit breakers (without time delay) was allowed by the National Electric Code (NEC) as discussed by the authors, provided the pickup can be adjusted above 700 percent to a maximum of 1300 percent of the motor full-load ampere rating.
Abstract: Over the years, various approaches including both thermal magnetic breakers and several types of fusible devices have been used in motor circuit protection schemes with acceptable results. Evidence reported in the trade magazines indicated that the level of protection from these types of devices was not totally effective. For the first time, with the printing of the 1968 National Electric Code, the application of instantaneous trip circuit breakers (without time delay) was allowed provided the pickup could be adjusted above 700 percent to a maximum of 1300 percent of the motor full-load ampere rating. After extensive testing the first product complying with these requirements was introduced to the market in 1969. Experience in motor failures indicates that most faults occur at relatively low levels of fault current just above lock rotor values rather than at higher levels. With rapid clearing of faults in the low-level range such as can be accomplished with the use of instantaneous trip circuit breakers, extensive damage to motors as well as to control equipment can be greatly reduced. By combining low-level protection obtained with the high interrupting capabilities of specially designed current limiters, a full range of coordinated protection is available for both high-and low-level faults.
2 citations
TL;DR: Most large-scale computer and control systems used in such critical applications as airline ticket reservations, air traffic controllers, and chemical processing plants are provided with redundant elements, automatic reconfiguration, or other safeguards to assure that data processing is not interrupted by computer element failures, but these systems are still subject to commercial power system problems.
Abstract: When guaranteed real-time access and reaction are required of a critical system, an uninterruptible power system is a must. Most large-scale computer and control systems used in such critical applications as airline ticket reservations, air traffic controllers, and chemical processing plants are provided with redundant elements, automatic reconfiguration, or other safeguards to assure that data processing is not interrupted by computer element failures. But despite such precautions, these systems are still subject to commercial power system problems. Regulating transformers and similar devices can help a data system coast over short power transients but, for full protection, an uninterruptible power system (UPS) is needed.
1 citations
TL;DR: The increased concern for human safety is one of several factors which makes the National Electrical Code increasingly important to engineers involved in plant electrical systems New requirements are extending into areas not previously covered by the Code as discussed by the authors.
Abstract: The increased concern for human safety is one of several factors which makes the National Electrical Code increasingly important to engineers involved in plant electrical systems New requirements are extending into areas not previously covered by the Code This paper discusses some selected major changes which are of most interest to industries using large amounts of power, and some changes which are apt to be controversial Included are: ground-fault protection, service entrance arrangements, autotransformers, transformer primary and secondary protection, separately-derived systems, and new product possibilities
TL;DR: In this article, a novel method for polyphase ground fault relaying with the help of a simple coincidence principle of the selected input quantities is described, and the general principle of operation, actual design and performance results have been discussed.
Abstract: The paper describes a novel method for polyphase ground fault relaying with the help of a simple coincidence principle of the selected input quantities. The general principle of operation, actual design and performance results have been discussed. The relay operates correctly for all single line to ground faults, as well as double line to ground faults with the same reach in each case. For line to line faults and 3-phase faults the relay remains completely inoperative. Like other reported relays of the same category it has the advantages of insensitivity towards balanced overload and power swings in the transmission line. Moreover it has greater tolerance for arcing faults and is less susceptible to transient over-reach or maloperation due to other spurious signals. The relay is also completely directional in nature.