THE RECENT occurrence of several serious switch-house fires has occasioned an unusual interest in the matter of bus protection. Acting upon the belief that a comprehensive survey of modern practices in such protection would be of some benefit to those interested, the relay subcommittee of the AIEE protective devices committee and the relay subject committee of the Edison Electric Institute electrical equipment committee jointly prepared and circulated a rather extensive questionnaire on the subject.
Instruments and Measurements: Chemical Analysis, Electric Quantities, Nucleonics and Process Control, Volume I covers the proceedings of the Fifth International Instruments and Measurements Conference, held in Stockholm, Sweden on September 13-16, 1960.Separating 120 lectures into 49 chapters, this book is divided into five sections. The first section discusses the advances in automatic process control instrumentation, including developments in pneumatic, electropneumatic, and electrohydraulic control. This section deals also with the stability, optimization, and use of fast digital computer for process control applications. The subsequent two sections consider the physical methods of chemical analysis and nuclear instrumentation. These sections survey the developments in gas chromatography, mass spectrometry, and quadrupole mass filter for chemical analysis. These topics are followed by discussions on some structural and analytical applications of high resolution nuclear magnetic resonance. The remaining sections explore the measurements of electric and magnetic quantities, as well as the reactor control. These sections are devoted to X-ray methods, UV spectroscopy, turbidimeter, and infrared techniques. Analytical chemists, process and instrumentation engineers, and researchers in instruments, chemical analysis, and process control fields will find this book invaluable.
A generalized criterion for stability of a closed tandem connection of double-dinodes is given by the expression A(λ) = a11+a22-|a|-1 = 0 in which the a11 are the appropriate terms of the transmission matrix of the tandem net-work prior to closing the loop. If the λ-roots of A(λ) have positive real parts, the closing the transmission loop; that is, the network is unstable. The generalized criterion is applicable to transmission loops incorporating bilateral amplifiers, and the transmission loop may be opened wherever desired without con-sideration of the impedances to the left and right of the cut. The criterion is not limited to transmission networks employing amplifiers; like-wise, it applies equally well to electro-mechanical networks or servomechanisms.
The fundamental possibilities of adapting the design of capacitors to meet the special stresses encountered in series capacitors are reviewed. The design of the Allmänna Svenska Elektriska Aktiebolaget units in the Swedish State Power Board's series capacitor at Alfta and of a new 50,000-kva bank now under production is described Possibilites of future improvements are outlined.
Very little has been published in the past regarding the hazard to the integrity of long control circuits due to possible excessive rise in ground potential at one end of the circuits during station faults; and the verification of the safety of such control circuits through actual tests. This paper describes the rather unique arrangement at Grand Coulee power plant wherein the plant is located at the bottom of the Columbia River Channel and one of the associated 230-kv switching stations is located on a rocky plateau approximately 600 feet higher in elevation, thus requiring control cables over 4,000 feet in length. By means of several fault tests staged specifically for this purpose, and as a by-product of subsequent high-interrupting capacity circuit breaker tests, the actual rise in ground potential was determined and the safety of the control circuits positively verified, under 60-cycle fault conditions.
A new method is described for supervising sectionalizing devices on distribution systems by utilizing a centrally transmitted, unmodulated carrier. This carrier is remotely modulated by equipment located on the load side of the monitored sectionalizing device, and the modulated carrier is received at a conveniently located receiver. A novel indicator gives instantaneous warning of operation of sectionalizing devices or equipment failure. Simplicity and low cost make its use on distribution systems feasible for monitoring of large numbers of sectionalizing devices.
The switching of capacitors differs from other switching by causing relatively large surge currents and possibly overvoltages. The performance of circuit breakers in this service has been found by recent experiments to depend on the power supply system as well as on the size of the capacitor banks. When circuit breakers open with no delayed restriking of the arc, they avoid the possibility of causing undesirably high current and voltage surges.
Development and evaluation of corona measurements have contributed greatly toward solution of the problem of determining satisfactory voltage stress levels in capacitors. Until recent years, short-time voltage breakdown tests were the only quick means of determining required dielectric thicknesses. However, practical operating voltage stress levels were established more by service experience than by short-time measurements. The time consumed in obtaining the service experience on new materials or designs made advances in design practice slow and uncertain. During the last 15 years it has become evident how closely the life of a capacitor in service is linked with the ionization voltage level of its dielectric. New measurement techniques have been developed, by means of which insulation ionization levels can be quickly and quantitatively established. Results of ionization tests have been correlated with long-time life tests and service experience. As a result, it now is possible to use the ionization test as a valuable guide in selecting improved dielectric materials, and in designing to meet new operating conditions. While this paper refers specifically to the very thin dielectrics used in capacitors, the techniques described can be applied also to evaluate electrical insulations for other devices.
A modified slot discharge detection method, which permits tests without Shutting down the machine or using auxilliary high-voltage test equipment, was investigated. The method involves connection of frequency sensitive equipment across all or part of the ntral impedance. Tests on eight vertical water wheel generators in the range of 20,000- to 40,000-kva capacity indicate that the method is generally applicable when there is a current transformer or some other impedance in the generator neutral.
THE CONTINUOUS operation of large synchronous machines and freedom from failures in service is of vital interest to every electric utility company. One of the major causes of unpredicted and unscheduled outage is the failure of stator coil insulation.
The success of the Presidents' Conference Committee (PCC) car in city service has led to the development of a standard lightweight rapid transit car through the collaboration of the American Transit Association, the Transit Research Corporation, and interested manufacturers. The basic features and equipment of the PCC streetcar have been retained except where conditions peculiar to rapid transit service dictated modifications.
Transformer-loss compensators provide an economical means for metering the loads of utility company customers supplied at transmission voltages on the low-voltage side of the power transformer bank by compensating the watt-hour meter to include the transformer losses in its registration. Improvements have been made in the basic compensator 1 by neutralizing the effect of the flow of meter potential circuit current through the copper-loss compensator. This improves the performance of the compensator, particularly on inductive loads, and makes possible its correct adjustment also for the higher values of losses incurred with var compensation. The burdens imposed by the compensator are sufficiently small to be acceptable in watt-hour metering practice, and for connection to the output side of standard var autotransformers. Under present-day conditions the use of transformer-loss compensators results not only in economies, but also in the conservation of critical materials that would be required for high-voltage instrument transformers on metering installations.
Essentially a d-c to a-c converter, this induction galvanometer is admirably suited for making sensitive d-c measurements. Its operating frequency may be in the megacycle region if desired, the conversion energy gain is high, and ample signal is obtained for a-c amplification.
Fundamentally, telephone traffic is the sum of accumulated holding times of switching channels. From this simple statement two important conclusions can immediately be drawn. First, that telephone traffic is completely equivalent to the length of occupancy of the switching channels; that it may be expressed in any convenient unit of time; and that the same traffic or occupancy can be made up by many calls of short holding times each, or a few calls of long holding times each, or in any conceivable mixture of these as long as the sum of the individual holding times add up to the total length of occupancy. Second, since a channel naturally cannot be occupied for more than one hour in any single hour, the traffic carried per channel in one hour cannot exceed one traffic unit. From this it is argued that any measurement of traffic can be reduced in the last analysis to the measurement of time, more specifically to the measurement of accumulated holding times. From the preceding it will be understood that the switch count process is a particular method of time measurement by sampling, and its accuracy can be appraised by comparison with direct measurement of time, for instance, by a clock, where the latter term is used in its broadest possible interpretation. If the laws governing the accuracy of peg count methods and holding time measurements are determined, we have the necessary tools available by which the accuracy of traffic measurements can be appraised. The former was recently studied and published by the author, who found that the commonly used peg counting methods provide an exactness well within that required for traffic measurements.
