摘要:

Several papers have been published recently on the subject of transductors; these have been concerned largely with transductors operated from voltage sources, and particularly with their performance when applied as magnetic amplifiers. When transductors are operated from current sources, although their characteristics do not differ greatly from those of voltage-operated transductors, their field of application is widened. The object of the present paper is to describe some of the many ways in which transductors may be used (not necessarily as amplifiers) to give to simple relay elements some of the special characteristics required in protective-gear work.In order to illustrate more clearly the principles involved, especially for protective-gear engineers who may not be familiar with transductors, some basic transductor characteristics (described elsewhere in greater detail) are included. Special control arrangements and constructional features are next considered; and the main body of the paper contains descriptions of a number of practical applications of transductors as protective relays.The transductor is shown to be a very versatile component for protective systems.

DOI:10.1049/pi-2.1952.0080

出版商:IEE    

年代:1952

数据来源: IET

摘要:

Various methods of measuring small currents and voltages with particular reference to the theoretical and practical limits of such measurements are discussed. Most of the methods described employ thermionic valves to amplify the signals to a level suitable for indication on a robust instrument. The more important methods of converting the signal into a modulation of a carrier frequency are described, as also are the basic principles of each type of amplifier, but no attempt has been made to discuss details of circuit arrangements.Limitations of sensitivity and frequency response of each method are discussed and the precautions necessary to obtain the best sensitivity are mentioned. It is shown that a contact modulator and a capacitance modulator can be used to measure a voltage from a low-resistance source and a current from a high-resistance source, respectively, almost to the theoretical limit of random fluctuations. A direct-coupled amplifier with a contact modulator to correct for zero drifts is the best available system for a source of medium resistance when a frequency response of a few kilocycles per second is required.

DOI:10.1049/pi-2.1952.0084

出版商:IEE    

年代:1952

数据来源: IET

摘要:

The paper is a sequel to the paper by Williams and Noble, entitled “The fundamental limitations of the second-harmonic type of magnetic modulator as applied to the amplification of small d.c. signals”, and it describes some of the considerations involved in the design of a practical and compact d.c. amplifier based on the previous work, with particular reference to an instrument designed and built at the Telecommunications Research Establishment.The paper includes a description of the following items, which were not considered in the previous paper:(a) A 1500-c/s oscillator of relatively simple design giving less than 0.0005% second-harmonic distortion.(b) A low-pass filter to prevent power from the oscillator reaching the input d.c. signal-source.(c) A phase-sensitive rectifier of unusual design.(d) Arrangements for range switching to cover a wide range of signal inputs.Considerable attention is devoted to the problem of applying overall d.c. negative feedback to the amplifier, which necessitates careful design of several sections of the equipment from the point of view of their gain and phase characteristics.The results of tests and measurements carried out on the completed equipment are also given.

DOI:10.1049/pi-2.1952.0085

出版商:IEE    

年代:1952

数据来源: IET

摘要:

The first of the two previous papers discussed the general principles of electrical control of dangerous machines and the second their particular application to interlocked guards. In this paper are examined various methods of remote supervisory control developed for large power systems but also used for other industrial processes, such as the distribution of gas and railway signalling.The paper is not concerned with details of construction, and is not intended to advocate any particular system or arrangement, but it analyses the underlying principles and assumptions of a number of different methods and attempts to deduce general requirements which all systems should fulfil.In introducing this subject, the author would point out that where opinions are expressed they are his own and do not necessarily represent the considered policy of his department. They are subject to modification in the light of further information or experience.Some suggestions and comments which are deliberately controversial or go beyond current practice have been included with the object of promoting discussion.In his choice of graphical symbols the author has not followed B.S. 530: 1948 exactly, but has used symbols which he hopes will be easily recognized by power engineers, to whom the paper is primarily addressed.

DOI:10.1049/pi-2.1952.0088

出版商:IEE    

年代:1952

数据来源: IET

摘要:

A method is developed for comparing the economic performance of transformers of differing electrical characteristics and cost, over a predetermined number of years during which the load increases exponentially, when the characteristics of the load and the energy costs are known.For special transformers, the method permits the evaluation of the optimum loss ratio when the rated output, the electrical efficiency and the cost of the transformer are fixed, and the load is increasing every year.

DOI:10.1049/pi-2.1952.0092

出版商:IEE    

年代:1952

数据来源: IET

摘要:

The sources of error in measuring high surge voltages with resistor, capacitor and mixed dividers have been investigated, and the responses of resistor and capacitor dividers to chopped waves have been compared with that of a shielded resistor divider in which the effect of earth capacitance has been eliminated.Errors arising from inductance in the connections between the divider and test object, and from the characteristics of the delay cable, have also been considered.Constructional details are given of dividers used at the National Physical Laboratory.

DOI:10.1049/pi-2.1952.0093

出版商:IEE    

年代:1952

数据来源: IET

摘要:

The main considerations affecting the choice of the sizes and groupings of power station boilers and turbines are security of supply and economics.Whilst the capital and operating costs per kilowatt of boilers and turbo-alternators decrease with increasing size of units, the amount of spare plant that must be held in reserve and the required strength of electrical interconnectors increases for a given degree of security of supplies, so that there is an economic size of unit for which the total costs are a minimum. On an interconnected system, this economic size depends, amongst other factors, on the total load in a load centre and on the distance between stations. The evidence suggests that the economic plant sizes for the British Grid during the next few years are, in most cases, 100 MW or above.Six alternative groupings of boilers and turbo-alternators have been examined (Fig. 1). For each of these groupings, system plant capacities have been so chosen that the degree of security of supply is the same when the stations are working on an interconnected network. An economic comparison of these groupings favours the arrangement in which the capacity of each boiler is equal to that of each turboalternator, the boilers and turbo-alternators are all connected to a common steam range and there is no spare boiler unit.

DOI:10.1049/pi-2.1952.0094

出版商:IEE    

年代:1952

数据来源: IET

DOI:10.1049/pi-2.1952.0097

出版商:IEE    

年代:1952

数据来源: IET

DOI:10.1049/pi-2.1952.0098

出版商:IEE    

年代:1952

数据来源: IET

DOI:10.1049/pi-2.1952.0099

出版商:IEE    

年代:1952

数据来源: IET