摘要:

The paper discusses precautions to be adopted in respect of fire in power stations and major system substations arising from failures of electrical plant.General considerations are discussed first, and it is pointed out that whilst electrical duplication or multiplication of plant is recognized as essential, its complement—true physical segregation of duplicates to secure against the fire or explosionrisk—has not received as much attention.It is, however, emphasized that the rare occurrence of serious fires or explosion justifies a different treatment and that it suffices in general to segregate duplicates in two separate groups. The condition of rarity is secured only by the use of sound plant and good protective gear, and it is essential that this condition should be maintained and desirable that it should be improved upon.It is emphasized, nevertheless, that despite all precautions fire cannot be absolutely precluded and that the only ultimate safeguard must be a reasonable fire-sectioning of the plant, so that a fire or explosion is limited in its worst effect to a section or group of plant items which can in emergency be done without.Given these two conditions, the prime requirements are met. The second stage is the limitation of the consequential damage following a fire to a degree which will ensure that the subsequent emergency state shall not continue too long, as during this period the essential principle of electrical duplication no longer holds and electrical faults are relatively frequent.This leads to the discussion of additional precautions which can be taken to decrease the consequential damage by improvements in design within the agreed fire sections, and by fire-fighting arrangements.General details are discussed and examples given, and the explosion risk is referred to.

DOI:10.1049/jiee-1.1937.0146

出版商:IEE    

年代:1937

数据来源: IET

摘要:

The paper deals briefly with the development of tap-changing gear and indicates some of the fields of application of tap-changing gear in power supply systems.The various circuit diagrams in common use, and the types of tap-changing equipment, are classified, and brief descriptions are given of a number of typical equipments. The fundamental principles of methods of remote electrical and automatic control are indicated, and the effect of impulse voltages on the design of tap-changing gear is referred to.The paper concludes with a brief section on economical types of voltage regulators for rural lines, and a section giving a statement of operating experience gained over a number of years, with some notes on earlier troubles and their remedies.It is not within the scope of the paper to make comparisons between regulation by tap-changers and by other forms of regulator, as the paper is restricted to transformer tapchanging gear and its applications.

DOI:10.1049/jiee-1.1937.0153

出版商:IEE    

年代:1937

数据来源: IET

摘要:

The paper opens with a discussion of the causes leading up to the general adoption of electric mine lamps, and an account is given of the awards in the Home Office prize competition of 1911. The evolution of the alkaline mine-lamp accumulator is next considered, and the principles of construction of Edison, Jungner, and Wolf accumulator plates are described. The stages are traced in the development of the Wolf alkaline lamp from 1912 to 1919, and the successive changes in the design of filling-hole stoppers and tools for handling, automatic devices for electrolyte level testing and filling, and prevention of alkali leakage, are discussed. The evolution of the two-part lamp is next considered, and improvements in contact plates, locks, locking systems, bulbs, and cover glasses, are examined. Comparative polar curves and Russell diagrams are given showing the advances in lighting values, and illustrations of typical “Schedule A” type electric hand-lamps are included. Reference is made to the present position regarding electric mine lamps with firedamp indicators. The final section of the paper deals with the new statutory mine lighting regulations.

DOI:10.1049/jiee-1.1937.0158

出版商:IEE    

年代:1937

数据来源: IET

DOI:10.1049/jiee-1.1937.0159

出版商:IEE    

年代:1937

数据来源: IET

摘要:

The paper is concerned with the design of apparatus for maintaining a chamber at a nearly constant temperature, above the ambient temperature, despite fluctuations of its environment. After brief discussion of thermostats in general, attention is confined to electrically-operated devices in which the temperature-sensitive element enters into a bridge configuration: departure of the temperature from the assigned working value, by throwing the bridge out of balance, effects a corrective change in the heat supply. By analysis and experiment published elsewhere, the author has shown that in such systems hunting, necessarily present if the heat supply is controlled in discrete quantities, will occur also if there is a continuous relation between temperature and heat supply, provided that the control sensitivity exceeds a critical threshold value. The bearing of this result on the design of fine temperature-regulating apparatus is examined, and the frequency and amplitude of hunting are considered. The relations of the factors determining the residual inconstancy of temperature are analysed. Amongst the conclusions reached are (roughly stated): (a) hunting does not depend on the heat capacity of the chamber; (b) the residual inconstancy does not depend on thoroughness of thermal insulation of the chamber; (c) there is a single figure of merit measuring the intrinsic effectiveness in resisting changes of ambient temperature and of supply voltage; (d) of these two factors, the former is of less practical importance than the latter; (e) the effect of temperature-difference between the chamber and the temperature-sensitive element must not be ignored; (f) identification of the temperature-sensitive resistor with the resistor carrying the controlled current, advocated by someprevious workers, is wrong in principle.The author's apparatus is described: it is the outcome of an attempt to obtain the smallest possible inconstancy consistent with derivation of electric supplies from the a.c. mains alone, and is in accord with the principles reached in the foregoing study. Difficulties experienced in measuring small temperature-changes are reported, and the significance of readings of mercury thermometers is assessed. Finally, it is shown that the author's design could be modified for large size and high temperature.A term not in common use has, for the sake of brevity, been employed throughout the paper: a “millideg.” (to be pronounced as written) stands for a thousandth of a degree Centigrade.

DOI:10.1049/jiee-1.1937.0160

出版商:IEE    

年代:1937

数据来源: IET