DOI:10.1049/ji-2.1943.0001

出版商:IEE    

年代:1943

数据来源: IET

摘要:

In this paper, an endeavour has been made to indicate the present position in this country of the insulating oils and compounds which are available for cables, and to describe their behaviour in impregnating plants.The oils are of the paraffinic and naphthenic types and either class may be used in oil-rosin compounds.

DOI:10.1049/ji-2.1943.0002

出版商:IEE    

年代:1943

数据来源: IET

摘要:

It is the purpose of this paper to familiarize the electrical engineer with the nature and characteristics of a material on the service behaviour of which is dependent the successful and continued operation of certain of the equipment for which he may be responsible.In spite of the advent of non-inflammable, liquid chlorinated hydrocarbons, mineral oil still remains the chief dielectric or insulating liquid used in oil-filled transformers and oil switches. Mineral oil has been chosen as a liquid insulating material because it has an electric strength greater that that of air and because, where necessary, it can function as a cooling medium and so maintain the operating temperature of the equipment at a safe value.The outstanding characteristic of mineral insulating oils to which attention is directed by manufacturer and user of h.v. equipment, oil producer, and oil chemist alike, is their stability in service.Efficient operation of mineral-oil-filled electrical equipment is dependent, therefore, to a large extent upon the ability of the oil to retain substantially unimpaired, in the presence of deteriorating influences, its initially good electrical properties, its inertnesr towards the solid insulating materials that are also present in most electrical equipment in which oil is used, and its ability to effect efficient cooling.

DOI:10.1049/ji-2.1943.0003

出版商:IEE    

年代:1943

数据来源: IET

摘要:

In the course of the last ten years the author has investigated a considerable number of accidents and dangerous occurrences due to the explosive failure of oil circuit-breakers and oil-immersed control gear, and in doing so it has become apparent that not all were due to inadequate rupturing capacity or defective insulation. This has been particularly true of a number of failures in recent years of the control gear for arc furnaces. Some of these have been due to defective mechanical design and steps now being taken will, it is hoped, go a long way to cure this. The present paper, however, is an attempt to assess what part deterioration of the switch oil may play. The importance of the problem may be judged from the fact that oil in such switches is now frequently changed every 2 or 4 weeks and at some works once a week.Many engineers responsible for the maintenance of switchgear have felt that while the tests laid down in British Standard Specifications may eliminate many new oils which are definitely unsuitable they provide no certain guide to the rejection of used oil after a period of service. A section has therefore been added in which the author suggests the initial tests he himself would take in the search for a more suitable basis if he had the necessary laboratory facilities.The subject is one in which there is little agreement among experts, but the author feels that the parer will have completely fulfilled its purpose if it succeeds in giving a new impetus to research and possibly a new direction, even if the tentative conclusions set out here have later to be discarded.

DOI:10.1049/ji-2.1943.0004

出版商:IEE    

年代:1943

数据来源: IET

摘要:

Insulating oil deteriorates in use, and the maintenance engineer has to see that the working conditions are such as to minimize this loss of quality. The oil must be reconditioned when the necessity for this is revealed by a system of regular observations on the condition of the oil.Reference is made to points which should be watched in the design and installation of plant, and it is suggested that of the oils specified in B.S. 148-1933 only Grade B.30 oil should be retained. The revised Specification should include high-viscosity oils which are frequently used in electrical apparatus.Routine tests for sludge and moisture contamination are universal, but determination of acid value may be important and the flash-point has to be determined occasionally. Suggestions are made as to what values of these should be permitted before purification is considered necessary. The type of contamination likely to be present and the apparatus available for its treatment and various methods of using it are discussed.A Table showing suitable maintenance periods is given, and it is pointed Out that as it is difficult to handle oil and to work on oil-immersed gear without causing deterioration, these periods depend more on the immersed apparatus requiring attention than on the oil.

DOI:10.1049/ji-2.1943.0005

出版商:IEE    

年代:1943

数据来源: IET

摘要:

An attempt is made to describe briefly the selection of oil crudes, and the choice of refinery methods best suited for the manufacture of various types of electrical oils, e.g. transformer and switch oils, and condenser and cable saturants. Methods of test are discussed and consideration is given to the changes undergone by these liquid dielectrics under high stresses. Highly paraffinic oils are shown to be undesirable in transformers, cables and condensers, and it follows that solvent processes are, in general, unsuited to the production of such oils. Rosin is shown to be a desirable constituent of cable saturants. It is not possible within the scope of this paper to give more than a small fraction of the available experimental evidence in proof of the statements made.

DOI:10.1049/ji-2.1943.0006

出版商:IEE    

年代:1943

数据来源: IET

摘要:

Before discussing the electricity supply aspects of ferro-alloy manufacture, the principal ferro-alloys, the method of grading and their uses are summarized and representative electricity consumptions per ton of finished alloy are given.In order to indicate the magnitude of the load, statistical information regarding the quantity of electrically manufactured ferro-alloys is next given over a period of years. This is followed by a description of the type of furnace used, together with brief notes on the electrical equipment and details of the electrodes.In order to indicate the importance of electricity costs the selling price of typical ferro-alloys is given and, for comparison, the proportion of the selling price that each tenth of a penny per kWh represents.It is also pointed out that supplies of raw material are as easily available in Great Britain as they are in the major ferro alloy producing countries, viz. Norway, Sweden, and the U.S.A.In order to establish the price at which electricity can be made available, typical costs of production for a 50 000-kW steam station are given and, on 1939 costs, aprice of ¼d. per unit arrived at. At the same time, comparison is drawn with hydroelectric power and it is shown that for equality of production costs, all other things being equal, the capital expenditure in a hydro-electric station could be as high as £72 per kW installed.The disadvantages of a number of private generating stations are obvious and it is shown that an electricity supply obtained from the Grid is more advantageous.Finally, some typical costs of production for ferro-alloys are given.

DOI:10.1049/ji-2.1943.0009

出版商:IEE    

年代:1943

数据来源: IET

摘要:

The law of the moving-iron instrument has been quoted in the form: Torqu=½I2dL/dθ, whereIis the current in the coil andd/dθ the rate of change of inductance with angular deflection. This law is deduced on the assumption that the current remains constant for a small change in deflection, but since a change in inductance is produced by a change in current, it does not seem justifiable to assume the current to be constant. The law then takes a more complicated form. Experiments are described showing that the simple law does not hold for a simple electromagnetic system.

DOI:10.1049/ji-2.1943.0010

出版商:IEE    

年代:1943

数据来源: IET

摘要:

The inductance formulaeF= ½I2δL/δxandT= ½I2δL/δθ are shown to be correct for iron-cored instruments if the magnetization of the iron does not exceed the maximum value permissible for accurate indication. For higher magnetizations the force or torque is higher than the value given by the formulae, and becomes twice as great when the iron approaches saturation.

DOI:10.1049/ji-2.1943.0012

出版商:IEE    

年代:1943

数据来源: IET