摘要:

This paper gives an account of the electrical equipment of the Singapore floating dock, designed by the Admiralty and built by Messrs. Swan, Hunter, and Wigham Richardson, Ltd., of Newcastle-on-Tyne.The dock, which is now completed, is one of the largest in the world, and has been built in record time. Its transfer to Singapore presents an important towage problem.The electrical equipment includes:—A 1000-volt 3-phase a.c. system for main generation and pumping.A 220-volt 2-wire d.c. system for auxiliary generation, lighting and power.A 20-volt, 2-wire d.c. system for control of dock operations.A complete telephone system, with central exchange.Provision for supplying ships in dock with electrical energy for lighting and power.Provision for supplying submarines in dock with electrical energy for charging the large storage batteries, etc.The paper gives a brief description of floating docks and the conditions to be met. Reference is made to earlier docks, and a description is given of the complete electrical installation of the 50 000-ton dock now built for Singapore

DOI:10.1049/jiee-1.1929.0029

出版商:IEE    

年代:1929

数据来源: IET

摘要:

The conditions which govern the eddy currents in the lead sheaths of a pair of single-core cables undergo a change a s the sheaths are moved from the position of intimate contact. The consequent changes in e.m.f. and eddy losses have been the subject of considerable discussion. The following notes record an attempt to settle the matter experimentally by tests on a cable with a Drysdale potentiometer. The conclusions reached are that while the sheath circuit e.m.f. appears to be proportional to logd/r, the change in the losses as this ratio passes through the value 2 is rendered indeterminate by other variables which cannot be separately measured.

DOI:10.1049/jiee-1.1929.0030

出版商:IEE    

年代:1929

数据来源: IET

摘要:

The accurate practical determination of inductive losses in an a.c. system of single-core lead-covered cables is considered in detail, and test-results which are correlated with calculations are quoted by way of illustration.Bridge methods have been developed for the measurement of both the total and individual losses in single-phase and 3-phase single-core systems. These methods are shown to be capable of great accuracy.The feasibility of armouring single-core cables has been discussed by various authorities, whose opinions are widely divergent. A series of tests has been carried out, the main results of which are given herein. These show clearly the practical limitations imposed by the inductive effects from armouring each cable separately with wire armour. They also provide a sound empirical basis from which the losses in any given system may be estimated.

DOI:10.1049/jiee-1.1929.0031

出版商:IEE    

年代:1929

数据来源: IET

摘要:

This paper has been prepared as a guide to the selection of methods of laying three separate unarmoured † singleconductor cables for the transmission of three-phase power. A wide extension of the use of cables of this type is contemplated for transmission at 66 kilovolts and upwards.There are two general practicable methods which may be adopted for laying such cables. They may be laid in a symmetrical manner, the axes of the cables being equidistant from one another; or they may be laid alongside one another with their axes in a plane. The electromagnetic effects when carrying three-phase alternating current are materially different in the two cases. The principal factors affected are :—(1) The voltage which may be generated in the sheaths.(2) The energy loss in the sheaths.(3) The impedances of the different cables.(4) The influence on communication circuits.The arrangement in a plane leads to asymmetry and inequality in several of the factors involved, such as voltage generated in the sheath, power loss, impedance and temperature-rise; and in addition the effects are materially greater on the whole than when the same current is transmitted by cables arranged symmetrically.The current-carrying capacity of the two systems for a given temperature-rise has been given some consideration in view of the possibly better cooling conditions of the plane arrangement; but it is found that, in general, the increased losses by separation or substitution of the flat arrangement substantially offset the better cooling conditions.The general conclusions are that, as regards the electromagnetic and heating effects, the symmetrical triangular arrangement, with spacing as close as possible and with cross bonds and transposition at every joint, should be adopted as standardThe difference between the effects of triangular spacing and of flat spacing with regular transposition is small and the latter is permissible when special circumstances render it desirable. These conclusions apply to cables laid both direct in the ground and in ducts.

DOI:10.1049/jiee-1.1929.0032

出版商:IEE    

年代:1929

数据来源: IET