✓ 103. Diagram of portion of the Manchester network, 104, 105. Arrangement of meters for three-wire circuit, 106. Arrangement of meters for five-wire circuit,

108, 109. Meters in two-wire installations supplied from network

111. Arrangement of apparatus for five-wire service, .

112. Faulty method of connecting meters,

293

296

118. Diagram of connections of battery sub-station for five-wire net

work,

314

119. Open skeleton switchboard (perspective),

315

120. Method of carrying bare copper rods for battery connections,

316

122. Mounting of voltmeters,

121. Diagram of regulating switch,

123. Mode of lowering arc lamp fixed on span wire,

124. Curve showing relation between cost and load factor,

324

333

CENTRAL ELECTRICAL STATIONS.

CHAPTER I.

INTRODUCTORY.

THE development of energy in central stations, and its distribution to a number of separate consumers in the vicinity, is a matter which has long attracted the attention of engineers, and the problem has been attacked in many ways with greater or less success.

It can readily be shown, indeed it may almost be taken as an axiom, that, quantity for quantity, it is more economical to produce energy in a form available for the service of man, on a large scale than on a small; the chief difficulty that has been experienced has been in the transmission of the energy from the central station at which it is produced to the points at which it is utilised. On the efficiency of this transmission depends the commercial success of the operation; obviously, the loss in transmission must be less than the saving by concentration of the producing plant if success is to be attained.

As an example of a means of transmission which has been tried and found wanting on an extended scale, may be cited compressed air, while gas, water under pressure, and electrical energy are instances of agents in practical every-day use, each of which has attained a large measure of usefulness in its own sphere.

With electrical energy only as a transmission agent is this book concerned. Its use for the purpose is of recent date, the application being well within the last quarter of a century, and its development has been rapid. Not unhealthily rapid, however; there has been no sudden rush to adopt it merely because of its novelty; on the contrary, its development in this country, at all events, was greatly hampered by legislation, and still more by dishonest commercial operations. For this very reason, it has made sure progress, having had to depend, as all real progress has to depend, on its own merits, and now the production of electrical energy in central stations, and its transmission over extended areas to numerous points of utilisation,

A

has become firmly established, and, in the near future, it appears probable that an enormous development of this branch of engineering will take place.

Progress has indeed been most rapid already. The first public supply station was established in this country in 1882, and already there are 190 such stations in active operation, with plant having an aggregate capacity of over a quarter of a million horse-power.

Electric lighting is increasing daily in popular favour on account of its manifold and manifest advantages, and as the cost of production diminishes, its use extends at an ever-increasing rate; indeed, if its price be sufficiently reduced, it is likely to be universally used as an illuminant. Its cost must always have remained high had not the concentration of the generating plant in large central stations been carried out.

Important as is lighting, the use of electrical motive power appears likely to eclipse it in importance. Already small users of power are adopting it wherever available; and even large factories, in which the power required is reckoned in hundreds of horse-power, are driven by means of electrical energy derived from central stations. Again, tramcars are rapidly being converted from horse to electric traction, and in America the use of horses for the purpose has nearly ceased. Smelting and chemical manufacturing processes are being operated from central stations, and every day sees new uses being found for energy delivered at a low rate of charge in an electrical form.

The more widely the field is extended, the greater are the opportunities of reducing the cost of the energy; and the establishment of electric central stations is opening up possibilities the full effect of which it is difficult to estimate.

It may be well here to define exactly what are the operations which take place in connection with a central station. In common speech there is necessarily, and very pardonably, much laxity of expression, and to be too precise savours of the pedant. In the course of this book, doubtless, inexact expressions will be used, which, taken literally, imply either impossibilities or absurdities. Thus, to speak of the 'generation' of energy is absurd, for it is as impossible for man to do this as to add one cubit to his stature. What is really done is to alter the form of energy already existing, part being raised in the scale and converted into a form more immediately available for the needs of man, and part, alas irrevocably, so far as we know, degraded. Again, we speak of consumers' of energy; obviously that which is indestructible cannot be consumed, and what really happens is the reconversion of the energy into some other special form. Provided that there be no misconception as to the real nature of the operations, and that the intended meaning is well known, this inexactness is of no moment, and the use of common expressions is convenient.

Let it be understood, then, that, in an electrical central station, energy, either in the form of kinetic energy resident in running water, for example,

or of potential energy in the form of chemical affinity, existing, say, in coal, is converted through one or more stages into electrical energy; this energy is transmitted in an electrical form through conductors, part being at once reconverted into potential chemical energy, or frittered away into low temperature heat, and the greater portion reconverted into heat, light, mechanical energy, chemical energy, or some other desired form.

In ordinary language, this process would be described by saying electrical energy is generated by water, steam, or gas power, is transmitted with a certain amount of loss, and the greater portion is consumed as heat, light, chemical action, or in some other way.

Although a certain amount of licence is admissible, too strong a protest cannot be made against the misleading use of terms, such as the confusion of power and energy, heat and temperature, etc.: such lapses show merely ignorance and obscure ideas.

Electrical science lends itself readily to exact statement, and central station work appears to have a special fascination for statisticians. Several most excellent works exist in which entirely reliable accounts are given of the system and plant in use in the various stations of this country, together with full details of their size, character, etc., and the financial results of the operation of the stations. This book is not intended in any way to cover this ground already so well occupied, but rather to discuss the general principles of central station design and operation, the training desirable for an engineer taking up this branch of the profession, and the field that he may reasonably expect to be open to him. It is intended partly for the use of students, but, more especially, for those who have already entered upon practical work, and have charge of stations of their own. It is hoped

that the former will find the matter none the less useful to them for its extended scope; indeed, it is hard to draw the line between student and engineer: the true engineer is ever a student, and the lesson he learns more thoroughly as time goes on is a consciousness of how very little he or any of his brother engineers really know.

It is the Author's desire to give a broad account of central station work as it is to-day, and to discuss the best way of meeting present and future demands in connection with it. It will be his endeavour to secure that all statements of fact are entirely accurate, and that the advantages and disadvantages of various systems are presented with absolute impartiality; but, so far as opinions enter into the matter, it is inevitable that some reflection of personal bias should be present, and this, it is hoped, will not be entirely a drawback, for every reader must form his own opinion, and it is better that he should weigh together a number of different and opposing opinions, expressed by different authors, than that he should merely have the facts before him, and draw his own unaided conclusions, which are not more likely to be correct than those of any one of the authors whose works he reads.

CHAPTER II.

CENTRAL STATION WORK AS A PROFESSION.

ELECTRICAL engineering is the most recently developed branch of the work of the civil engineer, and the latest phase of electrical engineering is central station work.

Modern engineering tends more and more to specialisation. There must be first the foundation of general principles, but the student soon learns that he must concentrate his attention on one particular branch, and already the electrical field has become so extended that the operations of any one man must be narrowed down to one particular portion of this if he is to excel.

At the present time, the main avenues open may be defined, broadly, as five in number, viz.: cable and telegraph engineering, including telephony; manufacturing; wiring work; central station supply; and consulting engineering.

Telegraphy possesses many attractive features, and there is always likely to be a steady demand for this class of engineer. But the good posts are filled up, and there is not the same rapid extension as in other branches; those starting now would probably find progress very slow compared with that in the classes named below.

Manufacturing offers very considerable scope, especially for the inventive faculty, and recent developments of the needs of central stations have raised this branch above the reproach of being little better than brass finishing, the work now undertaken being really heavy engineering, and calling for skilful design and the best engineering talent. Little doubt can exist that the importance of the work will greatly increase, and all kinds of general mechanical engineering will become part of the work of the electrical manufacturer. The ever-increasing number of applications of electrical energy to the needs of factories and workshops will contribute largely to bring about this result, and, in a few years, heavy railway work will almost certainly be included.

Wiring work may be taken as the antithesis of that last named, and, far from increasing in importance, it seems likely to diminish and settle down merely into a branch of plumbing. At one time, when the subject.