Electric Lighting and Public Safety

by Sir William Thomson

The North American Review, Volume 150, Issue 399, February 1890, published by the University of Northern Iowa


England and America are the freest countries in the world. Hence a remarkable feature of almost every city in the United Kingdom and the United States, which strikes with wonder all visitors from the continent of Europe—cirrus clouds of electric wire hovering perennially over the streets and houses. These clouds do not, to any sensible degree, diminish such light of heaven as the liberty-loving owners of domestic fire-places and steam-boilers allow to reach their fellow-citizens through the volumes of black smoke pouring from their chimneys. Some persons of taste object to the aërial wires as diminishing the beauty of our cities. The same people would complain of a forest of ships’ masts seen from London Bridge, or completing the vista of some broad avenue of New York, or relieving the dullness or the squalor of some little old city by the sea, if ships were an invention of this century and shipping industry not fifty years old.

Ruskin eloquently admires ships with their masts and sails as the most beautiful and picturesque of the works of man. Some future Ruskin will no doubt be equally enthusiastic about the beauty of the gossamer lines of telephone wire, with their gentle curves stretching away by hundreds from stately standards fixed aloft over our houses, or from high cathedral domes, or from future Eiffel towers, and ornamenting whatever the touch. Hitherto, however, conservative æstheticism has barred many cities of the continent of Europe from the larger benefit of electricity in the service of man already enjoyed by America and England; and would, in England, if it were permitted, sweep all electric cobwebs from the sky, and not concern itself with the question of expense involved in banishing all telegraphic, telephonic, and electric-light wires to below ground.

Public work in most cities of Europe is tremendously under authority, and, as a rule, authority, except in America and England, is very timid, even in respect to matters of taste. The more


serious questions of public safety which the large development of the high-pressure alternate-current system with transformers for electric lighting has forced upon us, in the last four years, have scarcely hitherto come into account in determining the rules and usages of continental cities as to overhead and underground wiring.

In Paris, the electric-lighting companies, bound under stringent regulations of the city authorities, have all their conductors underground. There are no exceptions to this; nor are there any overhead telegraph wires. Both telegraph and telephone wires are insulated in electric cables, and are placed underground in the excellent sewer system of Paris, except in some very rare cases where a subscriber lives in the outskirts of the town, and has an air-line to the nearest point of a cable-carrying sewer.

In Berlin, all the electric-light wires are underground, and the lighting is all done by continuous currents at low potential, much of it for out-of-doors, by arc lights in bridges of pairs, between conductors for the supply of indoor lighting, by Edison 100-volt lamps. No rules have been laid down in Germany to provide against personal danger, there being practically none to provide against with 100-volts’ potential; but rules to prevent danger from fire are imposed on makers and users of electric-light installations.

In Belgium, the telegraphic department issued, in 1887, a careful code of rules for the establishment and use of electric-light wires above ground in all parts of the Belgian dominion, and especially in the neighborhood of telegraphic and telephonic lines. Not one of these rules has reference to possible danger from conductors at high potential, because, in fact, in Belgium, as in Germany, there have been hardly any high-pressure electric installations of alternate current with transformers, and electric-lighting work has been chiefly by continuous currents at 100 volts or other low potential.

In Italy there is no law restricting electric industry. In Milan and many other towns of Italy there are small stations for electric light, supplied through underground wires at low potential. In Milan and Turin there are installations of aërial wires at 2,500 volts for forty arc lights in series. These isolated installations have no doubt been put up with great care, and do not seem to have been hitherto found dangerous to the public. A grand installation for electric light in Rome, by water-power of the Tivoli Falls, at thirty-seven kilometres’ distance, is now projected and


will no doubt be realized before long. It is designed to use 2,500 horse-power at the falls, which is to be transmitted by alternate current, at 5,000 volts, through aërial conductors over the country to the city gate. There, by a transformer, it is to be first reduced to 1,000 volts, and distributed by underground supply conductors to numerous transformers in different parts of the city, by which it is to be further reduced to the safe 100 volts for use.

In passing, I may remark that 100 volts in the house is perfectly safe to the user, whether the current be alternating or continuous, as is proved by large and varied experience in England.

There is, so far as I know, just one city in the world, outside of England or America or Italy, in which high-pressure overhead wires are used, and that is Temesvar, in Hungary, which has been thus supplied with electric light for many years.

In England, any individual or company wishing to carry wires above the houses and streets of our towns, or anywhere over the country, and having obtained permission from the proprietors to place the requisite bearing poles on roofs or other parts of buildings, or on unoccupied ground, has perfect liberty to do so as he pleases in the air over town and country; provided that he comply with whatever conditions may be prescribed to protect the public safety and the convenience of previous occupants of the air.

Two years ago the Board of Trade issued, under the Electric-Lighting Act of 1888, very stringent regulations for safety, to be observed throughout the United Kingdom, in every case of placing an electric conductor otherwise than wholly enclosed within a building. A copy of these regulations is appended to the present paper.* They have been approved by the Institution of Electrical Engineers in consultation with the officials of the Board of Trade. If they are thoroughly and permanently fulfilled in every case, I believe their object -- “the protection of the public safety and of the lines and works of the Postmaster-General, and of other electric lines and works”—will be effectually secured. So much being admitted—and I believe so much will be generally admitted—the question remains, Can these regulations of the Board of Trade be thoroughly and permanently fulfilled? All that is essential for public safety is provided for in regulations 1, 3, 7, and 9.

Regulation 3 places a problem before engineers which is certainly not beyond their powers of fulfilment. The bearing poles

*See page 194.


and standards, the strength of the porcelain insulators, and the tensions of the wires can certainly be so arranged that the whole structure of a set of aërial conductors will be as safe against breaking down as any railway bridge.

Under regulation 7, it may be remarked that the “crossing conductor” is the invader of a previously-occupied aërial province. The fulfilment of rule 3 by both the previous occupant and the invader secures, ipso facto, the fulfilment of rule 7. But rule 7 imposes on the new-comer—understood, no doubt, to be a provider of conductors for electric lighting—the obligation of guarding against an electric contact, even though the previously-existing telegraph or telephone wires violate rule 3 and break down.

If rules 1, 3, and 7 are fulfilled, rule 9 is unneccessary, unless for the protection of birds. If the two conductors, side by side or one over the other, constituting the mains of a “high-pressure” circuit of 2,000 volts, say, or of 10,000 volts, be bare copper, it would be instant death to a bird standing on one of them to touch the other with tail, wing, or beak. But no other creature could be endangered by bare aërial conductors, even at 10,000 volts, if they fulfil rules 1, 3, and 7. The protection of birds was certainly not thought of by the Board of Trade, and we infer that rule 9 implies a suspicion that the fulfilment of rules 1, 3, and 7 may occasionally fail in practice. The fulfilment of these rules can, indeed, be made practically certain. But at what cost? What of the cost for permanent maintenance of standards, suspending wires, “non-metallic ligaments”? And what of the “durable and efficient material” required by rule 9 as an insulating coating for the copper conductor, when we consider that every hitherto known insulating material that could be used for coating the wire experiences destructive deterioration in the course of years, especially if kept exposed to light and to the variations of outside atmosphere in our climate?

We are forced to conclude that in laying down these regulations, and in arranging for careful inspection to secure their fulfilment as far as practicable, the advisers of the Board of Trade felt that the danger from high-pressure overhead wires could not be absolutely annulled. This view is confirmed by the fact that in most or all cases in which provisional orders under the Electric-Lighting Act of 1888 have been granted to companies for the


electric lighting of cities or districts of cities, it has been stipulated that the conductors shall be altogether underground, except in cases in which aërial wires have already been placed and brought into action; and that even in these cases the conductors, if for high-pressure supply, shall be removed from the air and replaced by underground conductors within two years.

It may be considered, indeed, as now definitively resolved that the distribution of electric energy for light and power in towns of the United Kingdom shall be by underground conductors, and plans for carrying this into effect safely and economically are engaging the anxious consideration of electrical engineers. The telegraphic department of the Post-Office has already replaced nearly all the aërial telegraph wires of the larger cities by underground conductors.

The telephone wires alone remain in the air. Long may they hold their place there: they are perfectly harmless to the general public, and they are enormously less expensive where they are than they could be if placed underground.

As for the country, telegraph, telephone, and electric-light conductors must all be in the air. The cost of placing them underground would be absolutely prohibitory of the great public benefit to be obtained by placing more and more of them in the air. The Board of Trade rules given herewith are amply sufficient guarantees against danger to man or beast in country districts, from aërial electric-light conductors, whether for high or low pressure; high pressure they must generally be for long ranges over country. Indeed, I believe these regulations may be largely relaxed for electric-light wires in the country. Provided only that strong enough and sufficiently well-engineered standards or well-stayed poles be placed for carrying the wires, and provided the spans from standard to standard be short enough, it will, I believe, be found quite unneccessary in respect to public safety to have any coat of insulating material on the copper of conductor for electric light or power along a country road. Fifty years may well pass, with all their gales and snowstorms, without a single break-down, and there are no telegraph or telephone wires to fall upon the deadly copper with its 10,000 volts. Until, however, the security of the poles and wires, which I believe to be attainable, is satisfactorily demonstrated, and until it is also proved that this security can be attained at moderate enough cost, I would not suggest the slightest


relaxation of any of our Board or Trade regulations for the protection of the public safety, whether in town or country.

William Thomson.

[Appended copy of Board of Trade regulations regarding telegraphic, telephonic, and electric-lighting conductors]