[Trade Journal]
Publication: The Electrician Commercial and Industrial Supplement
London, England
no. 107, p. 45, col. 1-2
100,000-Volt Insulators. In the first issue of our Exhibition Supplements we referred to the 100,000-volt insulators which Messrs. Bullers (Ltd.) have on view at their exhibit, and which they have been showing as capable of withstanding this pressure under actual test conditions. The insulator employed is of the suspension type, and is a development of a pattern originated by the General Electric Co. of America.. It is being manufactured entirely by Bullers (Ltd.) at their Hanley works, and embodies improvements which have been introduced as a result of experiments at that establishment.
Apparatus has been fitted up on Butlers' stand for the mechanical testing of these insulators, and we understand that strains up to 4-1/2 tons can be applied before the insulated will break. The electrical testing apparatus comprises an oil-cooled transformer, on the secondary of which pressures varying up to 100,000 volts can be readily obtained. There is a circuit-breaker on the primary side, and this opens when the insulator flashes over. The tested insulator is suspended over a tank of water, and artificial rain can be applied so as to reproduce more or less faithfully the varying atmospheric conditions under which the insulator is designed to work. Surmounting the exhibit is a steel tower carrying pin insulators, which are suitable for three transmission lines for pressures up to 50,000 volts. These masts are the product of the Tipton works of Bullers (Ltd.), where the ironwork for their telegraph insulators has been made for so many years past. Lattice-work masts which the company is offering for extra-high-tension transmission service are also shewn. The shape of these is the result of a number of experiments, and is such as to provide an ample margin of safety against the various strains and stresses to which they will be subjected in service.
There is a possibility of considerable high-tension development in our important colonies, and it is to be hoped that the experimental work carried out by Messrs. Bullers with insulators and supporting masts, which extends over a period of several years, will meet that full measure of recognition at the hands of interested users of this class of plant which it fully deserves.
