High-Tension Power Transmission Volume 1 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1905 Excerpt: ...communicated By Letter. A. C. Pratt: --For maximum safety, oil-cooled transformers should be placed in a strong boiler-steel case, with the cover well bolted on. The latter should have a relatively large flap opening to act as a safety-valve, so arranged that it will not of itself remain in the open position. There seems to be no doubt that inflammable and explosive mixtures accumulate above the oil iji transformers; but the self-closing cover will promptly smother any fire which might be started from this cause. These gaseous mixtures seem to be formed, at least in part, by minute brush discharges in the oil, which break up the mineral oil into light volatile constituents and heavy asphalt-like residue. These effects "may be readily produced experimentally, even at pressures below 10 000 volts. There should also be a considerable air-space to allow for a possible boiling of the oil without boiling over. Such a transformer will most naturallly be ri. the water-cooled variety, and will always be mounted on a fire-proof foundation. Risk from external fire should be small. A large body of oil in a substantial case, with relatively small exposed surface, will pass through a fire, such as would make scrap of an air-cooled transformer, and be ready for service in a day or two, upon renewal of leads and bushings. Incidentally the transformer cover should be water-proof to such an extent that water from a hose will not fall into the hot oil. As a final precaution, arrangements should be made to drain spilled oil away from the building. communicated By Letter. H. A. Lardner: --In the discussion as to the relative fire-risk of oil-and air-blast transformers, the opinion developed that large oil-cooled transformers in boiler-iron cases with suitable covers and vent...