GB316378A - Improvements in the heat radiation systems of oil insulated transformers - Google Patents

Abstract

316,378. Digby, W. P., and Fairthorne, R. B. June 8, 1928. Transformers. - In oil-immersed transformers in which the tank is provided with heat - dissipating surfaces such as tubes or corrugations, cooling is augmented by supplying an evaporative liquid to the hotter parts of the surfaces, excess liquid being led awav before it reaches parts where the temperature approaches that of the liquid. In one form, Figs. 2 and 6, fibrous material 2 is wrapped round the upper parts of the radiator tubes 1 of the oil tank and is kept moist by water supplied to the upper clamping collars 3, excess water being led away clear of the lower parts of the tubes either by drip wires or by pipes 5. The collars 3 are fcrmed with annular grooves 8 communicating with axial grooves 12 and with a channel 9 to which water is supplied through a drip cock 11 from supply pipe 10 encircling the upper parts of the tubes. A second section of wrapping may be placed below the first section of wrapping on the tubes, a fresh supply of water being introduced at the lower level. Where the tubes 1 communicate with headers, the wrappings may be arranged to project into a tray, to which water is supplied, at the upper ends of the tubes, a collecting tray being provided at the lower end. Where clamping collars are not employed, the fibrous material may be wrapped helically round the tube and secured in place by lacing or snap fasteners. Alternatively it may be in the form of woven sleeves placed in position on the tubes before they are built into the tank. Where the fibrous material is applied to the corrugated walls 18 of a tank, it may be secured in place by wooden wedges 21, Figs. 11 and 12, disposed between the corrugations. Means for indicating, and if desired regulating, the amount of moisture in the wrappings may be provided. These may comprise conducting collars 25, Fig. 13, spaced apart on the wrappings so that sections 26 of the wrappings may be connected either in series or in parallel and incorporated in a Wheatstone bridge circuit. Variations in resistance of the wrappings due to variations of moisture content may thus be caused to operate an indicator or a control device associated with the water supply. The collars should be of a material electropositive to that of the tubes. In an alternative arrangement, collars of dissimilar metals are provided on the wrappings so that galvanic cells are formed. These are connected in two series groups normally balancing each other end associated with a differential relay so that in the event of unbalance arising due to deficiency of moisture in certain tubes an indication or correction is made. Condensation of moisture on the terminals of the transformer from the rising air above the tubes 1 is prevented by the provision of ducts through which the air rises by natural draught or by forced draught controlled by load variations.