GB660181A - Improvements in or relating to safety devices for electric transformers - Google Patents

Abstract

660,181. Transformers. SOC. SAVOISIENNE DE CONSTRUCTIONS ELECTRIQUES. July 13, 1949 [July 20, 1948], No. 18523/49. Class 38 (ii). A protective device for an oil-filled transformer combined with an oil reservoir arranged above the transformer comprises a pipe b connecting the top of the transformer container A with the oil reservoir R, the pipe carrying a float relay B of the Buchholz or a similar type, the upper end of the pipe ending in the reservoir above the highest level of the oil therein and a second pipe c which starts from the lower part of the container A and passes through the reservoir R with which it communicates by means of two openings d, e disposed at differing heights. Thus, during normal operation, the transformer breathes only through the pipe c by means of cold and only slightly oxidized oil, any impurities which may be mixed with the returned oil being deposited at the bottom of the container and which do not therefore harm the transformer windings. The valve C, of the non-return type, allows oil to flow in both directions during normal operation but should a large flow commence from the reservoir to the container, such as would happen if the container A received damage, the valve closes to prevent such a flow from continuing. If a slight fault occurs in the transformer the Buchholz relay B operates in known fashion but if a major fault occurs, causing a sudden disturbance of the oil, the relay B will operate to trip a circuit breaker and at the same time oil will flow along the pipe c to rupture a frangible diaphragm which connects the pipe c to an explosion funnel E. The reservoir R communicates with the ambient atmosphere by means of a pipe f and an air dryer F.