GB494197A - Improvements in and relating to devices for protecting electrical transformers and other apparatus - Google Patents

Abstract

494,197. Electromagnetic and magnetic switches ; protective cut-out systems; transformers. BUCHOLZ, K. F. Aug. 9, 1937, No. 21835. Convention date, Aug. 8, 1936. [Class 38 (v)] [Also in Group XXXV] A protective device responsive to a fault which results in evolution of vapour or gas, particularly applicable to a transformer or other oil - insulated electrical apparatus, comprises two members influencing one another magnetically or electromagnetically, one of which is arranged within a casing and is subject to displacement under the influence of the evolution of gas or vapour which accompanies the fault, while the other is arranged outside the casing and is adapted to operate a switch or indicator when the first member is displaced. In one construction, Fig. 1, a float 3 carrying a permanent magnet 4 is placed in a casing 2 connected to the cover 1 of a transformer tank. Under normal conditions, the magnet 4 attracts an iron plate 5 arranged outside the casing, but when the level of the oil, and with it the float 3, drops due to the collection of gases in the casing 2, the plate 5 is pulled away by springs 6 and completes a circuit at 7. In a modification, the permanent magnet 4 is replaced by an electromagnet energized by a coil which may either be mounted on the float or arranged outside the casing. In another construction, the iron plate is carried by the float, and the permanent magnet is movably mounted outside the casing. In the construction shown in Fig. 6, the float 3 carries a coil 23 connected to a source of current, and movement of the float causes an induced current in an external coil 24 which is adapted to actuate an alarm device. Fig. 7 shows an arrangement responsive both to accumulation of gas and also to the flow of oil, comprising an oil-filled casing placed in a conduit connecting the transformer with the conservator vessel. Accumulation of gas in the connecting chamber 26 causes a float 3 carrying a permanent magnet 4 to fall and release a plate 5, which springs upwardly and opens a contact or actuates a latch 27. A pivoted plate 28 responsive to the flow of oil is connected to a magnet 29 which normally attracts an armature 31 adjustably mounted on a lever 33 pivoted at 32, and holds the lever against a stop 34. When, in consequence of the expansion of the oil and evolution of gas, the flow of liquid attains a certain rate, the magnet 29 is withdrawn from the armature 31, and the lever 33 is rocked by a weight 35 to close a circuit at 36. The armature may be arranged to be normally outside the sphere of influence of the magnet, the magnet being sufficiently near to the armature to attract it in the event of a fault. The invention may also be applied to the protection of fermentation vats from excessive accumulation of gases. Specification 470,966 is referred to.