GB1475162A - Meidensha kk device for and method of detecting short circuit in a transfor mer winding - Google Patents

Abstract

1475162 Protective devices TOKYO ELECTRIC POWER CO Inc and MEIDENSHA KK 14 Aug 1974 [20 Aug 1973 5 Dec 1973] 35844/74 Heading H2K A method of detecting a short circuit in a cylindrical current carrying winding 20 of a magnetic circuit a transformer, the winding being coaxial with a magnetic core 28 and in a cylindrical housing 30 comprises detecting with an electrically conductive element 32 asymmetry in the distribution of leakage flux of the magnetic circuit about a point of symmetry of the winding, by producing across the element a voltage which is a measure of this asymmetry, and feeding this voltage to a level detector and switching means to produce an output signal when this voltage exceeds an adjustable predetermined level. Asymmetry in either the radial component or axial component of the leakage flux may be detected. The electrically conductive element may be a helically coiled conductor 32<SP>1</SP> mounted on an outer surface of the magnetic core 28 of the transformer and surrounded by the primary windings 20 or mounted on the inner surface of a side wall 30a of the transformer housing and so positioned relative to the transformer primary that the normally symmetrical distribution of leakage flux causes equal and opposite voltages which cancel in the conductor 32 but an asymmetrical distribution B2 of leakage flux due to a shortcircuit section 20a gives rise to a resultant voltage in the conductor which is fed to the level detector. In the case where the short circuited section is symmetrically placed in the primary however the leakage flux will still have a symmetrical distribution and to deal with this case a further embodiment is described, Fig. 8, wherein a pair of helically coiled conductors 48, 50, 48<SP>1</SP>, 50<SP>1</SP> are mounted on the transformer core 28 and housing wall 30a in addition to the first conductor 32, 32<SP>1</SP>, adjacent to and symmetrically on either side of the lengthwise mid point of the primary winding 20, their outputs also being fed to the level detector. As an alternative to the helically coiled conductors, field sensitive semi-conductor elements such as Hall effect or magneto-resistance effect devices are used.