GB396196A - Improvements relating to bushing insulator type of current transformers - Google Patents

Abstract

396,196. Current transformers. TRIGGS, W. W., 57, Lincoln's Inn Fields, London.-(Ohio Brass Co. ; Mansfield, Ohio, U.S.A.) May 23, 1932, No. 14565. [Class 38 (ii).] A bushing insulator type current transformer has a primary 10, Fig. 1, wound on an axial core 11 and associated with it a secondary 18 and one or more ring cores 15 on which are mounted secondaries 17. The windings 10, 18 function as a transformer having a core 11. The winding 10 also forms a single turn primary for the windings 17. The cores 15 form part of the return flux path for the core 11, and in order to effect a compensation, the secondaries 17 may be wound obliquely as shown in Fig. 4, so as to link with this flux. A relay may be provided for short circuiting the winding 10 when the current exceeds a given value. In a modification, Fig. 5, windings 21 may be constructed in series with the secondaries 17 or may be connected to an auxiliary winding on the core 15 to effect compensation. In a modification, Fig. 9, a relay 20 operates to short circuit the primary 10 when a predetermined current is reached and a relay 25 energized from part of the secondary 26 changes the connections of the burden from the secondary 26 to the secondary 28. In a modification the relay 25 operates when a predetermined current is reached and connects the burden to secondary 28 and a resistance across the secondary 26. In a modification a relay energized from a winding on an auxiliary core operates to change the burden from one secondary to the other. In a further modification the two secondaries may be in series or parallel and two relays energized from a winding on an auxiliary core control the insertion of series and parallel impedances for the purpose of effecting power factor and ratio correction. The insulator may be provided with means for modifying the electrostatic field to reduce the danger of discharge.