GB1299197A - High voltage d.c. systems including transformers or reactors - Google Patents

Abstract

1299197 Transformers; inductors LICENTIA PATENT-VERWALTUNGS-GmbH 22 Dec 1969 [23 Dec 1968] 62385/69 Heading H1T An oil-cooled transformer or reactor for use in H.V.D.C. systems has an at least partially bare control electride 5 which is at substantially the same D.C. potential as the adjacent end of a winding 3 and is positioned where oil enters or leaves the winding to ensure that an adequate proportion of the direct voltage on the winding is dropped across the oil and thus to relieve the solid winding insulation. The control electrode 5 may be situated in a zone of low electrical field strength between the winding 2 and a shielding ring 4, or may form part of a cylindrical, capacitive control shield (Fig. 4, not shown). One or more control electrodes 5 may be provided between winding discs (Fig. 7, not shown) or at the ends of winding layers as in Fig. 8. In the latter case, the electrode 5 is formed of high resistance conducting paper and contributes to the A.C. insulation while taking on a D.C. potential which is determined by solid insulation 7 and the area of the electrode 5. The conducting paper may be circumferentially slit to increase the axial resistance of the electrode.