GB1141390A - An improved method of preventing the formation of ice on an overhead power transmission line - Google Patents

Abstract

1,141,390. Current transformers. MULLARD Ltd. 24 April, 1967, No. 18670/67. Heading H1T. [Also in Division H2] The formation of ice on an overhead power transmission line is prevented by an automatically operating heating circuit comprising at least one conductor extending along the line, the heating current being derived from a secondary winding of a transformer of which the primary winding is the line itself. As shown in Fig. 1, a tubular ferrite core E, having a Curie point in the range 2‹ C. to 15‹ C. is mounted on the power line A, with one end of the secondary winding attached at B to the line A, and the other end attached to a heating conductor H, helically wrapped around the line A and connected to it at a remote point. The heating circuit is automatically brought into operation when the ambient temperature falls below the Curie point of the core. The secondary circuit may heat the core or a second core heating circuit may be provided in series or parallel with the secondary winding. The core material may be a tertiary or quaternary alloy, and the transformer may have cooling fins and be protected against moisture and corona discharge. In another form (Fig. 2, not shown) a silicon-iron cored transformer is used and a temperature sensitive switch (V) short circuits the heater at ambient temperature above about 7‹ C. A fall in temperature to the freezing point causes the switch to open and current to flow in the secondary circuit. Transformers of either type are mounted adjacent a tower support (Figs. 3, 4 not shown) or supported directly by the tower (Fig. 5, not shown). In a further embodiment (Fig. 6, not shown), a jumper conductor (S) between two power lines (A) supported by insulators (C) at a tension tower is threaded several times through the core to increase the number of primary turns of the transformer which is suspended from the tower by supports (T).