GB317099A - Means for, and methods of, improving the power-transmitting capacity of super-tension alternating current systems of electrical power transmission - Google Patents

Abstract

317,099. Taylor, A. M. Feb. 4, 1928, No Patent granted (Sealing fee not paid). Transmission conductor arrangements.-Long distance super-tension transmission between three-phase generating and consuming plant is effected through a two-phase transmission line and Scott-connected transformers, the trans mission line comprising four working cables, with or without spares, and switching arrangement whereby two transformer windings in 90 degrees phase relation and cables connected thereto may be associated with a cable connected to the neutral point for temporary transmission of the load in a quarter-phase system on failure of one of the cables, the cables being arranged in the ground in such a manner as to favour heat dissi pation at all times, and the arrangement being such that the magnetic fields of the cables or the electromotive forces induced in the lead sheaths are cancelled. Spare cables, normally connected to the neutral point, or a broken down cable may temporarily be used as a neutral conductor. Intersheath cables as described in Specification 264,196 may be used as main cables and spare cables. To reduce heating and cancel fields the cables are laid in pairs A, B, and C, D and the pairs well spaced, spare cables being also laid in pairs E, LT preferably between the others. Where the absence of telephone lines permits the cables may be laid separately and widely spaced, the lead sheaths being sectionalized and interconnected to cancel the sheath e.m.f. ; reactors may be arranged in the interconnections. The cancellation of cable fields may be effected through an additional insulated stranding of wires near the lead sheath these extra strandings being connected in a. closed loop whereby neutralizing currents may flow in them; armouring may be applied to such cables. To ensure a balance in cable currents after a breakdown series transformers ST may be arranged as in Fig. 3 with series connected secondaries or the cables may be re-connected, Fig. 4, where a spare low tension cable LT is provided so that it and the faulty cable B carry induced field cancelling currents assisted by the series transformers ST as shown. Where a low tension cable is connected to the neutral point a spark-gap in shunt to an earthing resistance, is used for protection. Where more than one spare cable is used the switching arrangements may make provision for succeeding breakdowns. Fig. 9 shows the interconnection of the sections of lead sheathings of two cables A, B and a spare cable E with reactors l in certain connections to prevent local circulation of sheath current whilst permitting any fault current to return readily bv the sheaths. An alternative method of sheath e.m.f. neutralization consists in cross-connecting core sections instead of sheath sections.