Cable practice in electricity-board distribution networks: 132 kV and below

The paper is intended for the general nonspecialised reader, but sufficient detailed information has been included for those whose work is closely associated with cables. Introductory Sections cover cable standards and codes of practice in current use, together with a brief historical review. Conductors are dealt with separately, and it is described how, for economic reasons, aluminium has now almost wholly superseded copper for power-cable conductors. Similarly, rating practice is treated separately, rating parameters being stated and discussion centred on performance of cables in practical situations. For the purpose of the paper, cables have been classified as (a) pressure assisted 132 kV to 33 kV, (b) 33 kV solid type, (c) 11 kV, (d) m.v./l.v. (i.e. 415/240 V) and (e) pilot/telephone. In each classification covered, cable construction, jointing practice and service performance are fully detailed together with technical reasons for selecting particular types of cable. Installation and construction practice is described and discussed covering topics such as legislation and codes of practice, depth of burial, protection against damage, selection of routes, multiple service trenches, identification of services, cable tunnels and duct systems, submarine cables and river crossings. Earthing and bonding is discussed with particular reference to single-point and crossbonded systems. Testing procedure is described, together with methods of fault location. Cables versus overhead lines are dealt with briefly to emphasise that the overhead system is not used in towns and cities. Comparative costs and fault statistics are quoted. Life expectancy of cables is discussed in general terms, and an attempt is made to assess what life expectancy one might expect for various, types. Finally, the paper discusses possible future developments, particularly regarding plastic-insulated cables.