Sheath and armour losses in single-core cables for single-phase and three-phase transmission

The accurate practical determination of inductive losses in an a.c. system of single-core lead-covered cables is considered in detail, and test-results which are correlated with calculations are quoted by way of illustration. Bridge methods have been developed for the measurement of both the total and individual losses in single-phase and 3-phase single-core systems. These methods are shown to be capable of great accuracy. The feasibility of armouring single-core cables has been discussed by various authorities, whose opinions are widely divergent. A series of tests has been carried out, the main results of which are given herein. These show clearly the practical limitations imposed by the inductive effects from armouring each cable separately with wire armour. They also provide a sound empirical basis from which the losses in any given system may be estimated.