METHOD AND APPARATUS FOR SIGNAL COUPLING AT MEDIUM VOLTAGE IN A POWER LINE CARRIER COMMUNICATIONS SYSTEM

摘要

An electricity supply network comprises a plurality of intermediate voltage switching and transformer substations (11-1 to 11-3, 12-1 to 12-3) connected together by underground cables. Each cable (22A, 22B) comprises at least one inner conductor and an outer sheath which is connected to the substation housing (20A, 20B). A PLC communication system comprises a plurality of transducers (23A, 23B) coupled to the cables at the substations. Each transducer is located on the side of its cable remote from the sheath connection to the substation housing, whereby the transducer is coupled to both the sheath and the conductor(s) of the cable. We have found that signals are adequately coupled to the cable conductors despite the shielding effects of the sheath. (The prior art technique requires the end of the sheath to be isolated from the housing and earthed by an earthing strap connected to the end of the sheath which is brought back through the transducer to the housing to effectively decouple the sheath from the transducer).