The Introduction and Operation of Distributed DC Power Systems into the British Telecom Switched Network

In 1982 a decision was taken to discontinue for new exchanges, the provision of traditional dc centralised power plant which had been in vogue for the previous 20 or so years. It was argued that with the modernisation of the switched network, with the digital switch replacing strowger, the opportunity should be taken to adopt a dc power system which would be compatible with the emerging equipment practice image, and be capable of enhancement as power electronics technology changed. A system was designed based on the philosophy of integrating and distributing relatively small and very reliable "blocks" of dc power, on dedicated racks, within exchange equipment area's. Hence the complete dc power rack was introduced and made its international debut at Intelec '82 in Washington DC. This paper will review the period since 1982, and describe the introduction of the new dc distributed power policy into an operating environment with its well established planning and service operating experience of large centralised power plant. This involved the re-education of local field planning, installation and service staff, the organisation of new and modern maintenance techniques, and the review of existing repair policies. The paper will go on to discuss the operating experience of the distributed power system and how an acceptable level of confidence was achieved prior to commissioning equipment for public service.