A unique approach to powering HFC networks that combines high reliability with low maintenance costs

摘要

Southern New England Telephone (SNET) has developed a unique approach to powering hybrid fibre coax (HFC) networks that combines high reliability with low maintenance costs. The SNET approach is to provide highly reliable three phase 480 volt 60 Hz AC power from the central office. This power is distributed by a hybrid communications cable containing high capacity conductors and an innerduct through which fiber can be installed. At the fiber node, this reliable power is converted by a simple, high reliability, controlled ferroresonant transformer to the lower voltages used by today's HFC field electronics. The central office power systems feature redundant UPS modules, switchgear and motor/generator sets. There are many advantages to such a system. Installation is relatively straight forward since pole mounted power nodes don't require costly and hard to obtain rights-of-way or site preparation. Field maintenance is minimized since there are no batteries and motor/generator sets in the outside environment. Since the power node is essentially a simple transformer that can be tapped as required, the approach provides maximum flexibility at the fiber node. Economies of scale can be achieved in the central office through the use of large UPS systems and conventional switchgear. A prototype of this power system has been undergoing trials in Connecticut since October, 1995 and performed without flaw through Connecticut's record winter weather.