UltraTM Capacitors for Short Duration Backup of DSL Cabinets

Abstract

Telephone companies have traditionally provided a minimum of 8 hours of battery backup at remote locations served by portable engine-alternators. In many areas, this is mandated by state law or other regulatory rules. For lifeline telephony service and 911 availability, this backup is critical. However, in the brave new world of data and video services, a TV signal is not critical for someone suffering from a heart attack. Cable TV and telephone companies provide different levels of battery backup (from none to a few hours) for data and video services. Rather than be driven by regulatory minimums, the backup is driven more by the market (the demands [real or perceived] and needs of the consumers). The closer the electronic equipment moves to the residential customer, the less important backup power becomes for video and data services (excluding plain old telephone service that may be derived from the same broadband pipe), since few residences have their own UPS systems to keep their TVs and computers working during commercial AC power outages. For example, in a fiber-to-the-home (FTTH) application, where the electronics are at the house, if the electronics lose power, it is highly likely the whole house (including the TV and the computer) has lost power. Qwest has pursued a policy of little to no battery backup for FTTC and FTTN video/data only architectures for the past 9 years. Equipment problems more than customer complaints have caused us to recently re-evaluate that decision and look to put in minimal backup. -48 VDC lead-acid and Li-ion battery systems have been evaluated, as well as traditional UPS systems, and supertrade or ultratrade capacitors. Tests have shown that over the expected lifetime of the field electronics, the capacitors may prove to be the most costly and reliable alternative for backup times of less than 1 minute. This paper will explore the equipment related problems associated with having no battery backup, and evaluate the performance, as well as initial and maintenance costs of both battery and capacitor solutions. The proper amount of backup time required will also be discussed in relation to average outage frequency and duration on the U.S. grid