When you lose a part of a multi-phase circuit, you usually get bleed through enduser devices that are still getting power through the other phases. Your 27VAC was probably bleen through a (or more likely several) three-phase motors that did not have phase-outage protection circuit breakers. They probably had stopped spinning and were slowly cooking themselves. A building I once worked at lost one of their phases and after an hour the fire alarm went off and we had to evacuate the whole 10 stories. A "temporary" compressor in a design model shop did'nt have adequate protection and cooked all it's lubrication, filling the shop with smoke. Apparently, phase-outage protection is not required in many installations where it should be. One data-center in the same building still had some three phase powered mini-computers (mini in name only) and they lost almost half their hardware. JMH Jim Browne wrote:
Downtown Sunnyvale around Carroll Street (including PacBell SNVCA01 and us) lost power (on one phase only) yesterday at 12:35 PDT. PG&E brought it back at 15:35. PG&E said that our area is using too much power and we blew the breaker on that phase. The odd thing was we were still getting about 27 VAC on that phase with the breaker "blown".
-- John Hall <j.hall@f5.com> F5 Networks, Inc. Senior Test Engineer 206-505-0800 One of the large consolations for experiencing anything unpleasant is the knowledge that one can communicate it. -- Joyce Carol Oates