A single piece of old, used and ”unpredictable” equipment caused a minor electrical fault to escalate into a raging fire in a Commonwealth Edison Co. substation, shutting off power to 40,000 West Siders for up to three days last summer and contributing to another blackout a week later, a state study has concluded.
A consultant to the utility-regulating Illinois Commerce Commission warned Edison to remove similar equipment on its distribution system and said a fire similar to the one July 28 at Edison`s Crawford substation remains a risk until then.
Edison, which released a similar account of the fire`s origin last month, has said it plans to replace the relay equipment and install a backup system at Crawford and similar substations.
But Paul McCoy, Edison`s operations manager, disputed that the relay was unpredictable, saying the Crawford incident was the only case in which it malfunctioned. Edison hasn`t yet seen the consultant`s report.
The Tribune obtained a copy of the report Tuesday. Commission Chairman Terry Barnich had planned to unveil the report at a Friday news conference.
The Maryland consultant, Forensic Technologies International, said a cable inside a switch house at the Crawford substation, 3501 S. Pulaski Rd., failed apparently because it was old, cracked and water had seeped into it.
But the consultant said that what would have been a minor fault escalated into a major blackout because the old piece of relay equipment failed to trip circuit breakers and prevent a fire.
The circuit breakers, similar to those in homes, would have shut off electricity, preventing the heat buildup and fire.
The relay equipment was a used part, designed in 1938, that Edison had installed at Crawford well after the manufacturer had replaced it with a better, improved model in 1960, the report said.
”Until these relays are replaced or their system applications modified, there is a definite risk of severe damage and catastrophic outages,” the consultant said.
The consultant also said Edison should review all equipment in the affected switch house, as well as conduct systemwide equipment inspections every year to 15 months instead of the current two years to 30 months.
