Starting at about 3pm on Friday March 8, thousands of residents and businesses in the Thorncliffe Park, one of Toronto’s most densely packed high rise neighbourhoods, suffered a blackout. Power was restored in a piecemeal fashion. Three large apartment towers were in the dark for about 33 hours.
Toronto Hydro has repeatedly suggested that aging infrastructure was responsible for the blackout. Here is Toronto Hydro Vice President, Blair Peberdy, on the CBC radio show Metro Morning March 11 repeatedly blaming the blackout on aging infrastructure and under-investment.
New information is emerging that the equipment failure that caused the blackout was relatively young in service age, that maintenance deficiencies with that specific equipment were well known to Toronto Hydro far in advance, and that Toronto Hydro allowed that specific equipment with known defects to deteriorate until the blackout occurred.
The immediate cause of the Thorncliffe Park blackout appears to have been the failure of a sulfur hexafluoride (SF6) gas switch. The particular switch in question is approximately 20 years old. The switch in question is widely used in the utility industry and is known to be safe and long-lived equipment when properly maintained. It is designed for a much longer service life than 20 years. Key to the safe operation of the switch is a secure seal around the pressurized cabinet containing the electrical equipment. A gasket seal on the cabinet door contains the SF6 gas. A pressure gauge on the cabinet measures the internal pressure. A drop in pressure indicates a leak.
Several months ago, the switch in question was reported to have a declining gas pressure indicating a leak. Rather than fix the gas leak and re-pressurize the system — a routine maintenance operation — the switch was instead left to run until failure.
About five weeks ago, this switch failed, but was relatively quickly reset and power restored.
The early leak detection followed by a small failure demonstrates negligence on behalf of Toronto Hydro in its decision to run that specific switch to failure. Negligent maintenance, not aging, caused the failure.
On March 8th the switch failed catastrophically.
Many SF6 switches on Toronto Hydro’s system are known to be leaking. Thorncliffe Park is just one of many such blackouts that will become more frequent until responsible maintenance practices are restored at Toronto Hydro.
Toronto Hydro’s practice of allowing maintenance to slide to the point of leaving customers in the dark is similar to the approach Toronto Hydro took to managing Hurricane Sandy last November. As documented previously, Toronto Hydro deliberately planned to leave customers in the dark during and after Hurricane Sandy.
Part 58 of this series will analyze the circumstances leading up to the Thorncliffe Park blackout. The analysis will include a review of the roles of Toronto Hydro’s Board of Directors and Ontario Energy Board in the blackout, and the false rate information reported by Toronto Hydro’s Vice President Mr. Peberdy on CBC’s Metro Morning March 11.
People with knowledge about the state of Toronto Hydro’s SF6 switches and the Thorncliffe Park switch in particular are invited to contact me through the response form on this web site.