The Portland Board of Light and Power (PBLP) has scheduled a shutdown for all customers starting at midnight on Friday October 15th until noon on Saturday October 16th. The purpose of the shutdown is to install new reclosers between the Consumers Energy substation, which provides about 95% of Portland’s power, and the city-wide electrical distribution system. The existing switches have reached end of service life and are no longer fit for reliable duty. Many city residents know we have natural gas and diesel fired generators that can provide power to the city in the case of an outage. With that knowledge it makes sense to ask can we run the generators during this planned outage? The simple answer is no. The equipment to be replaced is electrically located between our generators and the electrical distribution system. There is no safe way to conduct the planned maintenance activities and generate power during the outage. While power is isolated for the recloser installation, crews from Consumers Energy will be doing maintenance work on their substation and transmission line feeding the city. Simultaneously, crews from the PBLP will be conducting preventative maintenance on the de-energized system. For more information about what a recloser is and how it functions within an electrical distribution system, below is an excerpt from a technical bulletin prepared by the EATON corporation. In the event of a delay due to hazardous weather conditions, the recloser installation project and associated maintenance activities will be delayed one week and will be conducted at midnight on Friday October 22nd until noon on Saturday October 23rd.
What is a recloser? A recloser is an automatic, high-voltage electric switch. Like a circuit breaker on household electric lines, it shuts off electric power when trouble occurs, such as a short circuit. Where a household circuit breaker remains shut off until it is manually reset, a recloser automatically tests the electrical line to determine whether the trouble has been removed. And, if the problem was only temporary, the recloser automatically resets itself and restores the electric power. On high-voltage electric lines, 80 to 90 percent of trouble occurrences are temporary – such as lightning, windblown tree branches or wires, birds, or rodents – and will, by their very nature, remove themselves from the electric line if the power is shut off before permanent damage occurs to the lines. The recloser senses when trouble occurs and automatically shuts off the power. An instant later (the length of time may be noticeable only as a lightbulb flicker), the recloser turns the power back on, but if the trouble is still present, it shuts it off again. If the trouble is still present after three such tries, the recloser is programmed to consider the problem permanent and it remains off. A power company crew must then repair the problem on the line and reset the recloser to restore power. Examples of permanent problems include: power lines or other equipment damaged by lightning strikes, fallen tree limbs, or vehicle crashes. (Eaton Publication No. TD280027EN July 2017)