Self-Healing Grid
Updated September 2023
Self-healing grid technology essentially ties together sections of power lines from two different sources. If a fault occurs in a section of line within the feed, the reclosers can isolate the affected area and back-feed the unaffected portions from the alternate source. This “healed” portion of the distribution grid brings the lights back on for some members who would otherwise be out of power while waiting on repairs.
The impressive thing is, all this happens automatically within about a minute and can significantly reduce the number of members affected by an outage. Because REMC serves mainly rural areas, the cooperative is limited by geographic and operational considerations. As of September 2023, REMC has four self-healing grid schemes operational, with more planned for the future.
Earlier in August, afternoon thunderstorms became a routine event. On Monday night, August 28, 2023, storms erupted abruptly across the service area. At 11:26 p.m. circuit 44 in the Liberty Hill area of Montgomery County west of Troy, locked out, resulting in 1,116 members being out of power.
Since this circuit is part of our first self-healing grid installation, an alternate source rerouted power at 11:27 p.m., and the lights came back on for 1,108 of the affected members. So within a minute, all but 8 of the 1,116 members served by this circuit experienced only a momentary “blink.”
This outage was caused by a tree falling onto a power line that runs through the Uwharrie National Forest. REMC crews responded, removed the tree and repaired the downed power lines. Power was restored to the remaining 8 members at 1:42 a.m.
Without the self healing grid installation, not just 8 members, but the additional 1,108 members would have been out of power for 2 hours, 16 minutes. The self-healing grid scheme automatically saved a total of 150,688 potential outage minutes for those 1,108 members. This illustration shows the reason why REMC has invested in this technology. Sometimes a power “blink” can be a good thing.
Randolph Electric will continue making investments that bring value and will communicate those success stories to our members.
July 2022
During a winter storm, some REMC members experienced an outage from damage to power lines in their area. Three years ago, this outage would have lasted around six hours for most of those members. Because of self-healing technology, however, most members had their power restored very quickly. This is because REMC had installed intelligent switches that automatically detected trouble on the lines. The switches then rerouted the power flow from another distribution source. The switch isolated the problem to impact a smaller section of the grid.
Often, this self healing process can occur in just a few seconds, registering only as a blink or very brief outage for the majority of members affected by an outage. This means that in the future many members may not even realize that Randolph EMC’s GIS technicians have dispatched a repair crew to their area. REMC will finish repairs, then remotely restore the power flow back to its original configuration. Again, this can occur without members even realizing that there was an outage in their area.
Randolph EMC currently has two self-healing grid installations on the system: one in the Seagrove and Ulah area, and one in the Troy area. Unfortunately, it’s not feasible to install this technology systemwide because the cooperative faces some limitations. For instance, REMC is a more rural cooperative than most and will invest in placing switches only where it makes the most sense. In addition, the intelligent sensors will work only in locations that can provide alternate feeds. Moving forward, Randolph EMC will install this technology in key locations.
Randolph Electric seeks to advance resilience by building a modernized grid that can monitor itself and provide improved reliability and faster restoration for members.