Utility Economic Engineer
The Washington, DC, area was hit by two storms in 2012, each of which cause widespread electrical outages. A derecho hit the evening of June 29. Hurricane Sandy hit four months later on the evening of October 29. I sent surveys to people on the mailing list of the National Capital Area Chapter of the U.S. Association for Energy Economics (NCAC-USAEE) for both storms asking for a reply about the number of hours they were without power. (I experienced nine hours for the derecho and two hours for Hurrican Sandy.) My “Derecho Outage Survey” was included in USAEE Dialogue, Volume 20, Number 3 – 2012. Here I report on the outages related to Hurricane Sandy and compare the results to the outages related to the Derecho.
Table 1 replicates the form of Table 1 from my “Derecho Outage Survey.”
There were 93 survey responses, which I have summarized for five of the electric utilities in the Washington, DC, area. I report the number of customers who reported an outage to me and the duration of those outages in hours. I also include the number of customers who reported that their outage time was zero. Many of these zeroes may have actually been an outage of a few seconds to a few minutes. None of PEPCo’s customers in Washington, DC, reported an outage. I note that 22 PEPCo’s customers in Washington, DC, did participate in the survey, though each reporting 0 hours of outage.
Figure 1 presents a cumulative distribution function for the outages, including separate plots for BG&E; PEPCo-Montgomery County; and VEPCo; as well as a plot for the combination of all of the outage data.
Each plot has a convex shape, showing a rapid increase in the number of customers who have been returned to service, with a gradual degradation of the response rate as time accumulates.
The phenomenon of a convex cumulative distribution function is often referred to as “low hanging fruit” or “the most bang for the buck,” reflecting the incentives and policies that utilities have to concentrate on returning the most customers to service as quickly as possible. Thus, problems that can be resolved quickly for large numbers of customers are the first problems to be attacked. The result is the rapid early increase in the number of customers who are returned to service. Problems that affect individual customers are the last to be resolved, resulting in the plots turning horizontal as the outage duration time increases.
Figure 2 presents the cumulative distribution function for the outages of BG&E, comparing the outages for Hurricane Sandy with the outages for the derecho.
The plot for the four outages associated with the derecho does not have the convex shape described above. But with only four outages reported, the distribution of reported outages has a greater chance of not being representative of the distribution of actual outages.
Figure 3 presents the cumulative distribution function for the outages of PEPCo in Montgomery County, comparing the outages for Hurricane Sandy with the outages for the derecho.
PEPCo took some 72 hours to restore half of the customers who had outages associated with the derecho compared to only 3 hours to achieve the same restoration level for outages associated with Hurricane Sandy.
Figure 4 presents the cumulative distribution function for the outages of VEPCo, comparing the outages for Hurricane Sandy with the outages for the derecho.
VEPCo took 40 hours to restore half of the customers who had outages associated with the derecho compared to only 12 hours to achieve the same restoration level for outages associated with Hurricane Sandy.
Figure 5 presents the cumulative distribution function for all the outages reported in the two surveys, comparing the outages for Hurricane Sandy with the outages for the derecho.
The utilities in the DC area took 55 hours to restore half of the customers who had outages associated with the derecho compared to only 9 hours to achieve the same restoration level for outages associated with Hurricane Sandy.
The DC area electric utilities were severely castigated by government officials for the length of time that restoration efforts took after the derecho. Few comments were made about the restoration time in regard to outages in the DC area for Hurricane Sandy. Some of the differential in the length of the outages associated with the derecho versus Hurricane Sandy relate to physical phenomenon. Some relate to planning by the utilities.
The derecho occurred four months before Hurricane Sandy. The derecho is likely to have toppled many of the trees that Hurricane Sandy would otherwise have toppled. The utilities in the DC area also initiated a substantial tree trimming program after the derecho, further reducing the number of trees that would otherwise have been grist for Hurricane Sandy in causing outages. The derecho may also have had stronger winds. Together, these items are reflected in the large increase between the two surveys in the number of responses that showed no outages.
At least one utility in the DC area, PEPCo, pre-positioned contractors before Hurricane Sandy, as I wrote while sending out the survey.
When my wife and I drove to church Sunday morning, I was impressed with the dozen or more bucket trucks sitting in the parking lot of the Gaithersburg Holiday Inn, thinking I should call the television stations as a potential story for them to film. I didn't, but I was no longer impressed by yesterday's sight when I saw Channel 4's story today about noon from Gaithersburg, just across the street from the Holiday Inn. The Montgomery Country Fairgrounds seemed to have over a hundred bucket trucks, making the Holiday Inn parking lot scene look insignificant.
These pre-positioned contractors would likely have reduced the duration of the outages, just as the relative timing of the two storms, the tree trimming programs, and the relative strengths of the two storms likely contributed to the reduced fraction of customers who reported any outages and the increased fraction of customers who reported no outages at all.