Distribution Grids Need Rapid Restoration

Mike Edmonds, S&C Electric Co.

Distribution automation (DA) has long been effective at improving electric service reliability. Many DA solutions, however, meet only today’s service reliability requirements and likely won’t be acceptable down the road.

Most local utility commissions establish outage definitions based on an outage’s length. This data is then used to calculate utility reliability performance metrics. In the U.S., (and often in other areas) outages up to five minutes long are not counted. Thus, it’s not surprising that many DA solutions available today do not improve upon but conform only to these standards,enabling utilities to meet the minimum acceptable performance requirements. These solutions cannot meet future reliability standards. Many areas outside the U.S., which already recognize the need for better reliability performance, have outage reporting thresholds of one minute or less.

Countable outage durations are shrinking in the U.S., and for good reason. Think about how long a five-minute outage is for a business or a consumer, or even a three-minute or one-minute outage. For a retailer, it means that customers are leaving the store, resulting in lost sales. For an industrial customer, it means a decline in productivity. At critical facilities, it means that carbon-emitting emergency generators may have gone into service and will need to remain on for an extended period to avoid a cold shutdown. And, at home, it means that consumers may miss that big play during their favorite teams’ football games.

Although short outages may not show up in reliability metrics today, they certainly shape utility customers’ perceptions about their electric service. They also influence business decisions, including where to locate operations. These perceptions, and the real economic losses and negative impact to quality of life from outages, are especially concerning as businesses and consumers face rate increases to pay for smart grid technology. Consumers will not accept that the grid is somehow smarter when performance has not improved. In response to these considerations, utility commissions are driving down outage numbers which, in turn, requires distribution automation solutions that can restore service faster.

Looking down the road, an even greater concern is how reliability will be impacted if utilities don’t implement distribution automation systems that can respond rapidly to changing system conditions.

The penetration of renewable energy sources and stored energy throughout the distribution system is expected to increase significantly as utilities work to meet renewable portfolio standards. Because of the higher costs of distributed energy sources, however, centralized generation will continue to meet most of our electricity needs for the foreseeable future. Utilities therefore will need to balance centralized and distributed energy sources with fluctuating customer demand, while operating their systems so that renewable sources are used first, before fossil-fuel-fired generation.

To make this complex balancing act even more difficult, utilities will need to quickly and efficiently restore power to as many customers as possible in the event of a system disturbance, maximizing service reliability. To do so, they may need to operate service islands for limited periods; add load to existing islands; frequently move normally open points (so that the concept of having a normally open point itself becomes obsolete); or connect load to alternate, possibly centralized, generation sources. Advanced distribution automation capable of rapid self-healing response will be essential to address these challenging new requirements.

As utilities implement the smart grid of the not-so-distant future, distribution automation technology that cannot provide rapid self-healing will quickly become obsolete. Just as utilities are investing in advanced metering infrastructure to help meet future energy needs, investment in rapid restoration technology is essential today to meet requirements for tomorrow’s grid.

Mike Edmonds is global smart grid strategies director with S&C Electric Co.

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