Power quality: How to cut costly short interruptions - UK focus

S&C Electric talks to Engerati about the new smart technologies that can cut the growing problem of momentary outages.
Published: Mon 24 Apr 2017

With more and more electronic and digital devices in homes and businesses, any interruption in the electricity supply can cause frustration and expense. Clocks and security systems must be reset, electronic cash registers rebooted and, in the worst cases, damages must be repaired when assembly lines suddenly stop.

In the United States, for example, in what is regarded as the most comprehensive analysis on power interruptions, the Lawrence Berkeley National Laboratory has estimated their cost at approximately US$80bn in 2004 — rising to the order of US$110bn by 2014.

Utilities and regulators are rightly concerned about these outages and are constantly seeking to reduce them. However, their efforts have tended to focus on reducing the duration of outages and have paid little attention to reducing short or momentary interruptions lasting from mere seconds to a few minutes. Further adding to this problem, solutions for the former have exacerbated the issues associated with the latter.

In the Lawrence Berkeley studies, momentaries were found to attribute to more than half the total cost of outages.

Momentary outages in UK

In the United Kingdom, the problem of short interruptions – or ‘blinks’ as they are commonly known by consumers – has become so commonplace that they have become accepted as “normal,” despite the evident consumer frustration, says Chris McCarthy, Managing Director of S&C Electric Company.

McCarthy cites a domestic customer’s comment during a recent distribution network operator (DNO) stakeholder meeting: “For me, a power cut is when the power is cut off for any length of time.” Another customer commented on experiencing them “a lot” and called them “irritating,” while a business customer said, “even a short power cut can cause lots of knock-on issues.”

This upsurge in short interruptions, which are defined as up to three minutes in the UK, is clear in data collected by Ofgem (the Office of Gas and Electricity Markets). Since 2010-11, when the short interruptions reached a low of an average 64 per 100 customers, they have increased subsequently, running at 75 per 100 customers in 2015-16 (excluding one DNO group for which data was not available).

Noteworthy also in the data are large regional variations, where, for example, there were relatively high levels of short interruptions in the north of Scotland, South Wales and southwest England.

So what is causing this increase? McCarthy explains that in Britain, a key part of the way in which outages – measured in terms of customer interruptions and customer minutes lost – have been tackled is to replace fuses on tee or spur lines with sectionalisers.

This improves reliability in terms of reducing interruption durations because there is no longer the need for field crews to replace blown fuses caused by the most commonly experienced transient faults. However, the transients are still present, and when fuses are taken out and sectionalisers are used together with up-line breakers, the frequency of short interruptions increases significantly.

“This really took me by surprise because fuses have been the backbone of protection on the distribution system for a hundred years,” says McCarthy. “But the problem is that outage reduction in Britain has been driven by regulation, but there is no regulation on momentary outages. Also, because consumers often consider momentary outages acceptable, utilities are not motivated to invest money to improve this service.”

Ofgem RIIO-ED1 price control

Chris Watts, Regulatory Affairs Director at S&C Electric, contends that ultimately “strong regulation with significant financial ties” will be required to drive the behaviour to address the problem of short interruptions.

As part of the strategy work on Ofgem’s RIIO-ED1 price control (which set outputs for the DNOs for the period 2015-2023), his team at the time considered whether it was appropriate to include new incentives to reduce short interruptions as part of the price control.

However, Ofgem’s conclusion was that “stakeholder feedback indicated a preference for reducing the duration of interruptions over reducing the number of interruptions,” and the decision was taken not to introduce an incentive.

Ofgem also noted its concern that the short short-interruption data was not sufficiently robust to support a financial incentive. The data is also probably under-reported because common recording and reporting practices haven’t been developed in the same way as for customer interruptions and customer minutes lost.

Ofgem RIIO mid-period review

At the time, Ofgem indicated its intention to revisit the reporting of the short short-interruption data during RIIO-ED1 to improve network management.

With the RIIO-ED1 Mid-Period Review coming up and consultation due to start on the strategy for RIIO round 2, which includes the 8-year period from April 2023, there is now “an opportunity to do something more,” says Watts.

S&C proposes a solution founded on the use of the new generation of smart devices, which are able to report on performance for short interruptions through the recorded event logs.

“Instead of waiting for years to collect at best incomplete data to establish a baseline and performance criteria, we propose a reliability/monitoring incentive that is based on the actual installations of such devices and the recorded improvements in performance,” Watts says.

“This would motivate the DNOs to deploy smart technologies in the right places in order to best improve reliability and customer service, and there would be a direct correlation of field activity to the financial incentives earned.”

Florida Power & Light leads the way

As an example of a utility following this strategy to reduce momentary outages, McCarthy cites Florida Power & Light (FPL), which is carrying out a systemwide rollout of S&C’s TripSaver II Cutout Mounted Recloser to replace fuses.

The technology, which is effectively putting intelligence at the grid edge, both interrupts temporary faults and, via coordination with other protective devices, isolates sustained faults.

The approximately 80,000-device deployment is about midway complete. Based on the Lawrence Berkeley analyses, when completed, FPL can expect cost savings of as much as $500,000 annually for electricity users on each main feeder and gain significant reductions in operating expenses.

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