'Self healing' key to meeting smart grid promise
28/07/2012 - While smart meters receive the hype, reclosers are the true building blocks of the intelligent electrical distribution grid, underpinning its reliability. Peter Field
Smart grids are increasingly touted as a large part of the answer to combating climate change and fossil fuel reliance. By endowing the electrical distribution network with the flexibility to adapt to new patterns of 'green' usage and the variability of generation capacity from renewable sources such as wind, wave and solar, engineers hope to reduce wastage and improve reliability.
The International Transport Forum – an Organisation for Economic Co-operation and Development (OECD) intergovernmental body – for example, reports in its July 2012 Policy Brief "Smart Grids and Electric Vehicles: Made for each other?" that smart grid technologies make it possible for electric vehicles (EV) to proliferate without overloading the electric supply industry.
The report also notes that at the same time EVs, among other green technologies, are driving investment in smart grid technologies, a view echoed by US-based analyst IHS. The research firm says that the US has budgeted US$4.5 billion ($4.36 billion) for investment purposes while China is expected to become the largest smart grid market in the world, with US$586 billion ($568 billion) set to be invested in the electrical power supply infrastructure during the next 10 years.
But to meet this promise of flexibility, smart grids – electrical distribution networks that employ computers and modern communications to improve reliability, efficiency and robustness – must feature 'self-healing' properties that ensure rapid recovery from outages.
Traditional power grids are unidirectional and typically, just a single line feeds a suburb or city block. If the power fails, due to, for example, a lighting strike, consumers and industry in the area affected can be without power until the damaged line is repaired. With current technology it often takes several hours to locate the fault before an engineering team can be despatched and then several more hours to affect a repair.
Smart grids overcome this weakness by utilising bidirectional lines and distribution topologies that ensure a geographical area can be supplied from several alternative branches of the network. This endows the grid with the ability to self-heal; if failure occurs on a particular line, power can be re-routed via a different branch - reversing the flow of electricity if required – minimising the impact on the consumer.
"It’s all very well to talk about how smart grids will help us deal with the variability in supply that comes with increasing the amount of electricity generated from renewable generation capacity," Neil O’Sullivan, Managing Director of Brisbane-based recloser manufacturer NOJA Power said.
"That’s important, but even more important is ensuring the grid is totally reliable – no matter what the source of the power. And nothing underwrites that reliability more than reclosers."
Reclosers are the "intelligent circuit breakers" that endow the smart grid with its self-healing properties. These "computers on poles" – capable of handling between 10 and 38 kV and robust enough to resist vibration, temperature extremes and inclement weather, yet weighing in at just 100 kg - are mounted on transmission poles at critical points on the grid.
Reclosers are able to immediately cut the power if the line they are on suffers a failure, preventing further damage or a knock-on effect to other parts of the network.
"People like to talk about smart meters as key to this new electrical distribution technology because those are the devices with which the consumer identifies as the enabler for the smart grid," O’Sullivan explained.
"But while smart meters are indeed useful, they are a peripheral part of the infrastructure; reclosers are the true building blocks of the technology - although they remain 'unsung heroes' because they’re invisible to the public."
Because modern reclosers, like those manufactured by NOJA Power, utilise powerful microprocessor-based electronics and modern communications protocols they can do much more than just isolate a failed conductor.
"In the event of a power outage, because the recloser is linked directly to the control facility and can sense the line in both directions it will immediately inform the supervisor of the location of the fault," Oleg Samarski, NOJA Power’s Quality and Service Director, said.
"That means engineers can set out to make the repair in minutes.
"In addition, modern reclosers are also able to store useful data such as the time of the outage as well as local usage patterns that can be used by the utility to better manage the grid in the future."
According to Samarski, reclosers, unlike traditional circuit breakers that remain open until they are manually reset, are able to close and re-establish the power in seconds if the fault proves to be only temporary. Alternatively, reclosers working in groups can open and close in sequence to re-route power to the zone affected by the outage via a different line - giving engineers breathing space to fix the original fault.
"Smart grids are critical in the fight against climate change, as they have enormous potential to improve the efficiency of our electricity sector and transform the way we use energy in our homes and businesses," Senator Penny Wong (then Minister for Resources and Energy, now Minister for Finance and Deregulation) said on announcing that Newcastle, NSW would become the site of Australia’s first commercial-scale smart grid.
"If smart grid applications are adopted around Australia they could deliver a reduction of 3.5 megatonnes of carbon emissions per annum," Senator Wong concluded.
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