For 430,000 customers of distribution system operator Elenia, power outages will soon be a thing of the past. The company already started building a weatherproof network in 2009, more than two years before the notorious Tapani storm of winter 2011–2012. That storm, which occurred around Christmas time 2011, was followed by extensive power outages, and spurred the introduction of a new electricity market law in Finland. This came into force in 2013, aimed at ensuring comprehensive security of supply for the country as a whole. "We had decided as early as 2009 that we would no longer build new overhead line networks," explains Elenia’s chief operating officer Jorma Myllymäki.
Elenia has also pioneered the use of new secondary substation technology. Elenia now has approximately 25,000 secondary substations on its roughly 72,000 kilometers of network – and increasingly many of these are intelligent models that are irreplaceable in fault situations. “We are going to keep adding intelligence to the secondary substations where it is both sensible and cost effective to do so,” says Myllymäki.
Almost two thousand Elenia underground cable network secondary substations are equipped with remote control systems. The new ones often have remote-controlled breakers, which allow fault areas to be quickly isolated. The latest development in Elenia’s network is fault indication.
“Large-scale outages caused by storms do not occur in the underground cable network, instead there can be technical defects that are hard to pinpoint, or cables that may be accidentally broken by excavators. With grid automation and fault indication, the trouble spots are quickly found and can be isolated from the network. There are now more than a thousand fault indicators in our underground cable network,” says Myllymäki. “In addition, our overhead line network has more than two thousand remote-controlled disconnector switches," continues Myllymäki.
And the results are clearly visible. Currently, around 45 percent of Elenia’s network of over 100 municipalities is cabled. Storm Aapeli, which occurred around New Year 2019, hit Elenia’s network hard. The wind strengths in Elenia’s network area were almost in the same storm class as those of Tapani storm in 2011.
“Without the investments, the number of customers without electricity after the Aapeli storm would have been about three times higher. The power supply remained uninterrupted in built-up areas, and it was only in more sparsely populated areas served by overhead lines that outages occurred. Thanks to automation, however, we were able to narrow down the fault areas and effectively steer the repairs to the right places,” Myllymäki explains.
Myllymäki points out that automation does not actually prevent faults from occurring, but it does facilitate their repair. Without automation, solving problems would have to be done by hand, and this could take several days. Smart transformers and control room automation instead isolate the fault areas and automatically restore the electricity supply to unaffected areas in minutes.
“Fault indicators in the secondary substations can detect whether the fault is upstream or downstream of the secondary substation in the distribution line. With some fault types, it’s also possible to calculate the fault distance from the secondary substation,” says Dick Kronman, manager of the grid automation center of excellence at ABB in Finland.
As a trendsetter for network automation, Elenia has been an important development partner for ABB. “Joint development work has been going on for a long time. Initially, we developed a network that could be controlled remotely, and over the last few years we have focused on fault indication and fault management,” says Kronman.
For example, ABB’s patented fault indication technology was extensively tested in Elenia’s network in the autumn of 2016. Field tests ensured that the fault indication system operates as planned. “Through the tests in Orivesi, we got assurance that our new method and our new products will work,” adds Kronman.
Based on multifrequency admittance calculations, ABB's new fault indication method reliably identifies all fault types in both overhead lines and cables networks. “Our experience with fault indication is promising. The technology is constantly evolving and becoming more cost-effective,” explains Myllymäki.
Fault indication is an example of ABB’s continuing product development. The technology is based on decades of ABB’s expertise in protection and control relay technology. “When computers need to find and solve problems, the data provided must be very reliable. Our solutions are as reliable as the protection relays in electrical substations, for which the requirements are extremely rigorous,” says Kronman.
In new secondary substations, smart solutions, ranging from remote control to fault indication, are already commonplace. Myllymäki says that the major challenge is the installed base of secondary substations already in use.
“When you start to add intelligence to existing transforming components, the installation needs to be performed easily and without downtime.” Still, Myllymäki is confident that suitable products are on the way. “ABB is a big and knowledgeable company, a technology leader in many areas.”
Elenia has invested in electricity grid automation since the beginning of the 2000s. “In those days, it was the quickest way to improve the security of electricity distribution in sparsely populated areas,” adds Myllymäki.
Overhead lines will soon be history in many places, but the benefits of automation have not disappeared. In addition to improved security of supply, the safety of the network increases as the automation rate rises. “The more points there are on the network with sensors, the safer it is.”
Elenia was the first power company to introduce remotely readable electricity meters and began to use them for network monitoring as well. “Now we can always see what is happening over the entire network right up to the customer. Previously, the low-voltage network could not be controlled except by going to the site,” explains Myllymäki.
Elenia is already figuring out different ways in which the fault indication technology of smart secondary substations can be used in the future. "We think it can also be used to monitor the condition of the network and anticipate faults.”
Text: Petja Partanen
Photo: Olli Urpela