In January 2005, the storm known as Gudrun made its presence felt throughout the whole of southern Sweden. The impact on power distribution was severe, with interruptions lasting several days despite repair work around the clock. Even so, the staff at work in the control room of the Linköpings Kraftnät power company felt they had the situation under control thanks to the Tekla Solution for electricity utilities.
Linköpings Kraftnät went ahead with a decision to digitalize their network documentation system in 2001.
Two years later, the network model in Tekla's network information system Tekla NIS was sufficiently ready for Tekla DMS (Distribution Management System) to be taken into use. A full utilization of Tekla DMS was enabled when the company upgraded its remote control system the same year. The timing couldn’t have been better when little more than a year later the solution had a chance to show exactly what it could do.
“Even when the situation with Gudrun was at its worst it was easy for us in the control room to have a complete picture of the situation and stay in control of everything. The solution significantly relieved the stress often caused by crises like these. We also saved a lot of time in the aftermath because we were able to register and compile statistics for all interruptions and repair work,” says Thomas Gustavsson, one of five dispatch managers at Linköpings Kraftnät.
Gudrun struck on the evening of Saturday 8 January 2005. The storm hit hardest in the province of Småland where it snapped trees like matchsticks. Even though the Östergötland district was on the perimeter of the storm area, the Linkoping region has never been hit by such a powerful storm in living memory. The average wind speed was 30 metres a second with gusts exceeding 40.
“Three lines were down immediately and three more as I drove to work. Most of our lines, 29 out of the total 36, were under interruption during the night. All overhead lines in forest areas were down and 90 percent of our 5,500 customers in rural areas were left without power,” Gustavsson recalls.
The damage along the edge of the storm area was particularly extensive due to the unusually warm winter weather. At nine degrees, the trees had no support from ground that would normally have been frozen. Many were simply uprooted.
Even the centre of Linköping wasn’t free from damage. One switching station had its roof torn off and two out of three transformers broke down. 16,000 customers in southern Linköping were left without power for an hour and a half.
“We had a lot of technicians out during the night to section parts of the network, but there were so many trees down on the roads that they couldn’t get through. By morning almost everyone in the countryside was without power. We started repair work in the northern part of the network where it’s less densely forested,” Gustavsson says.
Because all switches and relays are linked to Tekla DMS, the distribution management system shows the parts of the network that don’t have electricity on-screen. When there’s a fault in the network, it is controlled by opening a disconnector.
“With Tekla DMS we immediately saw which areas and how many customers were affected and were able to inform the local radio station, for example. With our old system we had a CAD map where we marked the lines that had been lost with pins. We never had a comprehensive picture of such a complex situation and it was difficult to get information about the number of customers affected,” Gustavsson says.
The storm continued with less force for five days during which the network suffered new interruptions. It was Thursday evening before Linköpings Kraftnät was able to establish that all customers had power.
“Despite everything we saw the situation was improving all the time. When all connections on all lines could be assessed in relation to each interruption it was easy to stay on top of the situation as a whole. When information is in visual form, less time is spent understanding the overall situation. When new staff start their shift it’s easy to keep them appraised of the current situation,” Thomas Gustavsson says.
At the height of the storm, a new Tekla function was taken into use in the control room – the option to place electronic geographic memos directly into the system. Previously, a journal registering all faults was maintained in an Access database in addition to handwritten pieces of paper. However, an additionally large number of notifications for less acute faults made the situation chaos.
Tekla's solution provided precise information on the number of minutes each customer was affected by an interruption. The reporting carried out afterwards was very easy and quick to implement. All interruptions and the total customer interruption time were reported to the authorities as required by law, though at the time Gudrun struck, electricity companies in Sweden didn’t have to compensate customers for long interruptions. New legislation requires that compensation is paid, however, and with Tekla's solution, the task is perfectly straightforward.
Tekla Power System Analysis also calculates short circuit currents for all lines in a network. With interruptions where the fault currents are known, the system calculates the approximate location of the fault. Accurate to about 250 metres, the calculation saves a lot of time when looking for the source. At the time Gudrun hit, Linköpings Kraftnät only had fault localization installed for two overhead lines but has understandably decided to go ahead with further installations.
“We never thought that a situation anything like Gudrun could happen. Since then we’ve developed our customer service so that everything that happens locally shows straight away on the web. Some of our customers subscribe for interruption information by SMS,” Gustavsson says.
“With Tekla Solution, we’re better able to estimate the duration of shorter interruptions because it provides a lot of information about the network and geography. With our old system none of this would have been possible.”