Mission possible: A big step towards self-healing grids in Finland

2013-04-08 - ABB and Fortum, an energy company operating in the Nordic countries, Russia, Poland and the Baltics have taken an important step towards self-healing grids with a pilot installation in a grid area in Southern-Finland. With ABB’s innovative solution virtually all earth faults could be located in extensive field tests. Earlier it was impossible.

By ABB Communications

ABB's fault detection technology and applications are now in test use in the Masala substation. The tests have indicated that with the integrated grid automation and substation automation solution most of the grid faults can now be located and isolated and power quickly restored into the operable parts of the grid.

“This unique smart grid solution is a big step towards a self-healing grid” says development manager Antti Kostiainen from ABB.

“Earlier it has not been possible to locate earth faults in isolated networks in real time. Instead they have been located through manual sectionalizing. According to the field tests, the new system finds faults with a probability of almost 100%,” says development manager Dick Kronman from ABB. Almost 70% of distribution grid faults are caused by earth faults.

Control for transient earth faults
Earth faults in overhead lines are electric discharges or arcs between the conductor and the ground, typically caused by a fallen tree, an animal or a lightning.

According to Kronman, ABB's solution is unique in the sense that it can also locate short transient faults, which are most commonly caused by a tree branch, which has dropped on the conductor or is touching the conductor due to wind or snowfall. Transient earth faults are typically cleared by reclosings, ie, power is cut for less than half a second and is then automatically reconnected. In a society full of electronic devices the reclosings cause a lot of harm and damage.

Previously it has been very difficult to locate transient earth faults, and if repeated, they usually cause a permanent tripping of the feeder. Thus they also decreased the power quality.

“Ideally the fault can be located even before the outage and even before the transient fault can be noticed. Permanent faults can therefore be effectively predicted,” says Kronman.

Large field tests
ABB's latest technology and applications were tested in Fortum’s substation in Masala. The relays of the substation have been completely renewed with the latest 615 series in the Relion family. In addition, the automated grid utilizes wireless communication from Viola Systems.

The new solution was extensively field tested in June, with 100 different types of faults induced in the Masala grid area, 97 percent of them being earth faults. Faults were induced in four places: near the substation, in the midway of the feeder and at the far ends of the feeder.

“We can now locate the fault with the accuracy of 1-2 kilometers, which is sufficient for grid operators to find the right isolation zone,” says Kostiainen.

The Porkkalanniemi grid area in Kirkkonummi is demanding: the area is windy and vulnerable to storms, and it is not easy to install underground cables in the rocky terrain. The goal of Fortum and ABB is to significantly improve electricity quality in comparison to the current situation.

From research to products
According to Dick Kronman, the success of the Masala field tests is a remarkable step towards a self-healing grid, and it proves that smart grid deployment is proceeding. The system is now in test use and the long-term goal is that the system will automatically locate the faults, isolate them and restore power to the remaining grid.

The system is based on the IEC61850 standard and the network is isolated without earth fault compensation. In the next step ABB will pilot a solution for compensated networks together with Fortum.

This pilot is part of a five year research program called “Smart Grids and Energy Market, SGEM” funded by TEKES, the Finnish Funding Agency for Technology and Innovation and coordinated by CLEEN Oy, the smart research and technology network.

“The field test proved that the system and the new algorithms are really working. ABB has decided to productize the technologies used in the pilot. In the future we will offer them as commercial products which can clearly improve network solutions,” says Kronman.

The pressure from society to enhance the reliability of electricity distribution has constantly increased. Regulator authorities are developing models, which incentivize grid operators to reduce the outages.

Self-healing network
No such kind of magic that would make a grid repair itself has yet been invented. Self-healing refers here to the restoration of the power supply. A self-healing grid locates a fault location, isolates it by opening the closest disconnectors and restores power elsewhere in the grid. This requires a certain grid structure, ie, back-feed supply, grid automation and accurate locating of faults.

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