What caused the power cut?
In a power system containing several parallel 500-kilovolt lines, one line was out of action because a tower was being moved. During the outage, a disruption occurred on a different line, and the parallel circuit on this line also disconnected from the network, even though such a thing should not happen. The disconnection may have been due to a fault in the relay protection, but the precise cause is not yet known.
As a result of this confluence of disruptions, the network became too weak to transmit all the electricity on the remaining lines. The connections to the large hydroelectric power plants at Yacyretá Dam and Salto Grande Dam went down, and no electricity could be obtained from elsewhere to replace it, leading to a large-scale power cut in Argentina and Uruguay.
Could a similar incident happen in Finland?
Nothing is impossible, but the likelihood of so many faults arising at the same time is very low. Many measures have been taken with the aim of preventing the onset of such disruptions, and the networks are continuously being strengthened in Finland. However, 100-per-cent reliability cannot be guaranteed. For example, there was a disturbance in Sweden in 2003, where several, almost simultaneous faults brought down the network in southern Sweden.
What is being done to prepare for this situation?
Fingrid has contingency plans, which it is continuously developing. Various exercises are also arranged regularly. These involve rehearsing scenarios and testing how to work with the authorities and other electricity companies. On a practical level, means such as training simulators are used to practice restoring the electricity rapidly. The availability of spare parts is also assured and the other necessary support measures are put in place in advance.