Reliable network

Securing the continuity of supply is a cornerstone of our operations. We are determined to respond to the requirements of our customers and society by securing the continuity and reliability of our electricity distribution. We keep developing our electricity networks with a long-term view.

The electricity network in numbers

Network maintenance and development

Storms and extreme weather events have increased in number, and our digitalised society is increasingly more dependent on energy supply. As the largest electricity distributor in Finland, Caruna has a network some 79,000 km in size, which it maintains and develops in order to meet the requirements of its customers and society.

We invest approximately MEUR 200 into our network every year. Our investments are guided by the target level of the reliability of supply outlined in the legislation, the network’s age profiles, and growth that is mainly achieved through new network connections and advancements in society’s basic infrastructure, among other things.

Factors guiding our investments

The amendment to the Electricity Market Act that came into effect in 2013 emphasises the reliability of supply above all. Following interruptions caused by strong storms or heavy snowfall, it must be possible to restore the supply of electricity within six hours in urban or suburban areas and within 36 hours in rural areas.

We make investments related to the reliability of supply in the order of their customer impact; prioritising those that benefit our customers the most. Customer impact is composed of the quantity of distributed electricity and customer density. Our efficient network improvement programme started from suburban areas, but its focus is presently moving toward rural areas. We aim to reach the targets specified in the legislation by the year 2028.

Goals for the reliability of supply defined in the Electricity Market Act

Caruna’s Asset Management unit is in charge of managing the network assets and its principles. The management of assets is guided by network building and maintenance principles and the network development plan submitted to the Energy Authority every two years.

Reliability of supply in 2015

In 2015, our network was spared major damage caused by strong storms or heavy snowfall.

In 2015, our network was spared major damage caused by strong storms or heavy snowfall. The Suoma storm in April, however, was the primary reason for the longer-than-normal average repair times of faults. The CAIDI (Customer Average Interruption Duration Index) value reflects the reliability of supply: it is the average time a customer is subjected to a single outage. In 2015 it was 56 minutes. The availability rate of network service remained on the same level as the year before; 99.98%.

The figure reflecting the frequency of supply disturbances, SAIFI (System Average Interruption Frequency Index), was 2.3 (occurrences) in 2015. This means that, on average, customers were subjected to two interruptions of more than three minutes in duration during the year.

Better network through cabling and management of adjacent forest areas along power line corridors

We continued our extensive investment programmes aimed at improving the reliability of supply in all our network areas in 2015. Investment levels were increased and we reached all of our targets. We estimate that network improvement investments amounted to a total of MEUR 173 in all our network areas.

Additionally we invested MEUR

in high voltage networks in 2015...

...and will invest MEUR

more during 2016–2018.

The renovation of medium voltage networks remained our primary focus in network investment projects in 2015. We generally substitute overhead power lines with underground cabling, as these are safe from strong storms and heavy snowfall.

We carried on with structural and technical renovations aimed at shortening fault repair times. For instance, we were able to isolate faults and restore power supply to undamaged network sections faster, thanks to meshed networks and network automation.

In total, we built roughly 3,400 km of small- and medium-voltage cable networks. The cabling level of the entire network was 36% by the end of 2015.

We continued the maintenance programme for management of adjacent forest areas along power line corridors started in 2014. Management of adjacent forest areas along power line corridors allows us to prevent power outages caused by trees falling over the lines due to strong winds or heavy snowfall.

All in all, the project reviewed approximately 4,100 km of adjacent forest areas outside medium voltage networks and 660 km of side forests outside high-voltage networks, vulnerable to problems caused by trees, as well as 2,200 km of power line corridors on all of Caruna’s network areas. We completed the project on schedule in December 2015.


customers now have a more reliable supply

completed working hours

cubic metres of cut wood in total

landowners contacted

Preparedness for exceptional conditions

Society is increasingly dependent on the reliability of electricity supply under all conditions. The interdependencies between critical networks (electricity and IT networks) and customers were analysed in the study led by the National Emergency Supply Agency.

We strive to guarantee an electricity supply service that is as free from disturbances as possible.

We strive to guarantee an electricity supply service that is as free from disturbances as possible, but this is by no means a given. In its role as the operator of the distribution network, Caruna has to inform its customers and the authorities without delay if the supply of electricity is interrupted. At the same time, customers and the authorities must be provided with an estimate of the extent and duration of the fault.

The electricity outages map on our website offers our customers the most up-to-date information about outages and estimated fault repair times. Caruna also offers a free alert service (Caruna Sähkövahti) that informs the users of outages directly to their mobile phones or e-mail accounts. The service alerts the customer about planned and unplanned outages in medium-voltage networks, as well as estimates of their durations. The number of customers affected by interruptions in Caruna’s electricity distribution can also be viewed on the electricity map (Sähkökartta) application offered by Finnish Energy (ET=Energiateollisuus ry). We give our customers advice on how to prepare for electricity supply disturbances.

Caruna has drawn up a contingency and an emergency plan for normal network outages and exceptional conditions, as required by the Electricity Market Act. Caruna had these plans in place several years before they were required by law.

The contingency plan covers minor and major electricity network disturbances under normal conditions, such as outages caused by natural phenomena. The emergency plan, in turn, addresses emergency law conditions and offers guidance for actions in case of serious external or internal threats. Caruna keeps refining these plans on the basis of experience gained from disturbances and failures.

Security conditions

Caruna takes part in contingency and emergency organisation activities organised by the authorities, with the purpose of ensuring collaboration and preparedness in all situations. We have been an active participant in drills and exercises organised by the authorities, including their planning, as well as in the creation of collaboration guidelines for the sector.

The contingency and emergency plans required by the Electricity Market Act must be updated at a minimum interval of two years; in practice, this takes place on a yearly basis. We review our plans four times a year to ensure an appropriate level of continuity management. Caruna’s Network Operations unit is in charge of contingency and emergency plans. The Head of Security ensures the plans are up to date and appropriate reports are submitted to the authorities. The preparedness of electricity network operators is monitored by the National Emergency Supply Agency, working under the Ministry of Employment and the Economy.

Security of supply

As the largest distribution network operator in Finland, Caruna is considered a critical company for the security of supply. Security of supply means the ability to handle disturbances and states of crisis with a minimum amount of special arrangements and damage. We are prepared to maintain our ability to supply electricity on the current supply security level, even during a longer state of crisis. By investing in the reliability of our electricity network, we ensure the security and continuity of supply, particularly during disturbances caused by the climate.