Operation of the grid


Peak load in the year

The year’s peak in power fed into the grid was recorded on 25 February at 2,301 MW, which is 2.11% higher than the previous year’s peak. Total system demand in 2015 was 17,744 GWh, up 3.59% on the previous year. Transmission losses totalled 370 GWh, or 2.04% of generation, up by 2.39% year-on-year.

Growing operational risk

The load on the grid increased further in 2015. This was reflected in heightened operational risk, mainly owing to a general increase in firm load coupled with a substantial increase in load from consumers on non-firm transmission contracts, including data centres, increased tourism, fish processing and increased on-land freezing of catches by seafood companies. The need for inter-regional transmission has increased because generation has not grown in line with demand. At the same time, the grid’s strengthening is proceeding at a slow pace, which increases the need for maintenance, partly because the grid is ageing.


We constantly monitor transmissions through nine defined transmission cut-planes in the grid, shown on the above map. When grid disturbances occur, the risk of an outage is heightened when the level of transmission through a cut-plane nears or exceeds security limits. The graph below shows the level of transmission through eight cut-planes for the whole of 2015. As can be seen, the grid’s operation exceeded the security limits for a large portion of the year. In such conditions, Landsnet’s Control Centre must require generators to change their generation plans, i.e. make alterations as to where in the country the electricity is produced, in addition to persistent curtailments in certain regions. An operation of this kind entails inefficiencies for all those connected to the grid.

To mitigate against risks in the grid’s operation and to increase inter-regional transmission, Landsnet uses variable transmission limits that take account of the circumstances of generating units and load. Curtailment can be applied rapidly in the event of disturbances. Various technological solutions have also been tried. One example is a new circuit-breaker in the Sigalda substation and other modifications introduced there to increase operational security and transmission capacity through cut-plane IV.

Our Control Centre is also very advanced technologically when it comes to enhanced energy management and all grid operation. The Control Centre’s team is specially trained in assessing the grid’s performance and operational risks in accordance with pre-defined procedures.

Smart grid solutions ensure very rapid curtailment of load for consumers that have entered into contracts with Landsnet on non-firm, i.e. interruptible, transmission. These solutions also improve the inter-regional load balance through load management of aluminium plants, and control the splitting of the grid into separate components or “islands” during disturbances to ensure operational security for consumers. We are preparing faster controls of generating units during disturbances. Constant weather monitoring and preventive measures in co-operation with our customers are also designed to ensure an effective reaction to minimise the impacts of weather-related disturbances to power transmission.

Main grid disturbances

The number of grid disturbances rose by 29 year-on-year, from 69 in 2014 to 94 in 2015. The number of faults was also up significantly from the previous year, from 83 in 2014 to 159 in 2015, which means that more than one fault occurred in some instances. Energy not supplied as a result of grid disturbances totalled 897 MWh, which corresponds to just under 27 outage minutes. It should be noted that this excludes curtailments of electricity to consumers on non-firm contracts

The main grid disturbances causing outages and curtailment of power supply to customers were as follows:

On 8 January 2015, lightning struck the Hvolsvöllur Line 1 between Búrfell substation and the town of Hvolsvöllur. The line tripped and was damaged. A surge arrester at Transformer 1 at Hvolsvöllur exploded. This caused outages at Hvolsvöllur, Rimakot, Vík and in the Westman Islands. Firm energy not supplied was assessed at 23 MWh and non-firm energy not supplied was assessed at 36 MWh.

On 25 January 2015, the Glerskógar Line 1 tripped in severe weather. The West Fjords smart grid immediately activated the reserve power station at Bolungarvík, which mitigated against outages in the northern West Fjords. The Mjólká substation took care of the more southerly fjords, preventing all outages of firm load. Firm energy not supplied was approximately 5 MWh and non-firm energy not supplied was about 41 MWh.

On 31 January 2015an interference in telecommunications equipment at the Kolviðarhóll substation caused tripping at short intervals of the Kolviðarhóll Line 1 between the Geitháls and Kolviðarhóll substations and tripping of the Búrfell Line 2 between Kolviðarhóll and the Búrfell Power Station. This triggered tripping of all generating units in the Hellisheiði Power Station, underfrequency in the system and partial tripping of load for power-intensive consumers and consumers on non-firm contracts. Firm energy not supplied was assessed at approximately 150 MWh and non-firm energy not supplied was assessed at around 286 MWh.

On 6 February 2015an iron sheet blown by wind got stuck in the Suðurnes Line 1 at the Ásbrú substation during a heavy windstorm, causing outages throughout the Reykjanes peninsula and tripping of generating units in the Reykjanes Power Station and the Svartsengi Power Station. An outage occurred at Keflavik International Airport as reserve power failed. Firm energy not supplied as a result was assessed at about 22 MWh and non-firm energy not supplied at around 10 MWh.

On 7 February 2015a violent south-westerly storm hit northern Iceland, causing conductors to clash together on the Rangárvellir Line 1 between the Rangárvellir and Varmahlíð substations. This caused voltage to rise at Rangárvellir to 148 kV, which led to a fault in telecommunications equipment at Varmahlíð. Firm energy not supplied to power-intensive consumers as a result was approximately 27 MWh and non-firm energy not supplied was about 5 MWh.

On 14 March 2015Landsnet’s grid came under much pressure when a deep low-pressure area swept across Iceland, bringing a violent windstorm. The average wind speed was more than 40 m/s, with wind speeds exceeding 60 m/s in gusts. The storm was so severe that 220 kV lines were tripping – a rare occurrence. A total of 19 lines tripped during the storm, some more than once. The Sog Line 3/Búrfell Line 3 tripped seven times, the Glerskógar Line 1 tripped five times, the Neskaupstaður Line 1 tripped four times, the Hrútatunga Line 1 tripped three times and the Grundarfjörður Line 1 tripped twice. A total of 13 lines tripped once: the Laxárvatn Line 1, the Vatnshamrar Line 1, the Ísafjörður Line 1, the Breiðadalur Line 1, the Mjólká Line 1, the Kolviðarhóll Line 1, the Búrfell Line 3, the Laxá Line 1, the Hveragerði Line 1, the Tálknafjörður Line 1, the Búrfell Line 2, the Andakíll Line 1 and the Geiradalur Line 1. Firm energy not supplied was assessed at approximately 38 MWh and non-firm energy not supplied was assessed at 273 MWh.

22.7.2015 bilaði varnarbúnaður fyrir Vatnfellslínu 1 í Sigöldu. Aðeins tveir af þremur fösum línunnar leystu út og sló þá safnteinavörn í tengivirkinu út öllum aflrofum á teininum. Við það sveiflaðist tíðni í kerfinu frá 48,4 í 51,5 Hz og olli útleysingu hjá nokkrum stórnotendum og notendum á ótryggum flutningi  á Norðvesturlandi og skiptu þá kerfisvarnir í Blöndu og Hólum kerfinu í tvær eyjar. Skerðing á forgangsálagi var metið á um 144 MWst og 7 MWst hjá notendum á ótryggum flutningi.

On 22 July 2015, a fault occurred in protection equipment for the Vatnsfell Line 1 at the Sigalda substation. Only two of the line’s three phases tripped, causing the substation busbar protection to trip all circuit breakers of the busbar. This caused mains frequency to fluctuate from 48.4 to 51.5 Hz and resulted in tripping for a number of power-intensive consumers as well as consumers on non-firm contracts in north-western Iceland. Our Wide Area Protection Systems at Blanda and Hólar reacted by splitting the grid into two islands. Firm energy not supplied was assessed at about 144 MWh and non-firm energy not supplied was assessed at 7 MWh.

On 3 September 2015, a transformer at the Rimakot substation tripped, triggering outages in the Westman Islands and among RARIK customers in southern Iceland. As no fault was found in the transformer, repeated attempts were made to bring it back into service, but without success. Reserve power was activated in the Westman Islands and a reserve transformer was connected at Rimakot during the transformer’s repair. Extensive fault location attempts and analysis finally revealed a fault in the pressure sensor on the transformer’s tank. Firm energy not supplied was assessed at about 44 MWh and non-firm energy not supplied was assessed at about 22 MWh.

On 7-8 December 2015, a major storm hit the country, causing extensive outages and damage to the grid, in particular owing to heavy wind load and icing. The largest outage occurred in the Eyjafjörður region and the town of Akureyri in northern Iceland when both the Rangárvellir Line 1 and the Krafla Line 1 tripped. The situation was also challenging in the northern West Fjords, the East Fjords and southern Iceland. The greatest damage occurred in the West Fjords where 20 transmission towers gave way on the Breiðadalur Line 1 in Dýrafjörður fjord. In northern Iceland, two towers broke on the Rangárvellir Line 1 in the Skagafjörður region and four towers broke on the Kópasker Line 1. In East Iceland, four towers broke on the Teigarhorn Line 1 in addition to damage to the Eyvindará Line 1 and the Prestbakki Line 1 between the Sigalda substation and the Hólar substation at Hornafjörður. Total energy not supplied as a result of these disturbances was assessed at approximately 330 MWh for firm transmission services and approximately 3,000 MWh for non-firm services, including 2,600 MWh for consumers on non-firm contracts in the West Fjords, who were not brought back online until repairs on the Breiðadalur Line 1 were completed six days after the storm subsided.

On 17 December 2015, the Geiradalur Line 1 tripped in heavy weather, causing consumers in the Geiradalur valley and the West Fjords to go without power, except those served by the Keldeyri substation, which received firm load from the Mjólká Power Station. Reserve generating units at Bolungarvík were activated immediately. Approximately one minute later, power was restored to the northern West Fjords. Firm energy not supplied was assessed at approximately 35 MWh and non-firm energy not supplied was assessed at about 211 MWh.


Energy not supplied is electrical energy that cannot be delivered to one or more consumers as a result of a fault in the electricity system, changes to it, maintenance work or transmission constraints.

A line tripping. When a line stops transmitting electricity.

Island operation (or “splitting into islands”) is the temporary operation of two or more sections of the grid that have been disconnected from each other and are therefore asynchronous.

Grid’s security of supply

Measurements of outage minutes due to unplanned grid interruptions have been used to gauge the reliability of the Icelandic grid since 1987. Landsnet publishes this measurement in its annual Performance Report, which uses this indicator to present total outages for priority consumers.

Despite the increased number of disturbances in recent years and ever-growing risks relating to the grid’s operation due to rising transmission levels via the Inter-Regional Transmission Network, Landsnet has always managed to meet the target of keeping the number of outage minutes for priority consumers (firm load) within 50 per year.

Calculated outage duration only 27 minutes in 2015

The total number of unplanned grid interruptions in 2015 was 94, which is 50% above the average of the last 10 years. Nonetheless, the calculated outage duration for priority consumers was only 26.6 minutes. This performance is on par with our peers in the Nordic countries and elsewhere in Europe. Landsnet is proud to be able to provide priority consumers with such a reliable supply of electricity.

However, the criterion “outage minutes for priority consumers” does not give the entire picture as regards the reliability of the grid itself. For the broader picture, the volume of reserve power used during disturbances and the curtailments to consumers on non-firm contracts also need to be taken into account.

Where available, reserve power stations are always activated as soon as possible when a grid disturbance occurs to reduce outages for the priority consumers of distribution system operators. Power transmitted to consumers whose supply Landsnet is authorised to curtail without prior warning is also curtailed if necessary. With the ever-growing application of smart grid solutions, these curtailments are now carried out largely automatically. This has stepped up operating stability during grid disturbances and thereby security of supply for priority consumers.

 Curtailments to consumers on non-firm contracts are excluded here.

Use of reserve power increased tenfold in three years

The use of reserve power due to unplanned grid interruptions has increased tenfold over the past three years. Reserve power use in 2015 was largely because of disturbances that occurred during the major storm on 7 and 8 December when severe damage was sustained by the Breiðadalur Line 1 in the West Fjords and the Kópasker Line 1 in north-eastern Iceland. Generation by reserve power stations due to disturbances during the year totalled 1,951 MWh. Without access to reserve power, it is estimated that the number of outage minutes for priority consumers would have been 84.4 minutes instead of 26.6, or 57.8 more outage minutes than was actually the case.

Curtailments of non-firm service up fourfold in three years

Our review of the data also shows that curtailments due to disturbances for consumers on non-firm supply contracts with distributors went up nearly fourfold in three years. Total curtailable energy not supplied to consumers last year owing to disturbances amounted to 4,376 MWh. Had curtailment not been allowed, a power shortage of this scale would have had a major detrimental impact on our key performance indicator of outage minutes, the number of which would have been higher by 129.6 minutes for 2015.

Grid overloaded in many places

The marked increase in the use of reserve power during disturbances and the use of curtailments to consumers on non-firm service contracts clearly demonstrate a worrying trend and that the grid is overloaded in many places. In the absence of reserve power and curtailment allowances, the grid’s security of supply would currently be far below the reliability standards generally applicable to transmission systems. The grid’s actual performance would then have measured at around 214 outage minutes in 2015, instead of 26.6 minutes.

To ensure the grid’s security so that it can provide all consumers in Iceland with electricity, its infrastructure must be fit for purpose. Smart grid solutions and increased use of reserve power are only temporary “Band-Aid” expedients that neither address the grid’s transmission capacity nor its long-term reliability.

Security of supply in the West Fjords – first year with the smart grid and a new reserve power station

The year 2015 was the first full operating year of the new reserve power station at Bolungarvík and the smart grid in the West Fjords. Trial runs began in early December 2014, and over the course of 2015 the new equipment proved its worth unambiguously. Outage duration in the West Fjords has been reduced substantially for all lines, except the Tálknafjörður Line 1 between Mjólká and Suðurfjörður. This is clear from examining outages for priority consumers in the area in 2015. However, the use of reserve power has increased as have outages for consumers on non-firm contracts, who constitute 52% of the total number of electricity consumersin the West Fjords.

The protection equipment in our substations in the West Fjords is fitted with built-in smart grid capabilities, which have shortened the time it takes to activate reserve power and restore power to priority consumers from approximately half an hour to an average of a minute and a half. Energy not supplied to priority consumers in the West Fjords due to unplanned grid interruptions was measured at 64.5 outage minutes in 2015. Without the smart grid capabilities, this figure would have been nearly double, or about 117 minutes.

 Curtailments to consumers on non-firm contracts are excluded here.

While smart grid solutions have brought a major improvement to the security of supply for priority consumers in the West Fjords, the new reserve power station at Bolungarvík has contributed even more in this respect. Without it, outages for priority consumers would be counted in hours rather than minutes. The reserve power station cut outages by about 3,253 minutes in 2015. Other reserve power stations in the West Fjords prevented around 1,022 outage minutes. This excludes delivery to consumers on non-firm contracts, for whom energy not supplied due to unplanned disturbances totalled 13,577 MWh in 2015. If their outages are added to those of priority consumer in the region, the number of outage minutes increases by 8,794 minutes to a total of 147 hours.

Two unplanned grid interruptions – before and after the smart grid and reserve power station

The addition of Landsnet’s new reserve power station at Bolungarvík coupled with smart grid capabilities has cut outage minutes substantially for priority consumers in the West Fjords. This can be seen from the above chart comparing curtailment of firm load in the West Fjords due to a disturbance in the Mjólká Line 1 before and after the reserve power station and the smart grid were brought into service. The comparison excludes curtailments to consumers on non-firm contracts.

  • The Mjólká Line 1 tripped on 12 February 2014 because of icing, which caused outages throughout the entire West Fjords. Energy not supplied to priority consumers until reserve power was activated was assessed at about 25 MWh. Consumers on non-firm contracts were subject to curtailment for the entire time that the line was out of service.
  • The Mjólká Line 1 tripped on 11 March when a storm struck the country. A short outage occurred in the northern West Fjords until the smart grid took over and sent an activation signal to Landsnet’s reserve power station at Bolungarvík and curtailed transmission to all non-firm consumers in the West Fjords. The smart grid also tripped the Breiðadalur Line 1 so that the Mjólká Power Station could provide the southern West Fjords with firm load. Thanks to the smart grid’s high reaction speeds, energy not supplied to priority consumers was merely 0.36 MWh, whereas consumers on non-firm contracts were subject to curtailment for the entire time that the line was out of service.