Section 5 of the Regulations relating to the system responsibility in the power system stipulates that ”The Transmission System Operator shall divide into Elspot areas in order to handle major and prolonged bottlenecks in the regional and main grids.”

In the document ”Statnett’s practise of the system responsibility”, which is published on Statnett’s website, Statnett explains how the system responsibility is practised by Statnett. Handling of bottlenecks and determining capacities are also essential topics in the Nordic operating collaboration. The document ”Principles for determining the transfer capacities in the Nordic power market” is published on Nordpool Spot’s website.

 

 

Today’s area classification

On 16 October 2009, 420 kV Rød-Hasle was commissioned following fault rectification with 65% of its original thermal capacity. Prior to commissioning we had identified that the capacity reduction for this connection could lead to a reduced transmission capacity between Southern Norway (NO1) and Sweden (SE). A prerequisite was that full export capacity could mainly be provided in Hasle with an intact grid, but in the event of major import on the HVDC cables and export over Hasle (transit) and/or unfavourable production distribution between the Flesaker and Hallingdal corridors, it would be necessary to reduce the NO1-SE transmission capacity to avoid overloading of the 420 kV Rød-Hasle line. 420 kV Rød-Hasle is part of the Flesaker Corridor.  An unfavourable production distribution is in this context defined as relatively high production behind the Flesaker corridor and relatively low production in the Hallingdal corridor.

 

 

Rough sketch showing the corridors, Eastern Norway, Gudbrandsdalen, HVDC-cables, Hasle and Rød-Hasle

 

Upon commissioning of Rød-Hasle further requirements were introduced for operation of the cable in order to safeguard operational reliability in the connection. 420 kV Rød-Hasle has now been in operation for nearly two months. Full capacity has not been provided in Hasle in this period due to the limitation on Rød-Hasle. The Hasle capacity is used to limit the transmission on Rød-Hasle to the applicable transmission limit. During the entire period there has been more transmission in the Flesaker corridor than in the Hallingdal corridor. During the night there has been import on the HVDC cables and export to Sweden, which has increased the problems. The extent of the capacity reduction in Hasle has therefore occasionally been greater than expected. In order to better expolit the capacity in Hasle, power transmission in the Hallingdal corridor must be considerably greater than the transmission in the Flesaker corridor. Flows from the north and east in Easter Norway impact Rød-Hasle considerably less than flows from the west over the Flesaker section.

 

The transmission capacity in Hasle (with an intact grid) with a bottleneck at Rød-Hasle varies considerably with today’s area classification. It is dependent on exchange on the HVDC cables and production distribution between the Hallingdal corridor and the Flesaker corridor, in addition to the flow in Gudbrandsdalen and the load in Eastern Norway. The transmission capacity in Hasle is determined every morning based on forecasts of the said parameters. The Elspot result, which determines the first two parameters, is not available until the afternoon that same day. It then turns out that the Elspot capacity is often incorrect, as it depends on too many parameters that vary unpredictably. During the operation phase it is occasionally apparent that there is vacant capacity in Hasle, as the capacity is sometimes set too conservatively. In other periods the capacity is set too high, which entails strained operation to avoid overloading Rød-Hasle.

 

In today’s Elspot classification in Southern Norway, the dominating bottleneck is moved to Hasle. The Elspot limit does not reflect the bottleneck satisfactorily. The capacity is restricted in Hasle to manage the flow on Rød-Hasle, but at the same time restricts production in parts of the grid that have only insignificant impact on Rød-Hasle. Increased production in Hallingdal and Eastern Norway may enable improved exploitation of the capacity in Hasle. With today’s area classification the production in Hallingdal and Eastern Norway sometimes receives the wrong price signal.

 

The capacity in Hasle is today very dependent on exchange on the HVDC cables. It varies in the range from about 600 MW at full import on the cables to about 1900 MW at full export. At a given exchange on the cables there is also great variation in what can be transferred in Hasle, depending on the distribution of production between Flesaker and Hallingdal. This variation can be up to about 500 MW. There is therefore little predictability for the market players as to what future capacity they can expect. This entails that the capacity determination in Hasle (NO1-SE) is not very transparent. It will be very difficult for the market players to understand how today’s capacity emerges.

 

Could this have been resolved in some other way than by introducing a new area? The forecasts for the said factors could be improved, but the risk would not be removed. Special regulation to exploit the grid capacity in the best possible way would be problematic over an extended period of time and is better resolved through a new area classification. The restriction on Rød-Hasle has proved to be a major bottleneck. Flow in the Flesaker section must be limited to about 2000 MW to avoid overloading Rød-Hasle. This section limit was previously 3100 MW. The restriction on Rød-Hasle will continue until the connection over the Oslofjord has been reinforced with new cables. Statnett’s view is that this is a major and prolonged bottleneck.

 

New Elspot area classification

In order to remedy the said challenges concerning uncertainty regarding capacity determination and non-optimum exploitation of the grid, a separate Elspot area will be set up in South-western Norway, delimited by the Flesaker section and 300 kV Modalen-Refsdal, see description of area classification. When an Elspot area classification changes, the following factors will be assessed. Only a few of the factors are addressed below.

·         Size and duration of the bottleneck

·         Total number of Elspot areas in the same period

·         Delimiting the area (regional grid also)

·         Determining capacity

·         Number of players in the area

·         The area’s composition of production/price-flexible consumption

·         Suitability and operational reliability

 

The proposed area classification will reflect the Rød-Hasle bottleneck considerably better than today’s area classification. Uncertainty in determining capacity related to HVDC exchange and production distribution between the two production corridors will be minimised. There will still be some uncertainty regarding capacity determination, but considerably less than in today’s solution.

The proposed classification will entail enhanced exploitation of the grid. Production in the eastern area will not be restricted by Rød-Hasle. At the same time the Flesaker section will also be exploited in a better manner, as there will no longer be a need to forecast the exchange on the HVDC cables.

 

 

Determining capacity

The capacities given between the various areas are published in UMM on Nord Pool Spot. Even though the capacities will now be more predictable, the individual capacities will still vary in a range depending on several factors.

 

The NO2 (South-western Norway) capacity towards NO1 (Eastern Norway) consists of the connections in the Flesaker section and the 300 kV line Modalen-Refsdal. Flow on Modalen – Refsdal will vary depending on load and production conditions in the area. Statnett will forecast this flow before the capacity between NO2 and NO1 is determined. The distribution of power flow in the various lines in the Flesaker section will also vary. The expected distribution will affect how high a capacity is provided as this impacts the load on Rød-Hasle. Total capacity for NO2 - NO1 is estimated at between 1700 and 2700 MW.

 

The NO1 – SE capacity will also be impacted by the new classification. The load on the Rød-Hasle connection will be controlled by the NO2 - NO1 capacity from 11 January. This means that a higher capacity will normally be provided in Hasle towards Sweden than was the case this autumn. In the winter period, with a high level of consumption in the Oslo area, the NO1 - SE capacity will still have to be restricted. This is not new and is called the ”Hasle stairway” (Hasle-trappen). With a high level of consumption in the Oslo area there will be a flow towards Oslo in the Hallingdal corridor and in the Flesaker corridor. In such situations it will be possible to transmit 2050 MW in Hasle towards Sweden. Maximum transmission declines gradually in line with an increasing Oslo load (Oslo load is a net figure based on consumption and production in Mid-eastern Norway). With a new area in South-western Norway, the capacity over Hasle will be more predictable for both the players and for Svenska Kraftnät. This will improve the framework conditions for the power market as well as operational reliability in Sweden/the Nordic countries. Capacity determination will also be more transparent for the market players, as it is based on fewer variable parameters. The proposed classification also safeguards operational reliability for Rød-Hasle in a better manner, as the planned load flow over the bottleneck will be known.