T&D World Magazine

Iceland Seeks Stability

Wide area monitoring addresses long lines and weak interconnections.

At the Turn of the Millennium, Iceland Decided to Capitalise on its Vast Natural Energy sources to increase electricity generation capacity significantly. The country elected to base the industrial production of the new electricity generation on hydropower and geothermal power sources. This decision was attractive from both a financial and an environmental perspective. It would enhance Iceland's lead in the field of green electricity generation, as the country would produce more than 99% of its electrical energy from renewable energy sources.

Iceland's goal was highly feasible given that, with a geographical area of 103,000 sq km (39,768 sq miles) and a population of 320,000, it is the only country in Western Europe that still has great potential to further utilise its large quantities of renewable energy sources in an economical way.

Although feasible, the goal was still going to be a major challenge for Landsnet, the operator of Iceland's transmission system. Comprised of long transmission lines with weak electrical interconnections, Iceland's transmission system suffers from inherent stability issues. Aside from Canada, Iceland has the lowest population density in the world at 3 persons per square kilometer (7.8 persons per square mile). Supplying electricity cost effectively to this sparse population, with somewhat remote energy sources, has led to a transmission system that is relatively weak.

Landsnet was particularly concerned that the introduction of new generation sources on the scale planned for East Iceland would result in severe stability problems. Investment in bulk reinforcement of the network would have required major new transmission lines between regions, which would have incurred large investment costs.

To ensure the transmission system could absorb the large increase in generating capacity and overcome the long-term system-stability problems, Landsnet installed real-time monitoring of power-system dynamics using a wide area monitoring system (WAMS), as well as installing a new system protection scheme to ensure network reliability in case of fault situations.

STABILITY PROBLEMS

For the past decade, Landsnet had experienced problems with low-frequency oscillatory incidents that threatened system stability. These usually occurred on the 132-kV, 1000-km (621-mile) transmission line loop erected along the coastline of Iceland, with the generators in the north oscillating against the generators in the southwest. The 132-kV coastline circuit was electrically weak, and the problem was compounded by the two power plants connected to the circuit at Blanda and Krafla, which are large in relation to the capacity of the transmission system.

Landsnet conducted studies on the deployment of local power system stabiliser (PSS) devices to see if they would improve system stability, and simulations showed good results. However, to tune PSS devices to achieve optimum performance on the live system, and verify the results, is not an easy task. PSS devices that are not tuned properly can make the situation worse. Since Landsnet was never fully confident about the performance of the PSS devices that had been installed on various parts of the Icelandic network, the transmission system operator decommissioned them.

The crunch point came in 2007 when commissioning work started on a new hydropower plant and an aluminium smelter, both remotely sited in East Iceland. The 690-MW Karahnjukar hydropower plant was the biggest construction project Iceland had ever undertaken, designed to increase the installed generating capacity by 40%. With an initial production capacity of 346,000 tons, the new Alcoa Fjarðaál (meaning "aluminium of the fjords") aluminium smelter would take most of Karahnjukar's output.

The connection of the new hydropower plant to the transmission system created additional problems as far as system dynamics. Before the Karahnjukar plant was commissioned, the bulk of the generation and load was in Southwest Iceland, where two-thirds of the 320,000 Icelanders live clustered around the capital city of Reykjavík. The Karahnjukar hydropower plant increased the installed generating capacity in Iceland from 1700 MW to 2400 MW. With the connection of the new hydropower plant and additional load at the aluminium smelter plant, Landsnet was aware that without detailed information about network dynamics, increased system instability could be ungovernable. The increased generation capacity and increased smelter plant load were major concerns as there was a real possibility of damage to equipment or a blackout occurring. This prompted Landsnet to award a contract to Psymetrix (Edinburgh, Scotland), a company with extensive experience in the area of power system dynamics measurement, stabiliser tuning and performance assessment. Psymetrix also had proven experience in deploying the WAMS and providing real-time power-system dynamics information, including oscillatory monitoring and damping determination for transmission systems.

THE SOLUTION

Having successfully managed similar oscillation problems, albeit under different network conditions, for other customers in its global contract portfolio, Psymetrix was familiar with the challenges Landsnet faced. Working closely with Landsnet network operators to ensure knowledge transfer, Psymetrix installed a WAMS called PhasorPoint (formerly StormMinder). This system was designed so that Landsnet could acquire, manage, analyse and visualise data from different parts of the network in real time.

The WAMS contains a PhasorPoint server at the Landsnet control centre in Reykjavík, phasor measurement units (PMUs) at the substations and the PhasorPoint workbench software on users' workstation computers. This system would enable Landsnet to recommission its PSS devices safely and with confidence without disturbing the system, providing also the opportunity to evaluate the real benefits of a PSS device.

However, before recommissioning the PSS devices, it was necessary to establish a dynamics baseline. Seven PMUs were installed — the initial four were installed in just a week, along with PhasorPoint — and data was collected for a three-week period before commencing the project. With the dynamics baseline, Psymetrix was able to begin designing the PSS device control loops at the Blanda and Krafla power stations. These two plants were identified as having a significant impact on the system oscillatory behaviour.

Blanda is a hydroelectric power station with an installed capacity of 150 MW, and Krafla is a geothermal power plant with an installed capacity of 60 MW. The data collected by the seven PMUs and managed by PhasorPoint allowed Landsnet to:

  • Benchmark network conditions before, during and after installation of the stabilisers

  • Test and fine-tune the stabilisers in a variety of power flow conditions, including putting the generators on full and part load.

Following the successful tuning of the stabilisers at Blanda and Krafla, Psymetrix and Landsnet then went on to successfully tune and commission all the PSS devices at the Karahnjukar hydropower plant. With some 320,000 people and many industrial businesses depending on Landsnet for their electricity supply, it was important for Landsnet to demonstrate that the PSS devices were beneficial to network stability.

STABILITY ACHIEVED

The results of the field tests conducted at each power station by Psymetrix staff, in conjunction with staff from Landsnet and the National Power Co. (Landsvirkjun), could be seen clearly across the transmission network using PhasorPoint. This wide area dynamics view highlighted the importance of close monitoring of the transmission system to prevent problems elsewhere on the network.

The project proved to be a resounding success, enabling validation of the control loops, short-term performance and performance under several different switching scenarios. Landsnet also was able to observe and review the impact of the settings over the longer term.

There was rapid feedback on the effectiveness of the PSS devices during tuning in improving the damping of oscillations and similarly on their effectiveness during the comprehensive testing of different scenarios. Overall, network configurations that previously showed unsatisfactory damping of power oscillations are now fully stable.

The availability of real-time data from all sections of the transmission system has resulted in many benefits:

  • Potential problems can be pinpointed well ahead of time.

  • Remaining dynamic issues have been identified.

  • Recommended remedial action plans have been created.

  • System operators now have a much-better understanding of system dynamics.

  • The long-term benefits of the PSS devices have been identified.

  • WAMS records on system disturbances help in post-fault analysis and improve generator and system modeling.

Landsnet now has a real-time view of the network for "islanding" and reconnecting parts of the system. This is particularly valuable when it proves necessary to split five or six generators at Karahnjukar from the main power system to ensure continuity of supply to the smelter. Because of the support of Psymetrix's PhasorPoint system and power dynamics applications, Landsnet is now able to accept new generators with confidence, and this will be pivotal to Iceland as it strives to realise its economic ambitions with regard to green electricity generation.


Nils Gustavsson ([email protected]) is the manager of system operation at Landsnet, the power transmission company in Iceland. He has been in that position since the company was established in 2005, and prior to that he held the same position with Landsvirkjun, the National Power Co. When Gustavsson first joined Landsvirkjun 15 years ago, he worked as a specialist in system analysis, and later in protection and control systems. He holds a BSEE degree from the University of Iceland and a MSEE degree from the Technical University of Denmark.

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