Myllys M.,University of Helsinki |
Myllys M.,Finnish Meteorological Institute |
Viljanen A.,Finnish Meteorological Institute |
Rui O.A.,Statnett |
Journal of Space Weather and Space Climate | Year: 2014
We have derived comprehensive statistics of geomagnetic activity for assessing the occurrence of geomagnetically induced currents (GIC) in the Norwegian high-voltage power grid. The statistical study is based on geomagnetic recordings in 1994-2011 from which the geoelectric field can be modelled and applied to a DC description of the power grid to estimate GIC. The largest GIC up to a few 100 A in the Norwegian grid occur most likely in its southern parts. This follows primarily from the structure of the grid favouring large GIC in the south. The magnetic field has its most rapid variations on the average in the north, but during extreme geomagnetic storms they reach comparable values in the south too. The ground conductivity has also smaller values in the south, which further increases the electric field there. Additionally to results in 1994-2011, we performed a preliminary estimation of a once per 100 year event for geoelectric field by extrapolating the statistics. We found that the largest geoelectric field value would be twice the maximum in 1994-2011. Such value was actually reached on 13-14 July 1982. © M. Myllys et al., Published by EDP Sciences 2014.
Gustavsen B.,Sintef |
Runde M.,Sintef |
IEEE Transactions on Power Delivery | Year: 2015
A 420-kV gapped-core five-legged variable shunt reactor is modeled in the frequency range 5 Hz-10 MHz based on frequency sweep measurements and curve fitting using rational functions. Comparison with time-domain measurements at reduced voltage shows that the model can accurately predict the transient behavior of the shunt reactor, both for impinging overvoltages and circuit-breaker transient recovery voltages. Among the observations is that mutual coupling between the phases leads to a beat phenomenon in the reactor voltage following disconnection. Representing the shunt reactor by an LC parallel circuit leads to unrealistic results for steep-fronted incoming waves and high-frequency oscillating overvoltages, and for the attenuation of the transient recovery voltage following disconnection. © 2015 IEEE.
Vanfretti L.,Statnett |
Sevilla F.R.S.,KTH Royal Institute of Technology
IEEE PES Innovative Smart Grid Technologies Conference Europe | Year: 2015
This paper presents a three-layer voltage stability index computed using time-series obtained from dynamic simulations. The proposed index provides the distance with respect to voltage and power limits. Voltage, active and reactive power signals, which are determined using time series from dynamic simulations, are used to compute the index. The methodology assumes that no other information about the system (model) is available. A set of 3 different simulations at different loading levels and a given contingency are required to calculate the index. In the first layer, a two-element vector indicates if a power or a voltage limit was violated. In the second layer, a vector is used to specify which power and voltage loading level was violated and finally, in the third layer a matrix is used to retrieve precise information about which power and voltage limit has been violated in pre- or post-contingency. The index can analyze simultaneously different buses. The proposed index is illustrated using synthetic data and then tested using timedomain simulations on the KTH-Nordic32 system. © 2014 IEEE.
Lelekakis N.,Monash University |
Wijaya J.,Monash University |
Martin D.,University of Queensland |
IEEE Electrical Insulation Magazine | Year: 2014
Utilities need to understand the aging of paper insulation in order to prolong the life of transformers. If the paper becomes severely degraded, it loses its mechanical strength and thus its ability to insulate the windings. © 2006 IEEE.
Kishor N.,Aalto University |
Haarla L.,Aalto University |
Turunen J.,Statnett |
Larsson M.,ABB |
Mohanty S.R.,Motilal Nehru National Institute of Technology
IET Generation, Transmission and Distribution | Year: 2014
Using wide area monitoring systems (WAMS) offers a possibility for an integrated measurement-based and model-based control, which suits to the operation of large electric power system (EPS), along with online analysis. This study presents studies on fixed-order controller design through model identification approach with use of synchronous measurement data. Firstly, in the study, the coherent generator in each area of large EPS is determined by the mutual information theory. Then, state-space two-input two-output model is identified for the generator that has highest participation factor and thus referred as coherent generator. The model identification algorithms; least-square, instrumental variable and subspace state-space based generalised Poisson moment function are used. Next, WAMS level model is identified between the input controllable variable and speed deviation difference of coherent generator of each area. Finally, a local controller (decentralised) in each coherent area and a centralised controller at WAMS level between two coherent areas are designed by optimisation of the several design functions; H∞ norm, H2 norm, spectral abscissa and complex stability radius, as much as possible. These controllers feed supplementary control signal in addition to one fed by local conventionally tuned power system stabiliser. The centralised controller at WAMS level is demonstrated to stabilise the speed deviations of each generator between any two areas in the large EPS. The study is investigated with different input signal variables; ΔVref, ΔPm excited by different pattern of disturbances. © The Institution of Engineering and Technology 2014.
Aigner T.,Norwegian University of Science and Technology |
Jaehnert S.,Norwegian University of Science and Technology |
Doorman G.L.,Norwegian University of Science and Technology |
IEEE Transactions on Sustainable Energy | Year: 2012
The ongoing development in the electrical system and the transition from a mainly thermal dominated power system into a system widely affected by renewable production resources, requires a revision of future balancing strategies facilitating the secure integration of renewable energy. Especially the increasing wind power penetration with its uncertain production on all time scales will largely affect the system operation, requiring a higher flexibility and thus more reserve capacity providing balancing energy. Based on high resolution numerical weather prediction models and wind speed measurements, the actual and the forecasted wind power production is simulated for five scenarios covering the years 2010 and 2020. These scenarios are taken as an input to a Northern European regulating power market model, analyzing the procurement of reserve capacity and their activation. Further on, the potential benefit of integrating Northern European regulating power markets handling the varying wind power production is investigated. Due to remaining wind forecast errors, more reserve capacity is required in the electrical system. The simulations comprise frequency restoration reserves and replacement reserves. Based on the assumption of an integrated regulating power market, the determined results illustrate that the Nordic power system can provide such reserves at optimal cost. In 2020, an overall cost increase is recognized, concurrently displaying significant saving possibilities by a cross-border procurement of reserve capacity and the exchange of balancing energy. © 2010-2012 IEEE.
Lindeberg E.,Statnett |
Svendsen H.G.,Sintef |
Uhlen K.,Sintef |
Uhlen K.,Norwegian University of Science and Technology
Energy Procedia | Year: 2012
This paper presents a novel wind turbine control system which gives a smooth power output during transitions between different controllers. The paper presents an implementation of a control system designed for an offshore floating wind turbine using a linear Model Predictive Control approach. The performance is investigated in computer simulations, with emphasis on stability in the tower fore-aft motion and behaviour during transition between controllers. The results clearly demonstrate that the wind turbine using the proposed algorithm for smooth transition indeed exhibits a smooth system behaviour. In comparison to a case with sudden transition, the behaviour is found to be significantly improved. Moreover, tower oscillations are found to be stable, by virtue of the controller prediction horizon exceeding the natural periodicity of the tower oscillations. Smooth system behaviour is important to increase the lifetime of critical parts of the turbine. With increasing turbine sizes such considerations are of increasing importance, making the results obtained in this paper of particular relevance for large wind turbines, both onshore and offshore. © 2012 Published by Elsevier Ltd.
News Article | February 27, 2017
Statnett will start construction of the Bjerkreim substation in Rogaland County. The substation will connect the planned wind farms in Bjerkreim to the nationwide main grid.
News Article | August 25, 2016
The Stuxnet computer worm discovered in 2012 set alarm bells ringing in industry and public sector offices all over the world. This very advanced software worm had the ability to infect and disable industrial process control systems. The scary thing was that the worm had crept its way into many of the most common industrial control systems. If a state or a hacker is able to spread malignant software so widely, what can we expect next? The Internet of Things, virtually connecting everything to everyone, is rapidly proliferating to businesses, public sector offices and our homes. How can we defend ourselves against a threat when we don't know what it looks like, or where it will strike next? Researchers at SINTEF are working to find a way of counteracting such threats. They are developing methods that will enable companies and public sector agencies to manage threats and attacks, including those that no-one has thought of. "Society is under pressure from new threat and vulnerability patterns", says Tor Olav Grøtan, a Senior Research Scientist at SINTEF. "Standard approaches involving defence systems based on clear control procedures and responsibility are inadequate when the risk is moving around between a diversity of areas and sectors. There is an urgent need for innovative thought and new approaches", he says. Grøtan is heading the project "New Strains of Society", which is aiming to develop new scientific theories in the field of hidden, dynamic and, what researchers call, "emergent" vulnerabilities. SINTEF's research partners are the Norwegian University of Science and Technology (NTNU), the Norwegian Defence Research Establishment (FFI), and the University of Tulsa in the USA. Professor Sujeet Shenoi at the University of Tulsa is closely involved. He lectures his students on "ethical hacking", with the aim of raising expertise in the US public sector to the same levels as those possessed by malicious experts and hackers. For the last twenty years, Professor Shenoi has been instructing almost 400 Master's and Doctoral (PhD) students in how to hack into public and private sector networks. The students need security clearance and must undertake to work in the American public sector after they have qualified. With the consent of the owners, the students have penetrated deep into computer systems controlling payment terminals, smart electricity meters, gas pipelines, coal mines and wind farms. They have succeeded every time. "Someone or other, not necessarily us, has the ability to break into any computer system", says Shenoi. "We have to live with this and manage it, and that is why the concept of resilience (the dynamic ability to resist and adapt) is so important", he says. Professor Shenoi sees Norway as an ideal location for the development of such resilience. "Norway is one of the most digital countries in the world", he says. "With a relatively small population of 5.2 million, it can become a whole-world laboratory. This is not easy to achieve in the USA, which is too big and too diverse", he says. SINTEF and its partners are looking into three so-called 'threat landscapes': oil industry activity in the high north, a global pandemic, and ICT systems embedded in critical infrastructure in the oil and electrical power sectors. A workshop was held recently with the aim of addressing vulnerabilities in the energy sector. It was attended by representatives from the Norwegian Ministry of Justice and Public Security, the Norwegian National Security Authority (NSM), the Norwegian Communications Authority (NKOM), the US National Security Agency (NSA), the Norwegian Water Resources and Energy Directorate (NVE), the Norwegian Petroleum Safety Authority, research scientists, consultants and businesses. "We were there to test a new method of exposing unknown threats and vulnerabilities, and to prepare a stress test", says Grøtan. "People from the oil and electrical power sectors, who aren't normally thinking on the same wavelength, had the chance to work and reflect on issues together. We will apply this experience as the project progresses as part of our work to develop a stress test method designed to investigate how well an organisation is equipped to handle an unexpected situation", he says. And the need is urgent. In 2014 Statnett and hundreds of other Norwegian energy sector companies were subject to a large-scale hacker attack. They are not alone. All sectors of society are under attack and the number of attacks increases every year. For example, Statoil intercepts 10 million spam e-mails every month. Opening an e-mail attachment is a very common way of allowing malignant software to enter a company's computer systems. Another is when careless employees give system access to subcontractors and other external parties. Explore further: Iran says Duqu malware under 'control'
News Article | December 16, 2015
Someone hacks into the network companies that provide electric power, shutting down their systems. This will knock out the electricity in the entire region supplied by the network company, such as Lyse Elnett in Rogaland, Agder Energi Nett in the Agder counties, or Hafslund Nett, which supplies electricity to 1.5 million people in the Oslo area. A simultaneous attack on several network companies could affect large parts of the country. Trains would stop, planes would not be able to land, there would be no electricity, the water supply would stop and the sewerage system would break down. Hospitals have emergency generators and would manage for a while, but over a longer period of time, this would be critical for life and health. Add a cold winter, and it would not take much imagination to visualise the effects of such an attack. "This is the worst that could happen—a worst case scenario. The consequences for society would be huge", says Ruth Østgaard Skotnes. She is a researcher at the International Research Institute of Stavanger (IRIS) and Centre for Risk Management and Societal Safety (SEROS) at the University of Stavanger. She has recently completed a PhD in safety and security management of electric power supply networks. You may think that this sounds like a scene from an unrealistic disaster movie. "That's not the case", says Skotnes. "We must prepare ourselves for the improbable, and the threat to Norwegian energy providers is very much a reality." This is according to reports from, among others, the Norwegian National Security Authority (NSM), the Norwegian Police Security Service (PST), and the Norwegian Government's Cyber Security Strategy for Norway from 2012. "Everything indicates that we now must expect sophisticated attacks aimed at critical societal information, including information and communication technology (ICT) systems that operate industrial processes and critical infrastructure", says Skotnes. Over the past decades, modern ICT has been introduced for operation of the various parts of the electric power supply. Previously operated manually, electric power plants now control and monitor production and distribution systems from a few control centers. Process control systems were traditionally closed systems, however increased connectivity via standard ICT technologies has made these formerly isolated ICT systems vulnerable to a set of threats and risks they have not been exposed to before. Skotnes was therefore surprised to discover that the network companies themselves perceived this risk as relatively low, despite the fact that many of the companies had experienced attempts to hack into their process control systems. Some even reported about daily attacks from the outside. "Many network companies put too much trust in their own systems, and take it for granted that attacks will not be successful. This contrasts strongly with what research and reports from the authorities tell us", says Skotnes. Another reason may be that the network companies find it difficult to prepare for something that might happen, but hasn't happened yet. Up until now, Norway has been spared harmful cyber attacks on critical infrastructures. However, worldwide there have been several incidents of cyber attacks during the last few years. The best known of these, Stuxnet, was discovered in 2010. This was the first known computer worm that could spy on and reprogramme industrial control systems. Among other things, Stuxnet was supposed to have been used against and damaged the Iranian nuclear programme. The attacks on the twin towers in New York, the bombing of the Government Quarter in Oslo and the subsequent attack in Utøya on 22 July 2011 have taught us that the unthinkable can happen. "We need to be better prepared for attacks against critical infrastructure than we currently are in Norway", says Skotnes. So, how can the network companies protect themselves against cyber attacks? System updates and antivirus software are important measures, but vigilant employees and management commitment are just as important, according to Skotnes. Last year, around 50 companies in the oil and energy sector were exposed to the biggest cyber attack in Norway's history. In Statnett, the transmission system operator in Norway, the attempt was discovered by a vigilant employee, which meant that the company was able to prevent malicious software from being installed or run on computers within the company. "My study showed a strong relationship between management commitment to ICT safety and security, and the implementation of awareness creation and training measures for ICT safety and security in the network companies. I was told that it was difficult to implement measures if the management was not committed to the issue", says Skotnes. Involving the employees in the development of ICT safety and security measures can be a useful way to raise awareness in the network companies. This can make it easier for the employees to realize the benefits of these safety and security measures, and not consider practicality and efficiency as far more important for their work. Her thesis shows that there exists at least two different subcultures in today's network companies, depending on whether the people operating the process control systems have an education in ICT or a background from the electricity industry. The latter group generally focus on keeping the systems running without interruption. Downtime is not acceptable, and the most important thing for this group is constant supply of electricity. "Supply reliability is important, but this way of thinking has to change so that everyone understands how crucial ICT safety and security is", says Skotnes. Power production in Norway is more difficult to affect. Ruth Østgaard Skotnes chose to concentrate on power distribution because this is considered to be most critical for societal safety. She collected data for her thesis through a survey questionnaire that she sent to all the 137 network companies operating in Norway in 2012. Skotnes also interviewed representatives from the contingency planning department in the Norwegian Water Resources and Energy Directorate (NVE) who are responsible for safety, security, contingency planning and supervision in the Norwegian electric power supply sector. By 2019, smart meters (Advanced Metering Infrastructure) will be installed in all Norwegian households. Smart meters will provide increased capacity, reliability and efficiency of electric power supply, but will also increase the vulnerability to cyber attacks. "Society's vulnerability will increase because the number of possible entry points and paths for attacks are continually increasing. This is why we as a society need to take such threats seriously", says Skotnes. More information: Ruth Østgaard Skotnes: Challenges for safety and security management of network companies due to increased use of ICT in the electric power supply sector. Doctoral thesis, the Faculty of Social Science at the University of Stavanger, 2015