Jan Ove Gjerde

Wide Area Monitoring Experiences in Norway

In this paper, a wide area monitoring system (WAMS) for the 420 kV Norwegian bulk transmission grid has been evaluated. The robustness of the PMU measurements has been demonstrated by a direct comparison of phasor information from the PMUs and a state estimator (EMS). The paper highlights benefits of both off-line and on-line WAMS applications: a method for real-time detection of power oscillations, as well as the use of WAMS as input to power system stabilizers (PSS), is presented

A software development toolkit for real-time synchrophasor applications

This article presents a software development toolkit for Wide Area Monitoring Systems. By using this development toolkit, a researcher is able to manipulate synchrophasor data in the LabView environment, which enables fast software prototyping and testing. This toolkit makes full scale testing in real-time easier for researchers, liberating them of complex and time consuming synchrophasor data handling. The toolkit exploits the IEEE C37.118.2-2011 protocol making it independent of any specific equipment and their manufacturers. An application of the development kit is demonstrated in a laboratory environment with a specially designed experimental setup composed of a real-time digital simulator and four phasor measurement units (PMUs).

Monitoring amplitude, frequency and damping of power system oscillations with PMU measurements

Since 2005, Statnett (the Norwegian transmission system operator), ABB and Sintef Energy Research, have worked together on designing, implementing and deploying a Wide Area Monitoring System (WAMS) completely integrated with Statnettpsilas SCADA system. This paper focuses on the application for on-line monitoring of amplitude, frequency and damping of power oscillations as implemented in the WAMS.The power transfer capability in the Nordic transmission system is at times limited by the risk of instability due to inter- area power oscillations. With the WAMS in operation detailed operational data is available to alert operators and support identification of potentially unstable system conditions. In the past, such power swings would often go by unnoticed, and therefore this application can be of critical importance. WAMS recordings from a recent system disturbance leading to temporary sustained power oscillations are presented and used to discuss the ability to provide early detection of power oscillations in terms of amplitude, frequency and damping of the dominant mode. The main conclusion is that the system is able to identify accurately the amplitude and frequency of the main oscillatory modes. Identification of damping is difficult in an on-line application, particularly when the magnitude of the oscillations is similar to that of random load variations. The present measurements, however, show that as the magnitude of these oscillations increase, the indicator on damping also becomes more reliable.

Wide-Area Power Oscillation Damper implementation and testing in the Norwegian transmission network

This article reports the results from the implementation and testing of a Wide-Area Power Oscillation Damper (WAPOD) controlling a 180 Mvar TCR Static Var Compensator (SVC) installed in the Hasle substation of Norwegian 420 kV transmission grid. The WAPOD uses voltage phase angle signals from two distant locations in the Norwegian grid as inputs to the damping controller. The damping controller modulates the voltage reference set point used by the SVCs voltage controller, thereby creating a damping effect. The WAPOD is an extension to the existing Power Oscillation Damping (POD) controller that uses local measurements. A switch-over logic allows for the use of no damping control, local damping control or wide-area control. Field tests were performed during November 2011, and involved the disconnection and re-connection of a 420 kV transmission line. The performance of the WAPOD is compared to that of state-of-the-art local Phasor POD, and when no damping control is enabled. The testing results show that the WAPOD performed satisfactorily and according to the design expectations. These results show that the potential flexibility of the WAPOD to choose, among the different PMU signals, those that have the good observability of inter-area modes can be an advantage to the use of local feedback signals for damping control, as it is current practice today. Further testing of this WAPOD with other PMU signals from locations with stronger observability will be helpful to illustrate the advantage of this flexibility.

Coordinating power oscillation damping control using wide area measurements

In this paper, the potential benefits of a Wide Area Control System for coordinated power oscillation damping control is investigated for the Nordic power system, with an overall motivation to facilitate increased power transfer limits.

Synchrophasor network, laboratory and software applications developed in the STRONg 2 rid project

This paper presents the activities carried out in one of the work packages of the Nordic Energy Research funded project Smart Transmission Grid Operation and Control (STRONg2rid). The main objective of the work package is to deploy a state-of-the-art software and hardware for developing power system operation, protection, control and automation applications. Several PMUs have been deployed at partner universities and a network of synchrophasors has been set up. In addition the Smart Transmission System Laboratory (SmarTS-Lab) has been established. This laboratory serves as a test-bench to develop and verify smart transmission grid technologies. A software development kit (S3DK) was developed within the project. The S3DK has been used to implement PMU-based applications and deploy them in different targets, including smart phones and tablets. Several tools and software applications which utilize synchrophasor measurements (from the laboratory or the deployed university PMU network) to perform power system monitoring, sub-synchronous power oscillation detection, etc., have been developed and are presented herein.

Effects of forced oscillations in power system damping estimation

This article analyzes the impact of forced power system oscillations on mode damping estimation. Parametric (Yule-Walker) and non-parametric (Welch) methods for mode estimation are tested in the presence of forced power system oscillations. For mode damping estimation based on non-parametric methods, an application of Half Power Point method is proposed. Performances of the mode estimators are evaluated using both simulated and real synchrophasor data from the Nordic Grid. The presence of forced oscillations poses difficulties to mode damping estimators, these difficulties are identified, illustrated and explained herein.

A smart transmission grid for Europe: Research challenges in developing grid enabling technologies

Smart grids have attracted significant attention lately, and one can even speak of a hype. However, much of the attention is paid to the distribution side and consumer interaction. Nevertheless, also at the transmission level important improvements can be achieved through farsighted and careful intelligent grid design and implementation. This paper identifies different research areas and their respective boundary interactions in order to enable a practical “Smart Grid” implementation in the European power system. Emphasis is placed on three essential aspects of the Smart Transmission Grid. First, the necessary evolution of synchrophasor measurement technology is discussed, as well as the limitations towards and its full integration into power system operation and control. An important aspect to achieve this full integration is the necessity to test and integrate any proposed solution in an open and transparent environment. Secondly, the IT, data and communications paradigm is critically discussed. And lastly, the key questions that are open to the transmission system operators are discussed, specifically regarding the coordination within the pan-European power system and its security. Going beyond the purely academic point-of-view, this paper specifically aims to bring a realistic approach towards research for the transmission network.

Testing and validation of a fast real-time oscillation detection PMU-based application for wind-farm monitoring

This article provides an overview of a monitoring application, its testing and validation process. The application was developed for the detection of sub-synchronous oscillations in power systems, utilizing real-time measurements from phasor measurement units (PMUs). It uses two algorithms simultaneously to both detect the frequency at which the oscillatory event occurs and the level of energy in the oscillations. The application has been developed and tested in the framework of SmarTS Lab, an environment capable of hardware-in-the-loop (HIL) simulation. The necessary components of the real-time chain of data acquisition are presented in this paper, as well as testing and validation results, to demonstrate the accuracy of the monitoring tool and the feasibility of fast prototyping for real-time PMU measurements based applications using the SmarTS Lab environment.

Applications of Spectral Analysis Techniques for Estimating the Nordic Grid's Low Frequency Electromechanical Oscillations

For power networks such as the Nordic Grid, that have operation constraints limits imposed by the existence of low-damped electromechanical oscillations, the estimation of electromechanical mode properties is of crucial importance for providing power system control room operators with adequate indicators of the stress of their network. This article addresses the practical application of different spectral analysis techniques that can be used for the estimation of electromechanical mode properties using data emerging from real synchronized phasor measurement units (PMUs) located at both the low-voltage distribution and high-voltage transmission networks of the Nordic grid. Emphasis is made on providing systematic approaches to deal with imperfect data found in practice so that accurate estimates can be computed.