Srdjan Skok

Wide-Area Monitoring, Protection, and Control of Future Electric Power Networks

Wide-area monitoring, protection, and control (WAMPAC) involves the use of system-wide information and the communication of selected local information to a remote location to counteract the propagation of large disturbances. Synchronized measurement technology (SMT) is an important element and enabler of WAMPAC. It is expected that WAMPAC systems will in the future reduce the number of catastrophic blackouts and generally improve the reliability and security of energy production, transmission, and distribution, particularly in power networks with a high level of operational uncertainties. In this paper, the technological and application issues are addressed. Several key monitoring, protection, and control applications are described and discussed. A strategy for developing a WAMPAC system in the United Kingdom is given as well.

Benefits of Synchronized-Measurement Technology for Power-Grid Applications

Power grids traditional security assessment approach-based on SCADA data and off-line studies conducted long in advance of real time operations-are becoming increasingly problematic for real time operations because they cannot fully anticipate all the conditions faced by operators. New technologies that rely on accurate, high-resolution, real-time monitoring of actual (not hypothesized) system conditions using synchronized measurement technologies are needed to support the real-time operations. The purpose of these tools and systems is to monitor, assess, enable, and ultimately, automatically take the necessary control action to prevent or mitigate problems in real time. The proposed applications of synchronized measurements for power grids will provide the realtime operating staff with previously unavailable yet greatly needed tools to avoid grid instabilities, and to monitor generators response to abnormal excursions in system frequency. The objective of this paper is to point out benefits of using synchronized measurements for selected realtime applications, to summarize ongoing projects and experience worldwide, and emphasize the need for a practical roadmap toward greater deployment of the technology

Applications Based on PMU Technology for Improved Power System Utilization

Traditional security assessment approach - based on SCADA data and off-line studies conducted long in advance of real time operations - are becoming increasingly unreliable for real time operations. New technologies, which rely on accurate, high-resolution, real-time monitoring of actual system conditions using phasor measurement technologies, are needed to support the real-time operations. The purpose of these tools and systems is to monitor, assess, enable, automatically take the necessary control action to prevent or mitigate problems in real time. The proposed applications of phasor measurements will provide the real-time operating staff with previously unavailable yet greatly needed tools to avoid voltage and dynamic instability, and monitor generator response to abnormal significant system frequency excursions. The objective of this paper is to point-out benefits of using PMUs for selected real-time applications and present ongoing pilot projects and experience worldwide, and to give short and long term roadmap for future acts.

Multipurpose open system architecture model of wide area monitoring

This paper elaborates developed custom open system architecture for processing, archiving and visualization of phasor data with the extended archiving capabilities and managing such data. Presented multi-purpose and open system architecture is able to communicate and collect synchronized measurements from different sources such as the phasor data concentrator, virtual PMUs, SCADA and synchrophasor vector processor. Collected data are filtered and processed with the originally developed algorithm for power system real time monitoring purpose.

Monitoring and control of smart transmission grid based on synchronized measurements

The monitoring and control of smart power transmission grid represents active infrastructure capable of obtaining increased transfer and distribution of electrical energy, with considerable rate of generation from renewable energy sources without compromising the stability, security and reliability of power grid in different operating conditions. The development concept of intelligent protection and control systems of the entire smart power transmission grid defines: • use of complex information and communication technology (ICT) system, • sending selected local information to a remote location where this information is processed and • implementation of accurately defined automated actions to neutralize and stop the spreading of major system disturbances. Wide area monitoring of electrical power system, which is the initial step in developing the smart power transmission grid has found its place around the world and its expected increase of use in the daily work of system operators will result in more efficient and reliable use of ancillary functions during large scale disturbances. The intention of this paper is to point out the needs and developing possibilities of monitoring and control systems of the entire smart power transmission grid based on the System Integrity Protection Schemes (SIPS) and synchronized measurements technologies, to summarize accomplishments within ongoing projects and experience gathered worldwide, and to emphasize the need for making practical roadmap towards greater deployment of the technology. This paper will give the scheme of automatic transmission control system that aims to mitigate the possible overloading of existing transmission lines while maintaining the same rate of generation.

Transmission line impedance estimation based on PMU measurements

State estimation is one of the most important network management functions, responsible for determining the actual state of the power network based on the network model, available telemetry (analog measurements and digital device statuses) and pseudo measurements. Phasor measurement units (PMUs) provide valuable instantaneous information regarding power system stability and security, and thus have the potential to improve the reliability of the state estimator. Also, measured synchrophasors can be used for transmission line impedance estimation, which results in more accurate power system state estimation, in comparison with the traditional approach that uses catalogue values of the transmission line impedance.

Using WAM in Croatian Power System for Energy Transit Utilization

In the project of new 400 kV substations in Croatia and in the preparation phase for reconnection first and second synchronous zone in the UCTE system it was realized first Wide Area System in the Croatian power system. After detail analysis, first WAM system was put in the operation on the 400 kV line in the Croatian grid. Direction of significant energy transit through Croatian power system takes path form northeast to southwest. Significance can be explained with simple fact that power flows varies from 25% to 50% of overall national load (national load is -2500 MW). Optimization of energy transit considering stability of the system is a great challenge for dispatchers. This paper elaborates using of phasor measurement units (PMUs) and wide-area monitoring system (WAMS) applied to 400 kV transmission line for improved monitoring and optimization of energy transit.

Comparison of various neural network models applied to adaptive distance protection

This paper elaborates settings and modification of the operating characteristic of adaptive distance relays which protect a transmission line between two terminals. Operating characteristic should have such shape to satisfy all conditions in the power system. However it is known that there is no combination of characteristics which can satisfy all possible conditions. So the only solution is modification of the operating characteristic. Solution of this problem involves two types of neural networks, multilayered perceptron and the self-organizing neural network, the so called Kohonen network. Here the authors consider a two-terminal transmission line, confirm that fault resistance and location of faults can produce erroneous relay function and finally suggest ways to ensure the generation of the correct signal for relay operation. With the simple simulation, the authors present the advantages of the particular models and the credibility of the developed models.

Transmission line positive sequence impedance estimation based on multiple scans of Phasor Measurements

In the paper the proposed algorithm for estimation of transmission line parameters is tested and evaluated. The proposed algorithm uses the weighted least square method with multiple scans of measurements derived from Phasor Measurement Units (PMUs). The network topology and loading conditions in the transmission network change continuously, which can influence the estimation of transmission line parameters with synchrophasor measurements. The case studies in the paper assess the influence of usage of multiple scans of synchrophasor measurements during sudden change of loading and network topology conditions. In the paper the presented algorithm is tested using simulated PMU measurements with and without introduced random errors. High number of measurement scans improves the transmission parameter estimation results but at the same time the calculation time of the algorithm increases. To obtain the optimal results, a compromise between the number of measurement scans and calculation time is needed.

Automated control for Power Transmission System in urban area

Modernization of a power system involves development and deployment of an Intelligent System or a System Integrity Protection Scheme for a Power Transmission System. As the observed urban Power Transmission System has a ring topology, including overhead lines and underground cables, various scenarios of a closed loop and island operation are considered. Deficiencies of a traditional control solution are stated and a modern automated control of the urban transmission system, based on synchronized phasor measurements, is presented. A developed architecture is designed to provide real time monitoring and control functions. Control actions are based on different switching and operational states.