The role played by phasor measurement units (PMU) in power grid monitoring systems today showcases the importance and usefulness of this device. There is a significant challenge regarding the design and implementation of PMUs today. This challenge stems from the closed source philosophy employed by commercial PMU vendors who strongly protect their hardware and software designs keeping it away from researchers. This philosophy has motivated a number of researchers to develop their own PMU devices. This thesis presents the design and implementation of a PMU device utilizing off-the- shelf components to estimate power system parameters such as voltage magnitude, phase angle and frequency with key design information extracted from the OpenPMU group and the IEEE C37.118-2011 standard. The functionality of the PMU was tested by performing important power system experiments which compared measured result of voltage magnitude, phase angle and frequency of a balanced three phase signal from a rapid prototyping system with estimated results from PMU. The conducted experiments confirmed that the PMU could estimate voltage magnitude, phase angle and frequency approximately equivalent to the measured quantities of the input signal. / February 2016

Phasor measurement unit (PMU) applications on power grid monitoring systems have been implemented since the early ninety's. Large monitoring system network performance relies on the consistent measurements of PMUs across the system. This has become a major challenge for designers since large networks use PMUs from various manufacturers who likely implement different synchrophasor technologies to perform the phasor estimations. The current synchrophasor standard, the IEEE C37.118-2005 Synchrophasor Standard, covers adequately the steady-state characterization of PMUs but does not specify transient condition requirements. The North American Synchrophasor Initiative (NASPI) has developed a guide outlining the several tests required for dynamic characterization of PMUs. The National Institute of Standards and Technology (NIST) developed two PMU testing stands for steady-state conformance with the current standard and for dynamic performance testing. Since May 2010, Virginia Tech has been working closely with the NIST in developing a PMU testing system similar to the NIST designs for commercial testing of PMUs and research purposes, the Virginia Tech Calibration System. This thesis focuses on assessing the system accuracy differences between the designs, and the software interface modifications to adapt the new hardware. / Master of Science

Master of Science / Department of Electrical and Computer Engineering / Noel N. Schulz / As the size of electric power systems are increasing, the techniques to protect, monitor and control them are becoming more sophisticated. Government, utilities and various organizations are striving to have a more reliable power grid. Various research projects are working to minimize risks on the grid. One of the goals of this research is to discuss a robust and accurate state estimation (SE) of the power grid. Utilities are encouraging teams to change the conventional way of state estimation to real time state estimation. Currently most of the utilities use traditional centralized SE algorithms for transmission systems. Although the traditional methods have been enhanced with advancement in technologies, including PMUs, most of these advances have remained localized with individual utility state estimation. There is an opportunity to establish a coordinated SE approach integration using PMU data across a system, including multiple utilities and this is using Distributed State Estimation (DSE). This coordination will minimize cascading effects on the power system. DSE could be one of the best options to minimize the required communication time and to provide accurate data to the operators. This project will introduce DSE techniques with the help of PMU data for a system snapshot. The proposed DSE algorithm will split the traditional central state estimation into multiple local state estimations and show how to reduce calculation time compared with centralized state estimation. Additionally these techniques can be implemented in micro-grid or islanded system.

<p>Vattenfall and Svenska Kraftnät perform start-up tests, where hydropower generators are used to power up the electrical grid in case of a blackout. To monitor the electrical grid, Phasor Measurement Units (PMU) are used. Each PMU is individually equipped with a GPS-receiver to precisely timestamp the data relative to the official time UTC. During the test, it is also of interest to timestamp the measurement signals from individual hydropower generators to later compare with PMU-data, and thus study the power grids impact on the generator.</p><p> </p><p>The aim is to work out an appropriate method to make these measurements and to build a data acquisition system, capable of timestamp data relative to UTC, from a generator in one of Vattenfalls hydroelectric power stations. The problem is that the generator is located in an underground station which hampers the reception of GPS-signals and wiring should be avoided if possible.</p><p> </p><p>Time synchronization has been solved by using Vattenfalls network, which is synchronized by the network protocol NTP. The network includes the concerned hydropower stations and thus can wiring from the surface be avoided. The maximum error for the server in the specific hydroelectric power station is bounded within [-4.62, 3.18] ms relative to UTC. The conclusion is that Vattenfalls NTP-network meets the requirements to distribute time. A platform from National Instruments, programmed with the graphical language LabVIEW, has been used for data acquisition. The platform is programmed to synchronize its internal clock to a NTP-server, timestamp the input signals and save the data on the internal hard drive.</p>

Vattenfall and Svenska Kraftnät perform start-up tests, where hydropower generators are used to power up the electrical grid in case of a blackout. To monitor the electrical grid, Phasor Measurement Units (PMU) are used. Each PMU is individually equipped with a GPS-receiver to precisely timestamp the data relative to the official time UTC. During the test, it is also of interest to timestamp the measurement signals from individual hydropower generators to later compare with PMU-data, and thus study the power grids impact on the generator.   The aim is to work out an appropriate method to make these measurements and to build a data acquisition system, capable of timestamp data relative to UTC, from a generator in one of Vattenfalls hydroelectric power stations. The problem is that the generator is located in an underground station which hampers the reception of GPS-signals and wiring should be avoided if possible.   Time synchronization has been solved by using Vattenfalls network, which is synchronized by the network protocol NTP. The network includes the concerned hydropower stations and thus can wiring from the surface be avoided. The maximum error for the server in the specific hydroelectric power station is bounded within [-4.62, 3.18] ms relative to UTC. The conclusion is that Vattenfalls NTP-network meets the requirements to distribute time. A platform from National Instruments, programmed with the graphical language LabVIEW, has been used for data acquisition. The platform is programmed to synchronize its internal clock to a NTP-server, timestamp the input signals and save the data on the internal hard drive.

As the scale and complexity of an interconnected power grid has increased significantly, power systems can be operated close to the verge of voltage instability. With the application of Phasor Measurement Units (PMUs), dispatchers are able to monitor long term voltage stability in a real time operational environment. This research addresses the critical issues by proposing three different methods. Voltage Stability Assessment Index (VSAI) is a Thévenin Equivalent (TE) based method considering voltage dynamic mechanisms. To extend the model from one load bus to a critical load center, Optimal Power Flow-Loading limit (OPF-LI) is developed to assess the voltage stability margin. To utilize limited available PMU measurements, State Calculator (SC) is included in the algorithm to approximate the dynamic states at the buses where PMU measurements are not available. The online voltage regulating method in terms of On-load Tap Changer (OLTC) control is also investigated. The methods proposed in this research have been validated with the test cases from the WECC 179 bus system. / M.S. / This thesis proposed a hybrid solution of voltage stability monitoring and control in a power system. For the performance of motors, heaters or other loads in the power system, it is important that the customers are supplied with stable voltage. The variation of the voltage may cause damages to the load. Therefore, the methods in this thesis provides a feasible solution to monitor voltage stability of load centers in a power system. In addition, a novel approach for voltage control is proposed to prevent a voltage collapse of the system. The simulation results illustrate that the approach introduced in this thesis is promising for real time application.

SCADA is the primary system for control and monitoring of distribution grids. As the expectations on how the grid must operate changes with the increased use of renewable energy sources, it also requires new methods of monitoring. Phasor Measurement Units (PMU) measures the phase angle and amplitude synchronously with GPS. A collaboration between U.C Berkeley and Power Standard Lab researches the possibilities of implementing synchrophasors in distribution grids. These devices are called micro-PMU and will provide similar services available for transmission grids, though adapted for lower voltage levels. Synchrophasors are useful in the development of a smarter distribution network, which consequently makes them interesting for the Swedish electricity market. Martin Gahr, a student at Berkeley / ETH, has developed a method to determine the topology of a distribution grid using micro-PMU's. The method compares calculated values from SCADA with values from micro-PMU's. The smallest difference between the two readings clarifies the topology. In this thesis the method is used to study an existing distribution grid in central parts of a medium-sized Swedish city. The method gives a satisfactory result when it is implemented on the mashed parts of the distribution grid. There are also indications that micro-PMU's must not be placed at every node to provide a reliable result. Although the method seems to be working on mashed parts of a Swedish distribution grid, it is not particulary interesting to implement the method in reality.

Made available in DSpace on 2014-06-12T17:37:05Z (GMT). No. of bitstreams: 2 arquivo5314_1.pdf: 5108272 bytes, checksum: b9a316741b5b208712ad6ddf84c4fcd5 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2008 / Companhia Hidro Elétrica do São Francisco / Este trabalho apresenta uma metodologia que permite medir os parâmetros elétricos de linha, baseado na oscilografia dos registradores digitais de perturbação, e em seguida permite avaliar a precisão da metodologia desenvolvida em relação aos métodos de cálculo convencionalmente utilizados. A partir da metodologia proposta, foram desenvolvidas rotinas computacionais, utilizando-se o software MATLAB, que possibilitam aferir os parâmetros das linhas de transmissão, tendo como entrada de dados os registros de oscilografia dos registradores digitais de perturbação, desde que estes possuam suas medições e conversões analógico-digitais sincronizadas através de sistema de posicionamento global. A validação da metodologia utilizada e das rotinas computacionais desenvolvidas foi realizada através de simulações preliminares no software ATP. A partir de tais simulações, foi possível a geração de registros de oscilografia em dois terminais de uma linha de transmissão utilizada como teste. De posse desses registros, foram utilizadas rotinas computacionais desenvolvidas no MATLAB para aferição dos parâmetros. Em testes realizados em laboratório, foi validada a possibilidade de obtenção de fasores com erros inferiores a 0,1 graus elétricos em seus argumentos. Tal precisão representa a condição necessária para se obter os parâmetros elétricos de uma linha de transmissão com um erro inferior a três por cento. Como estudos de caso em campo, foram realizadas aferições dos parâmetros elétricos da LT da CHESF Messias-Recife II, de 500 kV.

Phasor measurement is a growth technology in the power grid industry. With new funding, grid reliability concerns, and power capacity margin motivating a smart grid transformation, phasor measurement and smart metering are taking center stage as the implementation methods for grid intelligence. This thesis proposes a novel concept for designing a next generation phasor measurement unit. The present generation phasor measurement unit relies upon venerable existing current and voltage transducer technology that is expensive, bulky, and not well suited to the modern age of digital and computerized control signals. Also, the rising proliferation of installed phasor measurement units will soon result in data overload and huge obligations for network bandwidth and processing centers. This brute-force approach is ill-advised. Forward thinking is required to foresee the future grid, its fundamental operation, and its sensor controller needs. A reasonably safe assumption is a future grid containing sensors numbering in the thousands or millions. This number of sensors cannot transmit raw data over the network without requiring enormous network capacity and data center processing power. This thesis proposes a novel concept—combining existing technologies such as improved current transducers and wireless precision time protocols to design a next generation phasor measurement unit. The unit is entirely self-contained. It requires no external connections due to inclusion of high performance transducers, processor, wireless radio, and even energy harvesting components. With easy, safe, and low cost installation, proliferation of thousands or millions of sensors becomes feasible. Also, with a scalable sensor network containing thousands or millions of parallel distributed processors, data reduction and processing within the network relieves the need for high bandwidth data transmission or supercomputing data centers.

Cyber-attack on synchrophasor data has become a widely explored area. However, GPS-spoofing and FDIA attacks require different responsive actions. State-estimation based attack detection method works similar way for both types of attacks. It implies that using state-estimation based detection alone doesn’t give the control center enough information about the attack type. This scenario is specifically more critical for those attack detection methods which consider GPS-spoofing attack as another FDIA with falsified phase angle data. Since identifying correct attack type is paramount, we have attempted to develop an algorithm to distinguish these two attacks. Previous researchers exploited low-rank approximation of Hankel Matrix to differentiate between FDIA and physical events. We have demonstrated that, together with angle unwrapping algorithm, low-rank approximation of Hankel Matrix can help us separating GPS-spoofing attack with FDIA. The proposed method is verified with simulation result. It has been demonstrated that the GSA with 3 second time-shift creates a low-rank approximation error 700% higher than that of normal condition, whereas FDIA doesn’t produce any significant change in low-rank approximation error from that of normal condition. Finally, we have proposed a real-time method for successful identification of event, FDIA and GSA. / M.S. / Cyber-attack on synchrophasor data has become a widely explored area. However, GPS-spoofing and FDIA attacks require different responsive actions. State-estimation based attack detection method works similar way for both types of attacks. It implies that using state-estimation based detection alone doesn’t give the control center enough information about the attack type. This scenario is specifically more critical for those attack detection methods which consider GPS-spoofing attack as another FDIA with falsified phase angle data. Since identifying correct attack type is paramount, we have attempted to develop an algorithm to distinguish these two attacks. Previous researchers exploited low-rank approximation of Hankel Matrix to differentiate between FDIA and physical events. We have demonstrated that, together with angle unwrapping algorithm, low-rank approximation of Hankel Matrix can help us separating GPS-spoofing attack with FDIA. The simulation result verifies the next chapter discusses our proposed algorithm on GPS-spoofing attack detection and its ability to distinguish this type of attack from conventional FDIA. The proposed method is verified with simulation result. It has been demonstrated that the GSA with 3 second time-shift creates a low-rank approximation error 700% higher than that of normal condition, whereas FDIA doesn’t produce any significant change in low-rank approximation error from that of normal condition. Finally, we have proposed a real-time method for successful identification of event, FDIA and GSA.