Line Impedance Estimation Based on Synchrophasor Measurements for Power Distribution Systems

Effective monitoring and management applications on modern distribution networks (DNs) require a sound network model and the knowledge of line parameters. Network line impedances are used, among other things, for state estimation and protection relay setting. Phasor measurement units (PMUs) give synchronized voltage and current phasor measurements, referred to a common time reference (coordinated universal time). All synchrophasor measurements can thus be temporally aligned and coordinated across the network. This feature, along with high accuracy and reporting rates, could make PMUs useful for the evaluation of network parameters. However, instrument transformer behavior strongly affects the parameter estimation accuracy. In this paper, a new PMU-based iterative line parameter estimation algorithm for DNs, which includes in the estimation model systematic measurement errors, is presented. This method exploits the simultaneous measurements given by PMUs on different nodes and branches of the network. A complete analysis of uncertainty sources is also performed, allowing the evaluation of estimation uncertainty. Issues related to operating conditions, topology, and measurement uncertainty are thoroughly discussed and referenced to a realistic model of a DN to show how a full network estimator is possible

Diagnostic Applications for Micro-Synchrophasor Measurements

This report articulates and justifies the preliminary selection of diagnostic applications for data from micro-synchrophasors (µPMUs) in electric power distribution systems that will be further studied and developed within the scope of the three-year ARPA-e award titled Micro-synchrophasors for Distribution Systems

Every Moment Counts: Synchrophasors for Distribution Networks with Variable Resources

Chapter 34 in the textbook, "Renewable Energy Integration: Practical Management of Variability, Uncertainty and Flexibility

Topology Detection in Microgrids with Micro-Synchrophasors

Network topology in distribution networks is often unknown, because most switches are not equipped with measurement devices and communication links. However, knowledge about the actual topology is critical for safe and reliable grid operation. This paper proposes a voting-based topology detection method based on micro-synchrophasor measurements. The minimal difference between measured and calculated voltage angle or voltage magnitude, respectively, indicates the actual topology. Micro-synchrophasors or micro-Phasor Measurement Units ({\mu}PMU) are high-precision devices that can measure voltage angle differences on the order of ten millidegrees. This accuracy is important for distribution networks due to the smaller angle differences as compared to transmission networks. For this paper, a microgrid test bed is implemented in MATLAB with simulated measurements from {\mu}PMUs as well as SCADA measurement devices. The results show that topologies can be detected with high accuracy. Additionally, topology detection by voltage angle shows better results than detection by voltage magnitude.Comment: 5 Pages, PESGM2015, Denver, C

An Assessment of PIER Electric Grid Research 2003-2014 White Paper

This white paper describes the circumstances in California around the turn of the 21st century that led the California Energy Commission (CEC) to direct additional Public Interest Energy Research funds to address critical electric grid issues, especially those arising from integrating high penetrations of variable renewable generation with the electric grid. It contains an assessment of the beneficial science and technology advances of the resultant portfolio of electric grid research projects administered under the direction of the CEC by a competitively selected contractor, the University of California’s California Institute for Energy and the Environment, from 2003-2014

Synchrophasor Assisted Efficient Fault Location Techniques In An Active Distribution Network

Reliability of an electrical system can be improved by an efficient fault location identification for the fast repair and remedial actions. This scenario changes when there are large penetrations of distributed generation (DG) which makes the distribution system an active distribution system. An efficient use of synchrophasors in the distribution network is studied with bidirectional power flow, harmonics and low angle difference consideration which are not prevalent in a transmission network. A synchrophasor estimation algorithm for the P class PMU is developed and applied to identify efficient fault location. A fault location technique using two ended synchronized measurement is derived from the principle of transmission line settings to work in a distribution network which is independent of line parameters. The distribution systems have less line length, harmonics and different sized line conductors, which affects the sensitivity of the synchronized measurements, Total Vector Error (TVE) and threshold for angular separation between different points in the network. A new signal processing method based on Discrete Fourier Transform (DFT) is utilized to work in a distribution network as specified in IEEE C37.118 (2011) standard for synchrophasor. A specific P and M classes of synchrophasor measurements are defined in the standard. A tradeoff between fast acting P class and detailed measurement M class is sought to work specifically in the distribution system settings which is subjected to large amount of penetrations from the renewable energy

Model Development and Validation for Wind Generation Transmission Systems

In this research a new benchmark system is proposed for wind energy transmission systems. New model development, validation, and calibration methods for power transmission systems are proposed and implemented as well. First, a model reduction criteria is chosen based on electrical interconnection and geographical information. Model development is then done using reduction techniques on an operation model provided by a transmission operator based on the chosen criteria. Then model validation is performed using actual PMU synchrophasor measurements provided by a utility company. The model development and validation process ensures the accuracy of the developed model and makes for a realistic benchmark system for wind generation transmission systems. The new proposed model development and validation methods are generic and can be used to model any power transmission system for various simulation needs. Nevertheless, the accuracy of the benchmark model is constrained by the accuracy of the initial operational model. In this research, a new parameter estimation technique for determining the bus admittance matrix (Ybus) is also proposed to further calibrate power system models. Ybus estimation is done using recorded PMU synchrophasor measurements. The approach proposed in this research is based on recognizing that bus injection currents Ibus can be viewed as signals produced by a random process. In this manner, the corresponding bus voltages Vbus are also stochastic signals that are related through a cross-covariance matrix to the vector Ibus. Using estimation techniques developed for statistical signal processing, the cross-covariance matrix is shown to be Zbus

Synchrophasor Based Islanding & Open phase fault Protection in Distribution Systems

With the rapid growth of renewable energy resources, energy efficiency initiatives, electric vehicles, energy storage, etc., distribution systems are becoming more complex such that conventional protection, control, and measurement infrastructure – typically concentrated at the main substation, with little to no access to information along the feeder – cannot maintain the reliability of the system without some sort of additional protection, control and measurement functionalities. As an example, a dedicated communication channel for carrying the transfer trip signal from the substation to the Point of Common Coupling (PCC) to prevent islanding operation of alternative resources, has been a requirement for many utilities. In the transformation of the distribution system from a simple radial system to a bidirectional energy flow network, integration of many intelligent devices and applications will also be required. Thus, this situation calls for investment in communication infrastructure, and augmentation of protection, control, and measurement functionalities. The value of power system communication technologies such as synchrophasor measurement technology – which includes the Phasor Measurement Unit (measuring and providing voltage and current phasors in the real time via communication), communication infrastructure, and Phasor Data Concentrator (PDC) – is being recognized through large-scale deployments around the world. However, these implementations are predominantly limited to some monitoring-type applications and are being realized primarily in transmission systems and bulk power systems (≥100 kV), where performance requirements are much more stringent compared to distribution systems. So contrary to transmission systems, the current status of synchrophasor measurement technology can be utilized to its full extent in distribution systems, as shown in current research for anti-islanding and open-phase faults in the distribution feeder protection application, where the number of PMUs and performance required is somewhat lower than the bulk of power energy. Thus, the opportunity to invest in the implementation of synchronized measurement technology in distribution system is timely as it can be coordinated with other investments in feeder modernization, distributed generation (DG) integration, and infrastructure enhancements that are underway, including “smart grid” initiatives. In the first use case of this research, the behavior of the major DG types during islanding is studied through accurate transient modeling of utility type distribution systems using PSCAD-EMTDC and MATLAB. The study proposes augmentation of PMU-based solutions to the current passive islanding protection elements, such as voltage and frequency, and improving the non-detection zone of the passive elements by adapting their settings based on normal loading conditions at closest known instant prior to the fault or islanding occurrence. The solution proposes a system architecture that requires one PMU at each PCC bus and in the main substation. The communication aspect is based on the IEC 6850-90-5 report, where the PMU can subscribe directly to the data stream of the remote PMUs such that the need for PDCs in this application is eliminated, yielding better performance. In the second use case, an open-phase fault – a major concern for distribution utilities from safety of public and equipment perspective – has been studied. Clearing the open-phase fault without identifying the type of fault could result in an attempt by the recloser to reenergize the downed wire; conversely, an undetected open-phase fault could initiate ferro-resonance, thereby stressing equipment and increasing the risk to public safety, both urban and rural. This work discusses comprehensive analysis of symmetrical components of various types of open-phase faults in the distribution feeder with the presence of distributed generators (DGs) and proposes the use of phasor measurement data located at substation and PCC to identify the open-phase fault. The proposed algorithm relies on the rate of change of the various current and voltage sequence components. In the study conducted, the utility type feeder and substation are modeled in PSCAD-EMTDC, and different types of open-phase fault and shunt faults are studied to verify the dependability and security of proposed algorithm