ARRA: Kentucky Smart Grid Roadmap Development

Project Summary Objective Transmission line parameters including series resistance, series reactance and shunt susceptance are indispensable inputs to various power system applications, thus accuracy of line parameters plays a pivotal role in ensuring reliable performance of the applications. Moreover, transmission lines are critical components for delivering power over distance. How to maximize the power delivered while ensuring adequate safety of operation is a challenging problem. This project intends to put forth a possible online method to estimate the transmission line parameters, line temperature and sag employing synchronized phasors obtained by Phasor Measurement Units (PMU). The estimated temperature and sag can be utilized for dynamic thermal rating for increased power transfer. The proposed algorithm harnesses the non-linear optimal estimation theory, and is capable of detecting and identifying bad measurement data, minimizing impacts of measurement errors and thus significantly improving the estimation accuracy. The solution will be based on the distributed parameter line model and thus fully considers effects of shunt capacitances of the line. In addition, this project will also develop an optimal approach for placing PMUs in the system such that a minimum number of PMUs need to be installed in order to determine the parameters, temperature and sag of all the concerned transmission lines. One distinctive feature of the proposed methods is that only PMUs are required and no additional sensors such as tension and weather sensors are needed. This will greatly reduce costs and complexity for practical applications. The PI will recruit students from underrepresented groups to work on the project, and also carry out educational outreach activities to stimulate high school kids’ interests in power systems. Intellectual Merit: First, the proposed work explores application of nonlinear optimal estimation theory for online determination of transmission line parameters. The proposed algorithms exploit PMU measurements to take full advantage of increasing deployment of PMUs in power systems. The methods could identify possible synchronization errors and bad voltage and current measurements, and thus greatly enhance estimation accuracy. Second, the proposed work may discover practical methods for estimating line parameters considering effects of multiple climate zones. Third, the proposed methods may be applicable to transposed and untransposed lines, single and double-circuit lines, and seriescompensated and non-compensated lines. Fourth, the proposed research will investigate the feasibility of employing estimated line resistance to determine the line temperature and line sag that may be harnessed as inputs for dynamic line thermal rating. The distinctive feature is that only PMU measurements are needed and no additional sensors like tension and weather sensors are required. Fifth, the proposed research will develop an optimal PMU placement scheme that minimizes the number of PMU installations or monitoring costs while providing sufficient measurements for estimating line parameters, temperature and sag of all concerned lines. Broader Impacts: First, the proposed methods may greatly improve the estimation accuracy of transmission line parameters and thus enhance the precision of analysis results of various power system programs and applications such as adaptive relaying system, wide-area monitoring, protection and control, dynamic line thermal rating, power flow, power angle stability analysis, etc. The idea of line temperature and sag estimation will significantly increase power transfer over transmission lines while ensuring operation within thermal limit. The project results may help realize a national smart grid. The increased efficiency and reliability brought about by the proposed research will contribute greatly to the welfare of the society. Second, the proposed research will provide guidance on optimal placement of PMUs for reduced costs, and increase the utilization and value of installed PMUs. Third, the project results will be utilized in the classroom to enrich the curriculum. The underrepresented students, especially women, African Americans and those from Appalachia will be encouraged and recruited to work on the project to give them more opportunities and increase their confidence in pursuing a bachelor, master or doctoral degree. Fourth, the project results will be promptly and broadly disseminated through technical publications, conference presentations, and seminars held at University of Kentucky and Kentucky Utilities.