More and more system operators are interested in calculating transfer capability in real-time using real-time power flow models generated from the Energy Management System (EMS). However, compared to off-line study models, EMS models usually cover only a limited portion of the interconnected system. In most situations, it is not practical to extend the EMS model to capture the impact of the external systems and therefore using an equivalent network becomes necessary. The development of equivalent circuits to represent external areas was a topic discussed over the last 50 years. Almost all of these methods require impedance information about the external area to develop the equivalent circuit. Unfortunately utilities do not have the external impedance information in the real-time. Therefore, normal industry practice is to use off-line studies to develop an equivalent circuit and use that circuit in the real-time operation without any validation. This can result in errors in the security assessment. Therefore, power industry need a method to develop or validate an equivalent circuit based on the available real-time information. This thesis work is focussed on meeting that industry need. The work on this thesis presents two new methods that can be used to generate an equivalent circuit based on the boundary conditions. This method involves calculating equivalent impedance between two areas based on the boundary stations voltages, voltage angles and power leaving the boundary stations into external areas. This thesis uses power system simulation between two areas to change the system condition to obtain different boundary bus voltages, voltage angles and power injections to generate necessary data. Regression analysis and least square method is then used to generate the equivalent circuit using these data. It is expected that system changes will provide necessary information in the real-time to generate the equivalent circuit. The proposed methodology is validated with modified three area 300 bus system as well as using Manitoba Hydro’s system. Contingency analysis, transfer level calcula-tion and PV curves analysis is used to validate the proposed method. Simulation results show that the proposed method produces adequate accuracy in comparison with detailed off-line system models. The main advantage of the proposed method as compared to other existing meth-ods such as Ward and REI is that the proposed method does not require external imped-ance information to generate the equivalent circuit. The ability to generate reasonably good equivalent circuit only using available boundary information will help utilities to generate or validate the equivalent circuit based on the current system conditions, which will intern help improve the accuracy of the security assessment / February 2017

Distance relays due to their selectivity and operating speed are used in HV/EHV line protection. The dynamic nature of Mho characteristic, which happens to be most primitive technique in line protection implemented with distance relaying, is built by using the measurement of local voltage and current signals. These signals have been influenced substantially by fault resistance and the source impedance feeding the line. In case of different generation sources, the source impedance and fault characteristic also change accordingly. Environmental benefit of wind turbine technology is making it a potential source of energy. These wind turbine-generating units (WTGU) use rugged induction/synchronous machines along with power electronics converters as controlling equipment. This gives a new challenge to distance relays, as the fault current contribution of these sources depends on the converter operational principle. In this thesis a typical wind farm of Indian systems are modeled in an IN-HOUSE tool developed as part of fault analysis on wind farm system. Directly connected and front-end converter based wind turbines with their interconnections are modeled in this simulation tool. Fault voltage and current waveforms are obtained for all types of wind turbine-generating units with both radial and LILO (Loop in Loop out) connection. PSCAD based modeling has been done for DFIG type of wind turbines. The fault waveforms are generated to evaluate relay performance. Five case studies having both Radial and Loop in Loop out (LILO) connection of wind farms are simulated. These case studies generate approximately 20000 cases, which are analyzed for distance relay performance studies. In addition, the analysis is further verified on relay hardware having three characteristics, namely Self Polarized Mho (SPM), Quadrature Polarized Mho (QPM) and Quadrilateral (QUAD) characteristics. The detailed studies are carried out in this thesis to ensure and suggest the system operators with appropriate relay characteristics to be used for transmission line protection in the case of wind farms interconnected to Grid. Based on the studies carried out in the thesis, LILO connection has no impact on distance relay characteristic. In radially connected wind farms, grid side relay will operate reliably for all types of faults. It has been recommended in the thesis that wind farm side distance relay characteristics should be adjusted based on the types of wind turbines (Type-1, Type-2, Type-3 and Type-4). Based on the investigations carried out in the thesis, voltage based phase selector has been recommended for Type-4 WTGU based wind farms.