Research On Power Grid Fault Diagnosis Based On Wide Area Measurement System

As the development strategy of "Strong Smart Grid" is being carried out; and at the same time the Ultra High Voltage Transmission and Large-scale Interconnected Power Grid come into formation, new challenges on the integration and stability of power grid have been under concern. New technologies, such as fast and accurate fault diagnosis and location are possible to be used to prevent the occurrence and expansion of blackouts. Besides, the Phasor Measurement Units (PMUs) based Wide Area Measurement Systems (WAMS) have been successfully implemented in power systems, which also provides a measurement and communication channel for power grid fault diagnosis. Under this situation, this thesis has studied the WAMS-based methods for power grid fault diagnosis. The main work of this thesis is stated as follows.Firstly, by comparison between WAMS the conventionally applied SCADA system, the potential of WAMS to be implemented in power system has been highlighted; and the feasibility and necessity of applying WAMS into power grid fault diagnosis has been concluded by analyzing the characteristics of current fault diagnosis methods.Secondly, the key work of this thesis--the power flow fingerprint based fault diagnosis method is proposed in order to overcome the current problems in fault diagnosis algorithms, for example, the uncertain mis-operation and loss-operation caused by the inaccurate fault information of switching signals, and the existing probability for switching signals to have errors. This diagnosis method only needs the electrical data of finger-print nodes, which decreases the requirement of information, and at the same time increases the real time characteristic and avoids much of the influence of the uncertainty of switching information to the results of fault diagnosis. Meanwhile, the thesis has proposed the optimal placement method by using the improved integer programming.Thirdly, PMUs are used as the measurement units to provide data from wide-area, and with high accuracy and updating rates, which is an improvement of the locally characterized faulty information from SCADA. Information Fusion Technology (IFT) is introduced to process the data from PMUs. In the decision level, by IFT the switching signals based fault diagnosis and electrical signals based diagnosis have been combined to improve the real time character and the ability to capture the identity of cascading failures.Fourthly, as the further study on fault diagnosis, in this thesis, a power grid fault location method which only needs the phasors of terminal voltages in one transmission line is proposed. A voltage phasor balancing standard is proposed as the decision criteria for fault location and the Traversal Searching method is used for searching the optimal decision of the fault location. The fault location method proposed here requires small amount of information and can at the same time avoid the impacts from current transformer saturation and Transition Resistance to the accuracy of fault location results.