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Electric power grids are critical infrastructure for delivering energy from generation stations to load centers. To maximize utilization of assets, it is desirable to increase the power transferred over transmission systems. Reliable protection of transmission systems is essential for safeguarding the integrity and reliability of the power grid. Distance protection is the most widely used scheme for protecting transmission lines. Most existing protection systems use local measurements to make a decision while pilot protection is used in some circumstances. Distance protection may fail under stressed operating conditions, which could lead to cascading faults. This paper proposes a system integrity protection scheme by utilizing wide area measurements. The scheme partitions the system into subnetworks or protection zones and employs current measurements to derive a fault identification vector indicating the faulted zone. Then the fault location is pinpointed based on wide area measurements and network data. The proposed method is able to deal with multiple, simultaneous faults, and is applicable to both transposed and untransposed lines. Evaluation studies based on simulation studies are presented.

With the rapid development of the Chinese electric power industry, the working load of staff members in some provincial power dispatching centers has increased tremendously and may cause potential threats to the secure operation of power systems. The working load can be reduced by transferring the dispatching rights of some equipment and power lines to the lower-level local dispatching centers, but the security of the power system will a major concern. The suitability of the dispatching right devolution for some parts of a power system depends mainly on the network structure and criticality of the system. In this work, a few indices are first developed to reflect the power network structure, and then a new method for the comprehensive assessment of the power network structure is presented through the combined use of the fuzzy comprehensive evaluation and the entropy weight decision-making method. The fuzzy set approach is employed to identify the membership degree of each index to various evaluation results, whereas the entropy weight method is used to acquire the sets of weighting factors. This method represents a unified one of the quantitative results obtained from the power structure data and the qualitative results based on the judgment of domain experts. Finally, practical examples are served for demonstrating the developed approach.

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