Phasor Measurement Techniques.- Phasor Estimation of Nominal Frequency Inputs.- Phasor Estimation at Off-Nominal Frequency Inputs.- Frequency Estimation.- Phasor Measurement Units and Phasor Data Concentrators.- Transient Response of Phasor Measurement Units.- Phasor Measurement Applications.- State Estimation.- Control with Phasor Feedback.- Protection Systems with Phasor Inputs.- Electromechanical Wave Propagation.

Synchronized Phasor Measurements and Their Applications

An adaptive protection scheme for optimal coordination of overcurrent relays

Post-fault studies of recent major power failures around the world reveal that mal-operation and/or improper co-ordination of protection system were responsible to some extent. When a major power disturbance occurs, protection and control action are required to stop the power system degradation, restore the system to a normal state and minimise the impact of the disturbance. However, this has indicated the need for improving protection co-ordination by
additional post-fault and corrective studies using intelligent/knowledge-based systems. A process to obtain knowledge-base using support vector machines (SVMs) is presented for ready post-fault diagnosis purpose. SVMs are used as Intelligence tool to identify the faulted line that is emanating and finding the distance from the substation. Also, SVMs are compared with radial basis function neural networks in datasets corresponding to different fault on transmission system. Classification and regression accuracies are is reported for both strategies. The approach is particularly important for post-fault diagnosis of any mal-operation of relays following a disturbance in the neighbouring line connected to the same substation. This may help to improve the fault monitoring/diagnosis process, thus assuring secure operation of the power systems. To validate the proposed approach, results on IEEE 39-Bus New England system are presented for illustration purpose.

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Application of support vector machines for fault diagnosis in power transmission system

An adaptive approach in distance protection using an artificial neural network

The development of a new differential protection scheme for tapped transmission lines using wavelet transform is presented. At each relay locations, using the most suitable mother wavelet, the measured three line currents are decomposed up to third level. Thereafter, third-level approximation coefficients are reconstructed and used to derive the operating and restraining quantities. The proposed scheme has been tested extensively using the PSCAD/EMTDC software package with fault data, generated by modelling UKAI-KAKRAPAR 400 kV line of the Indian power system. The proposed scheme eliminates many of the problems encountered with tapped transmission lines such as high resistance faults, out feed current in case of internal and external faults, insufficient current for tripping and provides better discrimination between external and internal faults in case of loss of generation at one end. At the end, a comparative evaluation of the conventional current differential protection scheme with the proposed scheme is also presented. Dependability and security have been studied separately.

New differential protection scheme for tapped transmission line

The concept of adaptive relaying is explained. The reasons for choosing adaptive relaying are examined, and various applications are described. These include load effect, cold load pickup, end-of-line protection, transformer protection, and automatic reclosing. The tradeoff between dependability and security of protection is discussed. The ability of computer relays to monitor themselves and to report their condition to a central location is also discussed. >

A.G. Phadke

Papers

Adaptive relaying