Informatics Publishing Limited

K. Prakasam ¹, D. Prabhavathi ¹, M. Surya Kalavathi ², B. Raveendranath Reddy ²

Affiliations
1 Siddartha Institute of Engineering and technology, Ibrahimpatnam, Hyderabad, Andhra Pradesh, IN
2 Jawaharlal Nehru Technological University, Kukatpally, Hyderabad, Andhra Pradesh, IN

Abstract

In order to determine the rate-of-rise of Very Fast Transient Overvoltag (VFTO) in a 800 kV GIS, simulations are carried out using EMTP-RV. Hence, it is necessary to estimate the magnitudes and the rate-of-rise of VFTO generated during switching operations for insulation coordination of GIS components.Gas insulated switchgear (GIS) has been in operation since last five decades due to its excellence in operation, high reliability and low maintenance. However, some of the problems like VFTO (very fast transient over voltages) are still in concern and need to be analyzed properly for insulation coordination, especially, in the case of EHV & UHV substations.. The simulations will be carried with the assumption that the enclosure is perfectly earthed. Effect of GIS earthing on TEV (Transient Enclosure Voltages) has been area of interest. To simulate TEV accurately, the modelling should present exact replication for the behavior of the enclosure surface of the GIS sections for all conditions which can cause initiation of VFTO & in turn, TEV in GIS. In this work, the GIS is modeled by a new approach to analyze the VFTO’s across different equipment and the simulation is been carried out by using MATLAB simulink. Very Fast Transients (VFT) originate mainly from disconnector switching operations in Gas Insulated Substations (GIS). Each component of the GIS is modeled by distributed line model and lumped model based on equivalent circuits.Also, the analysis of travelling wave using a lattice diagram is conducted to verify the simulation results.

Keywords

TEV, GIS, MATLAB, VFTO, EHV & UHV Sub stations.

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D. Prabhavathi ¹, K. Prakasam ¹, M. Surya Kalavathi ², B. Raveendranath Reddy ²

Affiliations
1 Siddartha Institute of Engineering and Technology, Ibrahimpatnam, Hyderabad, Andhra Pradesh, IN
2 Jawaharlal Nehru Technological University, Kukatpally, Hyderabad, Andhra Pradesh, IN

Abstract

Protecting transmission lines is one important task to safeguard electric power systems. The transient fault signal on transmission lines need to be detected, classified and located accurately and cleared as fast as possible. This research present an application of a discrete wavelet transforms (DWT) for fault diagnosis in underground cable system. Fault simulations are carried out using ATP/EMTP program, with a frequency-dependent transmission line model. Post-fault current signals are used in the analysis. The TS90 is the most advanced TDR fault locator based on Digital technology that provides distance to fault on cables. The mother wavelet daubechies4 (db4) is employed to decompose, high frequency component from the current fault signals. The time of positive sequence in first scale for detecting fault was used an input for travelling wave in order to identifying fault location. The comparisons of the coefficients DWT have been performed in order to classify fault types. The coefficients detail (phase A, B, C and zero sequence of post fault current signals) of DWT at the first peak time that positive sequence current can detect fault, are performed as comparison indicator. The results are shown that the wavelet transform is a powerful tool and gives satisfactory results. SIMply the best for locating underground cable faults Errors in fault location obtained from proposed technique are 0.4 km. In addition, the proposed algorithm can indicate fault types with the accuracy higher than 90%.Fault location on distribution systems has become an important issue due to the negative impact of a no continue and reliable service on distributor. There are many techniques and strategies proposed for this problem, however, it isn’t clear which one is the best. In that use transient state analysis to locate shortcircuit faults with low fault resistance in radial systems. The main conclusion is that, due to the commitment with the precision of the techniques, a combination of some strategies is needed for a real system implementation.

Keywords

Fault location, SIM, db4, Cable Thumping,TS 90, Transients Analysis, Wavelet Transform.

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G. Srinivasulu ¹, B. Subramanyam ², M. Surya Kalavathi ³

Affiliations
1 Associate Professor, Department of EEE, NEC, Nellore - AP, 524004, IN
2 Professor, Department of EEE, PBRVITS, Kavali - AP,524201, IN
3 Professor, Department of EEE, JNTUH, Hyderabad - TS, 500085, IN

Abstract

An electric power system plays a crucial role in the economic and social development of a country. Economic growth in India has spurred the need for more power and hence the infrastructure to transport the power. Sufficient transmission capacity is very essential in any long-term planning for improving the availability and supply of power. So Transmission Expansion Planning (TEP) is integral to the development of a stable and reliable power infrastructure. TEP infuture is a very complex task which needs a coordinated and analytical analysis of various scenarios and contingencies. In this work we have implemented a scheme for TEP which factors load growth and considers N-1 contingency. Both economics and technical considerations are considered in the appraisal of the most desirable transmission network. A multi objective optimization approach is suggested and the optimization of the expansion plan is done with the help of Backward Search (BS), Forward Search (FS), Hybrid Search (HS) and Genetic Algorithm (GA). The TEP is prepared for a 6 Bus-Roy Billinton Test System (RBTS). Transmission Planning Index (TPI) is introduced to provide a clear indication to the planner about the choice of the plan. The plans suggested by different optimization algorithms are compared in terms of performance measures and reliability indices.

Keywords

Transmission Expansion Planning (TEP), Backward search (BS), Forward Search (FS), Hybrid Search (HS), Genetic Algorithm (GA), N-1 Contingency, Reliability indices and Roy Billinton Test system (RBTS).

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