S.A. Gafoor

Bio: S.A. Gafoor is an academic researcher from Bapatla Engineering College. The author has contributed to research in topics: Current transformer & Fault (power engineering). The author has an hindex of 1, co-authored 1 publications receiving 9 citations.

A transient current based bus zone protection scheme using wavelet transform

Abstract: This paper deals with application of wavelet transform to detect busbar faults and to provide backup protection for external faults. The detail coefficients of a source CT current, feeder current and zone-2 current are obtained over a narrow moving window. The fault indexes of differential and source CT current signals obtained are compared with their respective threshold values to detect the internal faults. In the event of feeder and zone-2 faults, the d-coefficients of differential current have a time shift compared to that of source current. Further the external fault is located by comparing the polarities of peak d-coefficient of source, feeder and zone-2 currents. The scheme is tested for different types of external and internal faults with variation in incidence angles and fault impedance. The proposed scheme detects internal faults and locates external faults even in the presence of current transformer saturation.

Numerical busbar differential protection using generalised alpha plane

Abstract: This study presents a digital differential busbar protection scheme based on generalised alpha plane approach which combines the benefits of percentage differential approach and two-restrain alpha plane approach. The proposed scheme utilises one cycle current transformer (CT) secondary current signals of all the bays connected to the busbar to map the operating points on a complex alpha plane. The proposed scheme has been evaluated by modelling an existing 400 kV Indian power generating station in PSCAD/EMTDC software package. The performance of the proposed scheme has been evaluated on large numbers of cases with wide variation in system and fault parameters. In order to verify authenticity of the proposed scheme, a laboratory prototype of the proposed busbar protection scheme has been developed. From the developed prototype, CT secondary current signals are captured during internal faults and external fault with CT saturation condition. Comparison between the simulation and prototype results clearly shows the effectiveness of the proposed scheme in terms of higher sensitivity during internal faults and better stability in case of external faults. The proposed protection scheme has a high response speed (around 5 ms) and hence can be considered on par with modern busbar protection schemes.

Partial operating current characteristics to discriminate internal and external faults of differential protection zones during CT saturation

Abstract: To protect transformers, transmission lines and busbar systems, low impedance current differential protection schemes based on percentage restraint characteristics are widely used in power systems. The main application issue of these schemes is mis-operation due to current transformer (CT) saturation during close-in external faults. A comprehensive fault discrimination algorithm is highly required for current differential protection schemes to overcome the CT saturation issue. The purpose of this study is to introduce a methodology based on partial operating current (POC) characteristics which discriminate internal and external faults of differential protection zones. The study includes the mathematical model of POC characteristics, a fault discriminating algorithm using POC features, and bus differential protection zone results. The results documented encompasses various possible short-circuit (fault) scenarios and indicate the capability of the proposed algorithm in discriminating internal and external faults under CT saturation conditions.

Wavelet Transform Analysis to Applications in Electric Power Systems

Abstract: The wavelet transform has received great importance in the last years on the power system analysis because the multi-resolution analysis presents proprieties good for the transient signal analysis. This chapter presents a review on main application of wavelet transform in electric power systems. The study areas have been classified as power system protection, power quality disturbances, power system transient, partial discharge, load forecasting, faults detection, and power system measurement. The areas in which more works have been developed are the power quality and protections field, where both cover 51% of the articles analyzed.

Comparative analysis of fault discrimination algorithms on sensitivity to high impedance busbar faults

Abstract: Presently there is not one differential protection characteristic which is self-sufficient to detect all possible busbar faults accurately. Particularly, during close-in external fault, current transformer (CT) saturation creates high operating current which can cause mal-operation of differential relays. As a result, a fault discriminator is necessary to supervise the differential schemes to prevent undesired tripping operation. Most of the existing fault discrimination algorithms have been proven as an efficient external fault detector; however, they suffer from lack of sensitivity to high impedance internal faults. This paper presents a comparative analysis on sensitivity of three existing fault discrimination algorithms including Phase Angle Comparison Algorithm (PACA), Rate of Change of Differential Algorithm (ROCODA), and Alienation Coefficient Algorithm (ACA). Fault simulations were performed using a three-bus test system. The results documented in this paper show that the degree of sensitivity of ROCODA and ACA are similar and much higher than PACA. The comparative analysis presented in this paper can be employed as a useful guideline for selection of an appropriate protection scheme for busbar systems.

A Fault Zone Identification Scheme for Busbar Using Correlation Coefficients Analysis

Abstract: This paper proposes a new busbar protection scheme based on the analysis of correlation coefficients between the current waveforms of all lines connected to the busbar. The cross-correlation coefficients between current waveforms of each line in moving windows are calculated in a phase segregate manner with respect to a reference line. It's performance has been evaluated by modelling an existing 400-kV Indian substation in PSCAD/EMTDC software package. The proposed scheme is able to provide ultra-high-speed protection for the bus faults. It's stability has been tested against a wide range of external faults. It also solves the problem of CT saturation which is the biggest challenge in conventional low-impedance busbar differential protection schemes (87B).