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A NEW TECHNIQUE & FAST ALGORITHM IN CLASSIFYING TRANSMISSION LINE FAULTS USING WAVELET TRANSFORMS
ABSTRACT
Choice of rating, setting, and co-ordination of protective devices is very vital for improving the powerquality in power systems. This necessitates detection and classification of the faults quickly and accurately.In this paper Wavelet Transforms have been used to obtain the detailed and approximate coefficients of thefault signal. An algorithm is developed based on the histogram representation of these detailed andapproximate coefficients to classify the faults. The effectiveness of this new method is compared with thatof the fuzzy logic.
1. INTRODUCTION
Protecting transmission lines is one importanttask to safe guard electrical power system. Faultson transmission lines should be detected andclassified accurately for reliable operation ofpower system. Firstly such analysis facilitatesassessment of fault event and enables protectiveaction.. Secondly restoration measures can beunder taken soon after the fault. If we could notable to detect and classify the faults accurately thatmay lead to low power quality and can causeserious problems such as short life time,malfunctions, instabilities, interruptions of powersystems etc.Existing methods for detection andclassification of power disturbances are laborioussince they are primarily based on visualinspection of waveforms. More over most of theexisting methods are based on deterministicmethods. The deterministic methods do not havethe ability to adaptdynamically to the system operating conditionsand makes correct decisions if the signals areuncertain.The solution to over come the abovedifficulty can be Wavelet Transforms whichimplements multi resolution analysis. In this paperan algorithm is developed based on Histogramrepresentation of detailed and approximatecoefficients. The algorithm is fast in classifyingthe faults as compared to that of Fuzzy logic.Using MATLAB most commonlyoccurring faults (l-g, l-l-g, l-l-l-g, l-l) are initiallysimulated and they have been detected andclassified with new technique and fast algorithmand compared the effectiveness of this newtechnique with Fuzzy logic..
2. CLASSIFICATION USING FUZZY LOGIC
Most of the protection schemes that havebeen developed are based on deterministicmethods such as representing the transmissionlines either with first order (or) with second orderdifferential equations and traveling wavetechniques. Adaptability of these methods forsystem condition is major concern. Theoriesdeveloped in the field of digital relaying assumethat correct relay operations can be determined bymeans of deterministic computations on a welldefined model of the system to be protected.