Assignment Presentation -2 Wavelets and Applications

Assignment Presentation -2

WAVELETS AND APPLICATIONSTopic: Classification of Power System Faults using Wavelet Transform

bySevandhi P(14MR10)1Outline Introduction Need for Fault Analysis Objective Fault Classification Fourier to Wavelet Analysis DWT- MRA Identification of Fault type Identification of Fault location2Need for Fault Analysis Fault classification and location is very important in power system engineering in order to clear fault quickly and restore power supply as soon as possible with minimum interruption.

When faults occur in the power system, they usually provide significant changes in the system quantities (current, power, power factor, impedance, frequency and power or current direction).

3ObjectiveTo classify the faults according to the following parameters:1) Fault type2) Fault location4Effects of faults on power system Flow of excessive current Abnormal voltages Voltage elevation of system neutral Induce over voltages on neighbouring equipments Hazards to human, equipment and animals

5Fault Classification There are two main types of faults:1) symmetric faults- system remains balance- these faults are relatively rare, but are the easiest to analyze 2) Asymmetric faults: - system is no longer balanced- very common, but more difficult to analyze

6Types of Faults in Power SystemThe most common type of fault on a three phase system Single Line-to-Ground (LG) faults Line-to-Line (LL) faults Double Line-to-Ground (LLG) faults 3-Phase faults7% of OccurrenceFault% of OccurrenceLG70-80LLG10-17LL8-103-Phase2-38Fourier Analysis to Wavelet AnalysisFT: breaks down a signal into the sum of infinite series of sines and cosines of different frequenciesDisadv: Time information is lost

STFT: Under a fixed time window both t and f are examinedDisadv: time window is fixed and same for all f

9Wavelet Transform for Power system Analysis It applies windowing technique with variable sized regions Used in Power quality analysis and Power system protection

10DWT- MRA

11Wavelet MRA for fault signal

S=ak +dk+dk-1+.+d112Power system model Fault Type

Calculate, Sa, Sb, Sc, Sr, Qa, Qb, Qc and QrSa- sum of Nth level detailed coeff of line current IaSb- sum of Nth level detailed coeff of line current IbSc- sum of Nth level detailed coeff of line current IcSr- sum of Sa,Sb,ScQa- sum of Absolute values of Nth level detailed coeff of line current IaQb- sum of Absolute values of Nth level detailed coeff of line current IbQc- sum of Absolute values of Nth level detailed coeff of line current IcQr- sum of Qa,Qb,Qc

13Flowchart for Fault classification AlgorithmstartCalculate Q for normal conditions for all phases Qna,Qnb and Qnc Compute Qa,Qb,Qc for present conditionIs any (Qa/2Qna)>2 or(Qb/2Qnb)>2 or(Qc/2Qnc)>2 ?Is only one from(Qa/2Qna)>2 or (Qb/2Qnb)>2 or(Qc/2Qnc)>2 ?Are only 2 from(Qa/2Qna)>2 or(Qb/2Qnb)>2 or(Qc/2Qnc)>2 ?No faultLG faultLLL faultIs 0