| 摘要 |
A method for judging cause of power quality disturbances according to embodiments of the present invention may include: calculating S(τ, I0) through S-transform of a zero phase current IO obtained from single phase current of a three-phase power distribution line; acquiring harmonic components hk (2<=k<=N, N>=2) from a fundamental wave (h1) and a second harmonic (h2) and to an N^th harmonic (hN) on the basis of the S-transform result S(τ, I0) of the zero phase current IO; calculating average of harmonic value (AHV) from N harmonic components (hk) from the fundamental wave (h1) to the N^th harmonic (hN); and judging the cause of the disturbance as one of single-line-to-ground fault, operation of a transformer and unbalanced load or as one of capacitor switching or operation of a converter, according to the statistical characteristics of the AHV. [Reference numerals] (AA) START; (BB,EE,GG,II,KK) NO; (CC,DD,FF,HH,JJ) YES; (LL) END; (S11) Obtain zero phase current I_0 from phase current; (S12) Calculate S(τ,I_0) by S-transform of zero phase current I_0; (S13) Obtain harmonic components hk (2<=k<=N, N>=2) from fundamental wave (h1) and second harmonic (h2) to N^th harmonic (hN) on the basis of S-transform result S(τ, I0); (S14) Calculate average of harmonic value (AHV) from N harmonic components (h_k); (S15) Continuous sample difference >α?; (S16) AHV maximum value >β?; (S22) Operate transformer; (S24) Single-line-to-ground fault; (S25) unbalanced load; (S32) Operate converter; (S33) Capacitor switching |
