Resultsby applying regression analysis methods
Coimbatore Institute of Technology, Coimbatore, India-641014
raviprasath4291@gmail.com and devaki@cit.edu.in
Power quality affected by many factors such as Harmonics, sag, swell, noise, short and long interruptions, voltage unbalance, etc. But harmonics take important role to reduce the power quality.
“Harmonics are voltage or current with frequencies that are integer multiple of the fundamental frequency” being 50 Hz. If the fundamental frequency is 50 Hz, The second harmonic in 100 Hz, The third harmonic is 150 Hz, and so on. Harmonic frequencies from 3rd to 25th are the most common range of frequencies measured from electrical distribution systems.In modern test equipment today harmonics can be measured up to the 63rd harmonic. These harmonics causes (i) overheating (or) derating on transformer , (ii)overheating of wiring, (iii)Damaging of capacitor of capacitor banks, (iv)resonance, (v)distorted supply voltage, (v)malfunction of electronic equipment, (vi)communication interference [6,7].
Figure1. The experimental setup illustration
Experimental design
The experiments were performed according to the Box-Behnken design which is a kind of response surface methodology. It is well known that response surface methodology, or RSM, is a collection of mathematical and statistical techniques useful for the modeling and analysis of problems in which a response of interest is influenced by several variables and the objective is to optimize this response. It is an empirical modelization technique devoted to the evaluation of the relationship of a set of controlled experimental factors and observed results. To analyze a process mutually with a response, Y which depends on the input factors X1, X2,…, Xn, the correlation between the response and the input process parameters are described as
Table 2. The levels of variables choosen for trials
| Level of variables | Number of variables | ||||
| Variable | Motor | CFL | Tube light | ||
| -1 | 0 | 0 | 0 | ||
| 0 | 1 | 1 | 1 | ||
| +1 | 2 | 2 | 2 | ||
Mathematical modeling:
The quality of the fit of the polynomial model equation was expressed by the coefficient of determination. harmonic currents are chosen as dependent variable is being the THD produced by the single phase loads. For the evaluation of results, a statistical program was used.
Table 3. Box-behnken design for the three independent variables.
+1.45000×A×B+4.6250×A×C+6.4750×B×C
+3.4667×AA+2.3667×BB+7.9917×CC (3)
Figure 4. surface plot for the effects of the number of motor and tube light
Future work
Detuned capacitor
5. O. BaSudan, Y.G. Hegazy, “Probabilistic modeling of distribution system loads for harmonic studies”, IEEE, Vol. 3, pp. 1778-1781, 2001
6. R. Lamedica, C. Sorbillo, A. Prudenzi, “The continuous harmonic monitoring of single-phase electronic appliances: desktop PC and printers”, IEEE, Vol. 2, pp. 697-702, 2000