Harmonic Analysis of Distribution System for Power Quality Improvement
Prof. Y.S.Choupare Dr. Rakesh Kataria
Principal, S.T.B.S. College of Diploma Engineering Professor, Humber College and Seneca College
Varachha Road. Surat. Gujarat. Canada
Abstract: voltage and current wavefoRMS are preferably ideal sinusoids. Nowadays attractiveness of electronics and other non- linear loads are increased which causes distortion in these wavefoRMS. The divergence of ideal sine wave can be characterized by harmonics components having a frequency that is a multiple of the fundamental frequency. Hence it is essential to measure the harmonic components to estimate their effect. The division of a variety of frequency components with respect to the fundamental frequency is carried out to measure Total Harmonic Distortion (THD) which is useful to intend suitable filters to eliminate the harmonics.
This paper presents the estimation of harmonic of different equipments in distribution system to improve power qualit. The 11 bus distribution system is taken as case study and harmonic distortion of different elements of this system is identifier using Electrical Transient Analyzer Program (ETAP) software.
Keywords: Harmonics, Total Harmonic Distortion, estimation of Harmonics, Power Quality Improvement (PQI)
I. INTRODUCTION
An electricity supply should usually illustrate a perfectly sinusoidal voltage signal at every customer location. However, for a number of reasons, utilities often find it rigid to preserve such enviable conditions. The deviation of the voltage and current wavefoRMS from sinusoidal is explained in teRMS of the waveform distortion, often expressed as harmonic distortion. In the earlier period, harmonics caused a lesser amount of a problem due to the traditional design of power equipment and to the ordinary use of delta-grounded wye connections in distribution transformers. The escalating use of nonlinear loads in industry is custody harmonic distortion in distribution networks on the rise. The most used nonlinear device, static power converter is widely used in industrial applications. A situation that has raised waveform distortion levels in distribution networks even further is the application of capacitor banks used in industrial plants for power factor correction and by power utilities for increasing voltage profile along distribution lines [1]. The stochastic harmonic distortion analysis is proposed to evaluate the voltage harmonic distortion of the network precisely to offer effective executive for the strategy of harmonic alleviation [2]. Harmonic distortion issues due to trend in industries to replace Motor Generator (MG) sets
including rectifier results in reactive power loss during removing of synchronous motor. Harmonic analysis of the new rectifier and the design of the harmonic filter to correct harmonics and support voltage is described briefly in [3].
To avoid possible failures in the loss of the harmonic filter banks during utility power disturbances, redesign of the harmonic filters and the application of surge protection is express by analytical approach [4].
Uncharacteristic converter current harmonics under normal and abnormal converter operation are confirmed. [5]. In [7], The failure, analysis, and successful repair of series tuned harmonic filter used in an electric arc furnace application is addressed. . At the present time attractiveness of electronic and other non-linear loads are increased which produced distortion in wavefoRMS of electrical parameters. [10].
II. FUNDAMENTAL OF HARMONICS
An electrical system delivers power to loads by supplying current at the fundamental frequency. Only elementary frequency current can offer real power. Current delivered at harmonic frequencies is not able to deliver any real power to the load. Though currents of greater than one frequency is delivered, adding of the current values produce to a summed value that doesn't correctly represent the total effect of the multiple currents. Instead, a current is needed to add in a manner known as the RMS summation. RMS addition of currents equation is given by:
(1) So if systems flow 70Amp of fundamental current, produce 18Amp of 5th harmonic current, 14Amp of 7th harmonic current, and 11Amp of 11th harmonic current, the effective current would be RMS value of 74 Amp, neither the calculation sum of 113Amp. This 74Amp rate is correct rate to applicable in all power calculations. Same calculation is meaningful for harmonic voltages computation. To obtain the effective voltage for a system in which voltages of several frequencies are present.
Fig. 1 Current Measurement with Harmonics [12]
A. current measurement with harmonic
Computation of current carried by a nonlinear load is shown in Fig. 1. The RMS current contained fundamental and harmonics waveform. Value of current at each harmonic and RMS current are the same at each determining tip, system containing only fundamental current. The phrase distortion RMS is used to indicate the RMS value of harmonic current including fundamental keep out of the abridgment. The RMS current is principally the total effective load current.
The current total harmonic distortion (THD), which is the weighted or RMS assessment of all harmonics, approaches 100% for many of these devices. The expression for THD is as follows:
Where: THDI = current total harmonic distortion In = harmonic RMS current (in amps or %)
I1 = fundamental frequency RMS current (in amps or 100%) The harmonic substance and THD can be acquired for different levels of load for some devices. As example, a battery charger has a variable load characteristic and the harmonic content and THD diverging as a function of load. It is typically adequate to present the THD and % of individual harmonics at rated load.
At lower levels of load, the consequential percentages of individual harmonics and THD are generally compensated by the lower base current at that load. For example, with two loads having the same base current, one that produces 20%
THDI at 50% load is no inferior than one which produces 10%
THD at 100% load. They both generate the same distortion in
original and harmonics. Impedance increment causes harmonic current flow produce great harmonic voltage production. This is the contradictory direct influenced in impedance on the fundamental voltage same as fundamental voltage basis fundamental current flow, and harmonic current flow basis harmonic voltage.
From Fig. 2, it is seen that fundamental voltage is reduces from 480V at location 1 to 465V at location3, result of increasing in harmonic voltage produce RMS voltage with higher level at each evaluating location compare to fundamental voltage only.
Distortion RMS is the RMS value of the harmonic voltage with the basic of the summation, and it measurement from the source. THD can be calculated same equation (2).
Fig. 2 Voltage Measurement with Harmonics [12]
C. Effect of current and voltage distortion
Harmonic currents cause to raise I2Z losses in wiring and transformers. The transformer impedance is increasing with harmonic number; the impedance at the 5th harmonic is 5 times higher comparing to fundamental frequency. The 5th harmonic current is causes of 5 times higher as much heat as an AMP of primary current. In a system supplying phase-to-neutral connected loads, destructive effects are produced due to the harmonic currents using positive system capacity and dropping the importance supplied loads. Third harmonic currents cause a further destructive effect due to, additive in the neutral conductor. When a lot of computers, which are nonlinear loads, are coupled, the neutral current chiefly 3rd harmonic is higher to any of the phase currents. In the primary of the transformer, 3rd harmonic currents circulate [8].
Voltage distortion has little cause on job of nonlinear loads connected in either phase-phase or phase-neutral presented in )
2 .. (
1
2 2
7 2 5 2 3 1
2 2
I
I I
I I I
I
THDI n n
be overheated and perhaps stop to work. So 5th harmonic current from systems powering 3-phase loads is often main concern in industrial facilities must be removed.
III. CASE STUDY
A eleven bus distributed system [11] is presented in Fig.1.
There is a link to another network, modeled by a short circuit capacity of 1200 MVA. Detail data is given in Appendix 1.
Fig. 3 Eleven Bus Distribution System [11]
The System is also dividing in subpart as in following figures.
Fig. 4 Sub2a (Interlink Subsystem of Main System)
In Fig. 4, 500 KVA lump load is connected in Net1.
Fig. 5 Sub3 Net (Interlink Subsystem of Main System)
Fig. 6 MCC 3A (Interlink of Sub3 Net)
Fig. 7 Motor Composition (Interlink of (Sub3 Net)
Fig. 8 DC System (Interlink of Main System)
IV. RESULT AND DISCUSSION
The distortion due to harmonic in current at different equipment of this system is analyzed. The distortion of waveform at entire buses, cables and transformer are shown in Fig. 9, Fig. 10 and Fig.11 respectively (Refer Appendix – 3).
From Fig. 9, the wave form distortion at different buses is easily identified. The harmonic is not contained in fundamental waveform at main bus (34.5 kV). The low level of harmonic is presence at bus sub 3(4.16 kV), MCC1 (4.16 kV). The superiority of harmonic is shown in bus1 (0.48 kV) and bus 2 (0.48 kV). These two bus have DC system with converters and UPSs which are the main causes of producing the harmonics.
Same as buses, at the cable 2, the fundamental waveform does not contains the harmonic but, the waveform at cable 14 (a part of DC system) has harmonic with higher level of magnitude.
There is no harmonics effect at transformation and but at there is significant effect and at XFR3, higher level of harmonics is presence. From these figures, it is concluded that Harmonic effect is more nearer to nonlinear loads and power electronics devices. The detail harmonic distortion report is presented in Appendix 2, which is carried out using ETAP 12.5 software.
V. CONCLUSION
This paper presents the harmonics effect in distribution system with nonlinear loads and power electronics devices. The THD estimation can be calculated using detail examination of harmonic effect at various equipments of system i.e.
transformer, buses and cables. In the paper, the significant level of THD is presents in equipments near nonlinear loads and converting transformer. From detail report presented in Appendix 2, it is conclude that THD is increase due to nonlinear loads and converting devices. The presences of harmonics in waveform produce hazardous effects in electrical equipments. To overcome distortion in fundamental waveform, appropriate filter should be design.
REFERENCES
[1] Francisco C. De La Rosa, Harmonics and power systems. Taylor &
Francis Group, London, New York, 2006.
[2] Chen, C-S and Chuang, H. -J and Shiau, H. M., “Stochastic harmonic analysis of mass rapid transit power systems with uncontrolled rectifiers,” IEEE Gen. Trans. Distr. Vol. 150, no. 2, pp. 224-232, Mar.
2003.
[3] Allenbaugh, M.L. and Dionise, T.J. and Natali, T.J., “Harmonic Analysis and Filter Bank Design for a New Rectifier for a Cold Roll Mill,” IEEE Trans. Ind. Appl., vol. 49, no. 3, pp. 1161-1170 May 2013.
[4] T.J. Dionise, V. Lorch, B. Brazil, "Power Quality Investigation of Back- to-Back Harmonic Filters for A High-Voltage Anode Foil Manufacturing Facility", IEEE Transactions on Industry Applications, March/April 2010, Vol 46, Issue 2, pp. 694-702.
[5] L. Tang and D. Mueller, "Analysis of DC Arc Furnace Operation and Flicker Caused by 187 Hz Voltage Distortion," Paper presented at the IEEE-PES 1993 Summer Meeting, Vancouver, B.C.
[6] "IEEE Standard 519-1992", IEEE Recommended Practice and Requirements for Harmonic Control in Electric Power Systems, 1992 [7] D. Carnovale , V. Lorch , T. Dionise and T. Gerstnecker "Electric arc
furnace harmonic filter failure, analysis and repair", Proc. AISE Conf., pp.4 -5 2002.
[8] A. Mansoor, W.M. Grady, A.H. Chowdhury and M. Samotij, “An Investigation of Harmonic Attenuation and Diversity Among Distributed Single-Phase Electric Loads”, IEEE Transactions on Power Delivery, Vol.10, No.11, Jan. 1995, pp. 467-73.
[9] Pileggi, D.J. et al, “The Effect of Modern Compact Fluorescent Lights on Voltage Distortion”, IEEE Trans on Power Del., vol. 8, no. 3, pp 1451-59, July 1993.
[10] Power Electronics, Mohan, Undeland and Robbins, John Wiley and Sons, 1995
[11] “ANSI Model”, User Manual, ETAP software 12.5 demo version.
APPENDIX -1
Cable Input Data
Bus Input Data
Transformer Data
Machine Input Data
APPENDIX –2 VIHD (Individual Harmonic Distortion) Report
VTHD (Total Harmonic Distortion) Report
APPENDIX –3
Fig. 9 Harmonic Distortion Analysis of Buses
Fig. 10 Harmonic Distortion Analysis of Cables
Fig. 11 Harmonic Distortion Analysis of Transformers
