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Power Quality Innovation in Harmonic Filtering ABSTRACT: the Basic concept of harmonics, their generation, problems created by great Power quality has become a them concern FILTERATION as a solution for suppliers because for and the both their energy customers increasing use and HARMONIC this problem of Harmonics. of sensitive devices and the significant consequences of a poor power INTRODUCTION: quality for the competitiveness of the “POWER companies. QUALITY” is The increasing developments defined as “the concept of powering need increasing use of electricity. and grounding electronic equipment in While meeting this power demand, a manner that is suitable to the there causes a pollution in electrical operation of the equipment ina manner system The that is suitable to the operation of that harmonics are integer multiples of equipment and compatible with the fundamental premise wiring system called Harmonics. currents/voltages. Substantial presence of harmonics and other connected equipment. results in excessive overheating of the equipments and other problems. power quality has become a strategic Harmonics are created by non linear issue for the following reasons: loads that draw current in abrupt The economic necessity for pulses rather than in a smooth. businesses to increase their Different problems due to harmonics competitiveness. have different solutions. In this paper we are going to present you The widespread use of equipment which is sensitive to voltage disturbances and /or the voltage magnitude at a point in the generates disturbances itself. electric The deregulation of the System and lasting from 0.5 cycles to electricity market. few seconds. Either In this context, it is essential for operations or any type of faults as well the utility and the customers to prevent as fault clearing process can cause a and detect power quality problems and voltage dip. Switching like those to have solutions available to fix them. associated The power quality correction and disconnection of the supply or flow of harmonic filtering system give solution heavy currents associated with the to solve the problems of harmonic starting of large motor loads is the disturbances and voltage fluctuations. most common. These events maybe with a switching temporary originated at the utility side or at the customer site. MAIN POWER QUALITY VOLTAGE VARITIONS AND FLUCTUATIUONS:- DISTRUBENCES: Voltage variations are variations in the Power quality characterising usually low conducted involves frequency electromagnetic disturbances which can be ranked in rms value or the peak value with amplitude of less than 10% of the nominal voltage. Voltage variations are a series of voltage changes which are characterised by the frequency of different categories. variation and the magnitude. Voltage variations are caused by a VOLTAGE SAG:Voltage sag is a sudden reduction (between 10% and 90%) of slow variation of loads current wave shapes, which in turn cause harmonic currents to flow, back into other parts of the power system. Consumers Generating Harmonics: Harmonics are not generated by connected to the network and mainly power generators but are produced by due to rapidly varying industrial loads Non-linear loads as under: such as welding machines. Loads that make use of semi conductor devices HARMONICS:- like transistor, thyristor i.e., static Harmonics are currents or voltages rectifiers. with frequencies that are integer using multiples of the converters, static inverters like: - (AC/DC conversion SCRs), static frequency Static Power converters (AC – DC conversion using SCRs) - Static rectifiers - Static frequency converter - Static power supplies fundamental power frequency. The fundamental frequency itself is called - as the first Harmonic. i) The second uninterrupted Static induction regulators. Variable impedance loads, Harmonic as frequency twice that of using the fundamental, the third Harmonic furnaces, has frequency thrice that of the Fluorescent fundamental and so on. For example – discharge if the fundamental frequency is 50Hz control, brightness etc., then the second Harmonic is 100 Hz, the third Harmonic is 150Hz etc. ii) electric Loads welding magnetizing inductance, Harmonics are created by non-linear reactors etc., manner. These pulses cause distorted units, tubes, using Generation of Harmonics:- rather than in a smooth sinusoidal are lamps, saturated loads that draw currents abrupt pulses arcs, light strong currents, Transformers, furnaces, Office automation equipment like AC Filters: These are shunt connected computers, UPS, printers and fax AC machine etc., connected between AC busbars and PROBLEMS DUE TO LOW Damaging of computer filters. They are earth. They offer low impedance to harmonic POWER QUALITY: harmonic frequencies and high impedance to power frequency. Thus, hardware and memory. harmonic frequencies are passed to Motors fail to start due to low earth and are eliminated from the AC voltages network. Setting and resetting of electronic equipments will be out of control . Industrial and domestic loads will get damaged. Solution to Harmonic Distortion: Harmonic Filtration: Harmonics in AC & DC waveforms are minimized by following means: 1. Use of DC smoothing reactor. 2. Use of DC harmonic filters. 3. Use of AC harmonic filters. DC Smoothing Reactor: This is oil cooled, oil insulated reactor having high inductance (0.35H to 1H).It is connected in series on the DC side of the converter. It smoothen the ripple in the DC current. The DC reactor also AC shunt filters serve dual purpose on AC side: 1. They divert harmonics to earth and reduce the harmonic contents in main AC network. 2. They provide shunt compensation required on AC side for satisfactory converter operations. helps in reducing the rate of rise of current surges appearing on the DC side of the converter due to sudden changes in DC power flow due to faults or load change. CLASSIFICATIONS OF AC SHUNT FILTERS: Tuned AC shunt filters are used for suppressing lower order characteristic harmonics eg. Separate tuned branches for 5th, 7th, 11th, 13th harmonics. These branches may be either single tuned for of a double tuned AC shunt each characteristic filter consists of a RLC series frequency or each branch double tuned circuit in series with another for two frequencies eg. 5th/7th, 11th/13th, L2, C2, & R3, L3 parallel circuit. 23rd/25th, 3rd/36th etc., The values are selected such Tuned AC shunt filters are classified that the total filter has two into two types. resonant of the above a) A Single frequency tuned Shunt filters is a single RLC series circuit frequencies (One given by CLL2C2 & other by CR3 L3). connected between a phase and earth. The filter is tuned to one particular characteristic harmonic frequency. Separate branches are necessary for each lower characteristic harmonic frequency. The filter is tuned to the resonates frequency equal to the corresponding characteristic harmonic order. 1) High pass filter branches are arranged to suppress harmonics of higher order say 24th & above. With High pass AC shunt harmonic filter connected near AC Bus bars, all the higher harmonics are diverted to earth and are not allowed to proceed to the AC Network. b) A Double frequency tuned shunt filters has two resonant th th rd resonant frequencies, the circuit of the double tuned filter is th frequencies eg. 5 / 7 , 11 / th At equivalent to two parallel th 13 , 3 /36 . A typical circuit single tuned branches. A double frequency tuned filter Harmonic currents & voltage has lowest impedance at two distortion are becoming the most resonant frequencies. severe filters are also These called as Damped Filters. and complex electrical challenge for the electrical industry. So by designing and giving complete solutions in the form of detuned and tuned harmonic filter systems, Active DC Harmonic Filters DC filters are designed to filters and other protection systems for reduce DC harmonics to minimize the industrial installation that can ensure telephone the trouble free operation of electrical interference in voice frequency range (100Hz to 5 KHz). In installation for industries. addition to the telephone interference By defining and implementing these criterion, the DC filter is designed with solutions users will be provided with interior of avoiding the resonance the right quality of power supply for between DC filters & DC line at lower their requirements . order harmonics. CONCLUSION: Power quality has become a strategic issue for consumers. In this present economic context, the consequences of electrical disturbances become more and more serious.