Power Quality Innovation in Harmonic Filtering ABSTRACT: the Basic concept of harmonics, their generation, problems created by Power quality has become a them and HARMONIC great concern for both energy FILTERATION as a solution for suppliers and their customers this problem of Harmonics. because the increasing use of sensitive devices and the significant consequences of a poor power INTRODUCTION: quality for the competitiveness of the companies. “POWER 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 called Harmonics. The that is suitable to the operation of that harmonics are integer multiples of equipment and compatible with the fundamental currents/voltages. premise wiring system and other Substantial presence of harmonics 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 The widespread use of paper we are going to present you 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 switching 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 with a temporary 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 originated at the utility side or at the customer site. MAIN POWER QUALITY VOLTAGE VARITIONS AND DISTRUBENCES: FLUCTUATIUONS:- Voltage variations are variations in the rms value or the peak value with Power quality usually involves amplitude of less than 10% of the characterising low frequency nominal voltage. Voltage variations are conducted electromagnetic a series of voltage changes which are disturbances which can be ranked in characterised by the frequency of different categories. variation and the magnitude. Voltage variations are caused by a VOLTAGE SAG:- slow variation of loads Voltage sag is a sudden reduction (between 10% and 90%) of 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. (AC/DC conversion with frequencies that are integer using SCRs), static frequency multiples of the converters, static inverters like: - Static Power converters (AC – DC conversion using SCRs) - Static rectifiers - Static frequency converter - Static uninterrupted power fundamental power frequency. The supplies fundamental frequency itself is called - Static induction regulators. as the first Harmonic. The second i) Variable impedance loads, Harmonic as frequency twice that of using electric arcs, are the fundamental, the third Harmonic furnaces, welding units, has frequency thrice that of the Fluorescent tubes, fundamental and so on. For example – discharge lamps, light if the fundamental frequency is 50Hz control, brightness etc., then the second Harmonic is 100 Hz, ii) Loads using strong the third Harmonic is 150Hz etc. magnetizing currents, saturated Transformers, Generation of Harmonics:- inductance, furnaces, Harmonics are created by non-linear reactors etc., loads that draw currents abrupt pulses rather than in a smooth sinusoidal manner. These pulses cause distorted Office automation equipment like AC Filters: These are shunt connected computers, UPS, printers and fax AC harmonic filters. They are machine etc., connected between AC busbars and PROBLEMS DUE TO LOW earth. They offer low impedance to POWER QUALITY: harmonic frequencies and high Damaging of computer 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: AC shunt filters serve dual purpose 1. Use of DC smoothing reactor. on AC side: 2. Use of DC harmonic filters. 1. They divert harmonics to earth 3. Use of AC harmonic filters. and reduce the harmonic DC Smoothing Reactor: This is oil contents in main AC network. cooled, oil insulated reactor having 2. They provide shunt high inductance (0.35H to 1H).It is compensation required on AC connected in series on the DC side of side for satisfactory converter the converter. It smoothen the ripple in operations. the DC current. The DC reactor also helps in reducing the rate of rise of CLASSIFICATIONS OF AC current surges appearing on the DC SHUNT FILTERS: - side of the converter due to sudden Tuned AC shunt filters are used for changes in DC power flow due to suppressing lower order characteristic faults or load change. 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 of the above characteristic filter consists of a RLC series frequency or each branch double tuned circuit in series with another th th th for two frequencies eg. 5 /7 , 11 /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 frequencies (One a) A Single frequency tuned given by CLL2C2 & other by Shunt filters is a single RLC CR3 L3). series circuit 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. At resonant b) A Double frequency tuned frequencies, the circuit of the shunt filters has two resonant double tuned filter is th th th frequencies eg. 5 / 7 , 11 / equivalent to two parallel th rd 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. These severe and complex electrical filters are also called as challenge for the electrical industry. Damped Filters. So by designing and giving complete solutions in the form of detuned and DC Harmonic Filters tuned harmonic filter systems, Active DC filters are designed to filters and other protection systems for reduce DC harmonics to minimize the industrial installation that can ensure telephone interference in voice the trouble free operation of electrical 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.
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