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Capacitor as power factor improvement it’s installation and location Anubhav Ranjan Tiwari M.Tech Scholar Lovely Professional University Punjab [email protected] 1. Abstract In this paper we are using a capacitor for improvement of power factor and it’s installation and location is presented. Improving the power factor means reducing the angle of lag between supply voltage and supply current. Capacitors installed near the loads in a plant are the most economical and efficient way of supplying these kilovars. Capacitors can be Install between the contactor and the overload relay, the upstream circuit breaker and the contactor and also Install at the main distribution bus. 2. Aditya Gaddam M.Tech Scholar Lovely Professional University Punjab [email protected] capacity, improve voltage and reduced value of your power losses. 3. How capacitor works Induction moters, moters transformers and there are so many electrical loads which require magnetizing current (kvar) as well as actual power (kw). So for obtaining the apparent power from the right angle triangle kva2 = kw2+kvar2. For reducing the value of kva which is required for the any load. It is important to shorten the line that shows the kvar. This is precisely what capacitor do . Introduction The measure of electrical efficiency is known as Power Factor. The motors and other inductive equipment in a plant needs two types of electric power. One type is working power, determined by the kilowatt (kW). Secondly, inductive equipment needs magnetizing power to produce the flux necessary for the operation of inductive devices. The unit which we are using for the measurement of magnetizing or reactive power is the kilovar (kVAR). The working power (kW) and reactive power (kVAR) combindly make up apparent power which is measured in kilovolt tamperes (kVA). Most of the AC power systems require both kW (kilowatts) and kVAR (kilovars). Capacitors are installed near the loads in a plant are the most economical and efficient way of supplying these kilovars. Low voltage capacitors are basically a high reliability maintenance-free device. On the spot delivery of magnetizing current provided by capacitors means that kilovars do not have to be sent all the way from the utility generator to you. This relieves both you and your utility of the cost of carrying this extra kilovar load. The utility charges you for this reactive power in the form of a direct, or indirect power factor penalty charge. In this way, you'll get system By supplying kvar at the load, the capacitor relieve the burden of carrying extra kvar. This makes the transmission/distribution system more efficient. And reducing cost for the utility and their consumers. Selection of kvar for three phase moter To select the required amount of kvar required to correct the power factor we should have three informations: Kw Existing power factor in percent. Desired power factor in percent. 5. 4. Installation recommendation Option - A Install directly at the single speed induction motor terminals (on the secondary of the overload relay). Advantages l Can be switched on or off with the motors, eliminating the need for separate switching devices or overcurrent protection. Also, only energized when the motor is running. Since kVAR is located where it is required, line losses and voltage drops are minimized; while system capacity is maximized. Disadvantages Installation costs are higher when a large number of individual motors need correction. l Overload relay settings must be changed to account for lower motor current draw. OPTION B – Install between the contactor and the overload relay. With this option the overload relay can be set for nameplate full load current of motor. Otherwise the same as Option A. OPTION C Install between the upstream circuit breaker and the contactor. Advantages Larger, more cost effective capacitor banks can be installed as they supply kVAR to several motors. This is recommended for jogging motors, multispeed motors and reversing applications. DISADVANTAGES: Since capacitors are not switched with the motors, overcorrection can occur if all motors are not running.* Since reactive current must be carried a greater distance, there are higher line losses and larger voltage drops. OPTION D - Install at the main distribution bus. ADVANTAGES: Lower installation cost, since you install fewer banks in large kVAR blocks. DISADVANTAGES: Overcorrection can occur under lightly loaded conditions. A separate disconnect switch and overcurrent protection is required. Power Factor Correction Capacitors on Reduced Voltage Motors and Multi-Speed Motors The following shows capacitor connections for typical starting circuits for reduced value of voltage and multi-speed motors. Variations in these circuits do exist. It is important that your circuit exactly matches the circuit shown here before applying capacitors. Failure to do so may result in damage to the motor. The main contacts. shown in the diagrams below as M1, M2, M3, reference the contacts that must be closed to start or run the motor. Capacitors should be connected on the motor side of the main contacts. h = calculated system harmonic kVAsc = short circuit power of the system kVAR = rating of the capacitor Harmonic values of 5, 7, 11, and 1 3 should be avoided as they correspond to the characteristic harmonics of non-linear loads. The harmonic value of 3 should also be avoided as it coincides with harmonics produced during transformer energization and/or operation of the transformer above rated voltage. 7. Conclusion in this paper we are using capacitor for power factor improvement by means of capacitor we are improving the power factor and it’s installation and location of the capacitor bank in the system is also presented. 8. 6. Consider harmonics when applying capacitor System harmonics is to be considered when we are applying power factor correction capacitors. Although capacitors do not generate harmonics, under following conditions they can amplify existing harmonics. Harmonics are generated when non-linear loads are applied to power systems. These non-linear loads include adjustable speed drives, programmable controllers, induction furnaces, computers, and uninterruptible power supplies. Capacitors can be used successfully with nonlinear loads when harmonic resonant conditions are avoided. To minimize the occurrence of harmonic resonance, the resonant harmonic of the system including the capacitor should be estimated. The resonant frequency can be calculated by: where References [1] R. C. Dugan, D. T. Rizy, "Electric Power System Harmonics," Design Guide, McGraw-Edison Power Systems – Division of Cooper Industries., September 1987. [2] J. R. Linders, "Electric Wave Distortions: Their Hidden Costs and Containment," IEEE Transactions on Industry Applications, vol. IA-15, No. 5, pp. 458471, Sept/Oct. 1979. [3] J. F. Hibbard, Michael Z. Lowenstein, "Meeting IEEE 519-1992 Harmonic Limits," TCI Power Quality Solutions. [4] IEEE Recommended Practice for Electric Power Distribution for Industrial Plants. IEEE Std. 1411993. The Institute of Electrical and Electronics Engineers, Inc. [5] J. de los Reyes, A. Llamas, "Armónicas de Sintonía y de Resonancia Paralelo," Memorias de la Reunión de Verano de Potencia 97 del IEEE, Acapulco, México, 1997. Manual, Vancouver, BC, Canada, 1997. [6] B. Mirzaeian Dehkordi, M. Moallem,S. J Rezazadeh, O. Amanifar,M. Keivanfard, N. Sayadi, L. Kermani,“Optimal Capacitor Placement and Sizing in Tabriz Electric Power Distribution System Using Loss Sensitivity Factors and Particle Swarm Optimization (PSO) ,” International Journal on Technical and Physical Problems of Engineering (IJTPE),ISSN 2077-3528, Issue 7, vol. 3, Number 2 , pp.54-59, June 2011. [7] Khin Trar Trar Soe, “ Design and Economics of Reactive Power Control in Distribution Substation, ” World Academy of Science, Engineering and Technology, 48-2008, pp 416-421.