EE587_HW - Harmonics in Power Systems Chapter 9 Issued May...

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Harmonics in Power Systems – Chapter 9 Issued May 2010 Confidentiality: The information contained in the report is the property of E. I DuPont de Nemours and Co. and is confidential and proprietary to DuPont. The information is being disclosed, in confidence, solely for the private, non-commercial, limited use of the individual or entity to which it is addressed, in connection with their dealings with DuPont. No other use is authorized. The information shall not be used or reproduced in any form or by any means, or stored in a database or retrieval system, without the prior written permission of DuPont. The access and use of any provided information shall be governed by the laws of the State of New York. By accepting the information and not promptly returning it to DuPont, the individual or entity to which it is addressed hereby agree to all the above conditions regarding DuPont supply of the information. Prepared by State University of New York at Buffalo Students: Daniel A Olusola
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9.7.9 Effect of system loading The level of load of a power system does not have a significant effect on system frequency response characteristics, except when the system is operating near the resonant frequencies. The resistive component of the load becomes very important as a damping factor at a system resonance. The resistance path (which offers lower impedance) is taken by harmonic currents when a parallel resonance condition exists. Therefore, higher loading levels on the system tend to lower impedance near a point of parallel resonance. Power system response at varying load levels is illustrated in Figure 9-10 for a system that has a parallel resonance point near the fifth harmonic. 9.8 Effects of harmonics The intent of this section is to provide a broad understanding of the types of problems that can develop when harmonics are present, and the system configurations and operating conditions that may set the stage for harmonic problems. The effects of harmonics can be divided into three general categories: a) Effects on the power system b) Effects on loads c) Effects on communication 9.8.1 Effect on power systems The most significant impact that harmonics have on power systems is that they can cause additional losses due to heating and can cause control and monitoring equipment to register improperly. With the advent of power electronics and proliferation of non-linear loads in industrial power applications, power harmonics and their effects on power quality are a topic of concern. The effects of single phase power harmonics and neutral conductors are often a source of concern. Harmonics play an important role in single phase applications if the neutral conductors are undersized; however single phase harmonics are associated with phase-to-neutral loads . Non-linear loads create harmonics by drawing current in abrupt short pulses, rather than in a smooth sinusoidal manner . They occur in any electronic device using solid state power switching supplies to convert incoming AC to DC.
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