1 / 12

Locating Harmonic Sources System Impedance Impacts of Harmonics K-factor Interharmonics

Locating Harmonic Sources System Impedance Impacts of Harmonics K-factor Interharmonics. System Effects. Harmonic currents in a radial distribution system will generally flow back to the source (fig 5.23) unless they are diverted to a nearby capacitor bank (fig 5.24).

Download Presentation

Locating Harmonic Sources System Impedance Impacts of Harmonics K-factor Interharmonics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Locating Harmonic Sources • System Impedance • Impacts of Harmonics • K-factor • Interharmonics

  2. System Effects • Harmonic currents in a radial distribution system will generally flow back to the source (fig 5.23) unless they are diverted to a nearby capacitor bank (fig 5.24). • System impedance is generally inductive reactance XL = wL, so remember that for harmonic h, the reactance is Xh = h w0 L = h X1

  3. Capacitor banks • Capacitor impedance Zc = -j Xc where reactance Xc = 1/(w C) = 1/(2p f C) • Since capacitor banks are rated in terms of voltage and reactive power: Xc = (kV)2/MVAr = 1000(kV)2/kVAr • Again remember that Xc is proportional to 1/f, so at harmonic h: Xch = Xc1/h

  4. Effects of resistance • Resistance does not “damp out harmonics” • Resistance will tend to damp out resonance, which may alleviate (to some extent) effects of harmonics • Power factor correction capacitors are likely to cause some low-order harmonic resonance problems even with resistance in the circuit

  5. Effects of harmonics • Impact on Capacitors • Impact on Transformers • Impact on Motors • Impact on Telecommunications • Impact on Energy and Demand Metering

  6. Effects of Capacitors • Capacitors have some tolerances in ratings according to IEEE Standard 18-1992: 135% of nameplate kVAr 110% of rated rms voltage (including fundamental and harmonics) 180% of rated rms current (including fundamental and harmonics) 120% of peak voltage

  7. Effects on Transformers • Harmonics affect transformers by • increasing the rms current which increases the transformer copper loss (winding resistance loss) • increasing the eddy-current losses, which usually increase as the square of the frequency

  8. If voltage distortion is being caused by harmonics in the load current:

  9. K indicates how much extra loss is incurred due to harmonic currents increasing eddy-current losses.

  10. K factor Harmonics increase losses in transformers K factor is used to derate transformers 11

  11. Interharmonics and Losses 12

More Related