Harmonics We love them!

Transcription

1 Harmonics We love them! Eric van Riet Harmonics seminar 1

2 Welcome Eric van Riet Sr. Technical Sales Manager Fluke Europe B.V. Ing. Electronics 9 years in electronics service & maintenance 15 years in Test & Measurement Power Quality and Thermal Imaging specialist. Eric van Riet Harmonics seminar 2

3 How does our orchestra look like? Eric van Riet Fluke Nederland BV 3 Seminar Harmonischen

4 Back to basics Let s start at the beginning! Eric van Riet Harmonics seminar 4

5 Linear loads A linear load will draw a sinusoidal current when connected to a sinusoidal voltage. There are only 3 linear elements: AC Current AC Voltage Eric van Riet Harmonics seminar 5

6 Linear loads Inductive motor: The electrical equivalent is a combination of a resistor and a coil (inductance). The current is no longer in phase with the voltage Current can shift up to 90 degree s AFTER the voltage (Inductive) or 90 degree s BEFORE voltage (Capacitive) IR 200 L 100 IT IT Volt Hz 50Hz I -200 IL Eric van Riet Harmonics seminar 6

7 Non linear loads So then what are the non linear loads? And how does the current waveform look when we connect this load to a sinusoidal AC voltage. 400,0 300,0 200,0 100,0 0,0-100, Spanning Stroom -200,0-300,0-400,0 Eric van Riet Harmonics seminar 7

8 First steps in higher harmonics Time domain and frequency domain Eric van Riet Harmonics seminar 8

9 First steps in higher harmonics In the graph two frequency s are present One is three times as fast as the other Sinusoidal movement is also called harmonic oscillation If we call the lowest frequency the ground harmonic or fundamental then We will call the higher frequency a higher harmonic. In this case the third harmonic Volt Hz 150Hz Eric van Riet Harmonics seminar 9

10 Harmonics - Fourier Fourier series analysis Any periodic function can be decomposed as a sum of sinusoidal waveforms, whose frequencies are integer multiples of the frequency of the analyzed signal. Fundamental component. The sinusoidal waveform whose frequency matches that of the analyzed signal. Harmonic components. The resulting sinusoidal waveforms with frequencies multiples of the fundamental frequency. Jean-Baptiste-Joseph Fourier (March 21, 1768 Auxerre - May 16, 1830 Paris) French mathematician and physicist known for his work on the decomposition of periodic functions in trigonometric series convergent called Fourier series

11 First steps in higher harmonics A signal with two harmonics obviously will not give two values when measured The meter sees the total (added) end result of the signal (waveform) as can be seen in orange 400 Approach is normally reversed; We have a dirty signal so which harmonics does it contain? Volt Hz 150Hz Totaal -400 Eric van Riet Harmonics seminar 11

12 Harmonics We would like to know which harmonics are hidden in Stroom this signal 400,0 300,0 200,0 100,0 0,0-100, Stroom -200,0-300,0-400,0 Eric van Riet Harmonics seminar 12

13 Time domain Same signal with ALL harmonics in one view 400,0 300,0 200,0 100,0 0,0-100, Stroom 1e 3e 5e 7e -200,0-300,0-400,0 Eric van Riet Harmonics seminar 13

14 Frequency domain View in a histogram %f or %r Eric van Riet Harmonics seminar 14

15 Histogram - profile Many possibility s in harmonic content Often a very recognizable profile Example below is an ASD (adjustable speed drive) Eric van Riet Harmonics seminar 15

16 Single phase loads Source Effect DC power supply, PC, printers, PLC s, etc.) Dimmers Electronic light ballasts Millions of energy saving lights!! Generates 3rd harmonic current Can be cause of flat-topping in system voltage Eric van Riet Harmonics seminar 16

17 Three phase loads (rectifiers) Diode rectifiers are used in ASD s and UPS units Modern units often very good DPF or Cos φ, but Cause of 5th and 7th harmonic currents Eric van Riet Harmonics seminar 17

18 Harmonics evaluation Harmonic measurement, THD, FD Harmonic voltage Sinusoidal voltage whose frequency is a multiple of the fundamental frequency voltage Individually Relative amplitude (Uh) of each harmonic in relation tot he voltage of the fundamental component (U1) EVALUATION RMS value of each harmonic Total Harmonic Distortion THD 40 h 2 U U 1 2 h Globally Distortion Factor FD U 40 h 2 U 2 h TotalRMS With U h the rms value associated to the harmonic h

19 Harmonic profile Predominant higher harmonics then is starts to look like a sinewave with noise Normally only uneven harmonics Even harmonics indicate presences of DC in system 3rd and 5th are very common In 3 phase systems and rectifiers often 9th and 11th Eric van Riet Harmonics seminar 19

20 Example of harmonic measurement The spectrum shows amount of every harmonic frequency present in the measured waveform The Fluke 430-series can show harmonics for: Voltage Current Power Displayed in histogram of numerical (table) Up to the 50 th Harmonic Measures harmonics as %R (total signal reference) or %F (fundamental reference) Eric van Riet Harmonics seminar 20

21 Equivalent presentation You can also show a non-linear loads as below:.as GENERATORS of harmonics! Current Voltage 50 Hz 150 Hz 250 Hz 350 Hz Eric van Riet Harmonics seminar 21

22 Are harmonics causing problems? Effects of various harmonics in our powersystems Eric van Riet Harmonics seminar 22

23 Harmonic behavior, rotation Positive, negative, no (null) direction Direction Rotation Effects (like skin effect, eddy-currents, etc.) Positive Right Heating of conductors, breakers, etc. Negative Left Heating as above + motor problems Null No Heating + neutral current in Wye systems Effects of harmonics on rotation direction Name F 2 e 3 e 4 e 5 e 6 e 7 e 8 e 9 e Frequency Rotation Note: If there is no DC offset, then only even harmonics present! Eric van Riet Harmonics seminar 23

24 3e Harmonic In a 3-phase/4-wire system, 3rd harmonics collect in the neutral. 3rd harmonic in every phase conductor is in phase. There is no vector cancellation as with the fundamental currents (which are 120 shifted in phase). Harmonics who have NO direction, or collect in the neutral conductor are also called Triplen or Triples harmonics ØA ØB ØC x 0 Eric van Riet Harmonics seminar 24

25 Harmonics: skin effect Higher frequency s are causing the Skin-Effect: Skin-Effect: Impedance increases because the current will flow at the outside of the conductor. The effect increases as the frequency increases. Insulation Conductor Surface where Current flows Eric van Riet Harmonics seminar 25

26 Power Apparent Power (VA) Reactive or Magnetising Power (VAR) Active or Useful Power (W) Reactive power is bi-directional From energy stored in inductance & capacitance Power factor (PF) equals Cos in value

27 Non-sinusoidal power I F? V Active or Useful Power (W) Cos now meaningless (only used for fundamental power) PF includes all harmonics If there is a difference in value between PF and Cos you have harmonics present!

28 Real Power comparison Normal lamp 60W Ledlamp 6W 59 Watt/lamp 6.4 Watt/lamp Ledlamp 10 x less dissipated power(w)

29 Cos phi Normal lamp 60W Ledlamp 6W No difference in Cos phi

30 Apparent Power Normal lamp 60W Ledlamp 6W 60 VA/lamp 41 VA/lamp Apparent Power ledlamp 32% less

31 Harmonics Test object :Led Lamp Mains voltage with voltage THD of 8% (limit of EN 50160) Harmonics far above limits IEC (2005) class D

32 Transformer losses Transformer losses are proportional to frequency of the harmonic current times the amplitude of that harmonic. When a non-linear load is supplied from a transformer, it is sometimes necessary to de-rate the transformer capacity to avoid overheating The de-rating of a transformer is expressed by the k-factor

33 Unbalance The voltage unbalance is a state in which the effective RMS values of the phase voltages or the phase shift between consecutive phases in a three-phase, are not equal. The characterization of the unbalance can be performed using the method of symmetrical components, by the ratio of negative to direct sequence and the ration of zero component to direct sequence.

34 Unbalance Unbalance; negative and zero components I 1 I 2 V 1 I 3 V 2 V 3

35 Unbalance Unbalance; negative and zero components L1 L1 L2 L3 L3 U L3 120º 120º 50 Hz U L1 120º Unbalance voltages U L2 - Different amplitude - Different phase shift of 120º

36 Unbalance Unbalance. Negative and zero components How to measure the unbalance of an installation? Which parameters must we MEASURE? + + Direct sequence (L1 L2 L3) Negative sequence (L1 L3 L2) Zero sequence (L1=L2=L3)

37 Unbalance Unbalance. Negative and zero components

38 Harmonics What can you do about it? Eric van Riet Harmonics seminar 38

39 Dealing with harmonics Always anticipate the fact that harmonics will be present in the system: Proper dimensions of phase and neutral conductors. Avoid long conductors. Avoid placing power lines and data lines next or each other. Right dimensions of transformers (K-factor, THDF). Install K-Factor transformers. Be very, very careful when installing power factor correction capacitors. Remove harmonics from the system: Filtering. Eric van Riet Harmonics seminar 39

40 Food for thought In todays power systems harmonics are always present. The weaker the system (read: higher impedance) the more influence harmonics have on this system. Investing and engineering in order to save energy is a good thing. Blindly applying energy saving solutions is NOT a good thing. You can only improve a system or situation if you really know what is going on.

41 So MEASURE!