1. IEEE PES General Meeting, Tampa FL June 24-28, 2007 1 Chapter 3 Harmonic Modeling of Networks Contributors: T. Ortmyer, C. Hatziadoniu, and P. Ribeiro Tutorial on Harmonics Modeling and Simulation

2. IEEE PES General Meeting, Tampa FL June 24-28, 2007 2 Distribution System Modeling The initial decisions: - Three phase or single phase modeling - The extent of the primary model - Secondary distribution modelingThree phase or single phase modelingThe extent of the primary modelSecondary distribution modeling The NATURE of the issue and the GOAL of the study constrain these decisions.

3. IEEE PES General Meeting, Tampa FL June 24-28, 2007 3 A Typical Primary Distribution System

4. IEEE PES General Meeting, Tampa FL June 24-28, 2007 4 Things to note Any large or unique loads Capacitor banks/ cables(?) Transmission supply Any unusual operating conditions?

5. IEEE PES General Meeting, Tampa FL June 24-28, 2007 5 Decision 1: Per phase versus Three Phase Modeling  The three phase model is required when:  Single phase or unbalanced capacitors are present  Ground or residual currents are important in the study  Significant unbalanced loading is present  A combination of wye-wye and/or delta-wye transformers leads to harmonic cancellation*

6. IEEE PES General Meeting, Tampa FL June 24-28, 2007 6 The typical instances where a single phase model may be sufficient are:  A single large three phase harmonic source is the cause of the study  The remaining system is well balanced  Ground currents are not an issue

7. IEEE PES General Meeting, Tampa FL June 24-28, 2007 7 Decision 2: The extent of the system model  Model the entire primary system  Transmission source can be modeled by the 60 Hertz short circuit impedance if no significant transmission capacitance is nearby– but check that the transmission system is not a source of harmonics  Power factor capacitors and any distributed generation should be modeled in detail

8. IEEE PES General Meeting, Tampa FL June 24-28, 2007 8 Decision 3: Load and harmonic source modeling  Identify and model all significant harmonic sources  Determine present levels through measurements- also determine if harmonic levels peak at full or light load conditions  Develop aggregate load models based on measurements and load distribution  Validate with measurements taken as harmonic sources/capacitor banks are switched in and out

9. IEEE PES General Meeting, Tampa FL June 24-28, 2007 9 Representative secondary distribution system

10. IEEE PES General Meeting, Tampa FL June 24-28, 2007 10 Characteristics of secondary studies  Different voltage levels  Fewer capacitors, and more with tuning coils  Load data is more accessible- and more important  Measurements can be more economical

11. IEEE PES General Meeting, Tampa FL June 24-28, 2007 11 Modeling transformers Model the transformer connection Neglect the transformer magnetizing branch (usually ignore the transformer magnetizing harmonics) Model the harmonic reactance as the product of short circuit leakage reactance and harmonic number Model the harmonic resistance as the short circuit resistance. Correct for skin effect if data or model available. Include stray capacitance for frequencies above the low khertz range.

12. IEEE PES General Meeting, Tampa FL June 24-28, 2007 12 Line Models Distribution lines and cables should be represented by an equivalent pi. An estimated correction factor for skin effect can be included Model ground path for zero sequence harmonics

13. IEEE PES General Meeting, Tampa FL June 24-28, 2007 13 Capacitors Capacitors– model as capacitive reactance– 60 hertz reactance divided by the harmonic number. Be sure to note those single phase capacitors, and model as such. Model the capacitor as either grounded wye, or ungrounded wye or delta.

14. IEEE PES General Meeting, Tampa FL June 24-28, 2007 14 Load Models Linear Loads Induction and Synchronous Machines Non-linear Loads

15. IEEE PES General Meeting, Tampa FL June 24-28, 2007 15 Linear Passive Loads TYPES: Incandescent lamps, resistive heater, electric range, water heater, space heater, etc. CHARACTERISTICS: RL type loads with RL values independent of frequency.

16. IEEE PES General Meeting, Tampa FL June 24-28, 2007 16 Line Connected MOTOR/GENERATOR LOADS Induction Motor Fundamental Frequency Per Phase Equivalent Circuit

17. IEEE PES General Meeting, Tampa FL June 24-28, 2007 17 IM Per Phase Harmonic Model

18. IEEE PES General Meeting, Tampa FL June 24-28, 2007 18 For synchronous generators, the per phase model of the synchronous generator is similar– use a series combination of stator resistance and substransient reactance in the model. On all direct connected machines, make sure and account for the ground connection (or lack of one) in studies with zero sequence harmonics.

19. IEEE PES General Meeting, Tampa FL June 24-28, 2007 19 Nonlinear Loads Adjustable speed drives fluorescent lamps, computers and other electronic loads arc furnaces and welders These loads generate harmonic currents, and are modeled as sources at the harmonic frequencies

20. IEEE PES General Meeting, Tampa FL June 24-28, 2007 20 Load Model 1: Series Passive Load

21. IEEE PES General Meeting, Tampa FL June 24-28, 2007 21 Load Model 2: Parallel Passive Load

22. IEEE PES General Meeting, Tampa FL June 24-28, 2007 22 Load Model 3. Skin Effect Parallel Load Model

23. IEEE PES General Meeting, Tampa FL June 24-28, 2007 23 Load Model 4. Induction Motor plus Resistive

24. IEEE PES General Meeting, Tampa FL June 24-28, 2007 24 Load Model 5. CIGRE/EDF

25. IEEE PES General Meeting, Tampa FL June 24-28, 2007 25 Load Model 6. Inclusion of Load Transformer and Motor Damping

26. IEEE PES General Meeting, Tampa FL June 24-28, 2007 26 I. Case Study 1: Load Impedance Frequency Study

27. IEEE PES General Meeting, Tampa FL June 24-28, 2007 27 Case Study 1 Parameters Linear Load=743 kW. PF Cap.=741kVAr, (C=5.4  F). Injected Harmonic Currents (A): I 5 = 0.840I 7 = 0.601 I 11 =0.382I 13 =0.323

28. IEEE PES General Meeting, Tampa FL June 24-28, 2007 28 Case Study 1: Load Model 1, 2, and 3 results

29. IEEE PES General Meeting, Tampa FL June 24-28, 2007 29 Case Study 1: Load Model 4, 5, and 6 Results

30. IEEE PES General Meeting, Tampa FL June 24-28, 2007 30 Sensitivity of Impedance to Motor Penetration Level (Load Model 6, fixed PFC)

31. IEEE PES General Meeting, Tampa FL June 24-28, 2007 31 Sensitivity of Impedance to IM Penetration– w/changing PFC

32. IEEE PES General Meeting, Tampa FL June 24-28, 2007 32 Summary Define study needs Determine the modeling needs Get the data Validate the data Produce good results!!