16PESGM2316 Characterizing Transmission System Harmonic Impedances with R-X Loci Plots. David Mueller

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1 1 16PESGM2316 Characterizing Transmission System Harmonic Impedances with R-X Loci Plots David Mueller

2 2 Transmission System Harmonics Studies In the US, the closure of older coal fired plants is a driver to new investments in static var compensators (SVC) Some SVC equipment still utilize harmonic filters Harmonic filters need to be analyzed for their interaction with the grid

3 3 US Power Grid Transmission grid models can be very large!

4 4 IEEE Standard 1031 (2011) IEEE Guide for the Functional Specification of Transmission Static Var Compensators the harmonic impedances should be plotted on an R/X diagram to provide the harmonic impedance sector for each harmonic.

5 5 Equivalent Study System Evaluating the SVC filter component ratings (from IEEE 1031, Annex B)

6 6 Frequency Scan Analysis Also referred to as driving point impedance 1 amp injection and evaluate the response 24 Mva 7% 24 Mva 7% 161 kv 24 Mva 7% 13.8 kv Bus kv 13.8 kv 9 Mva 3.0 Mvar 5.94% 1 A Hz 1.8 Mvar 4.16 kv

7 Impedance (ohm) 7 Example Frequency Scan Result High values ( peaks ) indicate parallel resonance conditions Low values ( valleys ) indicate series resonance Example - Impedance Scan at Bus 1 conditions Frequency (h)

8 8 Representation of Loads There are many nuances to get correct results. [FromNode] Rt Lt One important aspect is the representation of loads. Rp Lp Rs Ls Parallel Component Series Component [ToNode]

9 Typical Transmission System Harmonic Model 9 This is generally done as a data import and conversion because a typical system may have: 340 two-winding transformers, 114 three-winding transformers, and 483 lines. Line charging capacitance values. 27 transmission system capacitor banks. 183 loads (for a total of 7433 MW and 1619 Mvar).

10 V o l t a g e ( V ) 10 Equivalent Source Damping At some point, even the large model is reduced with equivalent sources, which must be modified L a n d s to w n _ B a s e C a s e > A ( S C A ) L a n d s to w n _ E q S o u r c e _ D a m p i n g > A ( S C A ) Base Case With Source Equivalent Damping F r e q u e n c y (H p u ) E le c tr o te k C o n c e p ts T O P, T h e O u tp u t P ro c e s s o r

11 11 Simulation Cases Generally a few hundred cases (489 in one study) are run that represent: Operating conditions. No outages are assumed, and the system resonances are affected mostly by the number of capacitor banks in service. Contingency conditions. A line, a transformer or a generator is out of service. Some cases include double contingency. For various cases, different load levels are studied.

12 12 System Contingencies are Also Evaluated Line 1 Line 2 Line 3 Line 4 Line 5 Line 6 Transformer 1 Transformer 2 Transformer 3

13 Case List Combinations 13

14 V o l t a g e ( V ) 14 Inductive Case Results Simple case to start with! F r e q u e n c y ( H p u ) E le c tr o te k C o n c e p ts T O P, T h e O u tp u t P ro c e s s o r

15 V o l t a g e ( V ) 15 Adding Transmission Line Charging Capacitance Transmission line charging is a very important influence F r e q u e n c y ( H p u ) E le c tr o te k C o n c e p ts T O P, T h e O u tp u t P ro c e s s o r

16 V o l t a g e ( V ) 16 Different Load Levels L a n d s to w n _ C a s e 2 > A ( S C A ) L a n d s to w n _ C a s e 3 > A ( S C A ) Many cases are run at light (10%) load levels 600 L a n d s to w n _ C a s e 4 > A ( S C A ) L a n d s to w n _ C a s e 5 > A ( S C A ) F r e q u e n c y (H p u ) E le c tr o te k C o n c e p ts T O P, T h e O u tp u t P ro c e s s o r

17 17 R-X Plotting The resulting impedance from the scan cases are plotted together

18 2 nd Harmonic Results 18

19 3 rd Harmonic Results 19

20 4 th Harmonic Results 20

21 5 th Harmonic Results 21

22 7 th Harmonic Results 22

23 23 From IEEE 1031 Annex B IEEE 1031 Annex B Describing Search Areas

24 24 Psychology and Engineering Psychology has its Rorschach ink blot test, power engineering has R-X plots?

25 25 Conclusions Transmission system harmonic studies necessarily involve large, complicated models. Resonance involves conditions where X c =X r, so evaluation at boundary conditions is not sufficient. Correct line charging, equivalent source damping, and load representation are important.

26 26 Thank You! David Mueller 620 Mabry Hood Road, Suite 300 Knoxville, TN

Chapter 3 AUTOMATIC VOLTAGE CONTROL

Chapter 3 AUTOMATIC VOLTAGE CONTROL . INTRODUCTION TO EXCITATION SYSTEM The basic function of an excitation system is to provide direct current to the field winding of the synchronous generator. The excitation