Fault Location in Transmission Networks Using Modeling, Simulation and Limited Field Recorded Data

1. Fault Location in Transmission Networks Using Modeling, Simulation and Limited Field Recorded Data M. Kezunovic (P.I.) S. S. Luo D. Ristanovic Texas A&M University PSerc Review Meeting College station, Nov. 7, 2002 PSERC

2. Overview • Objectives • Testing procedure data requirements and test results • Potential problems and improvement • Design and User documentation • Conclusions • Future Research

3. Objectives • Defining procedure to be used for testing • Defining requirements regarding input data • Testing using fault data collected from Center Point Energy • Testing using fault data collected from other utility • Analyzing and evaluating the performance and proposing potential improvements • Improving the software and developing user interface • Developing the design and user documentation for facilitating future upgrades and practical use of the software

4. Testing procedure Using static system model • Obtaining the fault data file from utility and then converting into COMTRADE format • Producing the input data file based on the available DFR files • Checking the corresponding substation interpretation files based on the DFR configuration and system file • Running the software and obtaining the estimated location • Comparing the estimated result to the actual or calculated result When using updated system model • Extracting parameters from the model and producing the topology data file before executing the above steps

5. Data requirement When using static system model • Fault case data • fault data file in COMTRADE format (DFR raw data is need to be converted) • fault report (optional) • actual fault location (optional) • System data • Load flow and short-circuit model including topology • Interpretation file for each monitored substation

6. Data requirement, Cont. • Input data file generated by user based on available DFR files • Necessary fault information including the fault type, affected fault circuit • Options how to produce a list of possible faulted branch candidates • Algorithm parameter file • Including iteration number, crossover and mutation possibilities, population number… When the more accurate model is required • Additional real power flow data is needed

7. Testing • 15 fault cases obtained from Reliant Energy H&LP were tested • Power system simulator PSS/E is utilized • PSS/E models in versions 26, 27, 28 are tested • Sensitivity of results under different options is analyzed • Static model and tuned model are used

8. Testing • Using fault data collected from TVA or other utility to test fault location • The item was changed because data is not obtained • Instead, different power system simulation software was used • CAPE is a new selection • PSS/E system model is converted into CAPE database • Short circuit results obtained from the PSS/E and from CAPE are compared • The fault location software is customized for CAPE • Test result is not available because current version of CAPE is not perfect

9. Test results (1)

10. Test results (2)

11. Problems and improvements Some factors affected estimated fault location accuracy: • Fault cycle • Faulted branch candidates • Phasor calculation • Model • GA result

12. Problems and improvements Fault cycle - Problems • For each triggered DFR, correct cycle to calculate the during-fault phasor should be used. • For several triggered DFRs, the the same cycle to calculate the during-fault phasor should be use - Improvements • The criteria of determining fault cycle is improved • Additional measurements are taken to avoid using different fault cycles • In the user interface part, a new feature is added for user to specify the exact fault cycle

13. Problems and improvements Branch Candidates - Problems • The produced list of candidates must include the faulty branch, which creates a large number of choices - Improvements • Additional options are added for user to choose the method of producing candidates • user can check the detail list of possible faulted branch candidates and edit it before the fault location software runs

14. Problems and improvements Phasor calculation - Problems • Waveform includes DC offset and high frequency components, which affects the accuracy • Improvements • Using improved Fourier algorithm for obtaining the during-fault recorded phasor • Filter the noise contained in recorded waveforms

15. Problems and improvements Model - Problems • The static PSS/E model provided by utility may not reflect the real system operation condition when a fault occurs • Tuning generator and load power as well as tuning the system topology is required - Improvements • Using different version of PSS/E model with different topology and parameters • Tuning static parameters. Two situations are considered: • No additional real data is available. The concept of pre-fault phasor matching is introduced. Some cases show that tuning is effective • Additional real data is available, generator and load power scaling is utilized

16. Problems and improvements Genetic algorithm convergence - Problems • Fixed iteration number may not always approach the final solution • For different runs, GA result may vary within a specific range - Improvements • Using fitness scaling to solve the small population • Using multi-point crossover to increase the search space • Using new replacement of “weak parent” to make GA more robust • Studying behavior of the fitness value add a criteria using the average fitness • Adding a feature to give an exact result after using GA limit search range in the user interface part

17. Design and user documentation • Limited development of user interface for practical use • Fault location software design documentation and user’s guide are produced for software upgrade

18. Conclusion(1) • The test results show that the scheme of matching waveforms to locate a fault is feasible • Multiple triggered DFRs are helpful for improving location accuracy • It is suggested to use all the recorded currents and voltages for matching • It is suggested to use the same fault cycle to calculate during-fault phasors for each DFR

19. Conclusion(2) • Tuning system model and making it fit the operation condition when the fault occurs helps producing more accurate results, especially when additional real data is available. • It is suggested that the fault resistance is set within a reasonable range, especially in 345KV system • Producing a right list of faulted branch candidates before running fault location software is very helpful

20. Future research • How to obtain and incorporate more accurate model data • How to make the user’s knowledge more useful • How to incorporate an iterative approach between running the program and having the user look at the results and make some practical choices • How to interface the program to variety of short circuit programs • How to obtain more data for further evaluation of the performance

21. Thank you!