Power System Automation Lab 1 Overcurrent Protection for the IEEE 34 Node Radial Test Feeder Hamed B. Funmilayo, James A. Silva and Dr. Karen L. Butler-Purry Texas A&M University Electrical and Computer Engineering Department
2 Introduction Major use of the benchmark radial test feeders -- provide load-flow data for validating load-flow results from existing/novel loadflow algorithms Extend Current IEEE 34 node test feeder Provide overcurrent protection, considering offthe-shelf protective devices Make available for studies under new scenarios (such as DG impact)
3 Work Reported in This Paper Model of Test feeder in DIgSILENT PowerFactory 13.1 and conduct LF and SC studies Coordination studies for temporary and permanent faults for various fault situations Select OCP devices for the test feeder
4 IEEE 34 Node Radial Test Feeder Developed by DSA Subcommittee Majority at 24.9 kv (one 4.16kV lateral) Total load: 2060 kva at 0.86 pf Long, unbalanced radial system IEEE 34-Node Test Feeder system (modified from [1]) [1] Radial Test Feeders - IEEE Distribution System Analysis Subcommittee
5 Over Current Protective Devices Modeled in DIgSILENT 1 recloser, 12 fuses Fuse saving for fuses 1, 2, 3, 4, 6, 7, 8, and 11
6 Maximum and Minimum Fault Currents Comparison of Maximum Fault Current to IEEE TF Results Faulted IEEE* DIgSILENT DIgSILENT Node (A) (A) % Error 800 718.60 678.60 5.57 808 526.50 510.20 3.10 816 335.40 329.94 1.63 824 313.00 310.50 0.80 854 272.90 276.40 1.28 832 223.10 217.70 2.42 858 217.70 213.30 2.02 834 211.30 208.40 1.37 836 206.90 204.40 1.21 840 206.10 203.61 1.21 890 406.50 440.10 8.27 Comparison of Minimum Fault Current to IEEE TF Results Faulted IEEE* DIgSILENT DIgSILENT Node (A) (A) % Error 800 479.30 459.00 4.24 808 309.40 322.26 4.16 816 213.50 205.49 3.75 824 195.10 194.06 0.53 854 175.90 173.68 1.26 832 146.20 140.55 3.86 858 143.00 138.06 3.45 834 139.30 135.19 2.95 836 136.50 132.71 2.78 840 136.00 132.27 2.74 890 94.10 87.94 6.55
7 Recloser and Fuses Types Recloser Recloser's coordination range must provide adequate time to sense all downstream faults. Fuse Saving mode used A triple single-phase electronic recloser was used Load side fuses Similar types of fuse links were selected for all branches within the same nominal current range Voltage rating equal to or higher than the maximum bus voltage at the fuse location Interrupting current rating larger than the maximum symmetrical fault current at the fuse location Type K, T and X expulsion fuse links
8 Step Down Transformer (XMF-1) Fusing A type T external expulsion cutout on the primary side The voltage rating equal to or greater than the voltage at transformer's location The ampere rating equal to or greater than the anticipated normal loading level The symmetrical short-circuit interrupting rating equal to or greater than the maximum fault current Be able to withstand the inrush current generated when transformer is energized Be able to protect against transformer faults and secondary side faults (through faults) Serve as backup device by coordinating with the OCP device downstream of the lateral
9 Capacitor Bank Fusing Group fusing method is used. (One fuse protects the capacitor bank) Promptly isolate the failed capacitor unit on the line prior to any other protective device on the system 1-phase grounded fault current without fault impedance is assumed as the capacitor fault value.
10 Settings for Recloser and Load Side Fuses Recloser Settings No. of Instantaneous Trips 1 No. of Delay Trips 2 Nominal Voltage Minimum trip rating 14.4 kv, L-N 100 A Instantaneous trip curve type 103 Delay trip curve type 134 Load Side Fuse Settings Nominal Voltage Rating Nominal Current Rating of Each Fuse 24.9 kv, L-L or 4.16 kv, L-L Based on each branch s current Minimum Fault Current Observed at the Recloser For The Minimum Fault At Each Lateral Recloser Faulted Lateral I f recloser (A) Node Node number DIgSILENT 800 810 1 321.79 800 822 2 168.90 800 826 3 218.89 800 856 4 179.82 800 888 5 61.08 800 864 6 126.36 800 848 7 165.82 800 838 8 166.88 800 Cap- 844 7 167.93 800 Cap- 848 7 165.82 800 840 11 165.88
11 Coordination Studies Two terms for OCP operation Primary device Near to the fault and first to clear the fault Secondary (backup device) Backup of the primary device Coordination between recloser and fuse For temporary fault, K factor is used For permanent fault, fuse operates prior to recloser s delay trip Coordination between fuse and fuse Max clearing time of primary fuse will not exceed 0.75 times the minimum melting time of the secondary fuse
12 Fault Case Studies Fault on main feeder Fault on ordinary laterals Fault on laterals with reactive compensation Faults on laterals with step-down transformer
13 Fault on ordinary laterals Recloser operates on its instantaneous trip for temporary fault For permanent fault, fuse operates to clear the fault and isolates the lateral Delayed curve of recloser (backup) Fuse melting time Instantaneous trip of recloser Recloser-Fuse coordination for min fault at 810
14 Discussion of Results RECLOSER-FUSE COORDINATION TIME INTERVALS FROM DIGSILENT
OPD List for the Test Feeder 15
16 Summary/Conclusions A conventional overcurrent protection and coordination scheme was implemented on IEEE 34 Node Test Feeder computer model in DIgSILENT The final list of selected OCP was provided Coordination was achieved for different cases This may be used for easy comparison and assessment of future overcurrent protection studies regarding radial distribution system with or without additions such as DG
17 Acknowledgement The authors would like to thank F. J. Verdeja Perez, J. Mendoza, S. Duttagupta, M. Marotti, K. Mansfield, T. Djokic, and H. E. Leon for their contributions, along with the assistance of Prof. W. H. Kersting. This work was supported in part by the U.S. National Science Foundation under Grant ECS- 02-18309. Paper no. TPWRD-00792-2007.
18 Contact information: Dr. Karen L. Butler-Purry Email: klbutler@tamu.edu