Journal of Reliable Power - SEL

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An observation from Figure 6 is that the negative-sequence is the same when viewed from all ends of fault voltage ( V2F ) the protected line. Source S Z 1S Z 2S Z 0S I 1S Relay S I 2S Relay S I 0S Relay S mZ 1L mZ 2L mZ 0L V 2F + (1-m)Z 1L (1-m)Z 2L (1-m)Z 0L I 1R Relay R I 2R Relay R I 0R Relay R 3RF Source R Z 1R Z 2R Z 0R I TOTAL Figure 6 Connection of Sequence Networks for a Single Line-to-Ground Fault at m At Relay S: At Relay R: ( ) V = –I • Z + m • Z (8) 2F 2S 2S 2L ( ) V = − I • Z + (1− m) • Z (9) 2F 2R 2R 2L Eliminate V 2F from Equations 8 and 9 and rearrange the resulting expression as follows: ( Z2S + m • Z2L ) ( 2R + ( − ) 2L ) I2R = I 2S • Z 1 m • Z (10) To avoid alignment of Relay S and R data sets, take the magnitude of both sides of Equation 10 as follows: ( Z2S + m • Z2L ) ( 2R + ( − ) 2L ) I2R = I 2S • Z 1 m • Z Equation 11 is then simplified to Equation 12 below. I 2R = ( I 2S • Z2S ) + m •( I 2S • Z2L ) ( Z + Z ) − m •( Z ) 2R 2L 2L (11) (12) To further simply Equation 12, define the following variables: I • Z = a + jb 2R 2S 2S 2S I • Z = c + jd 2L Z + Z = e + jf 2L Z = g + jh 2L Substituting these variables into Equation 12 produces: I 2R = ( a + jb) + m •( c + jd) ( e + jf ) − m •( g + jh) (13) Taking the square of both terms of Equation 13, expanding and rearranging terms produces a quadratic equation of the form: 2 A • m + B• m + C = 0 (14) Equation 14 is solved for m using a quadratic solution. The coefficients of Equation 14 are given below. ( ) ( ) 2 2 2 2 2 2R A = I • g + h − c + d ( ) ( ) 2 2R 2 2 2 2 2 2R B = − 2 • I • e • g + f • h − 2 • a • c + b • d ( ) ( ) C = I • e + f − a + b (15) V. DISTRIBUTION SYSTEMS Fault location for distribution feeders uses the same basic principles as for transmission lines, but presents a great challenge for substation fault locators because of the diverse topology of the distribution system: laterals, spurs, and singlephase taps. On important feeders, some utilities model the line parameters to achieve a more precise fault location. One utility models a feeder using an Excel ® spreadsheet to show the line parameters. The spreadsheet includes node numbers, wire size, distance from the source, positive- and zero-sequence impedances, and fault currents. Figure 7 is an actual model of a feeder that is 5.47 miles long. Figure 7 Spreadsheet Model (See Appendix for Enlarged View) A graphical representation of the feeder is shown in Figure 8. 1 Figure 8 (distance in miles) 2 3 4 5 Actual Fault (3 miles) Distribution Feeder Topology 11 6 7 8 9 10 (1.41) (2.29) (3.29) 12 (3.06) 21 (5.39) 13 (3.27) 14 15 16 17 18 (3.66) (3.99) 23 (5.47) (2.56) 20 19 22 (4.47) 18 | Journal of Reliable Power
Figure 9 shows a screen capture of event report data from an actual fault. Figure 9 Distribution Feeder Fault Event Screen Capture The event report indicates that a B-phase-to-ground fault occurred 3.02 miles from the station. From the feeder topology, there are two possible locations for the fault. As it turns out, line crews found a fast growing skinny tree growing close to the line, approximately three miles from the substation on the main line near Node 12. VI. USE OF FAULT INDICATORS Fault Indicators can be applied on lines to help locate faults. If a fault occurs beyond the location of the fault indicator, line crews observe an LED or flashing light, indicating that fault current was sensed. Reset can be done manually, electrostatically, or through a timer, depending on the design. Figure 10 is an example of how fault indicators can be placed to assist line crews in finding the fault location. VII. TRANSMISSION FAULT LOCATION EXAMPLES A. Example 1: 345 kV Automatic Spraying System Background: Repeated phase-phase faults had occurred on a 345 kV line. There was no inclement weather or lightning in the area. The number of faults caused voltage issues and a negative-sequence overcurrent element went into an alarm state at a regional nuclear plant. Nuclear plant personnel were concerned about the possibility of tripping the unit off line. The line data for the transmission line: • Circuit 345-LINE is a 28.16 mile long, 345 kV line between terminals G and H. • 345-LINE—“We had dispatched linemen to the area based on fault location. The lineman was patrolling the line in the area when he observed an automatic spraying system operating very near the line. He went to the property owner’s home and learned that the automatic system runs along a track and sprays liquefied manure onto the open fields. The landowner checked the mechanism that controls the sprinkler and found that it had failed, causing the sprinkler to run under the line.” Figure 11 shows a one-line and event report screen captures. G C-A 17.28 mi Reported 17.8 mi from G 10.36 mi from H Actual 345-Line 28.16 mi C-A 10.00 mi Reported H Relay Figure 10 Example Location for Fault Indicators on Distribution Feeder Figure 11 Example 1: One-Line and Event Report Screen Captures Impedance-Based Fault Location Experience | 19
Page 1 and 2: $12.00 Journal of Reliable Power Vo
Page 3 and 4: Journal of Reliable Power Volume 1
Page 5 and 6: Capable of running protection calcu
Page 7 and 8: Both P and Q are two-input phase an
Page 9 and 10: TABLE 1: MHO ELEMENT POLARIZING CHO
Page 11 and 12: For an Aφ-ground fault on the syst
Page 13 and 14: The most onerous 3φ fault is one w
Page 15 and 16: If the angle is near +120°, then t
Page 17 and 18: Impedance-Based Fault Location Expe
Page 19: A. Simple Reactance Method From Fig
Page 23 and 24: The relay then performs “torque
Page 25 and 26: IX. LAB TEST SETUP Several line fau
Page 27 and 28: APPENDIX The following are the rela
Page 29 and 30: The following shows the analog math
Page 31 and 32: Digital Communications for Power Sy
Page 33 and 34: increasing security by a factor of
Page 35 and 36: The receiver amplifier is the major
Page 37 and 38: Noise from faults or other sources
Page 39 and 40: 80 60 40 20 R F 100 3 3 S 2 5 6 4 1
Page 41 and 42: 15. A POTT scheme implemented over
Page 43 and 44: Transmission Line Protection System
Page 45 and 46: One-Cycle Directional Element Figur
Page 47 and 48: element misoperation. Shunt reactor
Page 49 and 50: • SW2 is in Position 1 when there
Page 51 and 52: Complete reclosing relay supervisio
Page 53 and 54: IX. BIOGRAPHIES Armando Guzmán, P.
Page 55 and 56: 2 II. COMMON ZONE TIMING In June 20
Page 57 and 58: 4 ment 67N2 after a 1-cycle carrier
Page 59 and 60: 6 VI. ZONE 1 OVERREACH DUE TO CVT I
Page 61 and 62: 8 1_VA 1_VB 1_VC 2_VA 2_VB 2_VC 3_V
Page 63 and 64: 10 The phasors during the fault are
Page 65 and 66: 12 The prefault data from the backu
Page 67 and 68: 1 Adaptive Phase and Ground Quadril
Page 69 and 70: 3 C. Short Line Applications A shor
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5 II. QUADRILATERAL DISTANCE ELEMEN
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7 For the purpose of implementing t
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9 The three-phase fault detection e
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11 Zone 1 distance elements should
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13 Fig. 24 shows the apparent resis
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15 B. Adaptive Resistance Element F
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17 Fig. 34 and Fig. 35 illustrate t
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Line Protection Bibliography Issue
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Hou, Daqing, and Jeff Roberts. “C
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©2010 Schweitzer Engineering Labor
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