Journal of Reliable Power - SEL

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12 For the system in Fig. 4, Fig. 21 represents the values of Real(KR) as a function of m with a constant value of Rset. The increasing values of Real(KR) indicate that the maximum detectable Rf at no load decreases as the distance to the fault increases. 10 9 8 7 Real (KR) 6 5 4 Fig. 22. CT and VT error evaluation for Zone 1 Fig. 23 shows the Rmax pu as a function of Zset for θL1 equal to 40, 55, 70, and 75 degrees and θε equal to 2 degrees. 30 3 2 1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Fault Location (pu) Fig. 21. Factor Real(KR) for the system of Fig. 4 Another consideration in determining the setting of the resistive coverage involves VT and CT (current transformer) errors. Reference [22] indicates that a composite angle error in the measurement θε can be assumed. A. Zone 1 For a Zone 1 application, the requirement is that Zone 1 never overreaches for any fault at the end of the line. Assuming that for resistive faults at the end of the line there is an angle error θε, the effective path for increasing Rf will tilt down an extra θε degrees, as shown in Fig. 22. For increasing Rf, the intersection with the Zone 1 reactive line is the indication of the maximum Rset or Rmax. Using the law of sines and trigonometry, Rmax can be expressed as: sin ( θε + θ L1) Rmax = • ( 1− Zset _ pu ) • ZL1 (29) sin θε ( ) Equation (29) defines Rmax, the maximum secure resistive reach setting for Zone 1, taking into account CT, VT, relay measurement errors, and θε. Rmax is a function of the impedance reach setting Zset, the positive-sequence line impedance magnitude |ZL1| and angle θL1, and the total angular error in radians θε [22]. Maximum Resistive Reach Setting Rmax (pu) 25 20 15 10 5 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Impedance Reach Setting Zset (pu) Fig. 23. Maximum resistive reach setting as a function of the impedance reach due to measurement errors A typical Zone 1 impedance reach setting for short lines is 70 percent. For the system in Fig. 4, Zset_zone1 is equal to 1.4 ohms secondary. With Zset, |ZL1|, θL1, and θε, we can calculate Rmax using (29) or obtain the pu value Rmax_pu with respect to the total positive-sequence line impedance from Fig. 23. In this case, Rmax equals 17.17 ohms secondary, or Rmax_pu equals 8.58 pu. Additionally, we need to verify that the fault current is above the maximum relay sensitivity. In this case, the residual current is 3.0 A secondary, and the relay sensitivity is 0.25 A. Therefore, the relay can see the fault at 70 percent of the line with Rf equal to 25 ohms primary. 40 55 70 85 76 | Journal of Reliable Power
13 Fig. 24 shows the apparent resistance for different Rf values for a fault at 70 percent of the line. Note that with Rset_zone1 equal to 11.52 ohms, the quadrilateral element can see 3 ohms secondary or 25 ohms primary. 8 7 —— Rapp (ohms) Fault Resistance (ohms) 6 5 4 3 2 Rset = 11.52 ohms δ = 0 degrees 1 Fig. 24. Apparent resistance for a fault at 70 percent of the line Fig. 25 shows the margin of the selected Rset with respect to Rmax for the selected Zset. Fig. 25. Margin of Rset at Zset_zone1 equal to 0.7 pu Fig. 26 shows that the quadrilateral distance element can see up to 3 ohms for faults at 70 percent of the line for Rset equal to 11.52 ohms. 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Fault Location (pu) Fig. 26. Maximum Rf coverage with Rset equal to 11.5 ohms for faults along the line The analysis carried out for a phase-to-ground fault can also be applied for phase-to-phase faults. In these cases, the factor KR is equal to: 1 KR = (30) 2 • C1 For no-load conditions (δ equal to 0) and homogeneous systems, the resistive blinder of the phase quadrilateral element will assert for an Rf that satisfies (31) or (32). Rf ( ) Rset 2 • Real C1 < (31) ⎛ Vϕϕ ⎞ Rapp = Real⎜ ⎟ − m • Real ZL1 ⎝ Iϕϕ ⎠ ( ) (32) B. Zone 2 When considering overreaching zones, it is important to determine the maximum underreach and verify that the zone covers at least the expected Rf. For example, in a Zone 2 application, it is expected that all faults on the line and those at the remote terminal will be detected. It is a common practice to set the Zone 2 reach to 120 percent of the line length. However, in certain circumstances, this impedance reach would not guarantee coverage for faults with Rf, and a longer reach would be required. Adaptive Phase and Ground Quadrilateral Distance Elements | 77
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$12.00 Journal of Reliable Power Vo
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Journal of Reliable Power Volume 1
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Capable of running protection calcu
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Both P and Q are two-input phase an
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TABLE 1: MHO ELEMENT POLARIZING CHO
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For an Aφ-ground fault on the syst
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The most onerous 3φ fault is one w
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If the angle is near +120°, then t
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Impedance-Based Fault Location Expe
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A. Simple Reactance Method From Fig
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Figure 9 shows a screen capture of
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The relay then performs “torque
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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
Page 71 and 72: 5 II. QUADRILATERAL DISTANCE ELEMEN
Page 73 and 74: 7 For the purpose of implementing t
Page 75 and 76: 9 The three-phase fault detection e
Page 77: 11 Zone 1 distance elements should
Page 81 and 82: 15 B. Adaptive Resistance Element F
Page 83 and 84: 17 Fig. 34 and Fig. 35 illustrate t
Page 85 and 86: Line Protection Bibliography Issue
Page 87 and 88: Hou, Daqing, and Jeff Roberts. “C
Page 90: ©2010 Schweitzer Engineering Labor
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