10-56 L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUALFAULT LOCATOR CHAPTER 10: THEORY OF OPERATION10Figure 10-17: Relay connections for multi-ended fault locator exampleThe following settings are entered into the relays by you. These values are calculated in secondary ohms as shown in thefollowing tables.Table 10-40: Line impedance settings (all angles are 80.5°)Assume that the following signals are measured by the relays when the fault locator is triggered.Table 10-41: Relay measurements (physical inputs)These measurements are shown as follows in per-unit values of the CT and VT nominal of the 87L source.Table 10-42: Relay measurements (per-unit values)When subjected to the expanded Clarke transform in the previous section, the local currents yield the following values (inrelay per-unit values):• Relay 1: 1.3839 pu ∠–84.504°• Relay 2: 5.4844 pu ∠–85.236°• Relay 3: 1.2775 pu ∠–56.917°When subjected to the expanded Clarke transform in the previous section, the local voltages yield the following values (inper-unit values of the nominal primary phase-to-ground voltage):Value Relay 1 Relay 2 Relay 3Local to tap 1.0219 sec. ohms (relay 1 to tap inrelay 1 secondary ohms)6.0833 sec. ohms (relay 2 to tap inrelay 2 secondary ohms)1.0707 sec. ohms (relay 3 to tap inrelay 3 secondary ohms)Remote 1 to tap 1.7520 sec. ohms (relay 2 to tap inrelay 1 secondary ohms)3.5483 sec. ohms (relay 1 to tap inrelay 2 secondary ohms)1.3626 sec. ohms (relay 1 to tap inrelay 3 secondary ohms)Remote 2 to tap 0.8030 sec. ohms (relay 3 to tap inrelay 1 secondary ohms)2.7883 sec. ohms (relay 3 to tap inrelay 2 secondary ohms)2.3360 sec. ohms (relay 2 to tap inrelay 3 secondary ohms)Value Relay 1 Relay 2 Relay 3F1 10.64 A ∠–87.5° 8.592 A ∠–88.5° 9.652 A ∠–43°F2 1.652 A ∠88.9° 1.273 A ∠78.6° 5.201 A ∠–99°F3 1.66 A ∠–31.2° 1.614 A ∠–43° 6.269 A ∠139.3°F5 52.71 V ∠0.8° 76.943 V ∠24.579° 49.6 V ∠10.1°F6 58.21 V ∠–121.4° 86.321 V ∠–98.052° 57.1 V ∠–115.6°F7 58.93 V ∠121.9° 78.795 V ∠137.27° 59.12 V ∠130.8°Value Relay 1 Relay 2 Relay 3IA 2.128 pu ∠–87.5° 8.592 pu ∠–88.5° 1.9304 pu ∠–43°IB 0.3304 pu ∠88.9° 1.273 pu ∠78.6° 1.0402 pu ∠–99°IC 0.332 pu ∠–31.2° 1.614 pu ∠–43° 1.2538 pu ∠139.3°VA (VAB) 0.91304 pu ∠0.8° 0.92335 pu ∠24.579° 0.85917 pu ∠10.1°VB (VBC) 1.0083 pu ∠–121.4° 1.0359 pu ∠–98.052° 0.98909 pu ∠–115.6°VC (VCA) 1.0208 pu ∠121.9° 0.94557 pu ∠137.27° 1.0241 pu ∠130.8°
