9-48
Setting the Relay
Date Code 20010625
SEL-311L Instruction Manual
Zone 2 (OFF, 0.05–64.00
Ω
secondary {5 A nom.};
0.25–320.00
Ω
secondary {1 A nom.}) (see Figure 3.30)
Z2P = 2.75
Zone 2 phase distance element must detect faults along the entire length of the protected HV circuit
including the transformer high voltage terminals at Station T. Find the apparent distance in
secondary ohms as “seen” by Bus S with a fault at the high voltage terminals of the transformer.
Bus R should be in service to account for infeed.
Set Zone 2 phase distance equal to the fault study phase-phase impedance at station T times a
margin of 125%.
Z2P = 18.3
Ω
• (CTR / PTR) • 1.25 = 2.75
Ω
This element torque controls the phase time overcurrent element 51PT.
Zone 3 (OFF, 0.05–64.00
Ω
secondary {5 A nom.};
0.25–320.00
Ω
secondary {1 A nom.}) (see Figure 3.31)
Z3P = 1.76
Set Zone 3 to overreach Station R without reaching beyond Zone 1 protection of the next line. In
this example, set Z4P to 125% • Z1MAG.
Z3P = Z1MAG • 1.25 = 1.41
Ω
• 1.25 = 1.76
Ω
Mho Phase Distance Fault Detector Settings
Zone 1 phase-to-phase current FD (0.5–170.00
Α
secondary {5 A nom.};
0.1–34.00
Α
secondary {1 A nom.}) (see Figure 3.29)
50PP1 = 0.5
Set 50PP1 to its minimum value when LOP logic is enabled.
Mho Ground Distance Elements
Zone 1 (OFF, 0.05–64.00
Ω
secondary {5 A nom.};
0.25–320.00
Ω
secondary {1 A nom.}) (see Figure 3.32)
Z1MG = 1.13
Set Z1MG to 75–90% of distance from Station S to Station R.
Z1MG = Z1MAG • 80% = 1.41
Ω
• 0.8 = 1.13
Ω
Zone 2 (OFF, 0.05–64.00
Ω
secondary {5 A nom.};
0.25–320.00
Ω
secondary {1 A nom.}) (see Figure 3.33)
Z2MG = 2.75
Zone 2 ground distance protection must detect faults along the entire length of the protected HV
circuit as far as the transformer high voltage terminals at Station T. Find the apparent distance in
secondary ohms as “seen” by Bus S with a fault at the high voltage terminals of the transformer.
Bus R should be in service to account for infeed.
Set Zone 2 ground distance reach equal to the fault study phase-ground impedance (AG) at station
T times a margin of 125%.
Z2MG = 18.3
Ω
• (CTR / PTR) • 1.25 = 2.75
Ω
This element will be used to torque control the phase time overcurrent element 51GT.
Zone 3 (OFF, 0.05–64.00
Ω
secondary {5 A nom.};
0.25–320.00
Ω
secondary {1 A nom.}) (see Figure 3.34)
Z3MG = 1.76
Set Z3MG to the same values as Z3P.
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