Sel SEL-421 - Instantaneous Line Overcurrent Elements; Phase Overcurrent Element Settings

R.1.64
SEL-421 Relay Reference Manual Date Code 20111215
Protection Functions
Instantaneous Line Overcurrent Elements
Instantaneous Line Overcurrent Elements
The SEL-421 calculates instantaneous overcurrent elements for phase (P),
residual ground (G, vector sum of I
A
, I
B
, and I
C
), and negative-sequence (Q)
quantities. Four levels of instantaneous elements are available named 50P1–
50P4, 50Q1–50Q4, and 50G1–50G4, as shown in Tab le 1.53 through
Tab le 1.55, with settings shown in Table 1.50 through Table 1.52.
These overcurrent elements always operate on the line current (IW-terminal
current or the sum of the IW and IX terminal currents) according to the global
setting LINEI (Line Current Source). The instantaneous overcurrent elements
are inputs to the instantaneous directional (67Pn, 67Qn, 67Gn, where n = 1–4)
and definite-time directional overcurrent elements (67PnT, 67QnT, 67GnT,
where n = 1–4). See Directionality on page R.1.39 for details on the
directional control option. Note that the 67Pn and 67PnT elements are not
directionally controlled by the built-in logic; they can be made directional
through the use of the torque control settings 67P1TC – 67P4TC.
Each of the instantaneous directional elements includes a torque control
setting (67PnTC, 67QnTC, 67GnTC, where n = 1–4) to supervise the element
operation.
The enable settings (E50P, E50Q, E50G) control how many of each type of
instantaneous/definite-time overcurrent elements are available. For example,
if E50P := 2, only 50P1, 67P1, 67P1T, 50P2, 67P2, and 67P2T are processed.
The remaining phase instantaneous/definite-time overcurrent elements (n = 3–
4) are defeated, and the output Relay Word bits are forced to logical 0.
Table 1.50 Phase Overcurrent Element Settings
Setting Description Range
Default
(5 A)
Phase Instantaneous Overcurrent Elements
E50P Phase Inst./Def.-Time O/C Elements N, 1–4 1
50P1P Level 1 Pickup (A) OFF, (0.05–20) • I
nom
10.00
50P2P Level 2 Pickup (A) OFF, (0.05–20) • I
nom
OFF
50P3P Level 3 Pickup (A) OFF, (0.05–20) • I
nom
OFF
50P4P Level 4 Pickup (A) OFF, (0.05–20) • I
nom
OFF
Phase Definite-Time Overcurrent Elements
67P1D Level 1 Time Delay (cycles) 0.000–16000 0.000
67P2D Level 2 Time Delay (cycles) 0.000–16000 0.000
67P3D Level 3 Time Delay (cycles) 0.000–16000 0.000
67P4D Level 4 Time Delay (cycles) 0.000–16000 0.000
67P1TC Level 1 Torque Control SEL
OGIC Equation 1
67P2TC Level 2 Torque Control SEL
OGIC Equation 1
67P3TC Level 3 Torque Control SEL
OGIC Equation 1
67P4TC Level 4 Torque Control SEL
OGIC Equation 1