3.12
SEL-587Z Instruction Manual Date Code 20020903
Relay Elements
Overcurrent Protection
Figure 3.13 Negative-Sequence and Residual Overcurrent Elements.
Inverse-Time Overcurrent Element
Logic for the inverse-time overcurrent (TOC) phase element 51n is shown in
Figure 3.14. Output Relay Word bits from the logic include inverse-time
(51nT), instantaneous (51n), and reset (51nR) (where n = P, A, B, C, G, or Q)
outputs. The instantaneous and reset outputs are provided for testing purposes.
Pickup, torque-control, curve shape, time-dial, and reset characteristics are
programmed with settings. Definite-time negative-sequence overcurrent
element 51Q and definite-time residual overcurrent element 51G logic are
similar. The elements are torque controlled by setting the Relay Word bit
51nTC to either one (permanently energized) or zero (disabled) or by entering
a SEL
OGIC control equation. The latter provides conditional assertion of the
element as a function of the SEL
OGIC control equation.
Figure 3.14 Inverse-Time Overcurrent (Max) Element.
(Identical for Negative- [51Q] and Zero-Sequence [51G] Elements)
Figure 3.15 Inverse-Time Overcurrent
(A-Phase) Element (B- and C-Phase are similar).
_
+
_
+
50G1
50G2
50G2P
50G1P
3I
0
= IA+IB+IC
_
+
_
+
50Q1
50Q2
50Q2P
50Q1P
3I
2
= IA+IB•e-
j2π/3
+ IC•e
j2π/3
ResidualNegative Sequence
51PTC or
SEL
OGIC
control equation
Torque-Control Switch
Setting
51PP
51PT
51PR
51P
Relay
Word
Bits
51P Phase (max)
Time-Overcurrent
Element
Curve Timing and
Reset Timing
Settings
51PP (pickup)
51PC (curve)
51PTD (time dial)
51PRS (reset E/M)
51PTC (torque control)
51ATC or
SEL
OGIC
control equation
Torque-Control Switch
Setting
51AP
51AT
51AR
51A
Relay
Word
Bits
51A Phase
Time-Overcurrent
Element
Curve Timing and
Reset Timing
Settings
51AP (pickup)
51AC (curve)
51ATD (time dial)
51ARS (reset E/M)
51ATC (torque control)
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