Schweitzer Engineering SEL-351P - Residual Ground Vs. Neutral Ground

1-6 Factory-Set Logic Date Code 990430
SEL-351P Manual Técnico
Overcurrent Element Function with EZ Settings
Operative
Associated Settings
50N2P, 67N2D
67P1 High current lockout - phase 50P1P
67G1, 67N1 High current lockout - ground 50G1P, 50N1P
50P5 Effective min. trip for “Delay curve
- phase” when cold load pickup
scheme is active.
50P5P
50G5, 50N5 Effective min. trip for “Delay curve
- ground” and “SEF element” when
cold load pickup scheme is active.
50G5P, 50N5P
50P6 Threshold (set equal to “Min. trip -
phase”) to detect phase current
returning below the normal “Min.
trip - phase” level when cold load
pickup scheme is active.
50P6P
50G6, 50N6 Threshold (set equal to “Min. trip -
ground”) to detect ground current
returning below the normal “Min.
trip - ground” level when cold load
pickup scheme is active.
50G6P, 50N6P
50N4 Threshold (set equal to “Min. trip -
SEF”) to detect ground current
returning below the normal “Min.
trip - SEF” level when cold load
pickup scheme is active.
50N4P
50A4, 50B4, 50C4 Threshold (set equal to “Min. trip -
phase”) to detect faulted phases for
trip operation counters.
50P4P
The overcurrent elements are available for use in SEL OGIC Control Equations as “Relay Word
bits” (see Tables 9.3 and 9.4). The associated overcurrent element settings listed in Table 1.2
and SEL
OGIC Control Equations settings are found in the settings sheets at the end of Section 9:
Setting the SEL-351P Recloser Control. The factory default SEL
OGIC Control Equations
settings are explained in the remainder of this section.
Residual Ground vs. Neutral Ground
In the following logic explanations, reference is made to residual ground and neutral ground
overcurrent elements. The residual ground overcurrent elements (e.g., 51G1T) are derived from
phase current input channels IA, IB, and IC. The neutral ground overcurrent elements (e.g.,
51N1T) are derived from current input channel IN. If current channel IN is wired residually with
phase current input channels IA, IB, and IC, the residual ground and neutral ground overcurrent
elements see the same magnitude zero-sequence current.