Schweitzer Engineering SEL-351P, Quick Start Manual

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1-12 Factory-Set Logic Date Code 990215
SEL-351P Manual Técnico
t
Normal Min.
trip-phase
51P2P 50P5P
Effective Min. trip-phase when
cold load pickup scheme is
actively engaged for phase
elements
Delay curve-phase
(51P2T)
DWG: M351R086
I
Figure SECTION 1: .5: Disable Lower Portion of Delay Curve-Phase for Cold Load
Pickup
Disengage Cold Load Pickup Scheme (Phase Elements Example)
SV8 in Figure SECTION 1: .2 remains sealed in (and the cold load pickup scheme remains
actively engaged for the phase overcurrent elements) until one of the following occurs:
•
A natural return is made to normal Min. trip-phase
•
A forced return is made to normal Min. trip-phase
A natural return to normal Min. trip-phase occurs with the logic in Figure SECTION 1: .2
(bottom). The recloser closes and cold load pickup phase current goes below the normal Min.
trip-phase setting value (monitored by phase instantaneous element 50P6 – see Figure 3.2;
corresponding pickup setting 50P6P is set the same as the normal Min. trip-phase). All this is
time-qualified with timer SV7PU. Relay Word bit output SV7T unlatches SV8, disengaging the
cold load pickup scheme for the phase elements.
A forced return to normal Min. trip-phase occurs with the logic in Figure SECTION 1: .1
(bottom). The recloser closes and the Restore min. trips scheme is enabled for at least one
element. This is time qualified with timer SV5PU. Relay Word bit output SV5T then propagates
to Figure SECTION 1: .2 and unlatches SV8 if setting Restore min. trip-phase = Y (Relay Word
bit RPP = logical 1). This disengages the cold load pickup scheme for the phase elements.
Other Cold Load Pickup Scheme Details Involving Ground and SEF Elements
The logic in Figure SECTION 1: .3 and Figure SECTION 1: .4 operates similarly to the logic
operating in Figure SECTION 1: .2, which has just been examined. A few details need to be
explained concerning the operation of the cold load pickup scheme for the ground and SEF
elements: