Date Code 990430 Loss-of-Potential, Load Encroachment, and Directional Element Logic 4-7
SEL-351P Manual Técnico
!ZLOAD*!LOP logic discriminates between high load and fault current. If an LOP condition
occurs (LOP = logical 1), the pickup level of 50P6 becomes the effective pickup of phase time-
overcurrent element 51P1T (51P1T loses its sensitivity when an LOP condition occurs):
51P1TC = !ZLOAD*!LOP + 50P6 = !ZLOAD*NOT[LOP] + 50P6
= !ZLOAD*NOT[logical 1] + 50P6 = 50P6
Use SEL-321 Relay Application Guide for the SEL-351P Recloser Control
The load-encroachment logic and settings in the SEL-351P Recloser Control are the same as
those in the SEL-321 Relay. Refer to Application Guide AG93-10 (SEL-321 Relay Load-
Encroachment Function Setting Guidelines) for applying the load-encroachment logic in the
SEL-351P. Note that Application Guide AG93-10 discusses applying the load-encroachment
feature to phase distance elements in the SEL-321 Relay. Although the SEL-351P does not have
phase distance elements, the principles and settings example in this guide are still applicable.
D
IRECTIONAL
C
ONTROL FOR
N
EUTRAL
G
ROUND AND
R
ESIDUAL
G
ROUND
O
VERCURRENT
E
LEMENTS
The directional control for overcurrent elements is enabled by making directional control enable
setting E32. Setting E32 and other directional control settings are described in the following
subsection Directional Control Settings.
Three directional elements are available to control the neutral ground and two directional
elements are available to control residual ground overcurrent elements. These directional
elements are:
• Negative-sequence voltage-polarized directional element (to control residual ground and
neutral ground overcurrent elements)
• Zero-sequence voltage-polarized, residual-current directional element (to control
residual ground and neutral ground overcurrent elements)
• Zero-sequence voltage-polarized, neutral-current directional element (to control neutral
ground overcurrent elements only)
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