4.55
Date Code 20170927 Instruction Manual SEL-751 Relay
Protection and Logic Functions
Group Settings (SET Command)
DIR1 = N (no directional control for Level 1 overcurrent elements)
DIR2 = N (no directional control for Level 2 overcurrent elements)
DIR3 = N (no directional control for Level 3 overcurrent elements)
DIR4 = N (no directional control for Level 4 overcurrent elements)
With the above settings, the directional control outputs in Figure 4.34,
Figure 4.35, Figure 4.40, and Figure 4.41 assert to logical 1. The overcurrent
elements referenced in Figure 4.34, Figure 4.35, Figure 4.40, and Figure 4.41
are then not controlled by the directional control logic.
NOTE: Depending on relay model
and DELTA_Y := DELTA and
SINGLEV := Y, Group setting EDIR
might not offer the AUTO settings
choice, or EDIR might be hidden. When
EDIR is hidden, it is internally set to N.
See discussion following Table 4.21.
There is one case that does not allow Group setting EDIR := Y or AUTO. If all
three of the following are true, EDIR can only be set to “N.”
➤ The relay model has a 0.2 A or 0.05 A nominal neutral channel.
➤ Setting VSCONN := VS.
➤ Setting VNOM := OFF.
Settings Made Automatically
If the directional control enable setting EDIR is set:
EDIR := AUTO
then the following directional control settings are calculated and set automati-
cally:
Z2F, Z2R, 50QFP, 50QRP, a2, k2, 50GFP, 50GRP, a0, Z0F, Z0R, and
Z0MTA
NOTE: Settings Z2F, Z2R, Z0F, and
Z0R are calculated based on the line
impedance settings Z1MAG and
Z0MAG. Enter Z1MAG and Z0MAG
values appropriate for the application
when EDIR := AUTO.
If
EDIR = AUTO
then Z0MTA is set equal to Z0ANG and Z0MTA is hidden.
Once these settings are calculated automatically, they can only be modified if
the user goes back and changes the directional control enable setting to
EDIR := Y.
Setting EDIR := AUTO is designed for line protection applications where CT
polarity is such that the forward tripping direction is toward the line, as shown
in Figure 2.22. When EDIR := AUTO and negative-sequence or zero-
sequence voltage is low, the negative-sequence and zero-sequence directional
elements declare unbalanced faults forward. Where directional elements are
used in applications that do not involve lines, or where the CT polarity is
reversed, setting EDIR := AUTO might be inappropriate. See Application
Guide AG2009-17, Enabling Sensitive Directional Elements for Non-Line
Protection Applications with SEL-351 Series Relays, or contact SEL for assis-
tance.
The remaining directional control settings are not set automatically if setting
EDIR := AUTO. They have to be set by the user, whether setting
EDIR := AUTO or Y. These settings are:
NOTE: Group settings KGN and
INMTA are only available when
EDIR = Y.
DIR1, DIR2, DIR3, DIR4, ORDER, 50PDIRP, KGN, INMTA, 50NFP,
50NRP, a0N, 59RES, DIRWFP, DIRWRP, DIRWD, and EDIRIV
(EDIRIV is a SEL
OGIC setting)
All these settings are explained in detail in the remainder of this subsection.
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