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4.3
Date Code 20070117
Instruction Manual
SEL-351-5, -6, -7 Relay
Loss-of-Potential, Load Encroachment, and Directional Element Logic
Loss-of-Potential Logic
voltage inputs
VA
,
VB
, and
VC
(wye-connected PTs). This difference is
shown in
and
, where Relay Word bit 3V0 is used as
a block signal for the loss-of-potential signal. Relay Word bit 3V0 is
asserted (= logical 1) whenever global setting VSCONN = 3V0. Refer to
Settings for Voltage Input Configuration on page 9.39
.
Setting ELOP = Y
Additionally, if setting ELOP = Y and a loss-of-potential condition occurs
(Relay Word bit LOP asserts to logical 1), overcurrent elements set direction
forward (see NOTE 2 below) are enabled (see
,
, and
). These direction forward overcurrent elements effectively
become nondirectional and provide overcurrent protection during a loss-of-
potential condition.
As detailed previously, voltage-based directional elements are disabled during
a loss-of-potential condition. Thus, the overcurrent elements controlled by
these voltage-based directional elements are also disabled. However, this
disable condition is overridden for the overcurrent elements set direction
forward if setting ELOP = Y.
NOTE 2:
When global setting VSCONN = 3V0, the various ground-
directional elements that rely on zero-sequence voltage quantities
(ORDER settings V, S, P, and U) are not affected by a loss-of-potential
condition on relay inputs
VA
,
VB
, and
VC
, because these elements use the
3V
0
zero-sequence voltage that comes directly from voltage input
VS
,
rather than the zero-sequence voltage calculated from voltage inputs
VA
,
VB
, and
VC
(wye-connected PTs). This difference is shown in
, where Relay Word bit 3V0 is combined with Relay
Word bits 32NE and 32VE to create a block signal for the loss-of-
potential signal. When LOP is asserted and setting ELOP = Y1, the relay
will not force an enable of the ground elements that are set direction
forward when Relay Word bit 3V0 is asserted (= logical 1) and one of the
zero-sequence voltage-polarized ground directional element enables
(32VE or 32NE) is asserted. Refer to
Setting ELOP = N
If setting ELOP = N, the loss-of-potential logic still operates (Relay Word bit
LOP asserts to logical 1 for a loss-of-potential condition) but does not disable
any voltage-based directional elements (as occurs with ELOP = Y or Y1) or
enable overcurrent elements set direction forward (as occurs with ELOP = Y).
Содержание SEL-351-5
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