Schweitzer Engineering Laboratories SEL-700G Series, Instruction Manual

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4.116
SEL-700G Relay Instruction Manual Date Code 20170814
Protection and Logic Functions
Group Settings (SET Command)
negative-sequence voltage-polarized and positive-sequence voltage-polarized
directional elements are enabled and routed to control the negative-sequence
and phase overcurrent elements.
Figure 4.85 General Logic Flow of Directional Control for Negative-Sequence and Phase Overcurrent Elements
The directional control for negative-sequence and phase overcurrent elements
is intended to control overcurrent elements with pickup settings above load
current to detect faults. In some applications, it may be necessary to set a
sensitive overcurrent element to detect currents in one direction (reverse, for
example) and a less sensitive overcurrent element for the other direction
(forward). In such applications, with default relay logic, a reverse overcurrent
element with pickup setting below forward load may operate for some remote,
unbalanced, reverse faults. If possible, overcurrent element pickup settings
should be set above the current expected for load in either direction. If this is
not possible, refer to the technical paper, Use of Directional Elements at the
Utility-Industrial Interface, by Dave Costello, Greg Bow, and Martin Moon,
which is available on the SEL website, or by contacting SEL for assistance.
Internal Enables
Refer to Figure 4.74 and Figure 4.85. The internal enable DIRQE corresponds
to the negative-sequence voltage-polarized directional element.
Note that Figure 4.74 has extra internal enable DIRQGE, which is used in the
directional element logic that controls the neutral-ground and residual-ground
overcurrent elements (see Figure 4.72).
The settings involved with internal enable DIRQE in Figure 4.74 (for
example, settings a2, k2) are explained in Directional Control Settings on
page 4.121.
Directional Elements
Refer to Figure 4.85, Figure 4.89, and Figure 4.87. If a loss-of-potential
condition occurs (Relay Word bit LOP asserts), the negative-sequence
voltage-polarized and positive-sequence voltage-polarized directional
elements are disabled (see Figure 4.74 and Figure 4.87).
Refer to Figure 4.120 and the accompanying text for more information on
loss-of-potential.
q
Figure 4.74
w
Figure 4.86
e
Figure 4.87
r
Figure 4.88
t
Figure 4.89
y
Figure 4.90
u
Figure 4.59
i
Figure 4.54
o
Figure 4.58
a
Figure 4.54
FDIRP/
RDIRP
FDIRQ/
RDIRQ
DIRQE
(Disable)
50QF/
50QR
to Phase
Time-Overcurrent
Elements
to Phase
Instantaneous/Definite
Time Overcurrent
Elements
Level 1
DIRPF/
DIRPR
Negative-
Sequence
Voltage-
Polarized
Positive-
Sequence
Voltage-
Polarized
DIRQF/
DIRQR
Level 1
Level 2
to Negative-Sequence
Instantaneous/Definite
Time Overcurrent
Elements
Level 2
to Negative-Sequence
Time-Overcurrent
Element
Internal
Enables Relay Word
Bit Outputs Directional
Elements
Relay Word
Bit Outputs Relay Word
Bit Outputs
Direction
Forward/
Reverse Logic
Directional
Control
Directional
Element
Routing
1
2
3
4
5
6
7
8
9
10