Schweitzer Engineering Laboratories SEL-700G Series, Instruction Manual

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4.105
Date Code 20170814 Instruction Manual SEL-700G Relay
Protection and Logic Functions
Group Settings (SET Command)
Zero-Sequence Voltage Sources.
The directional elements that rely on
zero-sequence voltage 3V0 (ORDER setting choices V and U, shown in
Figure 4.78 and Figure 4.80) may use either a calculated 3V0 from the wye-
connected voltages VA, VB, and VC, or a measured 3V0 from the
VS
or
VN
inputs, which are typically connected to a broken-delta PT secondary (refer to
Figure 2.16). The possible zero-sequence voltages the relay could use on the
X side and Y side for the directional elements are presented below.
➤
For both X side and Y side, if DELTAY_m := WYE (m = X or
Y), the relay always uses zero-sequence voltage calculated from
the wye-connected voltages VAm, VBm, and VCm.
➤
On the Y side, if DELTAY_Y := DELTA, then no source of
zero-sequence voltage is available and choice V in the ORDER
setting is unavailable.
➤
On the X side, if DELTAY_X := DELTA, then the relay gives
you the option to connect external 3V0 to
VS
or
VN
inputs with
the help of the global setting EXT3V0_X := VS or VN,
respectively. If EXT3V0_X := NONE, then no source of zero-
sequence voltage is available and choices V and U in the
ORDER setting are unavailable.
➢
When EXT3V0_X := VS, the measured voltage on
terminals
VS
-
NS
is scaled by the ratio of Group settings
PTRS/PTR to convert it to the same voltage base as the
VAX, VBX, and VCX at terminals, and the resulting
signal is applied to the directional element 3V0 inputs.
➢
When EXT3V0_X := VN, the measured voltage on
terminals
VN
-
NN
is scaled by the ratio of Group settings
PTRN/PTR to convert it to the same voltage base as the
VAX, VBX, and VCX at terminals, and the resulting
signal is applied to the directional element 3V0 inputs.
When testing the relay, it is important to note that the METER command 3V0
quantity is only available for wye-connected PT inputs. The METER
command
VS
and
VN
quantities are always the measured values from the
VS
-
NS
and
VN - NN terminals, respectively. Refer to Figure 2.16 for various voltage connections.
Internal Enables.
Refer to Figure 4.74, Figure 4.75, and Figure 4.76.
Table 4.27 lists the internal enables and their correspondence to the ground
directional elements.
Note that Figure 4.74 has extra internal enable DIRQE, which is used in the
directional element logic that controls negative-sequence and phase
overcurrent elements (see Figure 4.85).
Additionally, note that under a loss-of-potential condition some or all of the
voltage-based directional elements are disabled. Refer to Loss-of-Potential on
page 4.106 for more information on how different ground directional elements
are disabled under a loss-of-potential condition.
Table 4.30 Ground Directional Element Availability by Voltage Transformer
Connections On Y Side
Element Designation in
ORDER Setting for Y Side
DELTAY_Y := WYE DELTAY_Y := DELTA
Q Yes Yes
V Yes No
I Yes Yes
NOTE:
When Group setting
ORDERX := U, EDIR cannot be set to
AUTO.