Schweitzer Engineering Laboratories SEL-351-5, Instruction Manual

Page: 396 / 706

9.40
SEL-351-5, -6, -7 Relay Instruction Manual
Date Code 20070117
Setting the Relay
Settings Explanations
PTCONN = WYE is the factory default value. PTCONN = DELTA, if selected,
allows an open-delta PT connection. See Delta-Connected Voltages (Global
Setting PTCONN = DELTA) on page 2.13 for connection details. When
PTCONN = DELTA, the relay presents some different group settings, and
there is a change in some relay element availability, as compared to PTCONN
= WYE. Comparing
Table 9.7 with Table 9.8 shows some of these changes.
This instruction manual explains these and other differences in relation to each
affected element or setting. To indicate the state of PTCONN in SEL
OGIC
control equations, Relay Word bit DELTA operates as shown in Figure 9.11 .
Refer to Voltage Input Configuration (See Settings for Voltage Input
Configuration on page 9.39) on page SET.24 .
VSCONN = VS is the factory default value, which leaves voltage input VS in its
traditional role of voltage input for the synchronism check elements. See
Synchronism Check Elements on page 3.33 . VSCONN = 3V0, if selected,
allows an external 3V
0
zero-sequence voltage source to be connected to relay
voltage input VS . See Broken-Delta VS Connection (Global Setting VSCONN
= 3V0) on page 2.14 . When VSCONN = 3V0, the measured value from relay
voltage input
VS
is used in certain relay elements, as shown in Table 9.7 and
Table 9.8 . When VSCONN = 3V0, some relay elements are unavailable or
cannot be selected. This instruction manual explains these differences in
relation to each affected element or setting. To indicate the state of VSCONN
in SEL
OGIC
control equations, Relay Word bit 3V0 operates as shown in
Figure 9.11 .
Refer to Current and Potential Transformer Ratios (See Settings Explanations
on page 9.37) on page SET.1 .
VNOM = 67.00 V secondary (when PTCONN = WYE) or 116.05 V secondary
(when PTCONN = DELTA)
is the factory default value. See Potential
Transformer Ratios and PT Nominal Secondary Voltage Settings on page 9.42
for details on using VNOM with numeric setting values. VNOM = OFF, if
selected, causes several relay elements and functions to be disabled or
nonselectable, as shown in
Table 9.9 . The relay interprets setting VNOM =
OFF as indicating that valid three-phase voltages are not connected to relay
terminals
VA
,
VB
,
VC
, and
N
. See Figure 2.23 for an example application that
uses VNOM = OFF. This selection is intended to allow the remaining relay
features to be used with just one phase voltage connected, without any of the
sequence-voltage-based elements misoperating because of erroneous
quantities.
Table 9.7 Main Relay Functions That Change With VSCONN, When PTCONN = WYE (Sheet 1 of 2)
Relay Function When VSCONN = VS When VSCONN = 3V0
Zero-sequence voltage-polarized
ground directional elements (ORDER
setting choices “V,” “S,” and “U”) Uses 3V
0
calculated from V
A
, V
B
, V
C
Uses
VS
•(PTRS/PTR) as 3V
0
a
Wattmetric and incremental conductance ele-
ments (ORDER setting choice “P”) Uses 3V
0
calculated from V
A
, V
B
, V
C
Uses
VS
•(PTRS/PTR) as 3V
0
a
Synchronism check elements Available Not available
Three-phase power elements
(EPWR = 3P1–3P4). See
Power Elements
(Available in Firmware Version 7) on page 3.56
No difference
Uses a three-phase power formula, including 3V
0
calculated from V
A
, V
B
, V
C
Three-phase power metering
(MW3P, MVAR3P, etc.) No difference
Uses the sum of the single-phase
power calculations from V
A
, V
B
, V
C
, I
A
, I
B
, I
C
(primary values)