Schweitzer Engineering Laboratories SEL-351A, Manual, Page: 348 / 666

9.38
SEL-351A Relay Instruction Manual
Date Code 20080213
Setting the Relay
Settings Explanations
Figure 9.11 Operation of DELTA and 3V0 Relay Word Bits
Table 9.8 Main Relay Functions That Change With VSCONN,
When PTCONN = DELTA
Relay Function When VSCONN=VS When VSCONN=3V0
Zero-sequence voltage-polarized
ground directional elements
(ORDER setting choices
“V,” “S,” and “U”) Not available Uses V
S
• (PTRS/PTR)
as 3V
0
a
a
The PTRS/PTR adjustment brings the broken-delta 3V
0
quantity to the same base voltage as
the relay impedance settings, which are based on the V
A
, V
B
, V
C
voltage base.
Wattmetric and incremental
conductance elements (ORDER
setting choice “P”) Not available Uses V
S
• (PTRS/PTR)
as 3V
0
a
Synchronism check elements Available Not available
Three-phase power metering
(MW3P, MVAR3P, etc.) Uses a three-phase
power formula,
without 3V
0
(primary value)
b
b
The three-phase power formula requires a 3V
0
quantity to correct for any unbalanced
conditions. In the case noted in this table, the metering accuracy will be reduced in conditions
of system unbalance.
Uses a three-phase
power formula,
including V
S
as 3V
0
(primary value)
Quantity “3V0” in Metering,
Fast Meter, and Distributed
Network Protocol (DNP) No difference
“3V0” is not shown in
METER command. Fast
Meter and DNP return 3V0 = 0.00 kV
Quantity “VS” in Metering,
Fast Meter, and DNP No difference
Uses V
S
as “VS” (primary value)
Table 9.9 Main Relay Functions That Change With VNOM = OFF (Sheet 1 of 2)
Relay Function
When VNOM = Numeric
Value
When VNOM = OFF
Undervoltage block for
frequency elements: 27B81 Requires all three voltages
V
A
, V
B
, V
C
(when
PTCONN = WYE) or V
AB
,
V
BC
, V
CA
(when PTCONN
= DELTA) to be greater
than setting 27B81P in
order to deassert
Requires one voltage V
A
(when PTCONN = WYE)
or V
AB
(when PTCONN =
DELTA) to be greater than
setting 27B81P in order to
deassert
Load encroachment logic
(enable setting ELOAD) Available Not available (can only set
ELOAD = N)
3V0
B
Logical 1
Logical 0
Switch B in "up" position when VSCONN = 3V0
Switch B in "down" position when VSCONN = VS
Switch A in "up" position when PTCONN = DELTA
Switch A in "down" position when PTCONN = WYE
DELTA
A
Logical 0
Relay
Word
Bits
Logical 1
Courtesy of NationalSwitchgear.com