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9.39
Date Code 20080213
Instruction Manual
SEL-351A Relay
Setting the Relay
Settings Explanations
Potential Transformer
Ratios and PT
Nominal Secondary
Voltage Settings
Refer to
Current and Potential Transformer Ratios (See Settings Explanations
Relay setting PTR is the overall potential ratio from the primary system to the
relay phase voltage inputs
VA-VB-VC-N
. For example, on a 12.5 kV phase-to-
phase primary system with wye-connected 7200:120 V PTs, the correct PTR
setting is 60. For the same 12.5 kV system connected through 12470:115 V
PTs in an open-delta configuration (global setting PTCONN = DELTA, and
the relay wired as shown in
), the correct PTR setting is 108.44.
NOTE:
VS voltage and PTRS setting
are not available in the SEL-351A-1.
Relay setting PTRS is the overall potential ratio from the synchronizing or
broken-delta voltage source to the relay
VS-NS
voltage inputs. For example, in
a synchronism check application (global setting VSCONN = VS), with phase-
to-ground voltage connected from a 12.5 kV phase-to-phase primary system
through a 7200:120 V PT, the correct PTRS setting is 60.
In an application that uses a broken-delta PT connection to create a 3V
0
zero-
sequence voltage signal (global setting VSCONN = 3V0, and the relay
VS-NS
terminals wired as shown in
), the step-down transformer, if
present, must also be included in the overall PTRS ratio calculation. For
example, if there are three PTs connected wye (primary)/broken delta
(secondary) with ratios of 7200:120, and a 400:250 step-down instrumentation
transformer in the circuit, the correct PTRS setting is 60 • 1.6 = 96.00.
Settings PTR and PTRS are used in event report and
METER
commands so
that power system values can be reported in primary units.
Settings PTR and PTRS are also used when global setting VSCONN = 3V0,
to scale the measured VS voltage into the same voltage base as voltage inputs
VA-VB-VC-N
for certain functions, as shown in
and
. If no PTs
are connected to voltage inputs
VA VB-VC-N
, make setting PTR the same value
as setting PTRS.
The ratio of the PTRS and PTR settings (PTRS/PTR) must be less than 1000
and greater than 0.001 when VSCONN = 3V0.
Relay setting VNOM is the nominal secondary voltage connected to voltage
inputs
VA-VB-VC-N
. For wye-connected PTs, VNOM is a phase-to-neutral
secondary voltage value. For open-delta connected PTs, VNOM is a phase-to-
phase secondary voltage value.
Negative-sequence and
positive-sequence voltage
polarized directional
elements
Available
32QE is disabled, F32P/
R32P disabled, ground
directional element ORDER
setting choice “Q” not
selectable
Phase and negative-
sequence element
directional control
(
–
)
Available
Not available (defaults to
“nondirectional” in levels
DIR1–DIR4
Loss-of-Potential Logic
(enable setting ELOP)
Available
Not available (can only
set ELOP = N);
Output Relay Word bits
disabled (LOP = logical 0,
V1GOOD = logical 0)
Table 9.9
Main Relay Functions That Change With VNOM = OFF
(Sheet 2 of
Relay Function
When VNOM = Numeric
Value
When VNOM = OFF
Содержание SEL-351A
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