4.55
Date Code 20080213 Instruction Manual SEL-351A Relay
Loss-of-Potential, Load Encroachment, and Directional Element Logic
Directional Control Settings (Not in SEL-351A-1)
Equation 4.29
Equation 4.30
These details are important in relay testing, when the signal applied to the
VS-NS terminals represents a 3V
0
zero-sequence voltage signal, and global
setting VSCONN = 3V0. When making test settings or interpreting test
results, remember that the relay scales the measured value by PTRS/PTR
before using it in the Petersen Coil directional element and in the various zero-
sequence voltage-polarized directional elements.
E32IV—SELOGIC Control Equation Enable
Refer to Figure 4.7 and Figure 4.8.
SEL
OGIC control equation setting E32IV must be asserted to logical 1 to
enable the zero-sequence voltage-polarized and channel IN current-polarized
directional elements for directional control of neutral-ground and residual-
ground overcurrent elements.
For most applications, set E32IV directly to logical 1:
E32IV = 1 (numeral 1)
For situations where zero-sequence source isolation can occur (e.g., by
opening a circuit breaker) and result in possible mutual coupling problems for
the zero-sequence voltage-polarized and channel IN current-polarized
directional elements, SEL
OGIC control equation setting E32IV should be
deasserted to logical 0. In this example, connect a circuit breaker auxiliary
contact from the isolating circuit breaker to the SEL-351A:
E32IV = IN106 (52a connected to optoisolated input IN106)
Almost any desired control can be set in SEL
OGIC control equation setting
E32IV.
32WFP W secondary (VS and IN base)
PTRS
PTR
---------------
• =
25W
96
60
------
• =
40.000 W secondary (VA, VB, VC, and IN base)=
32WRP W secondary (VS and IN base)
PTRS
PTR
---------------
• =
10.417W
96
60
------
• =
16.667 W secondary (VA, VB, VC, and IN base)=
Table 4.5 Affect of Global Settings VSCONN and PTCONN on Petersen Coil Directional Elements
Relay Function
When VSCONN = VS
and
PTCONN = WYE
When VSCONN = VS
and
PTCONN = DELTA
When VSCONN = 3V0
(PTCONN = WYE or DELTA)
Wattmetric and incremental
conductance elements
(ORDER setting choice “P”).
Use 3V
0
calculated from V
A
,
V
B
, V
C
as polarizing voltage.
ORDER cannot be set to
contain “P” (no zero-sequence
voltage source is available)
Use V
S
• (PTRS/PTR) as 3V
0
polarizing voltage.
a
a
The PTRS/PTR adjustment brings the broken-delta 3V
0
quantity to the same base voltage as the relay settings 59RES, 32WFP, and
32WRP, which are based on the VA, VB, VC voltage base.
Courtesy of NationalSwitchgear.com
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