3.16
SEL-351A Relay Instruction Manual Date Code 20080213
Overcurrent, Voltage, Synchronism Check, and Frequency Elements
Time-Overcurrent Elements
Time-Overcurrent Elements
Phase Time-
Overcurrent Elements
Four phase time-overcurrent elements are available. The elements are enabled
with the E51P enable setting as shown in Table 3.1.
The following is an example of 51PT element operation. The other phase
time-overcurrent elements operate similarly (note the similarity among the
logic in Figure 3.14, Figure 3.15, Figure 3.16, and Figure 3.17).
Settings Ranges (51PT Element Example)
Besides the settings involved with the Torque Control Switch operation in
Figure 3.14, the 51PT phase time-overcurrent element has the settings listed
in Tabl e 3 .2.
See Section 9: Setting the Relay for additional time-overcurrent element
setting information.
Table 3.1 Available Phase Time-Overcurrent Elements
Time-Overcurrent
Element
Enabled With
Setting
Operating Current See Figure
51PT E51P = 1 or 2 I
P
, maximum of A-, B-,
and C-phase currents
Figure 3.14
51AT E51P = 2 I
A
, A-phase current Figure 3.15
51BT E51P = 2 I
B
, B-phase current Figure 3.16
51CT E51P = 2 I
C
, C-phase current Figure 3.17
Table 3.2 Phase Time-Overcurrent Element (Maximum Phase) Settings
Setting Definition Range
51PP pickup 0.25–16.00 A secondary
(5 A nominal phase current inputs, IA, IB, IC)
0.05–3.20 A secondary
(1 A nominal phase current inputs, IA, IB, IC)
51PC curve type U1–U5 (US curves) see Figure 9.1–Figure 9.10
C1–C5 (IEC curves)
51PTD time dial 0.50–15.00 (US curves) see Figure 9.1–Figure 9.10
0.05–1.00 (IEC curves)
51PRS electromechanical
reset timing
Y, N
51PTC SEL
OGIC control
equation torque
control setting
Relay Word bits referenced in Tab le 9 .5 or
set directly to logical 1 (=1)
a
a
SELogic control equation torque control settings (e.g., 51PTC) cannot be set directly to
logical 0.
Courtesy of NationalSwitchgear.com
To Next Page
Loading...