Schweitzer Engineering Laboratories SEL-351-5, Instruction Manual

Page: 95 / 706

3.15
Date Code 20070117
Instruction Manual SEL-351-5, -6, -7 Relay
Overcurrent, Voltage, Synchronism Check, Frequency, and Power 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 follows:
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 following
settings:
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 electromechani-
cal reset timing Y, N
51PTC SEL
OGIC
control
equation torque
control setting
Relay Word bits referenced in Table 9.5 or set directly
to logical 1 (=1)—see note
NOTE:
SEL
OGIC
control equation
torque control settings (e.g., 51PTC)
cannot be set directly to logical 0.