Sel 421 - Table 6.7 Selectable Operating Quantity Time-Overcurrent Element (51 S1) Default Settings

U.6.21
Date Code 20090715 User’s Guide SEL-421 Relay
Testing and Troubleshooting
Test Methods
The relay uses Equation 6.1 and Equation 6.2 to determine the operating time
for the 51S1 element. For a current input 50 percent greater than the default
pickup, the test value, I
TEST,
is:
Equation 6.1
where M is the pickup multiple and 51S1P is the element pickup value (see
Table 6.7).
The operating time (t
p
) for a time dial (TD) equal to 1 for the U3 (Very
Inverse) Curve is:
Equation 6.2
For more information on the 51S elements, see Inverse-Time Overcurrent
Elements on page R.1.70.
In this example, use
ACSELERATOR QuickSet to configure the relay. You must
have a computer that is communicating with the SEL-421 and running the
ACSELERATOR QuickSet (see Making Settings Changes: Initial Global
Settings on page U.4.17). You also need a variable current source for relay
testing.
Step 1. Prepare to control the relay with
ACSELERATOR QuickSet by
establishing communication, checking passwords, and reading
relay settings (see Making Settings Changes: Initial Global
Settings on page U.4.17).
Step 2. Set the selectable operating quantity time-overcurrent element
for test operation.
a. Open the Group 1 > Relay Configuration > Time
Overcurrent branch of the Settings tree view (see
Figure 6.13).
b. In the Time Overcurrent dialog box, check that setting
51S1O Operating Quantity is at 3I0L.
Table 6.7 Selectable Operating Quantity Time-Overcurrent Element (51S1)
Default Settings
Setting Description Default 5A
51S1O 51S1 Operating Quantity (IAn, IBn, ICn, IMAXn, I1L,
3I2L, 3I0L, 3I01, 3I02)
a
a
n is L, 1, and 2 for Line, Circuit Breaker 1, and Circuit Breaker 2, respectively.
3I0L
51S1P 51S1 Overcurrent Pickup (0.25–16 amps, secondary) 0.75
51S1C 51S1 Inv-Time Overcurrent Curve (U1–U5, C1–C5) U3
51S1TD 51S1 Inv-Time Overcurrent Time Dial (0.50–15.0) 1.00
51S1RS 51S1 Inv-Time Overcurrent EM Reset (Y, N) N
51S1TC 51S1 Torque Control (SEL
OGIC control equation) 32GF
I
TEST
M • (51S1P)=
1.5 • (0.75 A) =
1.125 A=
t
p
TD • 0.0963
3.88
M
2
1–
----------------+



=
1 • 0.0963
3.88
1.5
2
1–
-------------------+=
3.2 seconds=
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