U.6.21
Date Code 20020501
User’s Guide
SEL-421/SEL-421-1 Relay
Testing and Troubleshooting
Test Methods
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
Elements on page R.1.69 in the Reference Manual
.
In this example, use the
AC
SEL
ERATOR
software to configure the relay. You
must have a computer that is communicating with the SEL-421 Relay and
running the
AC
SEL
ERATOR
software; see
Making Settings Changes: Initial
Global Settings on page U.4.19 in the User’s Guide
.
You also need a variable
current source for relay testing.
Step 1. Prepare to control the relay with the
AC
SEL
ERATOR
software.
Establish communication, check passwords, and read relay
settings; see
Making Settings Changes: Initial Global Settings
on page U.4.19 in the User’s Guide
Step 2. Set the selectable operating quantity time-overcurrent element
for test operation. Open the Group 1 > Relay Configuration >
Time Overcurrent branch of the Settings tree view (see
). In the Time Overcurrent dialog box, check that
setting 51S1O Operating Quantity is at 3I0L. Check the
remaining element configurations against
. In addition, set torque control 51S1TC to
1
to
constantly operate the 51S1 element; type
1
in the text box for
51S1TC. (For more information on using the
AC
SEL
ERATOR
software to change settings, see
Making Initial Global Settings:
Software on page U.4.25 in the User’s Guide
.)
Figure 6.13
Checking the 51S1 Overcurrent Element:
AC
SEL
ERATOR
Software.
Step 3. View SER settings. Click on the + mark next to the Report
branch of the
AC
SEL
ERATOR
software Settings tree view
structure shown in
. Click on the SER
Points and Aliases branch. You will see the SER Points and
Aliases dialog box (see
t
p
TD • 0.0963
3.88
M
2
1
–
----------------
+
è
ø
ç
÷
æ
ö
=
1 • 0.0963
3.88
1.5
2
1
–
-------------------
+
=
3.2 seconds
=
Summary of Contents for SEL-421
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