Date Code 20000421
Maintenance and Testing
7-11
SEL-251, -2, -3 Instruction Manual
What Should Be Tested
A full functional test includes the initial checkout procedure and the additional steps described
below. In general, these tests assure that the relay settings match your application rather than
checking relay performance. For commissioning purposes, your company policy may require
you to perform the full functional test. For maintenance purposes, a quick test of selected fault
types and elements should suffice.
Setting Test
Purpose:
Ensure that the relay accepts settings.
Method:
1. Gain Level 2 Access (see
ACCESS
and
2ACCESS
commands in
Section 3:
Communications
).
2. Change one setting in setting group 1. For example, change the ground/residual
time-overcurrent element pickup from 1.5 amperes secondary to 2.0 amperes
secondary.
Type
SET 1 51NP
and press
<ENTER>
.
Following the
51NP
prompt, type
2.0
and press
<ENTER>
.
3. To complete the setting procedure, type
END
and press
<ENTER>
. Type
Y
<ENTER>
at the prompt: "OK (Y or N) ?" The relay computes internal
settings and compares them against fixed limits. If all settings are within
acceptable ranges, the ALARM contact closes momentarily as the new settings
are enabled unless an alarm condition already exists (e.g., self-test failure).
4. Use the SHOWSET command to inspect settings. Make sure your change was
accepted.
Type
SHOWSET
1
and press
<ENTER>
.
5. Use SET and SHOWSET again to restore the initial values and check the
settings.
Meter Test
Purpose:
Verify that magnitude accuracy and phase balance. This test only requires a single
voltage and current test source.
Method:
1. Parallel all voltage inputs by connecting terminals 37, 38, and 39 with a jumper.
See Figure 7.4 for the test connections.
2. Series all current inputs as shown in Figure 7.4.