![Schweitzer Engineering Laboratories SEL-421-4 Instruction Manual Download Page 114](http://html.mh-extra.com/html/schweitzer-engineering-laboratories/sel-421-4/sel-421-4_instruction-manual_1216726114.webp)
3.10
SEL-421 Relay
Instruction Manual
Date Code 20171021
Testing
Checking Relay Operation
The relay asserts ground overcurrent elements when the 3I
0
calculation exceeds
the ground current element pickup setting. If balanced currents are applied to the
relay, the relay reads 3I
0
= 0 (load conditions) because the currents cancel in the
calculation; the relay does not pick up the ground overcurrent elements.
For testing, apply current to a single phase of the relay, causing the residual over-
current elements to operate. For example, assume 1 A of current on A-Phase and
zero current input on B-Phase and C-Phase:
3I
0
= 1 A + 0 + 0 = 1 A (a simulated ground fault condition)
Checking the Negative-Sequence Instantaneous Overcurrent Element, 50Q1
The procedure in the following steps tests the 50Q1 negative-sequence overcur-
rent element. Use a similar procedure to test other overcurrent elements.
Step 1. Configure the relay.
a. Start
AC
SEL
ERATOR
QuickSet SEL-5030 Software, and read the
present configuration in the SEL-421.
b. Click
Settings > Read
.
The relay sends all settings and configuration data to QuickSet.
c. Expand the
Group 1
settings and click the
Negative-Seq Inst
O/C
button of the
Settings
.
You will see the
Negative Sequence Instantaneous
Overcurrent
d. Click the arrow in the
Instantaneous and Definite Time
Overcurrent Element Levels E50Q
dialog box and select
1
.
e. For this test, set the
50Q1P
level to
1.00
and
67Q1TC
to
1
.
NOTE:
As you perform this test,
other protection elements can assert.
This causes the relay to assert other
targets and possibly close control
outputs. Be sure to isolate the relay
from the power system to avoid
unexpected system effects.
Figure 3.7
Negative-Sequence Instantaneous Overcurrent Element Settings: QuickSet
Summary of Contents for SEL-421-4
Page 6: ...This page intentionally left blank ...
Page 14: ...This page intentionally left blank ...
Page 30: ...This page intentionally left blank ...
Page 104: ...This page intentionally left blank ...
Page 128: ...This page intentionally left blank ...
Page 536: ...This page intentionally left blank ...
Page 584: ...This page intentionally left blank ...
Page 616: ...This page intentionally left blank ...
Page 696: ...This page intentionally left blank ...
Page 750: ...This page intentionally left blank ...
Page 755: ...Instruction Manual PM400 01 NB SEL 400 Series Relays Instruction Manual 20171006 ...
Page 776: ...This page intentionally left blank ...
Page 932: ...This page intentionally left blank ...
Page 976: ...This page intentionally left blank ...
Page 1024: ...This page intentionally left blank ...
Page 1038: ...This page intentionally left blank ...
Page 1064: ...This page intentionally left blank ...
Page 1128: ...This page intentionally left blank ...
Page 1206: ...This page intentionally left blank ...
Page 1316: ...This page intentionally left blank ...
Page 1350: ...This page intentionally left blank ...
Page 1464: ...This page intentionally left blank ...
Page 1468: ...This page intentionally left blank ...
Page 1492: ...This page intentionally left blank ...
Page 1518: ...This page intentionally left blank ...