U.6.32
SEL-421/SEL-421-1 Relay
User’s Guide
Date Code 20020501
Testing and Troubleshooting
Checking Relay Operation
Step 4. Display the F32Q and R32Q Relay Word bits on the front-
panel LCD screen. Access the front-panel LCD MAIN MENU.
Highlight RELAY ELEMENTS and press
{ENT}
. You will see
a RELAY ELEMENTS screen with SEARCH highlighted at
the bottom of the screen. Press
{ENT}
to go to the ELEMENT
. Enter
characters in the text input field using the navigation keys.
Highlight F and press
{ENT}
to enter the F character. Enter the
3, 2, and Q characters in like manner. Highlight ACCEPT and
press
{ENT}
. The relay displays the screen containing the
F32Q and R32Q elements, as shown in
.
Figure 6.28
RELAY ELEMENTS LCD
Screen Containing Elements F32Q and R32Q.
Step 5. Calculate impedance thresholds. For this test, apply an A-phase
voltage of V
A
= 3V
2
= 18.0
Ð
180
°
V secondary. Use
to find the current that is equal to
the reverse impedance threshold Z2R:
Step 6. Use
to find the current that is equal
to the forward impedance threshold Z2F:
Step 7. Use
to determine the applied current
angle (
Ð
I
TEST
):
Step 8. Apply a test current to confirm operation of R32Q and F32Q.
Connect a single current test source as shown in
. Apply an A-phase voltage of V
A
= 18.0
Ð
180
°
V
secondary. Set the current source for I
A
= 0.0
Ð
96
°
A. Slowly
increase the magnitude of I
A
to apply the source test current
..
Observe the RELAY ELEMENT LCD screen. Relay Word bit
R32Q asserts when |I
A
| = 0.4 A, indicating that the relay
negative-sequence current is greater than the 50RP pickup
threshold. R32Q deasserts when |I
A
| = 4.5 A, indicating that the
relay negative-sequence calculation Z2c is now less than the Z2
reverse threshold Z2R. (See
Reverse Threshold on page R.1.30
page R.1.30 in the Reference Manual
.) Continue to increase the
current source while you observe the RELAY ELEMENT LCD
screen. Relay Word bit F32Q asserts when |I
A
| = 4.62 A,
indicating that the relay negative-sequence calculation Z2c is
less than the Z2 forward threshold Z2F.
PRESS TO SEARCH
RELAY ELEMENTS
SEARCH
ROW 20
ROW 21
32SPOR =0 32IE =0
32SPOF =0 32VE =0
32QR =0 32QGE =0
32QF =0 32QE =0
R32Q =0 50GR =0
F32Q =0 50GF =0
R32P =0 50QR =0
F32P =0 50QF =0
I
TEST
3I
2
3V
2
Z2R
-------------
18.0 180
°
V
Ð
4.00
---------------------------------- 4.50
A
=
=
=
=
I
TEST
3I
2
3V
2
Z2RF
---------------
18.0 180
°
V
Ð
3.90
---------------------------------- 4.62
A
=
=
=
=
I
TEST
Ð
3I
2
3V
2
Ð
Z1ANG 180
°
84
°
96
°
=
–
=
Ð
–
=
Ð
=
Summary of Contents for SEL-421
Page 8: ...This page intentionally left blank ...
Page 30: ...This page intentionally left blank ...
Page 110: ...This page intentionally left blank ...
Page 204: ...This page intentionally left blank ...
Page 284: ...This page intentionally left blank ...