U.6.28
SEL-421 Relay
User’s Guide
Date Code 20090715
Testing and Troubleshooting
Checking Relay Operation
Figure 6.20
ELEMENT SEARCH Screen
Figure 6.21
RELAY ELEMENTS Screen Containing Element 50Q1
Step 4. Connect a test source to the relay.
a. Set the current output of a test source to zero output
level.
b. Connect a single-phase current output of the test source
to the IAW analog input (see
Step 5. Increase the current source to produce a current magnitude
greater than 1.00 A secondary in the relay.
You will see that the 50Q1 element state changes on the LCD
screen from 50Q1 = 0 to 50Q1 = 1.
Negative-Sequence
Directional Element
for Phase Faults
The SEL-421 features a phase directional element (represented by Relay Word
bits F32P/R32P) to supervise the phase distance elements and to control phase
directional elements. The negative-sequence directional element, F32Q/R32Q,
is a part of the phase directional element, F32P/R32P. Whenever the negative-
sequence directional element asserts, the phase directional element asserts.
The relay also contains a ground directional element, F32G/R32G, for
directional control of the ground distance elements and ground overcurrent
elements. For more information on directional elements, see
Directional Element on page R.1.27
, and
Section 1: Protection Application
Examples in the Applications Handbook
The SEL-421 calculates the negative-sequence impedance Z2 from the
magnitudes and angles of the negative-sequence voltage and current.
defines this function (the ‘c’ in Z2c indicates “calculated”).
Equation 6.3
ELEMENT SEARCH
A B C D E F
G H I J K L
M N O P Q R
S T U V W X
Y Z 0 1 2 3
4 5 6 7 8 9
-
ACCEPT BACKSPACE
PRESS to search
RELAY ELEMENTS
SEARCH
ROW 26
ROW 27
67Q4 =0
* =0
67Q3 =0
* =0
67Q2 =0
* =0
67Q1 =0
* =0
50Q4 =0
67Q4T =0
50Q3 =0
67Q3T =0
50Q2 =0
67Q2T =0
50Q1 =0
67Q1T =0
Z2c
Re V
2
1 Z1ANG
I
2
•
∠
(
)∗
•
[
]
I
2
2
-------------------------------------------------------------------------
=
V
2
I
2
--------- • cos
V
2
Z1ANG
I
2
∠
–
∠
–
∠
(
)
=
Содержание 421
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