Schweitzer Engineering Laboratories SEL-311C - Page 486

13.32
SEL-311C Relay Instruction Manual Date Code 20060320
Testing and Troubleshooting
Test Procedures
Step 19. Slowly increase the magnitude of I
A
, without varying the phase
angle.
The relay R32Q element asserts, closing OUT107 when |I
A
| = 0.5
amps. This indicates that Z2c applied is greater than Z2RT, 3I
2
is greater than 50QR, and I
2
is greater than a2 • I
1
, where a2 is
the relay setting.
Step 20. Continue to increase the magnitude of I
A
. R32Q deasserts
when |I
A
| = 3.3 amps, indicating that Z2c is now less than
Z2RT. F32Q asserts, closing OUT106 when |I
A
| = 23.4 amps,
indicating that Z2c is less than Z2FT.
Step 21. Verify that the relay operated properly by calculating Z2c
through use of Equation 13.1 and the test quantities listed
below.
For:
I
A
= 3.30 A ∠96°
V
A
= 49.0 V ∠0°
V
B
= 67.0 V∠–120°
V
C
= 67.0 V∠120°
V
2
= 6.0 V ∠180°
I
2
= 1.10
1 ∠Z1ANG° = 1 ∠83.97°
Equation 13.31
For
I
A
= 23.4 A ∠96°
V
A
= 49.0 V ∠0°
V
B
= 67.0 ∠–120°
V
C
= 67.0 V ∠120°
V
2
= 6.0 V ∠180°
I
2
= 7.80
1 ∠Z1ANG° = 1 ∠83.97°
Equation 13.32
Z2c
Re V
2
1 Z1ANG°∠ I
2
• ()*• []
I
2
2
-----------------------------------------------------------------------------=
Re 6 180° 183.97°∠ 1.10• 96°∠()• ∠ *[]
1.10
2
-----------------------------------------------------------------------------------------------------=
6.6 ohms
1.21
----------------------=
5.45 ohms Z2RT when Z2m = 5.45 ohms==
NOTE: As you perform this test,
other protection elements can assert,
causing the relay to close other
output contacts and assert relay
targets. This is normal and is not a
cause for concern.
Z2c
Re 6 180° 183.97°∠ 7.80• 96°∠()• ∠ *[]
7.80
2
-----------------------------------------------------------------------------------------------------=
46.8 ohms
60.84
-------------------------=
0.77 ohms Z2F when Z2m = 0.77 ohms==