Schweitzer Engineering Laboratories SEL-311C - Page 485

13.31
Date Code 20060320 Instruction Manual SEL-311C Relay
Testing and Troubleshooting
Test Procedures
Equation 13.26
Step 14. Because Z2R is positive, use Equation 13.7 to calculate Z2RT:
Equation 13.27
The R32Q element asserts when Z2c applied is greater than
Z2RT. As the magnitude of I
A
increases, the magnitudes of Z2c
and Z2m decrease. For magnitudes of I
A
less than 3.3 amps,
R32Q asserts, given the other test quantities. For I
A
magnitudes
greater than 3.3 amps, Z2c is less than Z2RT, so R32Q
deasserts.
For Z2F = 0.77 Ω:
Equation 13.28
Step 15. Calculate Z2m:
Equation 13.29
Step 16. Because Z2F is positive, use Equation 13.5 to calculate Z2FT.
Equation 13.30
The F32Q element asserts when Z2c is less than Z2FT. As the
magnitude of I
A
increases, the magnitudes of Z2c and Z2m
decrease. For magnitudes of I
A
less than 23.4 amps, F32Q
should not assert, given the other test quantities. For I
A
magnitudes greater than 23.4 amps, Z2c applied is less than
Z2FT, so F32Q asserts.
Step 17. Turn on the voltage sources.
Step 18. Apply:
V
A
= 49.0 V ∠0°
V
B
= 67.0 V ∠–120°
V
C
= 67.0 V ∠120°
I
A
= 0.0 A ∠96°
Z2m
V
2
I
2
---------=
6.0 V
1.1 A
-------------=
5.45 ohms=
Z2RT 0.75 Z2R 0.25 Z2m• +• =
0.75 5.45()0.25 5.45()• +• =
5.45 ohms=
I
A
3
6.0 volts
0.77 ohms
-------------------------
⎝⎠
⎛⎞
• =
I
A
23.4 amps=
Z2m
V
2
I
2
---------=
6.0 V
7.8 A
-------------=
0.77 ohms=
Z2FT 1.25 Z2F 0.25–Z2m• • =
1.25 0.77()0.25–0.77()• • =
0.77 ohms=