Schweitzer Engineering Laboratories SEL-321 - Page 314

7-44 Maintenance and Testing Date Code 20011026
SEL-321/321-1 Instruction Manual
°∠=
°∠=
°−∠=
0.00.0I
0.00.0I
42.825.2I
C
B
A
()
amps42.8283.0I
amps42.825.2I
2
3
1
2
°−∠=
°−∠⋅=
Using Equation 7.2 to calculate Z2, the result is:
() ( )
ohms91.2FT2Z
47.1525.077.025.1FT2Z
ohms47.15m2Z
ohms66.10c2Z
−=
⋅−⋅=
=
−=
The relay example Z2F setting is 0.77 Ω. Z2c applied (-10.66 Ω) is less than the
Z2FT threshold (-2.91 Ω), therefore, the 32QF element asserts when these signals
are applied. If Z2c applied is greater than the Z2FT threshold, select new test current
and voltages using the steps outlined above.
Step 5. Turn on the voltage sources. Apply V
A
, V
B
, and V
C
at the magnitudes and angles
listed in Table 7.4. Turn on the current test source. Set the current angle to -82°.
Slowly increase the magnitude of current applied until the Z2G element asserts,
causing OUT7 to close. This occurs when current applied is approximately 2.5
amps.
You may wish to test the distance element characteristic at impedance angles other
than the line positive-sequence impedance angle. To do this, you must adjust the
magnitude and angle of I
TEST
from the values shown in Table 7.4. As an example,
calculate the current signal necessary to test the distance element at an angle of
38.97°.
First, the new desired impedance angle (38.97°) is 45° less than the original test
impedance angle (83.97°). Add 45° to the angle of I
TEST1
.
°−=∠
°+°−=∠
°+∠=∠
97.128I
4597.173I
45II
2TEST
2TEST
1TEST2TEST
Calculate the magnitude of I
TEST2
using Equation 7.11.
()
sec,amps
Angle ImpedanceTest NewAngle Impedance Linecos
I
I
1TEST
2TEST
−
=
()
()
amps54.3I
amps
45cos
5.2
I
amps
97.3897.83cos
5.2
I
2TEST
2TEST
2TEST
=
°
=
°−°
=
Equation 7.11