GE MiCOM P40 Agile Technical Manual page 167

P543i/P545i
Phase k1 = 30%
Phase k2 = 100%
Therefore, settings in primary/secondary values for each device can be calculated as follows:
Setting
Phase CT Primary
Phase CT Sec'y
Phase Is1 [p.u.]
Phase Is1 (Primary)
Phase Is1 (Secondary)
Phase Is2 [p.u.]
Phase Is2 (Primary)
Phase Is2 (Secondary)
Note:
Settings shown in primary values at ends A and B appear different compared with end C. This is not a problem as the currents
at ends A and B will be multiplied by the Correction Factor, when the differential calculation is done.
Susceptance settings for Ends A and B
With a VT ratio 275 kV/110 V and CT ratio 4000/5:
R = 800
CT
R = 2500
VT
m S
B = 310
Secondary susceptance = 310
Susceptance settings for End C
With a VT ratio 275 kV/110 V and CT ratio 1200/5:
m S
B = 310
Secondary susceptance = 310
P54x1i-TM-EN-1
End A
4000A
5A
0.2
0.2*4000 = 800A
0.2*5 = 1A
2
2*4000 = 8000A
2*5 = 10A
m S(R m S
/ R )= 968
VT CT
m S(R
/ R )= 3.22 mS
VT CT
Chapter 6 - Current Differential Protection
End B
4000A
5A
0.2
0.2*4000 = 800A
0.2*5 = 1A
2
2*4000 = 8000A
2*5 = 10A
End C
1200A
5A
0.2
0.2*1200 = 240A
0.2*5 = 1A
2
2*1200 = 2400A
2*5 = 10A
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