BE1-46N Functional Description
3-5
I
full load
15 MVA x 1000
3 (13.8 (KV ))
627.55 A
I
full load
15 MVA x 1000
3 (13.8 (KV ))
627.55 A
I
secondary
627.56 x
5
800
3.92 A
I
secondary
627.56 x
1
800
0.784 A
I
2
1
3
(I
A
.
2
I
B
.
I
C
)
if, I
B
I
C
0
then, I
2
I
A
3
I
single
phase
3
j
I
2
pu
I
2
I
nominal
1
3
I
single
phase
I
nominal
I
nominal
1
3
I
single
phase
I
2
pu
I
single
phase
3(I
nominal
)(I
2
pu)
CALCULATION EXAMPLE
Assume the generator to be protected is rated:
5 Amp CT
1 Amp CT
15 MVA
13.8 kV
CT Ratio 800/5 A
15 MVA
13.8 kV
CT Ratio 800/1 A
The calculated full load current would be:
5 Amp CT
1 Amp CT
The current being applied to the relay would be:
5 Amp CT
1 Amp CT
The relay TAP ADJUST should be set for this value of full load current.
SETTING TAP ADJUST
Two methods for setting the TAP ADJUST are the single-phase and three-phase methods. In each of these
methods, the amount of negative sequence current at which the relay is to trip must be calculated and then
applied to the relay. The TAP ADJUST CAL control is then adjusted so that the PICKUP LED lights at that
amount of negative sequence current.
Method 1, Single-Phase
If a single-phase quantity is to be applied to the relay, the following equations need to be developed and
used in the calculations.
Solving for I
nominal
Equation A is:
Solving for I
single-phase
Equation B is:
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