Schweitzer Engineering Laboratories SEL-387E - Page 62

3-14 Protection Functions Date Code 20080110
SEL-387E Instruction Manual
that is,
IAW
n C = IAW n
IBW
n C = IBW n
ICW
n C = ICW n
The “1” setting performs a 30-degree compensation in the counterclockwise direction, as would a
delta CT connection of type DAB (30-degree leading). The name for this connection comes from
the fact that the polarity end of the A-phase CT connects to the nonpolarity end of the B-phase
CT, and so on, in forming the delta. Thus, for W
n CTC = 1, the relay uses the following
[CTC(
m )] matrix:
() []
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
−
−
−
=
101
110
011
•
3
1
1CTC
that is,
(
)
3
IBWnIAWn
IAWnC
−
=
(
)
3
ICWnIBWn
IBWnC
−
=
(
)
3
IAWnICWn
ICWnC
−
=
The “11” setting performs a 330-degree compensation (11 • 30) in the counterclockwise
direction, or a 30-degree compensation in the clockwise direction, as would a delta CT
connection of type DAC (30-degree lagging). The name for this connection comes from the fact
that the polarity end of the A-phase CT connects to the nonpolarity end of the C-phase CT, and so
on, in forming the delta. Thus, for W
n CTC = 11, the relay uses the following [CTC( m )] matrix:
() []
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
−
−
−
=
110
011
101
•
3
1
11CTC
that is,
(
)
3
ICWnIAWn
IAWnC
−
=
3
IAWnIBWn
IBWnC
−
=
(
)
3
IBWnICWn
ICWnC
−
=
The effect of each compensation on balanced three-phase currents is to rotate them
m • 30°
without a magnitude change.