4.21
Date Code 20170814
Instruction Manual
SEL-700G Relay
Protection and Logic Functions
Group Settings (SET Command)
Winding Connection Review.
Figure 4.13 shows the three basic winding
connections, consisting of a wye connection and the two possible delta
connections.
Figure 4.13
Winding Connections, Phase Shifts, and Compensation Direction
The wye connection consists of connecting one end of each winding to a
common or neutral point, leaving the other ends of each winding for the line
terminals. Because the windings do not interconnect at the line ends, the line
current equals the respective winding current, A, B, or C, and no phase shift
occurs in the line currents with respect to the winding currents. The neutral
point, if it is grounded, permits flow of zero-sequence current components in
the windings and line outputs.
There are two possible delta connections. In determining CTCn, it is essential
to know not only that the CTs or transformer windings are connected in delta
but in which delta. In this manual we call these delta connections DAB and
DAC. In the DAB connection the polarity end of the A winding connects to
the nonpolarity end of the B winding, and so on, to produce the delta. In the
DAC connection the polarity end of the A winding connects to the nonpolarity
end of the C winding, and so on, to produce the delta. In Figure 4.13, an
arrowhead indicates the polarity end of each winding.
These arrangements involve a connection point between two windings at each
line terminal; the line currents are not the same as the winding currents, but
are in fact the phasor difference between the associated winding currents.
Therefore, the line currents will shift in phase by some amount with respect to
the winding currents. In the DAB connection the line currents from the A, B,
and C line terminals are, respectively, A-B, B-C, and C-A in terms of the
winding currents. In the DAC connection the line currents from the A, B, and
C line terminals are, respectively, A-C, B-A, and C-B in terms of the winding
A
Connection
Line Outputs
Connection Phase Shift
ABC Rotation
ACB Rotation
WYE
DAB
DAC
(Xfmr. or CT)
A, B, C
A—B, B—C, C—A
A—C, B—A, C—B
A
C
B
C
B
0°
30° CCW
30° CW
0°
30° CW
30° CCW
A
C
B
A
B
C
B
C
A
B
C
CTCn
(CCW)
CTCn
(CW)
A
CTCn
Direction
Summary of Contents for SEL-700G Series
Page 14: ...This page intentionally left blank ...
Page 22: ...This page intentionally left blank ...
Page 32: ...This page intentionally left blank ...
Page 52: ...This page intentionally left blank ...
Page 106: ...This page intentionally left blank ...
Page 510: ...This page intentionally left blank ...
Page 560: ...This page intentionally left blank ...
Page 578: ...This page intentionally left blank ...
Page 588: ...This page intentionally left blank ...
Page 604: ...This page intentionally left blank ...
Page 634: ...This page intentionally left blank ...
Page 738: ...This page intentionally left blank ...
Page 802: ...This page intentionally left blank ...