Schweitzer Engineering SEL-387-0 - Page 66

3.16
SEL-387-0, -5, -6 Relay Instruction Manual Date Code 20170601
Differential, Restricted Earth Fault, Thermal, and Overcurrent Elements
Differential Element
Compensation matrix CTC(0) is intended to create no changes at all in the
currents and merely multiplies them by an identity matrix. Compensation
matrix CTC(12) is similar to CTC(0), in that it produces no phase shift (or,
more correctly, 360 degrees of shift) in a balanced set of phasors separated by
120 degrees. However, it removes zero-sequence components from the
winding current, as do all of the matrices with non-zero values of m.
Use the following guidelines to determine correct compensation settings for
each winding.
Step 1. Determine the phase shift as seen by the relay. The following
information is required to accurately determine this phase shift.
➢ Transformer winding connection diagram (transformer
nameplate)
➢ Three-line connection diagram showing: (1) system
phase-to-transformer bushing connections, (2) current
transformer (CT) connections, and (3) CT-to-relay
connections
Step 2. Choose one of the relay current inputs as the reference winding.
➢ If a delta winding exists and is wired into the relay,
choose it as the reference. Select matrix CTC(0) for the
compensation of the delta winding.
➢ If a delta winding does not exist, select matrix CTC(11)
for the compensation of one of the wye windings.
9 CTC(9) 270° CCW 270° CW
10 CTC(10) 300° CCW 300° CW
11 CTC(11) 330° CCW 330° CW
12 CTC(12)
0° (360°)
CCW
0° (360°)
CW
a
n = 1, 2, 3, 4.
Table 3.1 WnCTC Setting: Corresponding Phase and Direction of
Correction (Sheet 2 of 2)
WnCTC
Setting
a
Matrix Compensation Matrices
Amount and Direction of
Correction
ABC Phase
Rotation
ACB Phase
Rotation
1
3
-------
0 1 –1
–1 0 1
1 –1 0

1
3
---
1 1 –2
–2 1 1
1 –2 1

1
3
-------
1 0 –1
–1 1 0
0 –1 1

1
3
---
2 –1 –1
–1 2 –1
–1 –1 2
