Sel SEL-421 - Voltage Magnitude and Angle Compensation

R.2.56
SEL-421 Relay Reference Manual Date Code 20111215
Auto-Reclosing and Synchronism Check
Synchronism Check
Figure 2.24 Example Synchronism-Check Voltage Connections to the
SEL-421
Voltage Magnitude
and Angle
Compensation
The Figure 2.24 example continues in Figure 2.25. The Figure 2.25 example
demonstrates possible voltage input connections (presuming ABC phase
rotation). The synchronism-check voltage reference (V
P
) is from the A-phase
voltage (V
A
) of the line. You can connect phase-to-phase voltage V
BC
originating from Bus 1, and connect phase-to-neutral voltage V
C
from Bus 2.
Thus, Bus 1 voltage V
BC
lags synchronism-check voltage reference V
P
by 90
degrees, and Bus 2 voltage V
C
lags the synchronism-check voltage reference
V
P
by 240 degrees. To compensate for these steady-state angle differences, set
KS1A for Bus 1 and KS2A for Bus 2.
KS1A := 90 Synchronism Source 1 Angle Shift (0, 30, …, 330 degrees)
KS2A := 240 Synchronism Source 2 Angle Shift (0, 30, …, 330 degrees)
Bus 2
Bus 1
SEL-421 rear panel
(partial)
Three-phase line
voltage connections
Separate, single-phase
bus/source
voltage connections
Line
BK2
BK1
VAY VBY VCY
VAZ VBZ VCZ
1
3
1