R.2.66
SEL-421 Relay Reference Manual Date Code 20111215
Auto-Reclosing and Synchronism Check
Synchronism Check
Alternative
Synchronism-Check
Source 2 Settings
You can program alternative input sources for the synchronism-check function
in the SEL-421. Alternative inputs give you additional flexibility to
synchronize other portions of your power system.
The SEL
OGIC control equation ALTS2 determines when the relay uses
alternate Synchronism-Check Voltage Source 2 in place of regular
Synchronism-Check Voltage Source 2. When ALTS2 is logical 1, the relay
substitutes alternative Synchronism-Check Voltage Source 2 (ASYNCS2) and
corresponding settings AKS2M and AKS2A for the regular Synchronism-
Check Voltage Source 2 values SYNCS2, KS2M, and KS2A. The result is a
normalized synchronism-check voltage source V
S2
derived from the
alternative source.
EXAMPLE 2.2 Setting Alternative Synchronism-Check Source 2
Figure 2.32 shows an extra circuit breaker (BK3) and a generator
position added to the existing example system of Figure 2.21. You can
monitor the voltage at the generator position by connecting a single-
phase voltage to remaining voltage input VCZ (see Figure 2.24). Make
setting ASYNCS2 := VCZ to designate this relay voltage input as the
alternate synchronism-check voltage source.
ASYNCS2 := VCZ Alternative Synchronism Source 2 (VAY, VBY, VCY,
VAZ, VBZ, VCZ)
For this new synchronism source voltage connection, adjust the
source-to-reference magnitude ratio with setting AKS2M and the
source-to-reference angle compensation with setting AKS2A,
considering the settings for Voltage Magnitude and Angle
Compensation on page R.2.56.
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