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3.41
Date Code 20070117
Instruction Manual
SEL-351-5, -6, -7 Relay
Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements
Synchronism Check Elements
If the slip frequency is less than or equal to 0.005 Hz, the Angle Difference
Calculator does
not
take into account breaker close time—it presumes
voltages V
P
and V
S
are “static” (not “slipping” with respect to one another).
This would usually be the case for an open breaker with voltages V
P
and V
S
that are paralleled via some other electric path in the power system. The Angle
Difference Calculator calculates the angle difference between voltages V
P
and
V
S
:
Angle Difference = |(
∠
V
P
–
∠
V
S
)|
For example, if SYNCP = 90 (indicating V
S
constantly lags V
P
= V
A
by
90 degrees), but V
S
actually lags V
A
by 100 angular degrees on the power
system at a given instant, the Angle Difference Calculator automatically
accounts for the 90 degrees and:
Angle Difference = |(
∠
V
P
–
∠
V
S
)| = 10°
Also, if breaker close time setting TCLOSD = 0.00, the Angle Difference
Calculator does not take into account breaker close time, even if the voltages
V
P
and V
S
are “slipping” with respect to one another. Thus, synchronism
check elements 25A1 or 25A2 assert to logical 1 if the Angle Difference is
less than corresponding maximum angle setting 25ANG1 or 25ANG2.
Содержание SEL-351-5
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