3-80
Line Current Differential, Distance, Out-of-Step, Overcurrent,
Date Code 20011112
Voltage, Synchronism Check, and Frequency Elements
SEL-311L Instruction Manual
Angle Difference Calculator
The synchronism check element Angle Difference Calculator in Figure 3.54 runs if the slip
frequency is less than the maximum slip frequency setting 25SF (Relay Word bit SF is asserted).
Voltages V
P
and V
S
are “Static”
Refer to top of Figure 3.54.
If the slip frequency is less than or equal to 0.005 Hz or TCLOSD = OFF, 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
)
Voltages V
P
and V
S
are “Slipping”
Refer to bottom of Figure 3.54.
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