• The measured difference of the voltages is less than the set value of
Difference
voltage
.
• The measured difference of the phase angles is less than the set value of
Difference angle
.
• The measured difference in frequency is less than the set value of
Frequency
difference
.
• The estimated breaker closing angle is decided to be less than the set value of
Difference angle
.
Dead line or bus value
Live line or bus value
Difference angle
U_Bus
U_Line
Difference voltage
f
U_Bus
f
U_Line
Frequency[Hz]
f = abs(f
U_Bus
- f
U_Line
)
Rated frequency
Frequency deviation
=
U_Bus
-
U_Line
Difference frequency
Figure 844: Conditions to be fulfilled when detecting synchronism between systems
When the frequency, phase angle and voltage conditions are fulfilled, the duration
of the synchronism conditions is checked so as to ensure that they are still met
when the condition is determined on the basis of the measured frequency and
phase difference. Depending on the circuit breaker and the closing system, the delay
from the moment the closing signal is given until the circuit breaker finally closes
is about 50...250 ms. The selected
Closing time of CB
informs the function how
long the conditions have to persist. The Synchro check function compensates for
the measured slip frequency and the circuit breaker closing delay. The phase angle
advance is calculated continuously with the formula.
Closing angle = ∠ − ∠
( )
° + −
( )
× +
( )
× °
( )
U U f f T T
Bus Line Bus line CB PL
360
(Equation 352)
∠ U
Bus
Measured bus voltage phase angle
∠U
Line
Measured line voltage phase angle
f
Bus
Measured bus frequency
f
line
Measured line frequency
T
CB
Total circuit breaker closing delay, including the delay of the protection relay
output contacts defined with the
Closing time of CB
setting parameter value
T
PL
Output type dependent delay according to
Table 1505
Table 1505: Typical delays for different output types
Output type
Recommended value for T
PL
Semiconductor output (HSO, SPO) 0 ms
Mechanical relay output (POSP, PODP, PO) 6 ms
1MRS759142 F Control functions
REX640
Technical Manual
1547
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