ABB RELION 620 Series Technical Manual page 1006

Section 9
Control functions
1000
• In the synchronous mode, the closing is attempted so that the phase difference at
closing is close to zero.
• The synchronous mode is only possible when the frequency slip is below 0.1
percent of the value of f
• The voltage difference must not exceed the 1 percent of the value of U
In case Syncro check mode is set to "Asyncronous", the additional conditions must be
fulfilled.
• 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.
Difference angle
U_Bus
GUID-191F6C44-7A67-4277-8AD1-9711B535F1E1 V2 EN
Figure 515: 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.
.
n
= -
U_Bus U_Line
Difference voltage
U_Line
Live line or bus value
Dead line or bus value
Frequency deviation
1MRS757644 F
.
n
Difference frequency
f f f
= abs( - )
U_Bus U_Line
f
f
U_Line
U_Bus
Frequency[Hz]
Rated frequency
620 series
Technical Manual