ABB RELION 620 Series Technical Manual page 760

Section 9
Control functions
754
Synchro check
The Synchro check function measures the difference between the line voltage and bus
voltage. The function trips and issues a closing command to the circuit breaker when the
calculated closing angle is equal to the measured phase angle and if the conditions are
simultaneously fulfilled.
• The measured line and bus voltages are higher than the set values of Live bus value
and Live line value (ENERG_STATE equals to "Both Live").
• The measured bus and line frequency are both within the range of 95 to 105 percent
of the value of f .
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• The measured voltages for the line and bus are less than the set value of Max
energizing V.
In case Syncro check mode is set to "Syncronous", the additional conditions must be
fulfilled.
• 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 .
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• The voltage difference must not exceed the 1 percent of the value of V
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.
1MAC504801-IB E
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620 series ANSI
Technical Manual