ABB RELION RET670 Applications Manual page 701

1MRK 504 163-UUS A
Transformer protection RET670 2.2 ANSI
Application manual
expected to be outside the limits from the start, a margin needs to be added. A typical
setting is 600 seconds.
tMinSynch
The setting tMinSynch is set to limit the minimum time at which the synchronizing
closing attempt is given. The synchronizing function will not give a closing command
within this time, from when the synchronizing is started, even if a synchronizing
condition is fulfilled. A typical setting is 200 ms.
Synchrocheck settings
OperationSC
The OperationSC setting Off disables the synchrocheck function and sets the outputs
AUTOSYOK, MANSYOK, TSTAUTSY and TSTMANSY to low. With the setting
On, the function is in the service mode and the output signal depends on the input
conditions.
VHighBusSC and VHighLineSC
The voltage level settings must be chosen in relation to the bus or line network voltage.
The threshold voltages VHighBusSC and VHighLineSC have to be set lower than the
value at which the breaker is expected to close with the synchronism check. A typical
value can be 80% of the base voltages.
VDiffSC
The setting for voltage difference between line and bus in p.u. This setting in p.u. is
defined as (V-Bus/GblBaseSelBus) - (V-Line/GblBaseSelLine). A normal setting is
0,10-0,15 p.u.
FreqDiffM and FreqDiffA
The frequency difference level settings, FreqDiffM and FreqDiffA, shall be chosen
depending on the condition in the network. At steady conditions a low frequency
difference setting is needed, where the FreqDiffM setting is used. For autoreclosing a
bigger frequency difference setting is preferable, where the FreqDiffA setting is used.
A typical value for FreqDiffM can be10 mHz, and a typical value for FreqDiffA can be
100-200 mHz.
PhaseDiffM and PhaseDiffA
The phase angle difference level settings, PhaseDiffM and PhaseDiffA, shall also be
chosen depending on conditions in the network. The phase angle setting must be
chosen to allow closing under maximum load condition. A typical maximum value in
heavy-loaded networks can be 45 degrees, whereas in most networks the maximum
occurring angle is below 25 degrees. The PhaseDiffM setting is a limitation to
Section 15
Control
695