ABB 650 series Applications Manual page 112

Section 8
Control
106
The setting FreqDiffMin is the minimum frequency difference where the systems
are defined to be asynchronous. For frequency differences lower than this value,
the systems are considered to be in parallel. A typical value for FreqDiffMin is 10
mHz. Generally, the value should be low if both synchronizing and synchrocheck
functions are provided, and it is better to let the synchronizing function close, as it
will close at exactly the right instance if the networks run with a frequency
difference.
To avoid overlapping of the synchronizing function and the
synchrocheck function the setting FreqDiffMin must be set to a
higher value than used setting FreqDiffM, respective FreqDiffA
used for synchrocheck.
FreqDiffMax
The setting FreqDiffMax is the maximum slip frequency at which synchronizing is
accepted. 1/FreqDiffMax shows the time for the vector to move 360 degrees, one
turn on the synchronoscope, and is called Beat time. A typical value for
FreqDiffMax is 200-250 mHz, which gives beat times on 4-5 seconds. Higher
values should be avoided as the two networks normally are regulated to nominal
frequency independent of each other, so the frequency difference shall be small.
FreqRateChange
The maximum allowed rate of change for the frequency.
CloseAngleMax
The setting CloseAngleMax is the maximum closing angle between bus and line at
which synchronizing is accepted. To minimize the moment stress when
synchronizing near a power station, a narrower limit should be used. A typical
value is 15 degrees.
tBreaker
The tBreaker shall be set to match the closing time for the circuit breaker and
should also include the possible auxiliary relays in the closing circuit. It is
important to check that no slow logic components are used in the configuration of
the IED as there then can be big variations in closing time due to those
components. Typical setting is 80-150 ms depending on the breaker closing time.
tClosePulse
The setting for the duration of the breaker close pulse.
tMaxSynch
The setting tMaxSynch is set to reset the operation of the synchronizing function if
the operation does not take place within this time. The setting must allow for the
setting of FreqDiffMin, which will decide how long it will take maximum to reach
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