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 phase equality.
At the setting of 10 mHz, the beat time is 100 seconds and the setting would thus need to
be at least tMinSynch plus 100 seconds. If the network frequencies are expected to be
Section 15 1MRK 506 369-UUS -
Control
650 Line distance protection REL670 2.2 ANSI
Application manual
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