ABB Relion 650 Series Applications Manual page 123

1MRK 505 287-UUS B
In very stable power systems the frequency difference is insignificant or zero for manually initiated
closing or closing by automatic restoration. In steady conditions a bigger phase angle difference
can be allowed as this is sometimes the case in a long and loaded parallel power line. For this
application we accept a synchronism check with a long operation time and high sensitivity
regarding the frequency difference. The phase angle difference setting can be set for steady state
conditions.
Another example is the operation of a power network that is disturbed by a fault event: after the
fault clearance a highspeed auto-reclosing takes place. This can cause a power swing in the net
and the phase angle difference may begin to oscillate. Generally, the frequency difference is the
time derivative of the phase angle difference and will, typically oscillate between positive and
negative values. When the circuit breaker needs to be closed by auto-reclosing after fault-
clearance some frequency difference should be tolerated, to a greater extent than in the steady
condition mentioned in the case above. But if a big phase angle difference is allowed at the same
time, there is some risk that auto-reclosing will take place when the phase angle difference is big
and increasing. In this case it should be safer to close when the phase angle difference is smaller.
To fulfill the above requirements the synchronism check function is provided with duplicate
settings, one for steady (Manual) conditions and one for operation under disturbed conditions
(Auto).
SynchroCheck
V-Bus > 80 % of
V-Line > 80 % of
VDiffSC < 0.02 – 0.50 p.u.
PhaseDiffM < 5 - 90 degrees
PhaseDiffA < 5 - 90 degrees
FreqDiffM < 3 - 1000 mHz
FreqDiffA < 3 - 1000 mHz
ANSI10000195 V2 EN-US
Figure 42: Principle for the synchronism check function
10.1.2.3 Energizing check
The main purpose of the energizing check function is to facilitate the controlled re-connection of
disconnected lines and buses to energized lines and buses.
The energizing check function measures the bus and line voltages and compares them to both
high and low threshold values. The output is given only when the actual measured conditions
Busbar protection REB650
Application manual
Bus voltage
Fuse fail
GblBaseSelBus
GblBaseSelLine
Line voltage
Fuse fail
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Line
reference
voltage
ANSI10000195-2-en.vsd
Section 10
Control
M12310-3 v9
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