Section 4 1MDU07212-YN Rev. C
Protection and Control Function
20 REF601 / REJ601
Application Manual
4.5.2 Principle of Operation
The unbalance of network is detected by monitoring the ratio of negative sequence
current to positive sequence current I
2
/I
1
. The function operates when the ratio of
unbalance current I
2
/I
1
exceeds the set value. When the set definite time operation
timer has reached the value set by the operate delay time, the OPERATE output is
activated.
On occurrence of fault, fulfilling the trip condition of respective stage, the LED
“Trip” and programmable LED if configured will be activated. Additionally the
output relays (Trip and signalization) will be activated according the binary output
configuration.
The phase discontinuity protection will be inhibited when all phase currents fall
below 0.1 x In.
The protection could be blocked by settings or via binary input of the relay.
Table 11: Setting ranges Phase discontinuity protection
Parameter Value (Range)
Start value, ‘I2/I1>” 10…100%, in steps of 1%
Operate delay time, ‘tI2/I1>’ 0.1 … 64 sec, in steps of 0.1
Block the phase discontinuity
protection
0 = No, 1 = Yes
Operation accuracy ± 5.0% of set value
Operation time accuracy 3% of set or ± 30 ms
Reset ratio 0.98
4.6 Circuit breaker failure protection
4.6.1 Functionality
The circuit breaker failure protection function provides re-trip and back-up trip
signal in case circuit breaker under operation fails to open. Function is activated by
trip commands from the protection functions or via external protection trip using
binary input.
The function has two independent timers for trip purposes: a re-trip timer for the
repeated tripping of its own breaker and a back-up timer for the trip logic operation
for upstream breakers.
The protection could be blocked by settings of the relay.
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