1MDU07212-YN Rev. C Section 4
Protection and Control Function
REF601 / REJ601 19
Application Manual
4.4 Negative-sequence overcurrent protection
4.4.1 Functionality
The negative-sequence overcurrent protection is used for increasing sensitivity to
detect unbalance load or unsymmetrical feeder voltages.
The operate time characteristics is based on definite time (DT) i.e. function
operates after a predefined operate time and resets when the fault current
disappears.
4.4.2 Principle of Operation
The function is based on the measurement of negative sequence current. In a fault
situation, the function starts when the negative sequence current (I2) 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 protection could be blocked by settings or via binary input of the relay.
Table 10: Setting ranges Negative sequence overcurrent protection
Parameter Value (Range)
Start value, ‘I2>” 0.1…1.5 x In, in steps of 0.01
Operate delay time, ‘tI2>’ 0.1 … 300 sec, in steps of 0.1
Block the negative phase sequence
protection
0 = No, 1 = Yes
Operation accuracy ± 5.0% of set value
Operation time accuracy 3% of set value or ± 30ms
Reset ratio 0.98
4.5 Phase discontinuity protection
4.5.1 Functionality
The phase discontinuity protection is used for detecting unbalance situations
caused by broken conductors.
The operate time characteristics is based on definite time (DT) i.e. function
operates after a predefined operate time and resets when the fault current
disappears.
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