ABB RELION 620 Series Technical Manual page 456

Section 4
Protection functions
450
Level detector
The harmonics current is compared to the Start value setting. If the value exceeds the
value of the Start value setting, Level detector sends an enabling signal to the Timer
module.
Current comparison
The maximum of the harmonics currents reported by other parallel feeders in the
substation, that is, in the same busbar, is fed to the function through the I_REF_RES
input. If the locally measured harmonics current is higher than I_REF_RES, the
enabling signal is sent to Timer.
If the locally measured harmonics current is lower than I_REF_RES, the fault is not
in that feeder. The detected situation blocks Timer internally, and simultaneously also
the BLKD_I_REF output is activated.
The module also supervises the communication channel validity which is reported to
the Timer.
Timer
The START output is activated when Level detector sends the enabling signal.
Functionality and the time characteristics depend on the selected value of the Enable
reference use setting.
Table 451: Values of the Enable reference use setting
Enable reference use
Standalone
Reference use Communication
valid
Communication
invalid
The Enable reference use setting forces the function to use the DT
characteristics where the operating time is set with the Minimum
operate time setting.
If the communication for some reason fails, the function switches to use the Operation
curve type setting, and if DT is selected, Operate delay time is used. If the IDMT curve
is selected, the time characteristics are according to the selected curve and the
Minimum operate time setting is used for restricting too fast an operation time.
Functionality
In the standalone mode, depending on the value of the
Operating curve type setting, the time characteristics are
according to DT or IDMT. When the operation timer has
Operate delay time setting in the
reached the value of the
DT mode or the value defined by the inverse time curve,
the OPERATE output is activated.
When using the horizontal communication, the function is
forced to use the DT characteristics. When the operation
timer has reached the value of the
setting and simultaneously the enabling signal from the
Current comparison module is active, the OPERATE signal
is activated.
Function operates as in the standalone mode.
1MRS757644 F
Minimum operate time
620 series
Technical Manual