ABB RELION REX640 Technical Manual page 497

1MRS759142 C
REX640
Technical Manual
Table 530: 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.
In case of a communication failure, the start duration may change substantially
depending on the user settings.
When the programmable IDMT curve is selected, the operation time characteristics
are defined with the Curve parameter A, Curve parameter B, Curve parameter C,
Curve parameter D and Curve parameter E parameters.
If a drop-off situation happens, that is, a fault suddenly disappears before the operation
delay is exceeded, the Timer reset state is activated. The functionality of Timer in the
reset state depends on the combination of the Operating curve type, Type of reset
curve and Reset delay time settings. When the DT characteristic is selected, the reset
timer runs until the value of the Reset delay time setting is exceeded. When the IDMT
curves are selected, the Type of reset curve setting can be set to "Immediate", "Def
time reset" or "Inverse reset". The reset curve type "Immediate" causes an immediate
reset. With the reset curve type "Def time reset", the reset time depends on the Reset
delay time setting. With the reset curve type "Inverse reset", the reset time depends on
the current during the drop-off situation. If the drop-off situation continues, the reset
timer is reset and the START output is deactivated.
The "Inverse reset" selection is only supported with ANSI or the
programmable types of the IDMT operating curves. If another
operating curve type is selected, an immediate reset occurs during the
drop-off situation.
Protection functions
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
reached the value of the Operate delay time setting in 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.
Section 4
Minimum operate time
491