ABB RELION 620 Series Technical Manual page 231

1MRS757644 F
620 series
Technical Manual
A070554 V1 EN
Figure 110: Start value behavior with ENA_MULT input activated
Phase selection logic
If the fault criteria are fulfilled in the level detector, the phase selection logic detects
the phase or phases in which the measured current exceeds the setting. If the phase
information matches the Num of start phases setting, the phase selection logic
activates the timer module.
Timer
Once activated, the timer activates the START output. 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 Operate delay time in the DT mode
or the maximum value defined by the inverse time curve, the OPERATE output is
activated.
When the user-programmable IDMT curve is selected, the operation time
characteristics are defined by the parameters Curve parameter A, Curve parameter B,
Curve parameter C, Curve parameter D and Curve parameter E.
If a drop-off situation happens, that is, a fault suddenly disappears before the operate
delay is exceeded, the timer reset state is activated. The functionality of the 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 set Reset delay time value 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
Section 4
Protection functions
225