ABB RELION 620 Series Technical Manual page 241

Protection and control

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1MRS757644 H

Figure 120: 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

activates the timer module.

Once activated, the timer activates the START output. Depending on the value of

IDMT. When the operation timer has reached the value of

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

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

type , Type of reset curve and Reset delay time settings. When the DT characteristic

is selected, the reset timer runs until the set

When the IDMT curves are selected, the

"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

Technical Manual

Operating curve type setting, the time characteristics are according to DT or

Reset delay time setting. With the reset curve type "Inverse

Num of start phases setting, the phase selection logic

Curve parameter A , Curve parameter

Reset delay time value is exceeded.

Type of reset curve setting can be set to

Protection functions

Operate delay time in the

Operating curve