ABB RELION 620 Series Technical Manual page 251

1MRS757644 F
620 series
Technical Manual
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 programmable IDMT curve is selected, the operating time characteristics
are defined with the parameters Curve parameter A, Curve parameter B, Curve
parameter C, Curve parameter D and Curve parameter E.
The shortest IDMT operation time is adjustable. It can be set up with
the global parameter in the HMI menu: Configuration/System/
IDMT Sat point. More information can be found in the
function block features
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
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. The START output is deactivated when the reset timer
has elapsed.
The "Inverse reset" selection is only supported with ANSI or
programmable types of the IDMT operating curves. If another
operating curve type is selected, an immediate reset occurs during the
drop-off situation.
The setting Time multiplier is used for scaling the IDMT operation and reset times.
The setting parameter Minimum operate time defines the minimum desired operation
time for IDMT. The setting is applicable only when the IDMT curves are used.
The Minimum operate time setting should be used with great care
because the operation time is according to the IDMT curve, but always
at least the value of the Minimum operate time setting. More
information can be found in the
section in this manual.
The timer calculates the start duration value START_DUR, which indicates the
percentage ratio of the start situation and the set operation time. The value is available
in the monitored data view.
Protection functions
section.
General function block features
Section 4
General
245