ABB RELION 620 Series Technical Manual page 457

1MRS757644 F
620 series
Technical Manual
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.
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
protection.
Timer calculates the start duration value START_DUR, which indicates the
percentage ratio of the start situation, and the set operating time, which can be either
according to DT or IDMT. The value is available in the monitored data view.
More information can be found in the
Blocking logic
There are three operation modes in the blocking function. The operation modes are
controlled by the BLOCK input and the global setting in Configuration/System/
Blocking mode which selects the blocking mode. The BLOCK input can be controlled
by a binary input, a horizontal communication input or an internal signal of the
protection relay's program. The influence of the BLOCK signal activation is
preselected with the global setting Blocking mode.
Protection functions
IDMT curves for overcurrent
General function block
Section 4
features.
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