ABB RELION REX640 Technical Manual page 425

1MRS759142 C
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REX640
Technical Manual
If a drop-off situation, 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 user
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 operate and reset times.
The setting parameter Minimum operate time defines the minimum desired operate
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. For more
information, see the
in this manual.
The timer calculates the start duration value START_DUR, which indicates the
percentage ratio of the start situation and the set operating time. The value is available
in the monitored data view.
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
The Blocking mode setting has three blocking methods. In the "Freeze timers" mode,
the operation timer is frozen to the prevailing value, but the OPERATE output is not
deactivated when blocking is activated. In the "Block all" mode, the whole function is
blocked and the timers are reset. In the "Block OPERATE output" mode, the function
operates normally but the OPERATE output is not activated.
Protection functions
IDMT curves for overcurrent protection
Section 4
section
419