ABB RELION REX640 Technical Manual page 822

Protection functions
is selected, the reset timer runs until the set
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", the reset time depends on the current during the drop-off situation and the
value of START_DUR. The START output is deactivated when the reset timer has
elapsed.
The setting
The setting parameter
time for IDMT. The setting is applicable only when the IDMT curves are used.
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
The
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.
4.4.1.6 Application
Since the negative sequence current quantities are not present during normal,
balanced load conditions, the negative sequence overcurrent protection elements
can be set for faster and more sensitive operation than the normal phase-
overcurrent protection for fault conditions occurring between two phases. The
negative sequence overcurrent protection also provides a back-up protection
functionality for the feeder earth-fault protection in solid and low resistance
earthed networks.
The negative sequence overcurrent protection provides the back-up earth-fault
protection on the high voltage side of a delta-wye connected power transformer
for earth faults taking place on the wye-connected low voltage side. If an earth fault
822
Reset delay time setting. With the reset curve type "Inverse
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.
Time multiplier is used for scaling the IDMT operate and reset times.
Minimum operate time defines the minimum desired operate
Minimum operate time setting should be used with great care
The
because the operation time is according to the IDMT curve, but always
at least the value of the
information, see
in this manual.
Blocking mode setting has three blocking methods. In the "Freeze timers"
Reset delay time value is exceeded.
Minimum operate time setting. For more
Chapter 11.2.1 IDMT curves for overcurrent protection
Blocking mode .
1MRS759142 F
REX640
Technical Manual