ABB RELION REX640 Technical Manual page 457

1MRS759142 F
curves are selected, the
"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 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.
4.2.2.6 Directional earth-fault principles
In many cases it is difficult to achieve selective earth-fault protection based on
the magnitude of residual current only. To obtain a selective earth-fault protection
scheme, it is necessary to take the phase angle of Io into account. This is done by
comparing the phase angle of the operating and polarizing quantity.
Relay characteristic angle
The
Relay Base Angle or Maximum Torque Angle (MTA), is used in the "Phase angle"
mode to turn the directional characteristic if the expected fault current angle does
not coincide with the polarizing quantity to produce the maximum torque. That is,
RCA is the angle between the maximum torque line and polarizing quantity. If the
polarizing quantity is in phase with the maximum torque line, RCA is 0 degrees. The
REX640
Technical Manual
Type of reset curve setting can be set to "Immediate",
Reset delay time setting. With the reset curve type "Inverse reset", the
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"
Characteristic angle setting, also known as Relay Characteristic Angle (RCA),
Minimum operate time setting. For more
Chapter 11.2.1 IDMT curves for overcurrent protection
Blocking mode .
Protection functions
457