Level detector
The module compares differential currents I_A calculated by the peak-to-peak
measurement mode to the set
Operate value
. The Timer module is activated if the
differential current exceeds the value of the
Operate value
setting.
Timer
Once activated, Timer activates the START output. The time characteristic is
according to DT. When the operation timer reaches the value set by
Minimum
operate time
, the OPERATE output is activated. If the fault disappears before
the module operates, the reset timer is activated. If the reset timer reaches the
value set by
Reset delay time
, the operation timer resets and the START output is
deactivated.
Timer calculates the start duration START_DUR value, which indicates the
percentage ratio of the start situation and the set operating time. The value is
available in the Monitored data view.
The activation of the BLOCK input resets Timer and deactivates the START and
OPERATE outputs.
Blocking logic
There are three operation modes in the blocking functionality. The operation
modes are controlled by the BLOCK input and the global setting 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. 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.
4.3.6.6 Application
HIxPDIF provides a secure and dependable protection scheme against all types of
faults. The high-impedance principle is used for differential protection due to its
capability to manage the through-faults also with the heavy current transformer
(CT) saturation.
For current transformer recommendations, see the Requirements for
measurement transformers section in this manual.
High-impedance principle
The phase currents are measured from both the incoming and the outgoing feeder
sides of the busbar. The secondary of the current transformer in each phase is
connected in parallel with a protection relay measuring branch. Hence, the relay
measures only the difference of the currents. In an ideal situation, there is a
differential current to operate the relay only if there is a fault between the CTs,
that is, inside the protected zone.
1MRS759142 F
Protection functions
REX640
Technical Manual
775
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