parameter
Load current limit
. The maximum of measurements from the current
phases is used for blocking. By default, both the automatic operation and the
manual operation are blocked (
Table 1575
) when the set limit is exceeded.
The blocking status can be read from the output BLKD_I_LOD.
Block lowering voltage
The block lowering voltage feature blocks both raise and lower voltage commands
if the measured voltage is too low to be corrected by operating the tap changer.
Such a situation can occur due to a faulty measuring circuit, an earth fault or
an overcurrent situation. By default, only the automatic (also automatic follower)
operation is blocked when the undervoltage condition is met (
Table 1575
). This
operation can be adjusted with the setting parameter
Block lower voltage
.
The blocking status can be read from the output BLKD_U_UN.
However, there is no minimum limit for the undervoltage blocking. The blocking is
allowed even if the measured voltage is not connected or it temporarily has a very
low value. There is a minimum limit for the phase angle calculation based on the
voltage phasor magnitude.
Runback raising voltage
The manual raising command is blocked if the overvoltage limit is exceeded (
Table
1575
). However, in the automatic operation mode, the overvoltage situation triggers
the fast lowering feature. More information can be found in
Chapter 9.10.5.4 Manual
voltage regulation
. This operation can be adjusted with the setting parameter
Runback raise V
.
The blocking status can be read from the output RNBK_U_OV.
High Circulating Current
The circulating current value is calculated in the operation modes Negative
Reactance Principle (NRP) and Minimizing Circulating Current (MCC). Only the
automatic operation in these modes is blocked when the high circulating current is
measured (
Table 1575
). This operation can be adjusted with the setting parameter
Cir current limit
.
The blocking status can be read from the output BLKD_I_CIR.
LTC_BLOCK – external block input
With the PCM600 tool configuration possibilities, a desired blocking condition can
be built by connecting an outcome to this input. The blocking status can be read
from the output BLKD_LTCBLK. When activated, this input blocks only the automatic
operation of the regulator by default (
Table 1575
). For the fully automatic modes,
the signal activation resets the timer, and the monitored data BLKD_LTCBLK is not
activated.
Extreme positions
This blocking function supervises the extreme positions of the tap changer. These
extreme positions can be adjusted with the setting parameters
Raise block tap
and
Lower block tap
. When the tap changer reaches one of these two positions, the
commands in the corresponding direction are blocked (
Table 1575
). It depends on
the comparison between the
Raise block tap
and
Lower block tap
settings, which
1MRS759142 F
Control functions
REX640
Technical Manual
1719
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