ABB Relion 620 Series, Technical Manual

Page: 1064 / 1224

Table 1018: Blocking schema for selection "Custom disabled"
Acting
operation
mode
Comman
d
Load
current
Block
lowering
voltage
Runback
raising
voltage
High
circulatin
g current
External
Block
Extreme
positions
Manual Raise X X
Lower X
Table 1019: Blocking schema for selection "OC, UV, EXT"
Acting
operation
mode
Comman
d
Load
current
Block
lowering
voltage
Runback
raising
voltage
High
circulatin
g current
External
Block
Extreme
positions
Manual Raise X X X X X
Lower X X X X
Table 1020: Blocking schema for selection “UV, EXT”
Acting
operation
mode
Comman
d
Load
current
Block
lowering
voltage
Runback
raising
voltage
High
circulatin
g current
External
Block
Extreme
positions
Manual Raise X X X X
Lower X X X
Load current
The load current blocking is mainly used for preventing the tap changer from
operating in an overcurrent situation. For example, if the current is not high
enough to activate the protective IED of the substation, it can still be fatal for
the diverter switch of the tap changer. This operation can be adjusted with the
setting parameter Load current limit. The maximum of measurements from the
secondary-side current phases is used for blocking. By default, both the automatic
operation and the manual operation are blocked ( Table 1016 ) when the set limit is
exceeded.
The blocking status can be read from the monitored data BLKD_I_LOD.
Block lowering voltage
The block lowering voltage feature blocks both raising and lowering 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 1016
). This
operation can be adjusted with the setting parameter
Block lower voltage.
The blocking status can be read from the monitored data 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 has temporarily a very
low value. There is a minimum limit for the phase angle calculation based on the
voltage phasor magnitude.
Control functions 1MRS757644 H
1064 620 series
Technical Manual