Blocking Scheme - ABB RELION REX640 Technical Manual

Section 9
Control functions
9.10.5.9
1560
changer. By default, the external LTC_BLOCK has no effect when the active operation
mode is set to "Manual" or "Parallel manual".
The status of the TCO input can be read from the TCO input data.

Blocking scheme

The operation of the voltage regulator can be blocked for several reasons. The purpose
of blocking is to prevent the tap changer from operating under conditions that can
damage the tap changer or exceed other power system limits. The BLK_STATUS
monitored data does not imply actual blocking but reveals if the coming command
pulse is issued or not. The blocking itself happens when the corresponding bit in the
signal BLK_STATUS is active and the command pulse is started due to a timer elapse
or a local command. This is to avoid unnecessary event sending.
The BLK_STATUS monitored data is also packed. It contains information about the
blocking status as bit-coded output. The block status output does not indicate the
actual blocking but indicates if the coming command is successful. The actual
blocking is indicated by the corresponding output (BLKD_I_LOD, BLKD_U_UN,
RNBK_U_OV, BLKD_LTCBLK and BLKD_I_CIR) values.
meaning of different monitored data values. For example, block status value 9
indicates that there are conditional circulating current and load current blockings (8
+ 1 = 9) indicated. By default, the status is "0".
Table 1414: Bit-coded block status and the meaning of different bits
Bit Active value
6 (msb) 64
5 32
4 16
3 8
2 4
1 2
0 (lsb) 1
The cross (X) in the table defines when the operation is blocked (if the corresponding
bit is active in BLK_STATUS). For example, an overvoltage (runback raising
voltage) results in blocking only when the active operation mode is "Manual" and the
manual raising command is given.
Table 1414
Blocking reason
Lowest position reached
Highest position reached
External LTC_BLOCK
High circuit current
Overvoltage - Runback raise voltage
Undervoltage - Block lower voltage
Overcurrent - Load current
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REX640
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