If a component is removed from the single line diagram, the Modbus address becomes free and can be reassigned. The breaker
priorities are automatically reassigned for all the remaining components in the single line diagram. For example if we remove Genset
1 and the emergency genset from the example above the table will look as follows:
Table 17.4
Updated breaker priority values and Modbus addresses after removing components
Component
Modbus address (Holding
register and input register)
Breaker priority: Buffered
value
Breaker priority: Value
-
14001
0
0
Shore connection
14002
0
0
Bus tie breaker
14003
0
0
Shaft generator
14004
0
0
Genset 2
14005
0
1
-
14006
0
0
-
14007
0
0
If we add the emergency genset back into the single line diagram, and then add Genset 1 back into the single line diagram the table
will look as follows:
Table 17.5
Updated breaker priority values and Modbus addresses after adding components
Component
Modbus address (Holding
register and input register)
Breaker priority: Buffered
value
Breaker priority: Value
Emergency genset (TB)
14001
0
0
Shore connection
14002
0
0
Bus tie breaker
14003
0
0
Shaft generator
14004
0
0
Genset 2
14005
0
1
Emergency genset (GB3)
14006
0
0
Genset 1
14007
0
2
The table above shows that the breakers are assigned the first open Modbus address in the Modbus table. This means that it is
possible for an emergency genset to have its breakers assigned to Modbus addresses that do not follow directly on one another.
Because Genset 1 has a higher Modbus address (14007) than Genset 2 (14005), by default it is assigned a lower priority than
Genset 2 after the change was made in the single line diagram.
When you want to change the breaker priorities by using Modbus, write the desired priority value to the Modbus address in the
function group
Breaker priority: Buffered value
. When you are satisfied with the breaker priorities, activate
Breaker priorities: Write
values
to write the values to the controller. Only values between 1 and 128 are accepted inputs for breaker priorities. Breakers that
already have a priority of 0 assigned to them, cannot be changed. You cannot write the breaker priorities to the controller if there are
duplicate non-zero entries in
Breaker priority: Buffered value
. The tables below show the results after new breaker priorities were
written to the buffered values, and after the buffered values were written to the controller.
Table 17.6
Breaker priority values after writing new values to the buffer addresses
Component
Modbus address (Holding
register and input register)
Breaker priority: Buffered
value
Breaker priority: Value
Emergency genset (TB)
14001
0
0
Shore connection
14002
0
0
Bus tie breaker
14003
0
0
DESIGNER'S HANDBOOK 4189340911K UK
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