12.Secured Object Control - ABB REF 54 Series Technical Reference Manual, General

1MRS750527-MUM
5.1.13.11.
Feeder Terminal
Technical Reference Manual, General
The basic operation principle is that every time the output value is changed by the
configuration, the new value is propagated automatically over the LON network to
all communication inputs that are bound to the output. The network variable
connection can be from a single source to one or many sinks. An output can also be
unbound, that is, it is not transmitted to LON network at all. Also an input can be
unbound, that is, no updates will be accepted to this input.
Communication inputs acts as holding registers, they preserve the last received
value until next update is received. When a relay has been started, initially all inputs
will be zero and all invalidity flags will be TRUE. If an input is bound, the first
network variable update received will update the input and the corresponding
invalidity flag will be set to FALSE.
If the network variable connection is created using NV poll support, then the
receiving device can query the value from the sending device. This occurs at relay
startup and when open/close control of an object (for example COCB1) is selected
or executed. An input invalidity flag indicates the status of the poll. When the poll
is initiated, all input invalidity flags (with NV poll support) are set to TRUE. After
each successful NV poll the corresponding invalidity flag is set to FALSE. After all
polls are complete, the control command is allowed to be completed.
Communication outputs are prioritized by the number of the output. If multiple
output values need to be transmitted at the same time, the output with the lowest
number will be sent first. The relay configurations should be designed so that the
most time critical and least often changed signals are assigned to outputs with the
lowest numbers.
Communication outputs shall not change too frequently, otherwise outputs with a
low priority may not be sent to the network at all, or the updates may be delayed.
The maximum transmission rate is 50 updates per second for all communication
outputs together. If the limit is exceeded, loss of data will occur. The system is
however designed to always send the latest value when there is communication
bandwidth available. It may be necessary to use a data latch with timer mechanism
in the relay configuration to limit the update rate of an output.
Network variable connections are not supervised by the relay system software. For
example, a broken fibre will not be detected by the relay. For further information
about horizontal communication, refer to the Protection & Control Terminals REF
54_, RET 54_, REM 54_, REC 523 Configuration Guideline.
Secured object control
Secured object control refers to the two-step select-execute process in order to
execute open and close commands for controllable switching devices of the
switchgear. Which communication protocol, SPA or LON, is used to transfer the
remote select-execute commands affects the flow of actions in secured object
control. It is the command time-out parameter (F001V019) that determines which
scheme is used for secured object control.
In case of SPA communication, the command time-out parameter has to be shorter
than 1.5 sec. The default is 0.5 seconds. Furthermore, when parallel communication
is used, where LON is used for horizontal communication and SPA for control
commands, the command time-out parameter has to be shorter than 1.5 sec.
REF 54_
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