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28
Setting lockout (HMI)
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Unpermitted or uncoordinated changes by unauthorized personnel may cause severe
damage to primary and secondary power circuits. Use the setting lockout function to
prevent unauthorized setting changes and to control when setting changes are allowed.
By adding a key switch connected to a binary input a simple setting change control cir-
cuit can be built simply allowing only authorized keyholders to make setting changes.
Security can be increased by adding SA/SMS overrides that prevents changes even by
keyholders.
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Activating the setting restriction prevents unauthorized personell to purposely or by
mistake change terminal settings.
The HMI--BLOCKSET functional input is configurable only to one of the available bi-
nary inputs of a REx 5xx terminal. For this reason, the terminal is delivered with the
default configuration, where the HMI--BLOCKSET signal is connected to NONE-
NOSIGNAL.
The function permits remote changes of settings and reconfiguration through the serial
communication ports. The setting restrictions can be activated only from the local HMI.
All other functions of the local human-machine communication remain intact. This
means that an operator can read all disturbance reports and other information and set-
ting values for different protection parameters and the configuration of different logic
circuits.
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