Siemens SIMATIC ET 200SP System Manual page 204

Maintenance
12.1 Removing and inserting I/O modules
NOTICE
Risk of hazardous system states
If you remove and insert digital output modules with the load switched on or technology
modules with the supply voltage switched on, this can result in hazardous system states.
The ET 200SP distributed I/O system or the connected sensors may be damaged as a
result.
Therefore, a digital output module may only be inserted and removed when the load is
switched off and a technology module may only be inserted and removed when the supply
voltage is switched off.
NOTICE
Risk of hazardous system states
If you remove and insert the AI Energy Meter ST with the primary-side voltage switched on
at the current transformer, this can result in hazardous system states.
The ET 200SP distributed I/O system may be damaged as a result.
• For this reason, remove and insert the AI Energy Meter ST only when the measuring
• Only when a special current transformer terminal is used which short-circuits the
Operating principle with CPU/HF interface module
You can remove and insert any number of I/O modules during operation. The CPU/interface
module and the inserted I/O modules remain in operation.
NOTICE
Reaction of the CPU when removing and inserting the ET 200SP server module
Please note that the backplane bus is deactivated when you remove the server module,
regardless of the CPU operating state. Also note that the outputs do not adopt their
configured substitute value behavior when you remove the server module.
This means you should not remove the server module in the CPU operating states
STARTUP, RUN and STOP. If you have nevertheless removed the server module, perform
a POWER OFF/POWER ON after you have inserted the server module once again.
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voltage on the primary side is switched off
or
secondary end of the transformer when a module is removed. Do not remove or insert
the AI Energy Meter ST until you have removed this current transformer terminal. With
the special terminal, the process can continue because the current transformer is
isolated safely. However, the measuring voltage on the module at the connections UL1-
UL3 still needs to be isolated.
Distributed I/O system
System Manual, 12/2015, A5E03576849-AF