Siemens SIMATIC S7-1500 System Manual page 238

Causes for overload
An overload can still occur despite a positive power balance during planning. The cause for
overload can be a hardware configuration that does not correspond to the configuration in
STEP 7, for example:
• There are more communications processors in the actual configuration than in the STEP 7
project.
• A supply voltage L+ (24 V DC) required for operation was not connected when the system
voltage infeed via the CPU was specified during parameter assignment (see Configuring
system power supply (Page 306) section).
• A system power supply required for operation is not inserted.
• A system power supply required for operation is not switched on (power connection plug
or on/off switch).
• A system power supply required for operation has no U-connector inserted with the R-
system.
Response of the CPU to negative power balance or failure of system power supplies
As soon as the CPU detects a negative power balance/overload, the following actions are
executed:
• The CPU stores the retentive data.
• The CPU enters the event in the diagnostics buffer.
• The CPU carries out a restart and repeats this until the cause of the negative power
balance is resolved.
S7-1500R/H redundant system
System Manual, 01/2024, A5E41814787-AF
Application planning
6.8 System power supply
237