Siemens Simatic S7-1500 CPU 1512C-1 PN User Manual page 96

Wiring
4.3 Terminal and block diagrams
The figure below shows the reaction to interruption of the first ground cable.
Figure 4-16 Interruption of the first ground cable using the digital on-board I/O X11 as an example
If a wire break occurs on the first ground cable from the central terminal block to terminal 30,
the module can continue to operate without restrictions, as it is still connected to the ground
via the second cable from the central terminal block to terminal 40.
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CPU 1512C-1 PN (6ES7512-1CK01-0AB0)
Manual, 12/2017, A5E40898741-AA