Configuration With Ungrounded Reference Potential - Siemens Simatic 6ES7 157-0AD81-0 A0 Series Manual

Wiring
Diverting interference current
When modules are operated with ungrounded reference potential, any interference
current is discharged to the protective conductor via RC networks that are
integrated in the IM 157 and the DP/PA coupler (see Figure 4-3).
Figure 4-3
4-6
M
L
+
M
Ground bus

Configuration with ungrounded reference potential

22 nF 10 MΩ
M
Integrated RC network
DP/PA Link and Y Link Bus Couplings
A5E00193841-01 1