Internal Construction; Front Cover; Terminal Blocks - Siemens 7SG164 Ohmega 400 Series Manual

13.1 Internal Construction

The design for the internal arrangement of each module has been chosen to provide a high level of EMI
screening, using multi-layer PCBs with ground planes, RFI suppression components and earthed metal
screens.
The case is segregated internally into electrically noisy and quiet areas in order to improve noise immunity
and reduce RFI emissions. The only direct connection from the quiet components to the external
environment is via the serial communication interfaces. The optical interfaces are immune to radiated or
conducted interference.

13.2 Front Cover

After the relay has been commissioned, a clear plastic front cover is fitted. This allows the user to see the
entire front of the relay, but only allows access to the
previously to be viewed but not changed. The only 'action', which is permitted, is to reset the Fault Data
Display, latched output relays and the latched LEDs by using the TEST/RESET function of the

13.3 Terminal Blocks

These are of the standard Epsilon design, consisting of six blocks - behind modules A to F - with 28
terminals per block. All inputs and outputs (except for the serial communications interface) are made through
these connectors. Where CT's and normally closed output contacts are fitted the terminals are provided with
CT shorting contacts to provide system integrity when these modules are removed.
©2011 Siemens Protection Devices Limited
7SG164 Ohmega 400 Series Description of Operation
and buttons, allowing all of the menus discussed
button.
Chapter 1 Page 11 of 12