Static Earthing Relay System
There are applications where electrical contractors may need to provide a static grounding solution as part of a specialised instrumentation/automation project. To satisfy the requirements of bespoke projects designers are often limited by standard “off-the-shelf” static grounding solutions that cannot be customised to provide a good “fit” for their specific application design requirements. A suitable design trade-off is to specify static grounding relays that can monitor a range of resistance values.
Although installations of this type are limited by not having ground status indication provided at the point of grounding, the normal application for such relays is to monitor the ground status of permanent fixed equipment connections or rotating machinery and using an internal relay to provide outputs to PLCs or customised HMI panels or panel mounted indication.
Due to the design of bearings, etc. a good method of providing ground continuity is to use a non-hazardous area mounted ground monitoring relay to test the ground connection to the drum or impeller via a pair of carbon brushes or a slip ring, acting on the shaft.
Relays that have a range of resistance settings are normally mounted on DIN rails inside electrical panels installed in non-hazardous areas.
Using a compact panel mounted static grounding module that can monitor a range of resistances with an output relay to interlock with control circuits or motor starters can assist with improving the safety of processes.