Grounding and Shielding for Protection Systems

Properly grounding and shielding machine protection systems create unique challenges in large plants. When installing a protection system, numerous obstacles must be considered that are not an issue with smaller systems. Following best practices is not possible in many installations. As such it is important to know the limitations of each plant and plan the installation around them.

The consequences of poor grounding and shielding include: lightning vulnerability, false vibration spikes during switchgear activation, false vibration signals that appear even when the machine is off, loss of communications and false trips caused by interference (such as keying a radio near a sensor).

When designing a good grounding and shielding system keep in mind two clichés:

• When thinking of weak signals and signal integrity, current follows the path of least resistance.
• When thinking of high energy and safety, current will follow any path to ground it can.

When troubleshooting a potential ground fault issue, keep in mind that ground faults are safety hazards. Use proper isolation techniques until the ground fault can be identified and corrected. Do not attempt to correct the ground fault if you are not trained on proper procedures including Lock Out Tag Out, Arcflash hazards etc.  Continue reading the application note for further instructions and important recommendations on the above topic.