Grounding of Terminal Protection Devices

Terminal protection devices (TPDs) such as a variety of electromagnetic interference (EMI) filters and transient‐voltage surge suppression devices are commonly used to suppress undesired conducted electrical energy to tolerable levels by shunting, bypassing, absorbing, or reflecting the interference energy. This chapter provides a brief overview of filters and transient suppressors and focuses on the role of proper grounding for accomplishing their desired performance. For the purpose of common‐mode protection, well‐grounded terminal protection circuits should be implemented. The design and installation of terminal protection devices and circuits are an art as well as a science. Much depends on parasitics characterizing the components and their installation practices, for which bonding and grounding of the terminal protection circuit elements are of particular importance. Bulkhead‐installed filters, in which the TPD is directly mounted on the enclosure's boundary, provide optimal grounding and preclude EMI bypass of the device.