Abstract: Grounding and anti-interference are the key technical concerns in the unprotected field installation of intelligent electronic devices（ IEDs） in switch yard. This paper introduces traditional designs of secondary equipotential grounding grid and IED grounding methods, analyzes the complicated Electromagnetic compatibility envi-ronments and relevant specific problems in the unprotected field installation of IEDs in switch yard, recommends-design ideas for the secondary equipotential grounding grid in distributed switch yard,elaborates on the grounding methods for field installed IEDs and external cables in the unprotected installation in switch yard and design ap-proaches for higher anti-interference ability in field installed IEDs. In-house experimental results have verified the feasibility of the proposed methods.