Safe Utilization of Existing Grounding Systems for Expansions and Upgrades of Substations

Utilization of existing grounding systems for the expansions and upgrades of substations offers unique challenges. The identification of current conditions of grounding systems is crucial for safety and for the proper design of their expansions and/or upgrades, which may include the interconnection of an existing grid to a new one. It is also important to note that the evaluation of the conditions of existing substation ground grids may require personal protective equipment to be worn, as well as appropriate safety precautions. In this paper, the authors provide procedures to evaluate the prospective performance of existing grounding systems based upon measurements, as-built and/or contract drawings, site inspections, and examination of key grid points utilizing nonintrusive methods. Safety solutions that can be utilized during the construction phase of the project are also illustrated. A case study that addresses the upgrade of an existing grid is discussed. This paper seeks to clarify for practitioner engineers the problems and variables introduced by the work to be performed on older substation grounding systems. Readers will be provided with tools in compliance with applicable technical standards, which can assist in ensuring continued operation of the substation grounding system during construction.