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Project: T193700 #3726

Expansion of municipal services in major cities has resulted in buried and touchable metal objects such as chain linked fences, street lighting poles, and pipelines being placed near energized substations. Electric utilities often have little control regarding the placement of municipal infrastructure and services. These metal objects are subject to step and touch potentials that might pose risks to public safety and the reliable operation of electrical equipment. Existing standards such as IEEE and IEC provide guidance on substation grounding, hazards, and safety measures, but these rules and procedures are not comprehensive and leave a number of unanswered questions, which might result in incorrect decisions and hazardous conditions. Thus, this report: (i) provides an analytical review of the hand-to-hand touch potentials associated with isolated metal objects within 2 m of bonded substation fences; (ii) calculates hand-to-hand touch potentials for remotely grounded objects within 2 m of bonded substation fences; (iii) considers hand-to-foot touch potentials at remotely grounded objects, such as an energy meter or water tap on a house in proximity to a substation; (iv) reviews hand-to-foot touch potentials on neutral-connected objects where the neutral is tied to the station ground; (v) calculates hand-to-foot touch potentials on a fence outside a substation energized by a fallen phase conductor. A hazard index defined by these touch potentials divided by the allowable potentials helps identify where mitigation should be given high priority. The study includes new testing methods to measure these step and touch potentials and identify hazards. Finally, this report recommends effective methods for mitigating step and touch potentials associated with buried metal objects near substations to ensure public safety and effective operation.


Substation grounding, Fence grounding, Buried metallic objects, Touch potential, Hazard Index.