Ground Grid Analysis and Design

EES Consulting provides ground grid design as part of the substation design based on IEEE Standard 80. Soil testing and soil data is typically provided by others. Fault current computations may be obtained from the owner or calculated by EES Consulting. Using other key parameters, such as fault clearing times and substation surfacing type, we estimate limits for step and touch potentials within the station.

One of the most critical estimates in designing an economical and safe grounding system is the estimate of grid current, which is the share of the fault current flowing through the substation grid back to its current source. Over-estimating the grid current will result in a safe, but over-designed and unnecessarily expensive grounding system, and under-estimating the grid current will result in an unsafe grounding system, even though the analysis may show the system to be safe. The grounding condition of circuits external to the substation has a great impact on the grid current estimate. EES Consulting uses computer software to compute the step and touch voltages in and around the substation.

Grays Harbor PUD

EES Consulting was retained to provide engineering design and permitting support for replacement of an existing substation with the New Central Park 115 – 12.47kV substation consisting of two 115-kV transmission lines, ultimately two 15/20/25 MVA power transformers and two lineups of 15-kV metal-clad switchgear. EES Consulting prepared site development, retaining wall design, oil containment and drainage design, fencing design, and foundation design for a Public Works Contract, and steel support structure design, bus and electrical assembly design, conduit design and ground grid design for a District Work Package. We also prepared permitting applications and accompanying drawings for the necessary environmental and construction permits.