You're right to be questioning this. It sounds like the designer is potentially over-engineering the grounding for this project, or misinterpreting the code. Let's break down why

Understanding "Substation" and NEC 250.191 & 250.194
Substation

Generally, a substation is a facility containing transformers, switchgear, and associated equipment, used to step down or step up voltage for distribution to a large service area. Substations are typically used by utilities to route and distribute power to industrial plants, commercial districts, or even residential areas. The key function is to change the voltage to match the service area requirements.

NEC 250.191 (Grounding of Systems and Circuits of 1 kV and Over (High Voltage)) and 250.194 (Proximity of Grounded Components of Different Systems)

These sections of the NEC primarily address grounding requirements within or near substations or at facilities with high-voltage distribution systems (1 kV and over). They focus on safety measures to mitigate ground potential rise (GPR) during fault conditions and prevent dangerous touch and step potentials within the substation and surrounding areas. The reference to these code section imply that the designer may be trying to address step and touch potential concerns, but their applicability depends on whether your project falls under the scope of what the NEC consider a substation.

Why the Designer's Approach May Be Overkill1. 1000 kVA Pad-Mount Transformer is NOT Necessarily a Substation

A single 1000 kVA pad-mount transformer, owned and maintained by the utility, supplying your building is generally

NOT considered a substation from the perspective of NEC 250.191 or 250.
194. It's a service transformer providing power to your building.2. Utility Responsibility

Since the utility owns the transformer, they are responsible for the primary side grounding. Their grounding practices will comply with their own standards and applicable regulations, which are generally more stringent than the NEC. They will likely establish their own grounding grid for the transformer, but this is separate from your building's grounding system.3.

Building Grounding vs. Substation Grounding

Your building's grounding system (electrode system, equipment grounding conductors, etc.) is designed to provide a low-impedance path for fault current to return to the source transformer, protecting people and equipment within the building. This is different from a substation grounding grid, which is designed to manage GPR and prevent dangerous potentials over a larger area.

What Grounding IS Required for Your Building

Your building DOES require a robust grounding system, but it should be based on the general grounding requirements of NEC Article 250, particularly: 250.24 (Grounding Separately Derived AC Systems)

This section addresses grounding of the secondary side of the transformer if it is considered a separately derived system.

250.50 (Grounding Electrode System)

This section requires a grounding electrode system consisting of items like a metal underground water pipe, a concrete-encased electrode (ufer ground), ground ring, or ground rods.

250.52 (Grounding Electrodes)

Specifies the requirements for various grounding electrodes.

250.66 (Size of Alternating-Current Grounding Electrode Conductor)

Determines the size of the grounding electrode conductor based on the size of the service entrance conductors.

250.104 (Bonding of Piping Systems and Exposed Structural Metal)

Requires bonding of metallic water piping, gas piping, and structural steel to the grounding system.

Recommendation1. Clarify the Designer's Rationale

Politely ask the designer to specifically explain why* they believe NEC 250.191 and 250.194 apply to your project, considering it's a building service from a utility-owned transformer and not a utility substation. Ask them to show you the specific calculations and analysis that lead them to this conclusion.
2.

Inquire About the Finite Element Analysis

Ask the designer what specific risks they believe necessitate a finite element analysis. What step and touch potentials are they concerned about, and why? What is the cost of this analysis?3.

Consider a Second Opinion

If the designer cannot provide a clear and convincing justification, consider seeking a second opinion from another qualified electrical engineer experienced in building grounding.4.

Discuss with the Utility

Consult with the utility company providing the service. They can advise you on their grounding practices and any specific requirements they may have for your connection.5.

Focus on General NEC Grounding

Ensure your building's grounding system complies with the general requirements of NEC Article 250, focusing on a robust grounding electrode system, proper bonding, and appropriately sized grounding conductors.

In Summary

While a good grounding system is essential for safety, requiring a full-blown grounding grid analysis for a typical building service supplied by a utility-owned pad-mount transformer seems excessive and potentially unnecessary. The key is to ensure code compliance, understand the risks involved, and make informed decisions based on sound engineering principles.Good luck! Flag for review