Medium-Voltage Distribution for Data Center Campuses in 2026

Medium-voltage distribution for data center campuses is the network of feeders, switchgear, and unit substations that carries power from the campus substation to each data hall after it has been stepped down from transmission voltage. Once the high-voltage substation converts incoming transmission power to a campus voltage — most commonly 34.5 kV on large modern campuses — that power has to be distributed across a site that can span hundreds of acres to dozens of buildings, and the medium-voltage (MV) system is what does it. It comprises the MV switchgear at the substation, the underground or overhead feeders that fan out across the campus, the unit substations or pad-mounted transformers at each data hall that step the voltage down again to the building’s utilization level, and the protection and switching that keep a fault in one feeder from dropping the rest. The MV distribution design directly determines campus reliability, expandability, and how cleanly the site can grow from its first building to full buildout. Get it right and the campus scales smoothly with no single point of failure between the substation and the halls. Get it wrong and reliability or expansion is compromised in ways that are expensive to fix once concrete is poured.

ATK Energy Group engineers and builds the medium-voltage distribution as an integrated part of the campus power chain — substation, distribution, and unit substations under one coordinated scope. This guide explains how MV distribution works and what drives a good design.

What Does Medium-Voltage Distribution Do on a Data Center Campus?

The MV distribution system is the bridge between the substation and the buildings. The substation delivers bulk power at a campus voltage, but that voltage still has to be carried efficiently across a large site and subdivided to each data hall. Medium-voltage distribution does three things: it transports power across the campus at a voltage high enough to limit current and losses, it segments the campus electrically so faults and maintenance are contained, and it delivers power to unit substations at each building where it is stepped down to utilization voltage.

On a large campus, 34.5 kV has become the standard distribution voltage because it carries more power with fewer and smaller feeders than 13.8 kV, which matters across a sprawling site. The MV system feeds data center power infrastructure at each hall, and its topology — radial, loop, or primary-selective — sets the reliability of that delivery. This is the layer where campus-wide reliability is engineered, downstream of the substation but upstream of the building electrical systems.

What Distribution Topologies Are Used and Why?

The topology of the MV system determines how it behaves when a feeder or piece of equipment fails. A simple radial system runs a single feeder to each load — lowest cost, but a fault on the feeder drops everything downstream. A loop or ring system feeds loads from two directions so that a single fault can be isolated and power restored from the other side, improving reliability at moderate added cost. A primary-selective scheme gives each unit substation two independent feeders with automatic or manual transfer, so the loss of one feeder doesn’t drop the load at all.

Data centers, which cannot tolerate unplanned interruption, typically use loop or primary-selective topologies rather than simple radial, often with redundant feeders sized so the campus can lose any one and still serve full load. The choice cascades into feeder count, switchgear configuration, and conductor sizing, which is why it belongs in the earliest design discussions. ATK works the topology through with the owner as part of the overall utility infrastructure design, because it sets the campus reliability ceiling at the distribution layer.

How Is Medium-Voltage Distribution Built, Step by Step?

MV distribution construction for a data center campus follows a defined sequence, coordinated with the substation and the building program.

1. Load and topology definition. Establish per-building loads, redundancy requirements, and the distribution topology (loop, primary-selective, etc.).

2. Feeder routing and one-line design. Lay out feeder routes across the campus and design the MV one-line, switchgear, and protection coordination.

3. Equipment procurement. Order MV switchgear, unit substation transformers, and pad-mounted equipment, which carry their own lead times alongside the main substation equipment.

4. Duct bank and civil work. Build the underground duct banks, manholes, and pads that the feeders and transformers require — often the bulk of the field work.

5. Cable installation and terminations. Pull MV cable through the duct banks and terminate it at the switchgear and unit substations.

6. Switchgear and unit substation setting. Set and connect the MV switchgear and the unit substations at each hall.

7. Protection and controls. Configure feeder protection, automatic transfer, and SCADA so faults are isolated and switching is coordinated.

8. Commissioning and energization. Test the cable, switchgear, and protection, and energize the distribution as the halls come online.

Most data center MV distribution is underground, which ties the schedule closely to the underground utility construction — the duct bank work often paces the distribution build.

How Does MV Distribution Support Campus Expansion?

Data center campuses rarely build out all at once; they grow building by building over years. A well-designed MV distribution system anticipates that growth. It is sized and laid out so additional data halls can be added without rebuilding the backbone — with spare feeder capacity, switchgear positions left for future feeders, and duct bank routes stubbed for expansion. This foresight is what separates a campus that scales smoothly from one that needs disruptive distribution rework at each phase.

Designing for expansion means making decisions in phase one that only pay off in phase three: oversizing the substation low-side and MV switchgear, routing duct banks for the full buildout, and choosing a topology that extends cleanly. ATK engineers the distribution for the ultimate campus, not just the first building, so the power construction supports growth instead of constraining it. The cost of provisioning for expansion up front is almost always far less than retrofitting it later.

What Should You Look For in an MV Distribution Partner?

Because MV distribution sets campus reliability and expandability, the partner who builds it should be evaluated on system thinking, not just cable pulling. Look for the ability to engineer and build the full chain — substation, distribution, and unit substations — so the layers are coordinated rather than handed off. Look for MV protection and controls expertise, since the topology only delivers reliability if the protection and transfer schemes work. Look for self-perform underground and electrical construction capacity, because the duct bank work paces the schedule. Look for procurement strength on switchgear and transformers. And look for a partner who designs for the ultimate buildout, so the campus can expand without rework.

ATK Energy Group builds the medium-voltage distribution as an integrated part of the campus power chain, coordinated with the substation and the building program. The campus is only as reliable and expandable as its distribution, and ATK engineers that layer to carry the site to full buildout.