Interconnecting a large load—especially a data center sitting behind a Utility Tie with behind-the-meter generation—is not one study. It is a sequence. The utility (or ISO) owns the confidential grid model and runs screening, thermal loading, load flow, short circuit, TOV, and system-wide dynamics before anyone finalizes plant equipment. The engineer of record then designs the substation and POI using those published results; the OEM supplies converter models, harmonics, and package protection; the facility/EPC owns everything from the MV handoff inward. Commissioning is where harmonic compliance and ride-through settings stop being paper and start being measured. Mixing those scopes, or treating a calculated EMT setting as field-tuned, is how interconnection schedules slip.
Download the power study division-of-responsibility spreadsheet (xlsx)