Centralized and distributed photovoltaic (PV) transformation should be compared as complete electrical architectures. A lower transformer purchase price can be offset by a different cable network, more terminations, altered protection requirements or a larger common outage. Count the interfaces from inverter terminals to the collector connection before deciding which arrangement is simpler or less expensive.
Draw equivalent comparison boundaries
Use the same inverter capacity, export requirement, environmental conditions and project expansion assumptions for both alternatives. Identify where the voltage changes and where circuit ownership changes. Otherwise, one quotation may include medium-voltage switching while the other stops at transformer terminals.
A centralized arrangement may collect several inverter blocks before transformation. A distributed arrangement may transform close to individual blocks and collect power at a higher voltage. The actual topology matters more than the label: both terms can describe several different combinations of winding count, switchgear and cable layout.
General transformer application guidance addresses connections, rating and parallel operation. It supports the equipment review but does not determine the optimum plant architecture independently of the network and maintenance requirements. [1]
Count interfaces, not only transformers
List cable circuits, terminal sets, isolation points, protection zones and communication interfaces for each option. Include joints or transitions imposed by transport limits and physical routes. A shorter low-voltage route may reduce one burden while adding more local medium-voltage interfaces.
| Comparison item | Keep the assessment explicit |
|---|---|
| Electrical path | Voltage and current on each cable section |
| Switching | Number, duty and ownership of isolation points |
| Protection | Zones, coordination and common tripping consequences |
| Controls | Metering boundaries and plant-controller dependencies |
| Physical service | Access, replacement route and spare strategy |
Do not equate more components with worse availability automatically. Several smaller independent sections may preserve partial generation during an outage, while also increasing the number of components requiring maintenance. Evaluate both the failure consequence and the practical restoration strategy.
Compare operating cases on the same basis
The loss comparison should use the same production and reactive-power schedule. Nameplate efficiency at one loading point cannot describe different annual loading patterns. An energized but lightly loaded distributed unit and a heavily loaded common unit experience different combinations of excitation and load-related losses.
Where a thermal loading assessment is used, apply the guide appropriate to the transformer type and its operating conditions. Mineral-oil and dry-type loading guidance are separate documents; their models should not be exchanged without justification. [2] [3]
Include an outage case, planned maintenance and the intended expansion phase. Review whether the remaining transformer or collector section is expected to accept redistributed power, or whether generation is deliberately curtailed. A redundancy claim has little value if the cables, busbars or control limits prevent the proposed transfer.
Make the decision record auditable
Prepare a one-page architecture comparison linked to the single-line diagrams and equipment schedules. Record the scope included in each cost, the operating cases used, the common outage boundary and the assumptions about spare equipment. Keep unpriced interfaces visible rather than assigning them an assumed zero cost.
The preferred architecture should explain a tradeoff: fewer common transformation points, shorter high-current routes, greater section independence, simpler maintenance or another measurable project objective. Avoid presenting every advantage as simultaneously available.
For procurement, the most useful output is not “centralized is cheaper” or “distributed is more reliable.” It is a documented comparison showing which interfaces change, what operational consequence follows, and which project requirement makes that tradeoff acceptable.
Core procurement checkpoint: Standardize core variants without erasing electrical differences
Centralized and distributed layouts may create opportunities to repeat a core design, but identical plant megawatts do not prove interchangeability. Use a revision-controlled schedule linking each transformer design to its approved core drawing and quantity. Where common laminations are proposed, the transformer manufacturer should confirm that the geometry and magnetic design remain valid for every listed electrical configuration.
For the core enquiry: Core variant schedule; approved drawings; quantity per variant; permitted common parts; packet identification and revision control.