Draw the actual source-to-load arrangement
Start with a marked single-line diagram showing where the generator connects, which transformer it supplies and whether another source or transformer can be connected at the same time. State whether the transformer is energized before the load is connected or as part of a different approved sequence. A generic note saying “generator compatible” does not define those cases.
The oil-immersed transformer range and dry-type transformer range provide the product starting points. The transformer construction should suit the project; the generator-source study is an additional system review rather than a product label that applies automatically to every unit.
Build a study-input schedule with named owners
| Study subject | Information needed | Responsible contributor |
|---|---|---|
| Transformer energization | Design data, switching point and proposed energization condition | Transformer supplier and system engineer |
| Generator response | Applicable machine and control-system characteristics | Generator supplier |
| Load steps | Starting, transfer, reconnection and simultaneous-load cases | Owner and load designers |
| Voltage performance | Project acceptance limits and relevant operating cases | System engineer and owner |
| Fault protection | Generator-source and other-source study conditions | Protection engineer and equipment suppliers |
| Neutral and earthing | Switching arrangement, neutral connections and earthing design | Project electrical engineer |
| Acceptance | Required calculations, simulation, factory checks and site tests | Project approval authority |
Do not fill missing generator characteristics with utility-source assumptions. Ask the relevant supplier for the actual data required by the study and keep unresolved information visible in the tender comparison.
Separate energization from steady loading
A transformer can present a different requirement during energization than during established service. The inrush and protection brief describes the information needed to distinguish expected energization behaviour from faults. For a generator-fed installation, add the source characteristics and the approved switching sequence to that brief.
The generator supplier should review its response to the proposed energization and load cases. Procurement should not select a universal generator-to-transformer size multiplier or a fixed inrush allowance from another installation. Record the study method and the acceptance decision, including any proposed changes to switching sequence, loading or equipment. Those proposals need approval before being presented as part of the purchased solution.
Revisit protection and neutral interfaces
Fault behaviour and available protection information can differ between source states. The protection review should identify which settings and devices apply while the transformer is supplied from the generator and whether any changeover signals are required. The offer should identify control contacts, terminals, interlocks and site-test boundaries, rather than implying that the transformer supplier owns the complete generator control scheme.
Use the neutral-earthing RFQ guide to collect the connection and ownership information. Do not assume that the normal utility arrangement remains correct for every generator switching state. The project engineer must approve the earthing and switching design for the complete system.
Example: generator capacity looks sufficient at normal load
A project has a modest running load but proposes energizing an unloaded transformer before reconnecting several loads. A comparison of running kVA alone leaves the energization and reconnection cases unanswered. The useful RFQ response requests the missing generator data and evaluates the actual sequence rather than declaring compatibility from steady demand.
If parallel operation is permitted, add the relevant states to the diagram and use the parallel-operation procurement guide for transformer compatibility information. Parallel permission should never be inferred from the presence of a bus coupler or transfer arrangement.
Agree evidence and acceptance responsibilities
List the required transformer data, generator data, studies, approved operating narrative and test procedures in the document schedule. Identify which factory checks are possible on each supplied item and which integrated checks remain at site. A transformer routine test report does not prove the behaviour of a generator-transformer-load system that was not tested together.
Changes to transformer rating, impedance, generator selection or switching sequence should trigger a review of the affected study assumptions. Preserve the approved versions in the handover package so later modifications can be assessed against the installed arrangement.
RFQ checklist
- Marked source-to-load diagram and every permitted switching state.
- Transformer rating, voltage ratio, impedance, taps, connection and construction.
- Generator equipment identity and supplier-provided study characteristics.
- Energization sequence, load steps, reconnection and motor-starting cases.
- Project voltage-performance requirements and study approval authority.
- Protection settings, control signals, interlocks and source-state information.
- Neutral switching and earthing design responsibilities.
- Study deliverables, equipment data deadlines and declared exclusions.
- Factory checks, integrated site tests and final operating narrative.
Send the diagram and input schedule through transformer quotation or contact Jinxing. Compatibility must be confirmed through the project review of the proposed equipment and operating cases.