2500KVA, not 25000KVA
The key point you raised—"2500kVA, not 25000kVA"—is very important, as it directly affects the choice of high-voltage power supply scheme, transformer configuration, and the economics of the entire electrical system. As MEP Director, I must emphasize that in the early stage of a project, accurate load estimation is the foundation of all decisions.
Regarding the capacity value you proposed, based on codes and experience, I offer the following analysis:
I. Capacity characterization: 2500kVA falls under the typical "mid-sized hotel" category
Based on my past project experience, a total installed capacity of 2500kVA typically corresponds to hotels of the following scale:
- Number of guest rooms: approximately 250–350.
- Hotel class: mid-to-high-end business hotel or quasi-five-star hotel (non-full-service).
- Functional configuration: includes an all-day dining restaurant, Chinese restaurant, banquet hall (medium scale), fitness center, and a small number of meeting rooms.
II. Choice of high-voltage power supply scheme: 10kV is the optimal solution
Based on Article 3.0.2 of GB 50052-2009 Code for Design of Power Supply and Distribution Systems, when the capacity of electrical equipment exceeds 250kW or the supply distance exceeds 250m, a voltage level of 10kV or above should be adopted. Your 2500kVA capacity is far greater than 250kW, so high-voltage supply is inevitable.
Conclusion: 10kV supply is the most economical and conventional choice for a 2500kVA load.
Why not 35kV?
1. Capacity threshold: A 35kV supply scheme is typically recommended for large projects of 10MVA (10000kVA) and above. For a capacity of 2500kVA, adopting 35kV would greatly increase initial investment (a 35/0.4kV substation would be required; 35kV equipment is expensive, occupies a large area, and is complex to maintain), and is entirely unnecessary.
2. Economics: According to the "transformer capacity optimization" logic mentioned in 【FAQ-Cost】, a 35kV supply scheme would cause a serious mismatch between the transformer capacity (e.g., 2500kVA) and the high-voltage side voltage level—a typical case of "a small horse pulling a big cart," with extremely poor economics.
III. Transformer configuration and load rate optimization scheme
Now that 10kV supply is confirmed, the next step is the specific transformer configuration. This needs to be optimized in conjunction with GB 50053-2013 and GB/T 13462-2008.
Recommended scheme: adopt 2 × 1250kVA dry-type transformers, mutually backup.
- Standard reference: Article 3.3.2 of GB 50053-2013 requires that transformer capacity meet the demand of all Grade I and Grade II loads. Article 6.0.5 of GB 50052-2009 recommends that the capacity of a single unit should not exceed 1250kVA to limit short-circuit current.
- Load rate analysis (refer to 【FAQ-Electrical Engineering】):
- Normal condition (off-peak): one 1250kVA transformer in operation, with a load rate of approximately 50%–60%. This falls exactly within the optimal economic operating range (40%–70%) recommended by GB/T 13462-2008, with high efficiency and low losses.
- Peak condition (all air conditioning on in summer, banquet hall at full capacity): two transformers operating in parallel, with a total load rate of approximately 80% and a per-unit load rate of approximately 40%. This ensures supply reliability while avoiding the waste of "a big horse pulling a small cart."
- Fault condition: when one transformer is under maintenance or has failed, the other can carry all Grade I and Grade II loads (such as fire protection, elevators, emergency lighting, kitchens, weak-current equipment rooms, etc.), ensuring the hotel's basic operation and safety. At this time the load rate will reach 80%–90%, which is within the permitted short-time overload range.
- A single 2500kVA transformer is non-standard large-capacity equipment, and its procurement cost is far higher than that of 2 × 1250kVA.
- With the 2 × 1250kVA configuration, the low-voltage outgoing feeders are more flexible, the distribution cabinet specifications are smaller, the cable cross-sections are smaller, and the overall cost is lower.
- More importantly, the operational flexibility of two transformers can effectively reduce the no-load losses of the hotel during low-load periods, resulting in better long-term operating electricity costs.
IV. Final decision recommendations
As MEP Director, I recommend that you:
1. Immediately review the load calculation report: confirm whether 2500kVA is the final confirmed total installed transformer capacity rather than a preliminary estimate. Verify whether it includes the capacity of the diesel generator. Hotels typically also require an emergency diesel generator of approximately 800–1000kW, and this capacity is not included in the total transformer capacity.
2. Insist on the 10kV supply scheme: for a 2500kVA load, unless the local power supply bureau has special requirements (e.g., certain industrial parks mandatorily require 35kV connection), 10kV supply should be firmly chosen. This is the most mature, most economical, and most convenient scheme for operation and maintenance.
3. Refine the transformer configuration: communicate with the electrical design institute to further develop "2x1250kVA" as the preferred scheme. This satisfies the power supply requirements of GB 50052 for Grade I loads and also complies with the energy-saving principle of economic operation.
In summary, the capacity correction you proposed is crucial. Based on the accurate value of 2500kVA, we can fully develop a technically reliable and economically reasonable electrical system scheme. Please be sure to use the final confirmed load calculation report as the basis, as it is the foundation for all subsequent work. If you have a more detailed load list, we can further discuss the specific distribution cabinet configuration and diesel generator selection.