A transformer technical specification is the document that decides whether all bidders quote comparable equipment. In international tenders, vague statements such as “high-efficiency transformer as per IEC” or “supplier standard dry-type unit” usually produce inconsistent bids, hidden deviations, and later disputes over losses, tests, and site compliance. A complete specification should fix the rated duty, standards, losses, cooling, insulation, accessories, factory tests, documentation, and deviation rules before the bid opens.

The following framework is written for EPC contractors, utility procurement teams, and industrial buyers, and can be adapted to Xinda Transformer’s distribution, power, dry-type, amorphous-alloy, and special-transformer portfolio.

Project Scope and Supply Boundary

Start the specification with a clear scope statement so the price covers the same items for every bidder.

• Project background: new substation, industrial plant, renewable collector station, mining supply, urban distribution, or replacement.
• Quantity and type: for example, oil-immersed distribution, dry-type indoor, 110 kV/220 kV power transformer, amorphous-alloy unit, rectifier/furnace/special transformer.
• Voltage classes and system connection: incoming voltage, outgoing voltage, frequency, earthing system, and future expansion.
• Complete supply list: transformer main tank or dry-type active part, bushings, tap changer, radiators or cooling system, terminal boxes, control cabinet, accessories, spare parts, installation supervision, and technical documents.
• Interface responsibility: civil foundation, cable termination, switchgear, protection relays, SCADA, oil storage, and fire systems.

For Xinda’s product range, the scope can cover 10 kV oil-immersed models such as S11-M and S11-M.ZT/S13-M.ZT, 10 kV S13-M.RL three-dimensional wound-core units, D11 single-phase distribution transformers, 35 kV S11/SZ11, 110 kV and 220 kV oil-immersed power transformers, S(B)H15-M amorphous-alloy oil units, 10 kV SC(B)10 epoxy cast dry-type, SG(B)10 non-encapsulated dry-type, SCBH15-M amorphous dry-type, and special transformers including mining-general, high-overload, rectifier, and furnace types .

Rated Technical Parameters

This section must be numerical, not descriptive. Include every parameter that affects design and price.

• Rated power: kVA or MVA, continuous rating, and any overload profile.
• Primary and secondary voltage: for example 10 kV/0.4 kV, 35 kV/10 kV, 110 kV/10 kV, 220 kV/110 kV, as required.
• Frequency: 50 Hz or 60 Hz; do not leave this open for export projects.
• Tapping range: off-circuit tap changer or on-load tap changer, number of steps, percentage per step, and applicable tap positions.
• Vector group: Dyn11, Yyn0, YNd1, Yd11, or project-specific connection.
• Cooling method: ONAN, ONAF, AN, AF, or combined AN/AF for dry-type units.
• Insulation class and temperature rise: specify limiting values rather than only class names; for dry-type units confirm system class, winding temperature-rise limit, and monitoring method.
• Short-circuit impedance: percentage at rated tap, tolerance, and whether impedance must be coordinated with system fault level.
• Noise level: dB(A) at defined distance, especially for urban, hospital, data-center, and residential projects.

Xinda’s 35 kV dry-type product information uses AN/AF cooling options, Dyn11 as a standard connection example, F-class insulation, and IP20/IP30/IP40 enclosure options depending on requirement . These can be used as a template, but the tender should still state the exact project values.

Insulation, Dielectric Levels, and Protection

Specify insulation coordination instead of asking for “standard insulation.”

• Highest system voltage and insulation levels: lightning impulse, power-frequency withstand, and induced-voltage requirements according to the selected standard.
• Creepage and pollution class: define site pollution degree, outdoor/indoor installation, and minimum creepage distance for bushings.
• Dry-type enclosure protection: IP rating, access doors, ventilation openings, and restricted-access requirements.
• Oil-immersed protection devices: Buchholz relay, pressure-relief device, oil-temperature indicator, winding-temperature indicator, silica-gel breather or sealed-tank arrangement, oil-level gauge, and gas-detection function where required.
• Fire and environmental strategy: oil containment, fire walls, less-flammable fluid option, dry-type selection for indoor load centers, and local authority requirements.

Reference standards may include IEC 60076 series for power transformers, IEC 60076-11 for dry-type transformers, IEC 60076-3 for insulation and dielectric tests, and national equivalents such as GB 1094 and GB 1094.11 where the project is executed in China or uses Chinese standards .

Losses, Energy Efficiency, and Life-Cycle Requirements

Losses are the most frequently under-specified clause in transformer bids. The specification should require guaranteed values, not marketing words.

• No-load loss P₀: guaranteed maximum value and measurement conditions.
• Load loss Pₖ: guaranteed maximum value at reference temperature, usually 75°C for oil-immersed copper, or as defined by standard.
• No-load current: maximum percentage if relevant.
• Loss evaluation formula: capitalized value of losses, energy price, discounted payback, or tender scoring method.
• Efficiency class or standard: for example IEC 60076-20 efficiency classes for power transformers, local ecodesign rules, or China GB 20052 energy-efficiency grades where applicable.
• Tolerance on losses: state acceptable positive deviation; require bidder to declare measured routine-test losses and type-test losses separately.
• Special loss cases: harmonic-rich loads, rectifier/furnace transformers, data-center UPS duty, and continuous 24/7 distribution should use load-profile-based loss evaluation rather than nameplate-only comparison.

Xinda’s S13-M.RL uses a three-dimensional wound core for reduced no-load loss and noise; S(B)H15-M amorphous-oil and SCBH15-M amorphous-dry units are positioned for low no-load-loss duty; S11-M, S11-M.ZT/S13-M.ZT, and 35 kV/110 kV/220 kV oil units cover general and on-load regulation applications . The specification should still set the numeric loss limit for the tender rather than assuming a model name guarantees compliance.

Site Environment and Mechanical Conditions

Transformer design must match the installation environment. Request all site data in the bid document.

• Ambient temperature: maximum, minimum, average daily and annual values.
• Altitude: if above 1000 m, require dielectric correction, external insulation review, and cooling derating calculation.
• Humidity, rainfall, dust, and pollution: define ISO 12944 corrosion category for coastal, industrial, or mining sites; specify painting system and stainless or tropicalized hardware.
• Indoor/outdoor: ventilation, airflow, radiation heat, and clearance.
• Seismic requirement: specify IEC, IEEE, or local seismic standard; require cabinet/restraint design and test evidence if needed.
• Transport restrictions: site access road, bridge load, crane capacity, door height, gallery width, rail gauge, maximum single-piece weight, and tilt limitation.
• Special duty: mining methane/coal-dust zones, VFD harmonic load, mobile substation, high overload, or renewable intermittent output.

Xinda lists mining-general power transformers, high-overload transformers, and special transformers as separate categories ; for hazardous mining atmospheres, the specification must state Ex classification, applicable explosion-protection standard, temperature class, dust/gas group, and certification requirement instead of only requesting a “mining transformer.”

Tap Changer, Bushings, and Accessories

List all accessories as mandatory supply items to avoid budget gaps.

• Tap changer: off-circuit or on-load, maker or performance-equivalent approval, motor drive unit, position indicator, remote signalling.
• Bushings: HV, LV, neutral, material, creepage, flange size, oil-filled or dry-type, termination type.
• Monitoring instruments: oil/winding temperature indicators, pressure/vacuum gauge, liquid-level gauge, moisture-in-oil sensor, DGA port for large units.
• Protection devices: Buchholz, sudden-pressure relay, magnetic oil-gauge, relief valve, anti-condensation heater.
• Dry-type controls: temperature controller, PT100 sensors, fan control, alarm/trip contacts, IP-rated terminal box.
• Mechanical items: lifting lugs, jacking pads, wheels/rollers, earthing terminals, nameplate in project language, foundation bolts, control cables.

Standards, Type/Routine/Special Tests

Define the exact test scope. Generic “tests as per IEC” is not enough.

Applicable design and manufacturing standards:

• IEC 60076-1 general requirements
• IEC 60076-2 temperature rise
• IEC 60076-3 insulation and dielectric tests
• IEC 60076-5 short-circuit withstand
• IEC 60076-10 sound levels
• IEC 60076-11 dry-type transformers
• IEC 60296/60274 for mineral oil where applicable
• GB 1094 series, GB/T 6451, GB 20052, GB 1094.11 as required by project jurisdiction

Routine tests to require for every unit:

• winding resistance measurement
• voltage ratio and vector-group verification
• short-circuit impedance and load loss
• no-load loss and no-load current
• insulation resistance
• power-frequency withstand test
• induced overvoltage test
• for dry-type units, partial discharge check where specified
• oil dielectric tests for oil-immersed units, including breakdown voltage, moisture, and gas analysis for large transformers
• visual inspection, nameplate, dimensions, and accessory function test

Type tests to require when the tender demands them:

• temperature-rise test
• lightning impulse test for HV units
• short-circuit withstand test or valid type-test reference for the same design
• sound-level test
• partial discharge test for dry-type and special HV units

Special tests:

• zero-sequence impedance
• harmonic loss measurement for converter/rectifier duty
• on-load tap-changer cycling
• sealing/pressure test for oil units
• waterproof/dust test for enclosures
• third-party witnessed FAT, video record, and independent inspection agency if required

For EPC export projects, require routine-test reports before shipment, optional photo/video FAT, and witnessed type/special tests when contract value or risk justifies the cost .

Documentation, Drawings, and Compliance Matrix

The bid should be rejected if technical documents are incomplete. Require the following:

• Technical data schedule with guaranteed losses, impedance, dimensions, weights, and tap data.
• General arrangement drawing, foundation drawing, terminal arrangement, cable tray interface.
• Cooling and control schematic, tap-changer diagram, SCADA/modbus signal list.
• Nameplate drawing in English/project language, including standards, ratings, serial number, year, and manufacturer data.
• Routine-test report for each unit; type-test report references; certificate of conformity.
• Operation and maintenance manual, installation instruction, oil handling manual for oil units, spare-parts list.
• Deviation matrix: every clause answered as “compliant,” “deviation with explanation,” or “not applicable”; unsupported “fully compliant” statements should be clarified.
• Export documents as required: commercial invoice, packing list, bill of lading, certificate of origin, conformity certificates, local market-access certificates, IPPC mark for wooden packing, MSDS for insulating oil.

Xinda’s English site provides product categories, quotation contact, and export enquiry route; for each tender the supplier should return project-specific drawings and test files rather than only catalogue pages .

Packaging, Transport, Handling, and Site Acceptance

Transformer damage during transport is often preventable with clear specification clauses.

• Packing standard: moisture-proof, shock-proof, bushing protectors, separate accessory boxes, clearly numbered spare cartons.
• Shipping marks: gross/net weight, center of gravity, lifting points, “this side up,” fragile, and destination port.
• Oil-immersed transport: full/empty tank condition, nitrogen blanketing option, positive-pressure monitoring, impact recorder for large units, tilt limitation.
• Dry-type transport: moisture barrier, enclosure protection, terminal-box sealing, no outdoor storage without approved covering.
• Site acceptance: joint unpacking, visual check, document check, oil sampling if required, insulation tests, installation supervision, commissioning, and final acceptance criteria.
• Lead time: define from purchase order, drawing approval, material readiness, test window, and Incoterms such as EXW, FOB, CIF, or DAP.

Commercial and Warranty Clauses Linked to Technical Compliance

Technical specification and commercial terms must be connected.

• Guaranteed technical values become contract limits; any deviation must be in writing.
• Warranty period from delivery, commissioning, or acceptance, with separate obligations for design defect, material defect, and oil quality.
• Liquidated damages for delayed submission of drawings, tests, or delivery.
• Spare parts package: silica gel, gaskets, fuses, sensors, fans, bushings, oil filters, and special tools.
• Local service: installation supervision, training, remote technical support, and response time for critical projects.

Bidder Qualification Checklist for Transformer Tenders

Request only verifiable qualifications. For Xinda-based bids, the following company facts can be stated as capability evidence:

• Located at No. 38 Jingsan Road, Fenghuang Industrial Park, Dongchangfu District, Liaocheng, Shandong.
• Registered capital RMB 150 million; site area 150 mu; building area 53,000 m²; 470+ production and test equipment units .
• Staff 260+, including 4 senior engineers and 12 engineers; own product development team .
• Product scope: 10 kV oil-immersed, 10 kV dry-type, amorphous alloy, 35 kV oil, 110 kV/220 kV power transformers, special transformers, high/low-voltage switchgear, prefabricated substations, and cable branch boxes .
• Annual output stated as 5 million kVA in routine production information and up to 10 million kVA/year designed capacity for 220 kV and below transformers plus switchgear .
• Patents stated on the Chinese site as 1 invention and 14 utility models ; do not mix with separately published third-party profiles that list different patent counts.

For a specific tender, ask the bidder to submit valid ISO certificates, type-test reports matching the exact model and rating, reference projects with similar voltage and environment, and factory-audit records.

Ready-to-Use Transformer Specification Checklist

Use this checklist as the minimum bid-enquiry attachment:

1. Project scope, quantity, application, and single-line diagram
2. Rated power, primary/secondary voltage, frequency, vector group
3. Tapping range and tap-changer type
4. Cooling method and overload profile
5. Insulation class, temperature-rise limits, dielectric levels
6. Short-circuit impedance and tolerance
7. Guaranteed no-load loss, load loss, no-load current
8. Efficiency standard or loss-capitalization formula
9. Environment: altitude, temperature, humidity, pollution, corrosion class
10. IP/Ex requirement for dry-type or hazardous-area units
11. Bushings, terminals, cable boxes, earthing points
12. Protection accessories: Buchholz, pressure relief, WTI/OTI, breather, sensors
13. Monitoring: local indicators, SCADA signals, DGA, temperature alarms
14. Applicable standards IEC/GB/IEEE/local utility rules
15. Routine, type, and special test list
16. FAT/witness/third-party inspection rules
17. Drawings, datasheets, nameplate, O&M manual
18. Packing, transport mode, impact recorder, site-handling limits
19. Spare parts, tools, installation supervision, training
20. Deviation matrix, warranty, delivery Incoterms, qualification proofs

Conclusion

A complete transformer bidding specification should remove ambiguity in ratings, losses, standards, tests, site environment, and documents. Buyers who define numeric loss limits, impedance, insulation levels, cooling, and factory-test witness rules receive comparable bids and reduce commissioning risk. Xinda Transformer can respond with 10 kV S11/S13/SC(B)10/SG(B)10 and amorphous lines, 35 kV S11/SZ11, 110 kV/220 kV oil power units, and special/municipal/mining/high-overload products; for each tender, the binding offer should be based on approved drawings, guaranteed test values, and project-specific certificates rather than catalogue model names alone.

Preparing an international transformer tender?​ Send Xinda’s technical team the single-line diagram, load profile, site climate data, target standards, and required tests. We will return a compliant datasheet, deviation matrix, test plan, and export documentation list without suggesting performance values that the project has not verified.