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[IEC 60076-1: 2011] Power transformers – Part 1: General.
[IEC 60076-2: 2011] Power transformers - Part 2: Temperature rise for liquid-immersed transformers.
[IEC 60076-3: 2013] Power transformers -- Part 3: Insulation levels, dielectric tests and external clearances in air.
[IEC 60076-5: 2006] Power transformers -- Part 5: Ability to withstand short circuit.
[IEC 60076-8: 1997] Power Transformers - Application Guide.
[IEC 60076-10:2016] Power Transformers - Determination of Sound Levels.
[IEC 60156:2025] Insulating liquids - Determination of the breakdown voltage at power frequency - Test method.
[IEEE C57.12.00-2021] - IEEE Standard for General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers.
[IEEE C57.98-2011] - IEEE Guide for Transformer Impulse Tests.
[IEEE C57.91-2011] - IEEE Guide for Loading Mineral-Oil-Immersed Transformers.
[IEEE C57.12.36-2017] - IEEE Standard Requirements for Liquid-Immersed Distribution Substation Transformers.
The 330 kV oil‑immersed transformer is an extra‑high‑voltage three‑phase oil‑immersed power transformer (maximum system voltage Um=363 kV). It serves as the core main equipment for China’s Northwest 330 kV main transmission network. Main types include double‑winding power transformers, three‑winding autotransformers and generator step‑up transformers. Designed and manufactured in accordance with GB 1094, GB/T 6451, IEC and other standards, it relies on transformer oil for insulation and cooling, and is applied for long‑distance, large‑capacity electric energy step‑up, step‑down and power exchange.
Active Part: Core fabricated of high‑permeability cold‑rolled grain‑oriented silicon steel sheets with full mitred‑lap joints; oxygen‑free copper windings optimized via electric‑field and short‑circuit‑force simulation for strong short‑circuit withstand capability. Matching insulation parts, leads and compressing‑positioning structures meet long‑distance transportation requirements.
Tank and Cooling System: Sealed steel‑plate welded tank. Common cooling modes: ONAN‑Natural Oil Natural Air cooling, ONAF‑Natural Oil Forced Air cooling, OFAF‑Forced‑Oil‑Circulation Forced‑Air cooling, ODAF‑Forced‑Oil‑Directed‑Circulation Forced‑Air cooling. OFAF is widely adopted for large‑capacity main transformers.
Insulating Oil: Mineral insulating oil (environment‑friendly ester oil is optional), performing functions of insulation, heat conduction and arc extinction.
Auxiliary Components: HV/MV/LV bushings, on‑load / off‑circuit tap‑changers, oil conservator, gas relay, pressure‑relief valve, oil‑level indicator, temperature‑measuring elements, cooling fans, online‑oil‑monitoring devices (partial discharge, chromatogram, moisture content), etc.
Low Loss & High Energy Efficiency: Optimized design of core, windings and magnetic shields reduces no‑load loss and load loss, complies with national energy‑efficiency grades and cuts transmission losses.
Low Partial Discharge & High Insulation Reliability: Vacuum drying and vacuum oil‑filling processes, optimized insulation structure and electric‑field distribution, with strict control of partial‑discharge magnitude for stable long‑term operation.
High Short‑Circuit Withstand Capability: Transposed conductors are adopted for windings with end‑part reinforcement. Verified by short‑circuit mechanical simulation to withstand system short‑circuit impacts.
Low Temperature Rise & Strong Overload Capacity: Optimized oil‑circuit design avoids risk of oil‑flow electrification, delivers excellent winding temperature‑rise control and permits short‑time overload operation.
Low Noise & Leak‑Proof Sealing: Core vibration‑damping and tank sound‑insulation structures; fully‑sealed construction reduces oil leakage and moisture ingress and lowers maintenance workload.
Intelligent & Expandable: Configurable with online oil‑chromatogram monitoring, online partial‑discharge monitoring and vibration monitoring for connection to smart substation monitoring system.
330 kV regional hub substation: Autotransformers realize power conversion among 330 kV / 220 kV / 110 kV voltage levels.
Large‑scale thermal power plants, hydropower plants and new‑energy collection stations: Generator step‑up transformers (363 kV side connected to 330 kV power grid).
Long‑distance power step‑up / step‑down for large industrial‑mining enterprises and new‑energy bases.
Expansion and renovation projects of 330 kV backbone transmission grid in Northwest China.
SFP‑240000/330: Three‑phase, forced‑air‑cooled, double‑winding oil‑immersed power transformer, rated capacity 240 MVA, high‑voltage rating 330 kV.
SSP‑360000/330: Three‑phase forced‑air‑cooled three‑winding transformer.
ODFPS‑250000/330: Single‑phase, forced‑oil‑directed‑circulation forced‑air‑cooled autotransformer (single‑phase bank combination for large‑capacity applications).
Common vector groups: YNd11, YNad11 (autotransformer). Tap‑changing modes: off‑circuit tap‑changing, on‑load tap‑changing.
