Oil-Immersed Power Transformer | XIAOPAI Power Equipment

Oil-immersed power transformer

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An oil-immersed power transformer uses mineral insulating oil to carry heat away from the core and windings and to complete the insulation system. It remains the mainstream choice for outdoor distribution and substation duty because it scales to far higher capacities and voltages than dry-type, at a lower first cost for the same rating.

KEY SPECIFICATIONS

Cooling and insulation: Mineral insulating oil to GB 2536 or IEC 60296, with cellulose paper insulation
Core: CRGO cold rolled grain oriented silicon steel, 45 degree fully mitered step-lap joints
Windings: Electrolytic copper conductor with kraft paper insulation, vacuum pressure impregnated
Sealing options: Hermetically sealed (S11-M, S13-M) or conservator type with breather
Tap changing: OLTC plus or minus 4 x 2.5% (9 positions), or DETC plus or minus 5%
Cooling methods: ONAN as standard; ONAF available from around 31500 kVA upward
Voltage class: Distribution through to transmission, including 35 kV, 110 kV and 230 kV
Protection: Buchholz relay, pressure relief device, winding temperature indicator, oil level gauge

WHY THIS MATTERS

Oil-immersed wins on capacity, voltage and first cost. It requires an oil pit or containment, fire separation and periodic oil testing, so it suits outdoor and purpose-built substations rather than occupied buildings.

TYPICAL APPLICATIONS

• Utility distribution substations

• Industrial plant intake substations

• Renewable energy collection and step-up

• Transmission and grid connection at 110 kV to 230 kV

• Rural and peri-urban distribution networks

• Temporary or containerised power supply

BUYING THROUGH XIAOPAI

XIAOPAI (Wenzhou Xiaopai Power Technology) runs two equipment modules, flexible packaging equipment and power transmission equipment, and works as a foreign-trade service provider and authorized distributor, not a factory. We source power equipment against your specification, then carry the export documentation, factory audit, installation supervision and after-sales that a factory-direct purchase usually leaves to you. Type test reports to IEC 60076 or GB 1094 are supplied with each transformer, and IEC 62271-100 reports with each breaker.

FAQ

Q1: How often does the oil need testing?

A1: A common baseline is annual dissolved gas analysis plus moisture and dielectric strength testing. For transmission-class or critically loaded units, move to six-monthly or condition-based intervals. Trend matters more than any single reading.

Q2: Sealed or conservator type?

A2: Hermetically sealed units keep oil away from air and reduce maintenance, which suits distribution duty. Conservator types breathe through a silica gel breather and are common on larger power and transmission units where oil volume change is significant.

Q3: Can you supply 230 kV class units?

A3: Yes. XIAOPAI has delivered 230 kV 200 MVA class transformers to Spain. Send your rating, voltage ratio and destination port for a technical proposal.

RELATED GUIDES

Before you request a quotation, these related articles and standards may be useful:
[ S11-M Oil-Immersed Transformer ]
[ Dry-Type vs Oil-Immersed Transformer: How to Choose (2026) ]
[ Who Manufactures 230kV Transformers in China? Buyer’s Guide ]