35kV three‑phase oil‑immersed power transformer (800‑31500 kVA) for 50/60Hz grids. Low‑loss build with strong short‑circuit resistance, IEC & GB certified. Equipped with conservator tank and copper windings, suited for industrial and renewable‑energy projects. Customizable specs, strict factory testing and global after‑sales service.
A 35 kV network has to come down to something the plant can actually use. This three-phase oil-immersed power transformer does that work: it takes the 35 kV supply and delivers a low-voltage output for distribution boards and process equipment, at capacities from 800 kVA to 31,500 kVA and at either 50 Hz or 60 Hz. Ratings, tap range, connection group and cooling mode follow your system rather than a fixed catalogue item.
Inside the tank, a heart-type laminated core carries concentric copper windings immersed in insulating oil. Outside, the light-grey steel tank is fitted with high-voltage bushings, an integrated conservator tank, corrugated radiators and a control cabinet, with the on-load tap changer mounted on the cover. That arrangement keeps the output steady while the incoming voltage or the plant load moves through the day.
The unit suits medium-voltage substations, industrial distribution rooms and renewable-energy sites — installations where the transformer is expected to run for years on routine checks alone. It is specified by projects that care about losses, about surviving a downstream fault rather than being rewound after one, and about documentation that holds up in a technical review.
Because the design is built around your network, the useful starting point is your own system data: the high-voltage and low-voltage levels, capacity and load profile, the impedance your protection is set for, and the conditions at the site. Send those with your enquiry and our engineers confirm the configuration before production begins.
| Parameter | Specification |
|---|---|
| Rated Capacity | 800 kVA – 31,500 kVA |
| Phase | Three phase |
| Rated Voltage (HV) | 35 kV (or customized) |
| Rated Voltage (LV) | 6.3 kV / 6.6 kV / 10.5 kV / 11 kV (customizable) |
| Frequency | 50 Hz / 60 Hz |
| Connection Group | Dyn11, YNd11, or per customer requirement |
| Short-Circuit Impedance | 6.5% – 8.0% |
| Cooling Method | ONAN / ONAF (oil natural / forced air) |
| No-Load & Load Losses | Low-loss design per IEC 60076 / GB standards |
| Temperature Rise | Oil ≤ 60 K, Winding ≤ 65 K |
| Ambient Temperature | -25 °C to +40 °C |
| Tap Change | On-load (OLTC) with ±2 × 2.5% or ±5% range |
| Design Standards | IEC 60076, GB 1094, GB/T 6451 |
The magnetic circuit is built from high-permeability, grain-oriented cold-rolled silicon steel, laminated in a heart-type arrangement with multi-step round columns and equal-section yokes. Full mitered multi-step joints and precision shearing reduce the air-gap effect at the corners, and that is where no-load loss, no-load current and operating noise are largely decided. Lower no-load loss is a running cost that stays with the plant for the entire service life of the unit.
The windings are concentric and wound from high-purity oxygen-free copper. Transposition and lead arrangement are optimised so circulating currents and stray losses stay low, which keeps load loss down at the currents a heavily loaded 35 kV transformer really carries.
The tank is welded from steel plate and finished in light-grey anti-corrosion paint, with bolted mounting feet and a bolted access door. High-voltage bushings are porcelain and cover-mounted, and an integrated conservator keeps the oil surface under control as load and temperature change. A control cabinet carries the auxiliary and monitoring wiring. Everything is arranged for outdoor installation and straightforward site handling.
Steel, copper and core laminations are metals that are routinely recovered and recycled once a transformer reaches the end of its service life, which matters on projects that carry an end-of-life disposal requirement.
Partial discharge is the slow degradation path in transformer insulation: small discharges in voids, at winding ends or on sharp metal edges that erode the insulation year after year until a fault finally appears. Keeping discharge low is a design habit rather than a single component, and it shows in how the insulation and the electric field around it are arranged.
Angle rings sit at the winding ends, where the field is strongest. Edges are rounded, burrs are removed from conductors and structural parts, and every joint and metal component inside the oil is shielded so the field does not concentrate on one point. The result is a more even field distribution along the winding, which is what holds partial discharge at low levels under normal operating voltage and during dielectric testing at the works.
For the buyer this has two practical consequences. Insulation ages more slowly, so service life is not quietly shortened by an internal defect that never appears in a routine reading. And site testing is more likely to come back clean, which keeps commissioning and periodic checks free of the follow-up work an abnormal discharge reading triggers.
Because shielding, rounding and deburring are built into the assembly before the tank is closed, the insulation geometry that passed the factory dielectric tests is the same geometry that goes into service after transport and installation.
A transformer that has to be opened, lifted and re-clamped during commissioning costs a project days it rarely has. The core and winding assembly here is held by advanced axial clamping and new-style fasteners, and the structure is reinforced to take the shock loads of road and sea transport. In practice the unit can be positioned, filled, tested and energised without a core inspection.
The design also keeps its clamping force in service. Fasteners that resist loosening and a rigid assembly mean the windings do not shift or settle as the transformer goes through years of thermal cycling, so an inspection is a visual and instrument check rather than a mechanical intervention.
What remains is genuinely routine work: reading oil level and temperature, checking the breather and watching the oil surface for signs of moisture, looking for oil seepage at gaskets and valves, and drawing an oil sample on the schedule your maintenance plan sets. The unit ships with maintenance guidelines that spell out these checks, and our engineers are available remotely when a reading needs interpreting.
Care before energisation does most of the work. Keep the transformer on a firm, drained surface with accessories protected until installation, follow the pre-energisation checklist, and the first years of service are usually uneventful.
Every project starts with our engineering team. Share your duty conditions, drawings or existing nameplate data, and we help confirm the right rating and configuration before production begins — selection assistance, model matching, and troubleshooting before and after delivery. Backed by more than fifty years in transformer manufacturing, our engineers travel to site for installation and commissioning guidance and stay reachable remotely once the unit is energised. Functions and parameters can be customised to your project, and our quality system holds ISO9001 with IEC, CSA and CTQC testing.
It works on electromagnetic induction. Alternating current in the primary winding sets up a magnetic field in the core, and that field induces a voltage in the secondary winding. Because the two windings have different numbers of turns, the voltage changes while power is transferred — which is how a 35 kV line is stepped down for a plant without any rotating machinery or moving parts.
It sets the voltage level. The incoming 35 kV supply is stepped down to the level the plant's distribution boards, motors and process equipment use, and the on-load tap changer corrects the output while the supply or the load moves. That keeps downstream equipment inside its voltage window instead of exposing drives, contactors and control electronics to persistent overvoltage or undervoltage.
Yes, provided the two transformers match on the points that govern parallel operation: connection group, tap position and short-circuit impedance. We can build toward the impedance value your existing transformer runs at so the load divides evenly between them. Send the existing nameplate data with your enquiry and our engineers will confirm what is achievable.
Dyn11 puts a delta winding on the high-voltage side and brings a neutral out of the star-connected low-voltage winding, which is the usual choice where plant distribution needs a neutral for single-phase and control loads. YNd11 places the star winding on the high-voltage side and is used where the 35 kV system itself needs a neutral point. Both are built in this range, and the right choice follows your earthing and protection design.
It can, and it often does. Where a furnace transformer supplies the melting furnace, this unit feeds the plant's own distribution from the same 35 kV bus. Melting load is cyclic and draws heavy current, so we ask for the furnace transformer's rating and connection group at the design stage and coordinate impedance, protection and tap settings across both units.
Yes. Our works builds a rectifier transformer range for electrolysis, hydrogen production and other DC process lines. Where a project needs both a power transformer and a rectifier set, the two can be designed, tested and documented together. Share the DC voltage, current and pulse number with your enquiry and we will line the designs up.
Outdoor installation is the normal case for this unit. The tank is finished with anti-corrosion paint, the breather is sealed, and the bushings, conservator and radiators are arranged for weather exposure. Tell us at the enquiry stage if the site is coastal, dusty, unusually humid or at high altitude, and confirm any local clearance rules that apply at the installation point.
