S11-M-30~2500/10 Three-Phase Oil-Immersed Fully Sealed Distribution Transformer (Dual Voltage)
S11-M series is a three-phase oil-immersed non-excitation voltage regulation fully sealed distribution transformer designed for 30–2500kVA capacity range with primary voltage up to 10/20kV. This product is a dual-voltage transformer, suitable for both 10kV and 20kV supply areas — enabling grid voltage conversion without requiring transformer replacement, thereby reducing equipment waste, saving capital investment, and minimizing construction time and installation effort.
The transformer features a fully sealed oil tank design with corrugated wall construction for natural cooling, eliminating the need for an oil conservator and breather — the sealed design prevents moisture ingress and oil oxidation, significantly extending transformer service life and reducing maintenance requirements compared to conventional open-breathing transformers.
Technical Specifications
| Item | Specification |
|---|---|
| Rated Capacity | 30 – 2500 kVA |
| Rated Voltage (HV) | 10kV / 20kV (dual voltage — field selectable by tap changer) |
| Rated Voltage (LV) | 400V / 415V |
| Rated Frequency | 50Hz / 60Hz |
| Connection Group | Dyn11 / Yyn0 (selectable) |
| Voltage Regulation | ±5% (off-circuit tap changer, 2 steps) |
| No-Load Loss (S11) | Compliant with GB/T 6451 — typically 30–40% lower than S9 series |
| Load Loss (S11) | Compliant with GB/T 6451 — typically 10–15% lower than S9 series |
| Cooling Method | ONAN (Oil Natural Air Natural) — corrugated wall tank |
| Insulation Level | LI 75 / AC 35 (HV) / LI 40 / AC 5 (LV) |
| Transformer Type | Oil-immersed, fully sealed, non-excitation voltage regulation |
| Tank Construction | Fully sealed corrugated wall type — no oil conservator or breather |
| Oil Type | Mineral insulating oil (or ester fluid — optional) |
| Degree of Protection | IP44 / IP54 (tank and bushings) |
| Ambient Temperature Range | -25°C to +40°C |
| Altitude | Up to 1000m (derating required for higher altitudes) |
| Standards | GB/T 6451, GB 1094, IEC 60076 |
Key Features
- Dual-Voltage Design (10kV / 20kV): The transformer is designed with a split-primary winding configuration that can be reconfigured between 10kV and 20kV operation by simple off-circuit tap changer adjustment — one transformer serves both 10kV and 20kV distribution networks, eliminating the need for separate transformer inventory for different grid voltage zones. This is particularly valuable during grid voltage upgrade programs where distribution networks are progressively converted from 10kV to 20kV operation
- Fully Sealed Oil Tank Construction: The corrugated wall tank is hermetically sealed with no oil conservator, breather, or silica gel air dryer — the sealed design prevents moisture absorption by the insulating oil, eliminates oil oxidation from atmospheric exposure, and prevents formation of sludge and acidic compounds that accelerate insulation degradation in conventional open-breathing transformers. Service life is extended by 30–50% compared to open-breathing designs
- Corrugated Wall Cooling: The tank walls are formed from thin steel plate pressed into corrugated panels, which expand and contract with oil volume changes while providing efficient natural convection cooling — the corrugated design eliminates the need for separate cooling radiators, reduces overall transformer dimensions, and provides built-in expansion compensation without requiring a separate oil conservator
- Low-Loss S11 Amorphous Core Design: The S11 series achieves significantly lower no-load losses compared to conventional S9 and S10 series transformers through optimized grain-oriented silicon steel core material, improved core joint design, and reduced flux density — no-load losses are typically 30–40% lower than S9 equivalents, delivering measurable energy savings over the transformer’s 20+ year service life
- Non-Excitation Voltage Regulation: An off-circuit (de-energized) tap changer provides ±5% voltage regulation in two steps, enabling field adjustment of the voltage ratio to match local distribution network voltage conditions — the tap changer operates only when the transformer is de-energized and provides reliable, maintenance-free voltage ratio adjustment capability
- Reduced Installation and Commissioning Time: The sealed, oil-filled design eliminates the need for on-site oil filling, oil processing, oil sampling, and breather installation required by conventional transformers — the transformer arrives factory-filled, factory-tested, and ready for immediate installation and commissioning, significantly reducing site installation labor and time
Applications
- Urban and rural 10kV/20kV distribution networks — pole-mounted and ground-mounted installations
- Industrial and commercial facility power supply — step-down transformation
- Residential community and building complex power distribution
- Infrastructure — schools, hospitals, public facility power supply
- Grid upgrade projects — 10kV to 20kV conversion without transformer replacement
- Oil and gas field distribution power supply
- Agricultural and rural electrification