All four share the identical tank, core, and winding architecture — they differ only in no-load and load losses, defining their efficiency class under GB 20052-2020: (1) S11 — legacy/economical entry model, baseline losses, for budget-sensitive markets and legacy grid retrofits. (2) S13 — GB 20052-2020 Class 3, ≈20% lower no-load loss than S11, for mainstream urban and rural grid projects. (3) S20 — GB 20052-2020 Class 2, lower losses still, for high-duty-cycle industrial sites and long operating hours. (4) S22 — GB 20052-2020 Class 1, lowest losses in the series, for green buildings, data centers, and regions with mandatory high-efficiency standards. Exact loss values (W) for each capacity follow GB 20052-2020 Table 1; contact us for the type-test report of your required capacity. The physical footprint and spare parts are identical across all four, so upgrading from S11 to S13/S20/S22 does not change the installation.

Conventional oil-immersed transformers use an oil conservator (a reservoir above the tank) and a breather with silica gel to accommodate oil expansion/contraction with temperature while keeping air out. The S11 eliminates both: (1) The tank walls are pressed from thin steel into corrugated panels — these panels flex outward as the oil heats and expands, and contract inward as it cools, providing built-in volume compensation. (2) The entire tank is hermetically sealed (welded, no gaskets exposed to atmosphere), so the oil never contacts outside air. (3) This prevents moisture absorption (which lowers dielectric strength) and oil oxidation (which forms sludge and acids that degrade insulation). (4) The corrugated panels also act as cooling fins, increasing surface area for natural convection (ONAN) without separate radiators. The result is a more compact, maintenance-free transformer with 30–50% longer service life compared to open-breathing conservator-type designs.

Yes. The S11 primary (HV) winding has a split configuration that can be reconfigured between 10kV and 20kV operation via the off-circuit tap changer. This means: (1) One transformer can be specified that will work on either a 10kV or 20kV distribution network, reducing the need to stock two separate transformer models for different voltage zones. (2) It is especially valuable during grid-upgrade programs where distribution networks are progressively converted from 10kV to 20kV — the same transformer can be re-tapped at the new voltage rather than replaced. (3) The voltage change is performed by the off-circuit tap changer, which requires the transformer to be de-energized and locked out before adjustment. (4) Note that the ±5% tap regulation is separate from the 10kV/20kV selection — the ±5% provides fine voltage adjustment within the selected primary voltage level to match local network conditions. Always confirm the primary voltage and tap positions with the utility and have qualified personnel perform any tap-changer adjustment.

Yes — the S11 is designed for outdoor pole-mounted or ground-mounted installation: (1) Protection rating — IP44/IP54 on the tank and bushings, suitable for direct exposure to rain, snow, and dust. (2) Corrosion resistance — the tank uses corrosion-resistant paint suitable for outdoor service; for coastal or highly corrosive environments, special anti-corrosion paint can be specified. (3) Temperature range — -25°C to +40°C ambient; for lower temperatures (e.g., -45°C) we can supply transformer oil with a suitable low-temperature pour point. (4) Altitude — rated up to 1000m; above 1000m, derating of the rated capacity is required per IEC 60076 (typically about 1% per 100m above 1000m) due to reduced air cooling, so confirm your altitude when ordering. (5) For enclosed substations (indoor kiosks) the S11 can also be installed inside a YBM prefabricated substation enclosure. Always follow local utility and installation regulations for spacing, clearances, and protective devices.

Capacity (30–2500 kVA) and connection group (Dyn11 or Yyn0) depend on your load and network: (1) Capacity — select based on the total connected load with a 20–30% margin for future growth; for example, a 500 kVA transformer serves roughly 400 kW of load at 0.8 power factor. For fluctuating loads or motor starts, consider oversizing. (2) Dyn11 — HV delta, LV star with neutral brought out; provides 3-phase + neutral (400V/230V), better harmonic suppression, and is the most common choice for commercial/residential mixed single-phase/three-phase loads. (3) Yyn0 — HV star, LV star with neutral; suitable for mostly balanced three-phase loads and where the utility requires a star primary. Dyn11 is generally preferred for modern distribution. (4) Also specify: HV voltage (10kV or 20kV), LV voltage (400V or 415V), frequency (50Hz or 60Hz), winding material (copper or aluminum), and efficiency class (S11/S13/S20/S22). Provide your single-line diagram and we will recommend the optimal configuration.

The S11's fully sealed design substantially reduces maintenance compared to conventional conservator-type transformers: (1) No oil conservator, breather, or silica gel — eliminates the need for periodic silica gel replacement, conservator oil-level checks, and breather cleaning. (2) Sealed oil — no moisture ingress or oxidation means oil does not need periodic testing or replacement under normal conditions (recommended oil sample check every 5–10 years for large units, vs. annually for open-breathing types). (3) No sludge/acid formation — insulation degradation is slowed. (4) Installation — arrives factory-filled and tested, so no on-site oil filling, processing, or sampling. (5) Recommended maintenance for the S11: periodic visual inspection of the tank, bushings, and paint; check tightness of bolted connections; verify tap-changer position; clean bushings; and inspect the grounding connection. Because the oil is sealed, there is no routine oil top-up. The expected service life is ≥20 years, with the sealed design extending it by 30–50% over open-breathing designs.