Oil-Immersed Transformer

S20-M (NX2) Energy-Efficient Oil-Immersed Transformer

The S20-M series is an energy-efficient oil-immersed transformer for distribution networks that remain energised around the clock. Designed to meet China's national Grade 2 energy-efficiency requirements, it helps limit energy losses throughout continuous service. The range covers 30 to 2,500 kVA, with 6, 6.3 or 10 kV primary voltages and a 0.4 kV secondary.

Its fully sealed corrugated tank accommodates oil expansion without a separate conservator, helping reduce routine oil maintenance. Yyn0 or Dyn11 connections and ±5% or ±2 × 2.5% tapping options allow the transformer to match the network's connection and voltage requirements.

Technical Specifications

Rated Capacity	30 – 2500 kVA
HV Voltage	6 / 6.3 / 10 kV
LV Voltage	0.4 kV
Vector Group	Yyn0 / Dyn11
Tap Range	±5% or ±2×2.5%
Short-Circuit Impedance	4% (30–500 kVA); 4.5% (630–1600 kVA); 5% (2000–2500 kVA)
Core Material	Cold-rolled silicon steel
Tank Construction	Fully sealed
Energy Efficiency	National Energy-Efficiency Grade 2

Key Features

Meets China’s national Grade 2 energy-efficiency requirements.
Lower losses reduce lifetime operating cost.
Ideal for 24/7 energized distribution networks.
Fully sealed tank designed to reduce routine maintenance; inspection follows the equipment manual and operating conditions.

Typical Applications

Manufacturing plants and industrial parks
Residential developments
Commercial complexes

Installation & Aftercare

Prepare the site, plan routine checks and keep service records.

What needs to be ready before installation?

Catalogue normal conditions: altitude at most 1000 m, maximum ambient +40 °C and minimum outdoor temperature -25 °C.
Provide a stable foundation and open airflow around the corrugated tank; keep access to bushings and fitted protection accessories.
Coordinate cable clearances, earthing and oil containment with the supplied layout; specify sites outside the listed climate conditions separately.

What should operators check during routine rounds?

During rounds, check for tank or bushing leaks, unusual sound and abnormal temperature indications where fitted.

What is covered during planned maintenance?

At planned isolation, qualified personnel clean bushings and cooling surfaces and inspect cable terminals, earthing and tank condition.
The sealed tank has no separate conservator to service; oil testing and leak repair still follow the delivered unit’s condition and maintenance plan.

Customization Options

Define the electrical configuration and the details needed for your site.

Capacity & voltage: Published capacity 30 – 2500 kVA; HV 6 / 6.3 / 10 kV; LV 0.4 kV. Specify the required rating and voltage combination.
Connection & taps: Yyn0 / Dyn11. Listed tapping ±5% or ±2×2.5%.
Losses & impedance: Required no-load and load losses, short-circuit impedance and compatibility with any units operating in parallel.
Site & installation: Foundation footprint, terminal positions, cable connections and oil-containment interface; declare altitude and environmental exposure.
Monitoring & finish: Temperature or oil-level indication, alarm contacts, corrosion protection, paint colour and nameplate language.

Project-specific options and accessories are confirmed in the quotation and approved drawings.