High Capacity S 13/20/22-M Oil Immersed Power Distributiontransformer 20000kVA

• Customization: Available
• Application: Power
• Phase: Three
• Model NO.: S 13/20/22-M series Oil-Immersed Transformer
• Core: Core-type Transformer
• Cooling Method: Oil-immersed Type Transformer
• Winding Type: Two-winding Transformer
• Certification: ISO9001-2000, ISO9001, CCC
• Usage: Single-phase Transformer, Power Transformer, Distribution Transformer
• Frequency Characteristics: Power Frequency
• Shape of Core: Ring
• Capacity: 30kVA~20000kVA(20mva)
• Nx(Energy Efficiency): Level 1 /Level 2 Energy Efficiency, (Nx1/Nx2)
• Quality Guarantee: 30 Years of Maintenance-Free
• Guaranteed to Be Brand New: New Silicon Steel Sheet
• Transport Package: Composite Board
• Trademark: CHBEB
• Origin: China
• HS Code: 8504220000
• Production Capacity: 10000pieces/Year

Product Description

 

 

 

Overview
The S-M series oil-immersed distribution transformers are high-performance transformers designed to deliver reliable, efficient power for modern networks. Filled with insulating oil and fully sealed in corrugated steel tanks, these transformers efficiently step down medium-voltage power (e.g. 10-35 kV) to low-voltage distribution levels (0.4 kV) for end-use. They are widely used across urban utility grids, industrial parks, commercial centers, and rural electrification projects

. By combining robust construction with advanced engineering, the S--M series ensures stable operation in diverse environments - from dusty mining facilities to humid coastal substations - with minimal maintenance and long service life. In short, this product line provides the critical link in power delivery, bringing safe and steady electricity to factories, businesses, and communities.

Model Lineup: S11-M, S13-M, S20-M, S22-M

The S-M series encompasses several major models - S11-M, S13-M, S20-M, and S22-M - each representing a new generation of efficiency and performance improvements. All models share common quality features like a hermetically sealed oil tank, high-grade copper windings, and state-of-the-art safety protections, yet each successive design introduces enhancements in loss reduction, noise control, and materials. Below we introduce each model and its key characteristics:

S11-M - Proven Efficiency and Reliability
The S11-M is the classic workhorse of the series, offering solid efficiency and dependable service in a fully sealed, oil-immersed design. It was developed as an improvement over older S9 series transformers, achieving about 30% lower no-load losses than its S9 predecessors

.The core is crafted from high-quality grain-oriented silicon steel, and the S11-M set a new benchmark for energy-saving performance in distribution networks during its introduction. It also features reduced no-load current (by roughly 45-80% vs. previous designs) for better efficiency under light loads

.With its robust construction and lower losses, S11-M became widely adopted in standard distribution applications - from city substations to rural utility poles - as a reliable, cost-effective choice. Like all models in the series, it employs a fully sealed tank, eliminating an external conservator; this means the oil is never exposed to air, preventing oxidation and moisture ingress and significantly prolonging the transformer's service life

.Overall, S11-M delivers a balanced mix of efficiency and durability, making it a proven solution for general-purpose power distribution needs.

S13-M - High Efficiency Low-Loss Design
The S13-M model builds on the S11's success with a design focused on further energy savings and noise reduction. Using an advanced core made of high-permeability, cold-rolled silicon steel and a 45° full mitered (five-step) lap structure, the S13-M achieves approximately 30% lower no-load losses than the S11 series

This dramatic improvement in core loss performance represents the industry's trend toward energy-efficient distribution transformers, and indeed the S13 series has been widely recognized for its remarkable energy-saving effect

. In addition to cutting losses, S13-M also operates quieter: by reducing core magnetostriction (through lower flux density design) and using vibration-damping construction, its noise levels are lower than those of S11, improving the environmental footprint of installations


The transformer's winding structure was upgraded as well - S13-M typically employs copper foil windings on the low-voltage side (in place of traditional round wire) to better distribute current and withstand short-circuit forces

Like all later models, it is a hermetically sealed unit with corrugated tank walls acting as cooling fins and "breathing" elements for oil expansion. This results in a compact, leak-proof design with no need for an oil conservator, thus reducing overall height and simplifying installation

With its superior efficiency and reliable sealed construction, S13-M has become the new standard for many utilities - an upgrade product poised to replace older S11 units in networks aiming to reduce losses and operating costs

S20-M - Ultra-Low Loss, High-Performance Model
Representing the next leap in transformer efficiency, the S20-M series is engineered to meet more stringent energy performance standards. The S20-M achieves further loss reductions beyond S13 models - roughly 10% lower no-load losses than S13, and about 20% lower load losses under full load

. In fact, compared to the original S11 generation, S20's no-load losses are about 40% lower, which translates to significant energy savings over the transformer's lifetime

. This improvement qualifies S20-M units as Level 2 energy efficiency transformers per the latest national standard GB 20052-2020

 - a clear indicator of their advanced design. Achieving these gains required the latest materials and design techniques: S20-M uses high-grade oriented steel cores (with precision step-lap construction) and optimizes the winding configuration to minimize resistance and leakage. The windings are made of 100% oxygen-free copper - HV coils use high-strength enamelled copper wire, while LV coils often use wide copper foil - yielding a uniform ampere-turn distribution that greatly improves short-circuit withstand capability

. Enhanced cooling channel designs in the coil help dissipate heat efficiently, resulting in lower temperature rise and the ability to handle overloads better

. Mechanically, the S20-M features an improved core-and-coil bracing structure that gives it higher mechanical strength and stability under transient stresses

. Like its predecessors, it is fully sealed and maintenance-friendly - the corrugated tank provides excellent cooling and also flexes to accommodate oil expansion, so no gas space is needed

. For end users (utilities and industrial power managers), the S20-M offers a highly attractive proposition: its lower losses directly reduce energy waste and operating cost, and its robust design ensures high reliability in service. This makes S20-M ideal for projects where efficiency and performance are paramount, such as large commercial complexes, greener industrial facilities, and utility networks aiming to cut distribution losses.

S22-M - Top Efficiency, Next-Generation Solution
At the pinnacle of the S-M series is the S22-M model, which represents the latest in distribution transformer technology with ultra-efficient, first-class performance. The S22-M is designed to meet and exceed the highest efficiency standards currently in effect - its no-load and load loss levels conform to Level 1 (the top tier) energy efficiency as defined by GB 20052-2020
 
. In practical terms, this means S22-M transformers have the lowest losses of the entire series, achieving further reductions beyond S20 models to save even more energy during operation. Utilities deploying S22 units can expect minimal iron losses around the clock and reduced load losses during peak demand, translating to lower heat generation and significant lifecycle cost savings on energy. To reach these best-in-class figures, S22-M uses the most advanced core materials available along with refined construction techniques. The core may feature an even lower-loss silicon steel grade and carefully optimized geometry to eliminate hotspots and hysteresis losses. Manufacturing is done with extremely tight tolerances - for example, step-lap core joints and multi-step circular cross-sections in the core legs ensure a very uniform magnetic flux, which cuts down on stray flux and noise
 
. The result is not only high efficiency but also very quiet operation; S22-M transformers produce low noise levels well below traditional norms, ensuring they can be sited in noise-sensitive areas (like residential neighborhoods or hospital campuses) with minimal acoustic impact
 
. Naturally, S22-M retains all the proven features of the series: a sealed, durable oil tank with anti-corrosion coating, top-mounted porcelain bushings for high/low voltage connections, and a full array of safety devices (pressure relief valve, alarm/trip gas relay, temperature gauges, etc.) for dependable operation
 
. This model can also be customized for various voltage systems (for instance, 6 kV, 10 kV, 20 kV class) and capacity requirements, giving flexibility to tailor it to specific network needs
 
. As the flagship of the S-M series, the S22-M is the transformer of choice for forward-looking projects that demand the utmost in energy efficiency, such as sustainable smart grids, large-scale data centers, and progressive utility upgrades. It delivers an unbeatable combination of loss reduction, longevity, and reliability, making it a wise investment for any operation focused on long-term performance and cost savings.

Technical Highlights and Comparison

To help prospective clients choose the right model for their needs, here we highlight the key technical differences and advantages of the S11-M, S13-M, S20-M, and S22-M transformers. Each successive model in the series builds upon the strengths of the previous, introducing improvements in specific performance metrics and design features:
 

Energy Efficiency & Loss Reduction

Efficient Performance Across Models: All S--M transformers are engineered for low losses, but the series shows a clear progression in efficiency with each newer design. The S11-M already offered a major efficiency leap over earlier designs (≈30% no-load loss reduction vs. S9 series)
 From there, the S13-M cut core losses by a further 30% compared to S11
setting a new standard for energy-saving distribution transformers. The S20-M model pushed the envelope even more - its no-load losses are about 10% lower than S13, and load losses ~20% lower
 amounting to roughly 40% reduction in total losses versus S11 units
Finally, the S22-M achieves best-in-class efficiency, meeting the strict Level 1 energy efficiency criteria of the latest national standards

In practice, choosing a higher-series model (S13, S20, S22) means dramatically less energy wasted as heat: end users will benefit from lower operating costs and reduced cooling requirements. These transformers are truly "energy-saving" devices, ideal for projects where loss reduction and life-cycle cost are critical considerations.
Reduced No-Load and Load Losses: Technically, improvements in core materials and design largely drive the no-load (core) loss reductions from S11 through S22. Each model uses high-grade grain-oriented silicon steel, but later models use thinner and higher permeability steel laminations, which cut eddy current and hysteresis losses. For example, the S13's core uses an advanced 23ZH high-magnetic steel, significantly lowering hysteresis compared to S11's core steel
The core joint design evolved to a fully oblique 45° step-lap in S13 and beyond, eliminating air gaps and reducing magnetizing current. This yielded a substantial drop in no-load current - by 70-85% on average relative to S11 in the S13~S22 series
- meaning the transformer consumes far less idle excitation power. On the load loss side, improvements come from better winding materials and lower resistance: all models use pure copper windings (with larger cross-sections in newer models to reduce I²R losses) and improved winding geometry. By S20 and S22, the winding resistance and leakage reactance are optimized such that load losses are markedly lower than in older models. The bottom line is that an S22-M transformer will waste far less energy under both no-load and full-load conditions than an S11-M, making the newer models especially attractive in long-run installations where every watt saved translates to cost savings.

 

Quiet, Low-Noise Operation

Advanced Noise Reduction: As efficiency improved, the S--M series also became progressively quieter. Transformer noise mainly originates from magnetostriction in the core and vibration transmission to the tank. With each design upgrade, the core structure was refined to mitigate these effects. S13-M units, for instance, operate at a lower magnetic flux density than S11 (by design), which significantly cuts down the magnetostriction forces and thus core hum
The introduction of the 45° step-lap core construction in S13 also helps distribute flux more evenly, avoiding localized saturation that can cause noise. Furthermore, manufacturers applied simulation-based acoustic analysis and added damping features starting in the S13 generation - for example, flexible connections between core, windings, and the steel clamping structure to absorb vibrations
 Thanks to these measures, transformers from S13 onward achieve noise level reductions of about 10-15 dB compared to conventional older models

 This is a dramatic decrease, perceivable as a far quieter operation especially under no-load conditions.

Urban-Friendly Design: The low noise performance of S--M transformers is a significant benefit for installations in or near residential and commercial areas. The S20-M and S22-M models continue the trend by employing the same noise-reduction techniques and even larger core laminations (reducing flux density further) to ensure noise is kept to a minimum. Field experience and tests have shown that these transformers easily meet and exceed national noise standards for distribution equipment
Many utilities and facility managers choose S20 and S22 models specifically to comply with strict noise regulations in city centers, hospitals, schools, and office complexes. In essence, the S--M series delivers quiet power - clients can be confident that upgrading to a newer model will not only save energy but also reduce the acoustic footprint of their substations. This quiet operation underscores the series' suitability for noise-sensitive environments and reflects the careful engineering that goes into each unit's core and assembly.

High-Quality Materials & Design

Premium Core and Coil Construction: All transformers in the S--M family are built using high-quality materials to ensure longevity and performance. The core of each unit is made from grain-oriented, cold-rolled silicon steel sheets with excellent magnetic properties. As the series evolved, the grade of steel improved (lower loss grades) and the core architecture became more sophisticated. By the S13-M, the core features a multi-step circular cross-section and equal cross-section yokes and legs, which means the core's magnetic path is smoother and more uniform
 This design innovation reduces hot spots and noise, as well as contributes to loss reduction. S20-M and S22-M cores continue this approach and are manufactured with extreme precision - modern laser cutting and lamination stacking techniques ensure a near-perfect core build, minimizing gaps and resulting in very low exciting currents.
On the winding side, the series is distinguished by copper windings of superior craftsmanship. S11 models typically used cylindrical windings of enamelled copper wire. Starting with S13-M, many designs adopted foil or sheet copper for low-voltage windings
Foil windings have the advantage of reducing axial stress and spreading the current uniformly across the width, which lowers eddy losses in the winding and improves the transformer's short-circuit strength. High-voltage windings are made of high-grade enamel-insulated copper conductors, with careful layer insulation to withstand surge voltages. The winding assemblies are tightly clamped and wrapped, and in S20/S22 models, additional structural support is included to prevent any movement under high fault currents. This attention to mechanical design gives the transformers excellent short-circuit durability, a critical indicator of build quality. In fact, the S--M series is known for its strong short-circuit impedance characteristics - the advanced models can endure the mechanical forces of an internal fault or external short without winding deformation, thanks to their reinforced coil spacers and secure bracing

Fully Sealed, Robust Tank: Another hallmark of the series' design is the robust, sealed oil tank that houses the core-coil assembly. All S--M transformers use a fully oil-filled, hermetically sealed tank made of high-strength steel. The tank's exterior features corrugated wall panels (radiators) that serve dual purposes: providing efficient heat dissipation for cooling, and flexing to accommodate thermal expansion of the oil
Because the corrugated tank sides act as a sort of built-in "breathing" system, these transformers do not require an oil conservator at the top - the elimination of the conservator and associated plumbing not only reduces overall size but also removes points of potential oil leakage. The result is a simpler, compact profile that is easier to install in tight spaces and has a clean, modern appearance
 Moreover, the sealed design means the insulating oil is never exposed to ambient air. This is crucial for longevity: by preventing oxygen and moisture from contaminating the oil, aging of the oil and insulation is greatly slowed, giving the transformer a much longer service life without requiring oil replenishment
The tank itself is coated with advanced paint systems - for example, a layered phosphate coating plus polyurethane or epoxy paint - to resist corrosion in harsh outdoor environments
S--M transformers can thus withstand extreme weather, pollution, and even chemically aggressive atmospheres (such as near industrial plants) without the tank rusting or the seals degrading. In summary, the materials and design philosophy of the S--M series prioritize durability and performance: from core to coils to tank, each component is built to high standards, ensuring that these transformers will perform reliably over decades of operation.

Reliability and Safety Features

High Operational Reliability: Customers choosing the S--M series benefit from transformers that are not only efficient but exceptionally reliable. The hermetically sealed construction contributes heavily to reliability - with no exposure to air, there is minimal risk of moisture ingress or oil degradation, meaning the internal insulation system stays in optimal condition for many year
. This translates into lower failure rates and extended intervals between maintenance. The sealing technology itself has been honed over successive models: by S22-M, even the tank gaskets and welds have improved designs to ensure absolutely tight seals under all operating conditions
 Each unit undergoes rigorous leak testing at the factory to verify that it is completely oil-tight. Additionally, the use of high-quality cellulose insulation (paper/oil) and careful drying (vacuum oil filling under heat) during manufacturing removes any moisture from the , which helps prevent partial discharges and insulation weakening over time. Together, these factors give the S--M transformers a long service life with many units reliably serving 20, 30, even 40+ years in the field.
Built-in Safety and Protection: The S--M series comes equipped with a full suite of protection features to ensure safe operation and quick fault detection. Every transformer from 30 kVA upwards includes a spring-loaded pressure relief valve on the tank cover
In the rare event of an internal fault causing sudden gas/pressure buildup, this valve will vent to relieve pressure and avert tank rupture. In addition, all medium and large kVA models can be fitted with a gas relay (Buchholz relay) that monitors gas accumulation in a small chamber connected to the tank
If an internal fault generates gas, the relay triggers an alarm or trips the transformer off-line to prevent damage - a vital protective feature for oil-filled units. The S--M transformers also include oil temperature monitoring: a glass-enclosed thermometer is installed in the top of the tank to give local readings
 and larger units (usually ≥1000 kVA) feature an outdoor-readable dial thermometer with electrical contacts for remote temperature alarms/fan controls

These devices help operators keep the unit within safe operating temperatures and provide early warning of any abnormal heating.

From a structural safety standpoint, the transformers are built to withstand surges and lightning strikes. They use robust Dyn11 phase connections (vector group), which inherently help mitigate harmonic disturbances and balance loads 
The high-voltage bushings are made of porcelain or silicone composite with arcing horns to divert lightning surges. S--M units are tested for impulse voltage withstand according to IEC/GB standards, ensuring they can survive lightning-induced transients. Internally, S20-M and S22-M models even incorporate designs refined through lightning impulse simulations, resulting in improved clearance distances and barrier placements that enhance their impulse strength

 To guard against thermal overloads, the transformers have ample cooling and are rated with a certain overload capacity - and optional fans or heat exchangers can be added for S22 units in very high demand scenarios. Overall, these transformers are designed with a fail-safe mindset: they not only minimize the chance of faults through quality engineering but also include multiple layers of protection to handle unforeseen events safely. This means peace of mind for operators and a solid, dependable performance in the field.

Table 1 Energy efficiency rating of 10 kV oil-immersed three-phase double-winding non-excitation voltage-regulating distribution transformer
Rated capacity kVA	S22              1 Class        SH25						S20         2 Class         SH21						S13        3 Class       SH15						Short circuit impedance %
	Electrical steel strip			Amorphous alloy			Electrical steel strip			Amorphous alloy			Electrical steel strip			Amorphous alloy
	No-load loss   W	Load loss W		No-load loss   W	Load loss W		No-load loss W	Load loss W		No-load loss   W	Load loss W		No-load loss   W	Load loss W		No-load loss   W	Load loss W
		Dynl1/Yznll	Yyn0		ynl1/Yznl	Yyn0		Dynll/Yznl	Yyn0		Dynl1/Yznl	Yyn0		Dyn11/Yznl	Yyn0		Dynl1/Yzn1	Yyn0
30	65	455	430	25	510	480	70	505	480	33	535	510	80	630	600	33	630	600	4.0
50	80	655	625	35	735	700	90	730	695	43	780	745	100	910	870	43	910	870
63	90	785	745	40	880	840	100	870	830	50	930	890	110	1090	1040	50	1090	1040
80	105	945	900	50	1060	1010	115	1050	1000	70	1120	1070	130	1310	1250	60	1310	1250
100	120	1140	1080	60	1270	1215	135	1265	1200	75	1350	1285	150	1580	1500	75	1580	1500
125	135	1360	1295	70	1530	1450	150	1510	1440	85	1615	1540	170	1890	1800	85	1890	1800
160	160	1665	1585	80	1870	1780	180	1850	1760	100	1975	1880	200	2310	2200	100	2310	2200
200	190	1970	1870	95	2210	2100	215	2185	2080	120	2330	2225	240	2730	2600	120	2730	2600
250	230	2300	2195	110	2590	2470	260	2560	2440	140	2735	2610	290	3200	3050	140	3200	3050
315	270	2760	2630	135	3100	2950	305	3065	2920	170	3275	3120	340	3830	3650	170	3830	3650
400	330	3250	3095	160	3660	3480	370	3615	3440	200	3865	3675	410	4520	4300	200	4520	4300
500	385	3900	3710	190	4380	4170	430	4330	4120	240	4625	4400	480	5410	5150	240	5410	5150
630	460	4460		250	5020		510	4960		320	5300		570	6200		320	6200		4.5
800	560	5400		300	6075		630	6000		380	6415		700	7500		380	7500
1000	665	7415		360	8340		745	8240		450	8800		830	10300		450	10300
1250	780	8640		425	9720		870	9600		530	10260		970	12000		530	12000
1600	940	10440		500	11745		1050	11600		630	12400		1170	14500		630	14500
2000	1085	13180		550	14000		1225	14640		710	14800		1360	18300		720	18300		5.0
2500	1280	13360		670	15450		1440	14840		860	16300		1600	21200		865	21200

 

 

Product Parameters

Certifications

 

Our passionate team actively engages in international power exhibitions,
where we confidently interact with clients to present CHBEB's premier products on the global stage.