What is the lead time for oil-immersed transformers?

7 days for standard ratings on expedited terms, 15–30 days for regular orders, 25–35 days for custom or export builds. Per contract.

How do I choose between S11, S13, S20 and S22?

By loss class and duty. S11 for cost-sensitive intermittent duty; S13 for continuous operation where energy cost matters; S20/S22 for efficiency scoring and tenders; SBH amorphous for long light-load duty.

Do you build above 35 kV?

No. We focus on 35 kV and below, up to 20,000 kVA per unit.

OIL-IMMERSED TRANSFORMER

S11 / S13 / S20 / S22
Oil-immersed power transformers, 10–35 kV

30–20,000 kVA, amorphous SBH available; two-winding, split-winding, on-load tap changing and export voltage ratios built to order.

01 / SPECIFICATIONS

Technical data

Ranges below are our standard build; project-specific values are per technical agreement and routine test report.

Item	Range / note
Series	S11 / S13 / S20 / S22; SBH15 / SBH21 / SBH25 (amorphous alloy)
Rated power	30 – 20,000 kVA (distribution 30–2,500 kVA; larger ratings at 35 kV)
Voltage ratio	10/0.4, 20/0.4, 35/0.4, 35/10.5 kV; other ratios to destination standard
Phases / windings	Three-phase or single-phase; two-winding, split-winding optional
Tap changing	Off-circuit (standard), on-load (optional)
Cooling	ONAN (standard), ONAF (optional)
Vector group	Dyn11, Yyn0 and others per project
Insulation / temperature rise	Class A; temperature rise per GB 1094 and contract
Standards	GB 1094 / GB/T 6451; IEC 60076 or customer standard for export
Efficiency class	Grade 1 / 2 / 3 available — as stated on the routine test report
Finish	Outdoor, anti-corrosion paint; tropical, salt-spray and high-altitude versions available

02 / HOW TO CHOOSE

Which series fits

S11

Classic distribution. Lowest first cost and fastest supply; adequate for intermittent duty and budget-driven projects.

S13

Low loss. Lower no-load loss; on continuously energised units the energy saving pays back the price gap within a few years.

S20 / S22

High efficiency. For efficiency audits, green building credits and tenders where loss figures are scored.

SBH amorphous

Ultra-low no-load loss. Best where units sit lightly loaded for long periods — PV, wind, night-heavy-load feeders.

Send the duty profile — rating, voltage ratio, average loading, hours energised — and we will calculate the loss difference before recommending. We do not upsell a series you do not need.

03 / LEAD TIME

Delivery

Type	Lead time	Conditions
Standard rating, expedited	7 days	Model on stock list, drawing confirmed, down payment received
Regular order	15–30 days	Standard parameters, scheduled batch
Custom / export build	25–35 days	Special voltage, frequency, IP rating, certification

04 / TESTING

Routine tests on every unit

Reports ship with the goods. Lightning impulse, temperature rise and sound level tests can be added on request.

#	Test	Purpose
1	Visual and nameplate check	Confirm rating, ratio and arrangement against drawing
2	Insulation resistance	Detect moisture and insulation defects
3	Winding DC resistance	Verify joints and detect turn faults
4	Voltage ratio and vector group	Confirm turns ratio and connection
5	No-load loss and current	Verify core performance and efficiency class
6	Load loss and impedance	Verify winding design and thermal margin
7	Power-frequency / induced overvoltage	Verify major and longitudinal insulation

05 / FAQ

Common questions

What is the lead time?

Standard ratings on expedited terms: 7 days. Regular orders 15–30 days. Custom or export builds 25–35 days. All per contract.

S11, S13, S20 or S22?

By loss class and duty: S11 for cost-sensitive intermittent duty, S13 for continuous operation, S20/S22 where efficiency is scored, SBH for long light-load duty.

Oil-immersed or dry-type?

Oil-immersed where a dedicated transformer room exists and cost or overload capability matters; dry-type for indoor, underground or fire-sensitive locations. The larger the rating, the bigger the cost advantage of oil.

Can you build above 35 kV?

No. We focus on 35 kV and below, up to 20,000 kVA. For higher voltage we would rather refer you than take the order.

Export voltage and frequency?

Yes — designed to IEC 60076 or your standard, including 60 Hz, local voltage ratios, enhanced anti-corrosion finish, English nameplate and neutral packing.

What do you need to quote?

Rating or kVA, voltage ratio, quantity, application, and whether export documents are needed. A drawing gets you a price the same day.

S11 / S13 / S20 / S22Oil-immersed power transformers, 10–35 kV