What Are 33/11kV Oil Immersed Transformers?

33/11kV oil immersed transformers are three-phase power distribution transformers designed to step down high voltage (33kV) to medium voltage (11kV) in regional substations or large-scale infrastructure. These transformers use mineral or biodegradable insulating oil for both cooling and electrical insulation, ensuring safe and reliable power delivery even under heavy load conditions.

They play a key role in medium-voltage distribution systems, especially in utility grids, industrial zones, and municipal power networks.

Why Use 33/11kV Oil Immersed Transformers?

High Efficiency:
Equipped with low-loss silicon steel cores and precision-wound copper or aluminum coils, these transformers achieve excellent energy efficiency. Loss levels meet or exceed international low-loss standards, such as IEC 60076 and DOE 2016.

Long Service Life:
Robust mechanical design with hermetically sealed steel tanks, high-grade insulation, and corrosion protection ensures over 25 years of reliable operation in both indoor and outdoor installations.

Voltage Adaptability:
Supports multiple voltage series including:

• 11kV Series

• 15kV up to 36kV Series

• 33kV Series

• 35kV Series
  You can easily navigate technical datasheets for each voltage range.

Key Features of 33/11kV Oil Immersed Transformers

• Core and Windings:
  High-permeability cold-rolled silicon steel core + high-conductivity copper or aluminum windings for reduced load and no-load losses.

• Cooling System:
  Standard ONAN (Oil Natural Air Natural) cooling, with optional ONAF for high-capacity models. External radiators or corrugated tanks provide effective heat dissipation.

• Protection & Safety Devices:
  Includes Buchholz relay, pressure relief valve, oil level gauge, temperature sensor, and optional surge arresters or on-load tap changers (OLTC) for stable voltage regulation.

• Low Noise and Vibration:
  Typically <55–60 dB(A) for 1000kVA, suitable for installation near residential or urban zones.

• Environmental Options:
  Available with biodegradable oils and sealed tank design to prevent leakage and minimize ecological impact.

Applications of 33/11kV Oil Immersed Transformers

• Utility Substations

• Industrial and Mining Projects

• Commercial Complexes and Data Centers

• Renewable Energy Plants (Solar, Wind)

• Municipal Infrastructure Projects

Standards and Compliance

• Design Standards:
  IEC 60076, ANSI/IEEE C57.12, GB, AS, CSA

• Testing:
  100% routine tests per IEC/IEEE standards; optional type and special tests available on request

• Certifications:
  CE, ISO9001, ISO14001, ISO45001, RoHS (on request)

Advantages of CHBEB 33/11kV Oil Immersed Transformers

• Stable, Low-Loss Performance

• High Thermal and Short-Circuit Strength

• Adaptable to Harsh or Humid Environments

• Factory Customization Available (Impedance, Tappings, Tank Type)

• Cost-Effective Solution for Long-Term Distribution Projects

Choose CHBEB

Choose CHBEB 33/11kV oil immersed transformers for a safe, efficient, and long-lasting distribution solution. Backed by 60+ years of manufacturing experience, CHBEB delivers customized transformer solutions for projects across Asia, the Middle East, Africa, and beyond.

👉 Need detailed specs?
Browse our product tables under:

• 11kV Series

  Capacity (kVA)	Voltage Combination			Vector group	No-load loss (W)	Load loss (W) (75°C)	Impedance voltage (%)	No-load current (%)
  	HV	Tapping range of HV	LV
  25	6 kV 6.6Kv 10.5kV 11kV	±5%,±2×2.5%	0.38 kV 0.4 kV 0.415 kV 0.48 kV	Yyn0 Dyn5 Dyn11	100	600	4.0	1.7
  50					130	870		1.6
  63					150	1040		1.5
  80					180	1250		1.4
  100					200	1500		1.3
  125					240	1800		1.2
  160					280	2200		1.1
  200					340	2600		1
  250					400	3050		0.9
  315					480	3650		0.9
  400					570	4300		0.8
  500					680	5100		0.8
  630					810	6200	4.5	0.7
  800					980	7500		0.6
  1000					1160	10300		0.55
  1250					1360	12000		0.5
  1600					1640	14500		0.45
  2000					1940	18500	5.5	0.4
  2500					2300	20500		0.4

   

• 15kV up to 36kV Series

  Capacity (kVA)	Voltage Combination			Vector group	No-load loss (W)	Load loss (W) (75°C)	Impedance voltage (%)	No-load current (%)
  	HV	Tapping range of HV	LV
  630	13.2kV 13.8kV 15 kV 20 kV 22 kV 33 kV 34.5 kV	±5%,±2×2.5%	0.38 kV 0.4 kV 0.415 kV 0.48 kV	Yd11	1150	6200	4.5	0.9
  800					1400	7500	5.5	0.8
  1000					1650	10300		0.7
  1250					1950	12800		0.6
  1600					2300	14500		0.6
  2000					2650	17100		0.6
  2500					3100	20000		0.6
  3150					3650	23700		0.5
  4000					4450	28100		0.5
  5000					5200	32700		0.5
  6300					6150	36900		0.5
  8000					8900	44000		0.4
  10000					11600	50600	6.5	0.4

   

• 33kV Series

  Capacity (kVA)	Voltage			Vector group	No-load loss (W)	Load loss (W) (75°C)	Impedance voltage (%)	No-load current (%)
  	Primary	Tapping range (%)	Secondary
  50	33 kV	±5%	0.38 kV 0.4 kV 0.415 kV 0.48 kV	Yyn0	6.5	1210	6.5	2.0
  100					305	2020		1.80
  125					340	2380		1.75
  160					360	2830		1.65
  200					430	3300		1.55
  250					510	3950		1.40
  315					610	4750		1.40
  400					735	5750		1.30
  500					870	6900		1.30
  630					1040	8250		1.25
  800					1250	9900		1.05
  1000					1480	12150		1.00
  1250					1760	14600		0.90
  1600					2130	17500		0.85
  2000					2500	20680		0.75
  2500					2975	24500		0.75

   

• 35kV Series

  Capacity (kVA)	Voltage			Vector group	No-load loss (W)	Load loss (W) (75°C)	Impedance voltage (%)	No-load current (%)
  	Primary	Tapping range (%)	Secondary
  50	33 kV	±5%	0.38 kV 0.4 kV 0.415 kV 0.48 kV	Yyn0	6.5	1210	6.5	2.0
  100					305	2020		1.80
  125					340	2380		1.75
  160					360	2830		1.65
  200					430	3300		1.55
  250					510	3950		1.40
  315					610	4750		1.40
  400					735	5750		1.30
  500					870	6900		1.30
  630					1040	8250		1.25
  800					1250	9900		1.05
  1000					1480	12150		1.00
  1250					1760	14600		0.90
  1600					2130	17500		0.85
  2000					2500	20680		0.75
  2500					2975	24500		0.75

Or contact us for a quote and technical consultation.