Transformers

Oil-immersed Transformer Equipment

An oil-immersed transformer operates by immersing the windings and core in insulating mineral oil. This oil performs two critical functions: it cools the transformer by dissipating heat and provides dielectric insulation between components. This dual-action design makes it an ideal solution for power distribution networks, substations, renewable energy projects, and industrial plants.

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Unlike dry-type transformers, oil-immersed units can handle higher voltage ratings and larger capacities due to the efficiency of liquid cooling. Models are available in sealed oil immersed transformers for minimal maintenance or breathing designs with conservators for extended oil management. Depending on application, customers can choose distribution oil immersed transformers for local networks or power-grade models for grid-level operations.

Main Features

  • Efficient cooling system using high-grade mineral oil.
  • Durable tank design for outdoor and indoor installations.
  • High dielectric strength ensuring insulation reliability.
  • Wide capacity range from small kVA ratings to multi-MVA systems.
  • Multiple cooling classes including ONAN (natural), ONAF (forced air), and OFAF (forced oil).
  • Customizable designs for industrial, commercial, and utility needs.
4.Technical Parameters of 10kV Class SH15-M Series Amorphous Alloy Oil-immersed Transformer
Rated
Capacity
(kVA)		 Voltage
Combination
(KV)		 Low
voltage		 Connecion
group
designation		 Loss(kW) No-load
current
(%)		 Short-
circuit
mpedance
(%)		    Weight(Kg) Overall
Dimensions(mm)
(Length  L×Width  B
×Height H)		 Torque
(Longitudinal/
Transverse)
No-load Load(75℃) Body
Weight		 oil weight Total weight
30 11
10.5
10
6.3
6		 0.4 Dyn11 0.033 0.600 1.7
1.3
1.2
1.1
1.0
0.9
0.7
0.7
0.7
0.5
0.5
0.5		 4 240 80 410  920×600×980 400×550
50 0.043 0.870 310 110 510  950×620×1040 400×550
63 0.050 1.040 350 125 570  990×670×1040 400×550
80 0.060 1.250 410 135 630 1030×720×1040 400×660
100 0.075 1.500 475 150 720 1060×770×1070 400×660
125 0.085 1.800 550 170 830 1060×900×1070 400×660
160 0.100 2.200 630 190 960 1060×930×1150 400×660
200 0.120 2.620 670 210 1040 1110×930×1170 550×820
250 0.140 3.050 750 240 1160 1180×1010×1180 550×820
315 0.170 3.650 810 264 1240 1180×1010×1180 550×820
400 0.200 4.300 860 290 1330 1200×1010×1180 550×820
500 0.240 5.150 950 320 1460 1270×1160×1200 660×1070
630 0.320 6.200 0.3
0.3
0.3
0.2
0.2		 45 1120 380 1860 1450×1240×1330 820×1070
800 0.380 7.500 1340 410 2230 1520×1380×1460 820×1070
1000 0.450 10.30 1620 540 2700 1720×1460×1510 820×1070
7250 0.530 12.00 1900 640 3180 1780×1500×1690 820×1070
1600 0.630 14.50 2560 680 4240 1880×1540×1970 820×1070
2000 0.750 17.40 0.2
0.2		 5 2900 980 4920 2080×1580×1970 820×1070
2500 0.900 20.20 3940 1160 6560 2350×1580×2020 820×1070
Note:High voltage tapping range:±5%or2×2.5%;Frequency:50Hz;Insulation level:L175AC35/L10AC5.

Key Advantages

  • Superior thermal management for heavy loads.
  • Extended service life due to oil immersion reducing stress on windings.
  • Flexible configurations – sealed, conservator, or hermetically sealed types.
  • Cost-effective performance with reduced downtime.
  • Proven safety through international certifications and testing.

Applications

Oil-immersed transformer equipment is widely used in:

  • Utility substations for medium to high-voltage conversion.
  • Industrial manufacturing plants requiring reliable energy supply.
  • Renewable energy grids including solar and wind farms.
  • Commercial complexes such as airports, malls, and hospitals.
  • Infrastructure projects like railways, ports, and smart cities.

Installation & Maintenance

Installation steps:

  1. Place the transformer on a firm, vibration-free foundation.
  2. Verify oil level and quality before energizing.
  3. Connect HV/LV terminals securely and test grounding.
  4. Inspect the cooling system for leaks or obstructions.

Maintenance tips:

  • Perform oil sampling to monitor dielectric strength every 12–18 months.
  • Inspect gaskets, bushings, and seals regularly.
  • Monitor temperature and load indicators to avoid overheating.
  • Clean radiators and ensure free airflow for efficient cooling.

How to Select the Right Oil-immersed Transformer

  • Load capacity – match kVA/MVA ratings with system demand.
  • Cooling class – choose ONAN, ONAF, or OFAF based on load cycles.
  • Voltage levels – ensure compatibility with primary and secondary grid requirements.
  • Environmental factors – sealed models are better for humid or dusty areas.
  • Compliance standards – IEC, ANSI, or local grid specifications.
  • Manufacturer reputation – select a certified, experienced supplier.

FAQ

What is the difference between oil-immersed and dry-type transformers?

Oil-immersed models use mineral oil for cooling and insulation, while dry-type relies on air or resin.

How long does an oil-immersed transformer last?

With proper maintenance, it can operate for 20–30 years or more.

Can oil-immersed transformers be installed outdoors?

Yes, their robust tank design makes them suitable for outdoor substations.

Is oil testing necessary?

Yes, regular oil analysis ensures insulation strength and prevents breakdown.

What cooling options are available?

Options include ONAN (natural), ONAF (forced air), and OFAF (forced oil circulation).

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