ZTELEC Electric Technology (Zhengzhou) Co., Ltd. manufactures reliable oil-immersed transformers for power distribution, substations, industrial facilities, renewable energy projects, and utility networks. Oil-immersed transformers use transformer oil as both an insulating and cooling medium, providing efficient heat dissipation, stable electrical performance, and reliable long-term operation.

Compared with dry-type transformer designs, oil-immersed transformers are particularly suitable for medium- and high-capacity power distribution applications where efficient cooling, high reliability, and economical operation are required.

Oil-Immersed Transformer Construction

The main components of an oil-immersed transformer include the iron core, windings, transformer oil, tank, and bushings. The iron core provides a low-reluctance path for magnetic flux, while the windings generate the electromagnetic field required for voltage transformation.

The windings are manufactured using high-strength enameled wire or paper-covered conductor and are carefully insulated according to the transformer's rated voltage. As voltage increases, the insulation system is designed with appropriate insulation distances and materials to ensure safe and reliable operation.

Bushings provide an insulated connection between the transformer windings and the external power distribution system. The transformer core and windings are immersed in insulating oil, which absorbs heat generated during operation and transfers it to the transformer tank and cooling system.

How Does an Oil-Immersed Transformer Work?

During operation, electrical energy is transferred between the primary and secondary windings through electromagnetic induction. Heat generated by the core and windings is absorbed by the transformer oil. The heated oil circulates naturally through convection, transferring heat from the active part to the tank and external cooling surfaces.

For smaller-capacity transformers, heat can be dissipated directly through the tank surface. Larger oil-immersed transformers can use corrugated tanks or external radiators to increase the cooling area and improve thermal performance.

Applications of Oil-Immersed Transformers

Oil-immersed transformers are widely used in power distribution networks, substations, industrial plants, renewable energy projects, commercial facilities, and utility power systems. Their high capacity and efficient cooling performance make them suitable for applications requiring continuous and stable power supply.

They can be installed on the ground, transformer platforms, concrete foundations, or other suitable outdoor installations according to project requirements. Oil-immersed transformer solutions are commonly used for utility distribution, industrial power supply, solar and wind power systems, and infrastructure projects.

Benefits of Oil-Immersed Transformers

Oil-immersed transformers offer efficient heat dissipation and reliable insulation, making them suitable for demanding power distribution applications. Their efficient cooling system helps control winding and core temperatures, supporting stable operation and extending transformer service life.

For high-capacity power systems, properly selected oil-immersed transformers can help reduce energy losses and improve overall power distribution efficiency. Their proven construction and relatively simple cooling principle also contribute to dependable operation and economical lifecycle performance.

Key Features of ZTELEC Oil-Immersed Transformers

Fully Sealed Oil Tank Design

The fully sealed transformer adopts a fully oil-filled sealed structure. Its corrugated oil tank can accommodate changes in transformer oil volume caused by temperature variations through the elastic expansion and contraction of the corrugated sheets.

This sealed construction helps isolate the transformer oil from direct contact with atmospheric moisture and oxygen, reducing oil oxidation and moisture contamination. It can improve insulation reliability and reduce maintenance requirements during normal operation.

High-Quality Grain-Oriented Silicon Steel Core

The transformer core is manufactured from high-quality cold-rolled grain-oriented silicon steel sheets. Automatic cross-cutting and step-lap manufacturing processes help optimize the magnetic flux distribution within the core.

The optimized core structure helps reduce core vibration, operating noise, and no-load losses, contributing to improved energy efficiency and stable transformer performance.

Reliable Transformer Windings

The windings are manufactured using high-strength enameled wire or paper-covered conductors. Depending on the transformer design, cylindrical or disc-type winding structures can be used to achieve a uniform ampere-turn distribution and optimized insulation arrangement.

The carefully designed winding structure provides strong mechanical strength and improved resistance to short-circuit forces, supporting reliable operation under demanding electrical conditions.

Anti-Loosening Transformer Body Structure

The transformer active part adopts an anti-loosening fastening structure. Lock nuts are used at key fastening points to improve mechanical stability. The non-suspended core design also helps prevent components from becoming loose during long-distance transportation and handling.

Corrugated Oil Tank Without a Conventional Conservator

The corrugated oil tank replaces the conventional oil conservator in the fully sealed design. The corrugated tank expands and contracts according to changes in transformer oil volume, helping isolate the oil from the atmosphere.

This design reduces the risk of moisture entering the transformer and helps slow the deterioration of transformer oil and insulation materials. As a result, the transformer can maintain reliable operation with reduced routine maintenance requirements.

Temperature and Pressure Monitoring

ZTELEC oil-immersed transformers can be equipped with a remote-monitoring signal thermometer and pressure relief valve. These monitoring and protection components provide important operating information and help improve transformer safety and operational reliability.

Oil-Immersed Transformer for Reliable Power Distribution

With optimized core construction, reliable winding technology, sealed oil tank design, effective oil cooling, and integrated monitoring and protection components, ZTELEC oil-immersed transformers provide a dependable solution for modern power distribution systems.

Performance parameters

Rated Capacity (kVA)	Voltage Group		Vector Group	Loss (W)		No-Load Current (%)	Impedance Voltage (%)	Boundary Dimension (L × W × H, mm)	Weight (kg)
	HV (kV)	LV (kV)		No-Load Loss (W)	Load Loss (W)
30	20 / 22 / 24	0.4	Dyn11 or Yyn0	100	690 / 660	2.1	5.5	670 × 310 × 615	346
50	20 / 22 / 24	0.4	Dyn11 or Yyn0	130	1010 / 960	2.0	5.5	700 × 325 × 630	417
80	20 / 22 / 24	0.4	Dyn11 or Yyn0	180	1440 / 1370	1.8	5.5	755 × 355 × 690	556
100	20 / 22 / 24	0.4	Dyn11 or Yyn0	200	1730 / 1650	1.6	5.5	785 × 360 × 685	619
125	20 / 22 / 24	0.4	Dyn11 or Yyn0	240	2080 / 1980	1.5	5.5	805 × 370 × 720	703
160	20 / 22 / 24	0.4	Dyn11 or Yyn0	290	2540 / 2420	1.4	5.5	850 × 385 × 735	794
200	20 / 22 / 24	0.4	Dyn11 or Yyn0	340	3000 / 2860	1.3	5.5	865 × 405 × 805	935
250	20 / 22 / 24	0.4	Dyn11 or Yyn0	400	3520 / 3350	1.2	5.5	905 × 415 × 935	1086
315	20 / 22 / 24	0.4	Dyn11 or Yyn0	480	4210 / 4010	1.1	5.5	925 × 440 × 915	1226
400	20 / 22 / 24	0.4	Dyn11 or Yyn0	570	4970 / 4730	1.0	5.5	970 × 465 × 960	1468
500	20 / 22 / 24	0.4	Dyn11 or Yyn0	680	5940 / 5660	1.0	5.5	1035 × 500 × 1010	1758
630	20 / 22 / 24	0.4	Dyn11 or Yyn0	810	6820	0.9	6.0	1110 × 525 × 1075	2074
800	20 / 22 / 24	0.4	Dyn11 or Yyn0	980	8250	0.8	6.0	1190 × 580 × 1155	2840
1000	20 / 22 / 24	0.4	Dyn11 or Yyn0	1150	11330	0.7	6.0	1205 × 560 × 1195	2842
1250	20 / 22 / 24	0.4	Dyn11 or Yyn0	1380	13200	0.7	6.0	1185 × 590 × 1205	3168
1600	20 / 22 / 24	0.4	Dyn11 or Yyn0	1660	15950	0.6	6.0	1225 × 565 × 1345	3800
2000	20 / 22 / 24	0.4	Dyn11 or Yyn0	1950	19140	0.6	6.0	1310 × 615 × 1435	4633
2500	20 / 22 / 24	0.4	Dyn11 or Yyn0	2340	22220	0.5	6.0	1390 × 660 × 1510	5329

As an experienced transformer manufacturer, ZTELEC Electric Technology (Zhengzhou) Co., Ltd. can provide oil-immersed transformer solutions according to rated capacity, voltage level, installation environment, cooling requirements, and project specifications. Contact ZTELEC for technical consultation and customized transformer solutions.