Oil-Immersed Transformers

S11 (S13) Series Oil-Immersed Transformers

 

Oil-immersed transformers have the characteristics of good heat dissipation, low loss, large capacity, and low price. At present, most of the power transformers running in the power grid are oil-immersed transformers.

 

Product Highlights:

High-Quality Materials: Selected high-performance silicon steel sheets for superior electromagnetic performance.

Precision Technology: Each core is meticulously processed and rigorously tested.

Strong Durability: Designed for a long service life with a low failure rate.

 

We look forward to partnering with your company to expand our market reach. For detailed quotations or further information, please don't hesitate to contact us!

 

1. What is an Oil Immersed Transformer?

An oil-immersed transformer, also called Oil filled transformer, Liquid-Filled Transformer,is a kind of voltage transformation device utilizing the oil cooling method to reduce the transformer temperature. Unlike the dry type transformer, the body of the Oil-immersed transformer is installed in the welded steel oil tank filled with insulation oil. When an Oil-immersed transformer in operation, the heat of the coil and iron core firstly is transformed into the insulation oil and then to the cooling medium. And according to the capacity sizes, it can be divided into an immersed natural cooling transformer and an immersed forced air cooling transformer.

 

Oil-immersed transformers consist of two or more coils (primary and secondary windings) and an iron core. These coils and cores are soaked in insulating oil to maintain their cooling and insulating properties.

 

2. Structure and operation principle of Oil-immersed transformer

The iron core and winding constitute the important parts of the oil-immersed transformer. In addition, there are oil tanks, oil conservators, bushings, breathing apparatus, radiators, tap changers, gas relays, thermometers, oil purifiers, etc.

The basic elements of an oil-immersed are consist of the magnetic core, windings, and bushings. The magnetic core provides a path for magnetic flow. Windings create a magnetic field and consist of a conductor coil, wrapped around the core and insulated with pressboard barriers and screens. The thickness of the winding insulation increases with voltage. Bushings connect transformer windings to a substation.

Oil-type transformers are used in power distribution or electrical substations. Their core and coils are immersed in Oil, which cools and insulates. Oil circulates through ducts in the coils and around the coils and core assembly, moved by convection. The Oil is cooled by the outside of the tank in small ratings, and by an air-cooled radiator in larger ratings.

 

Transfomer Iron Core

 

What does the iron core do in a transformer?

The iron core is the main magnetic circuit of the transformer, and its main function is to conduct magnetism. It converts the electrical energy of the primary circuit into magnetic energy, and from the magnetic energy into the electrical energy of the secondary circuit.

 

The iron core in the transformer is generally made of silicon steel sheets stacked, and the silicon steel sheets are insulated from each other. The silicon steel sheet mainly affects the no-load loss of the transformer.

 

According to the arrangement of the windings in the iron core: there are two types of iron core type and iron shell type. The three parts of the iron core column, the high and low voltage windings, and the iron yoke constitute the closed magnetic circuit of the transformer.

 

GNEE ElECTRIC's iron core is made of cold-rolled oriented silicon steel sheet, with 80, 85, 90, 100, and 110 grades of silicon steel sheet. The smaller the grade, the lower the no-load loss, the better the transformer performance, and the iron core structure. There are cooling oil passages in the iron core of the large-capacity transformer to achieve a good cooling effect.
 

GNEE ElECTRIC also can offer Dry-type transformer core,Oil-immersed transformer core,Main transformer core,silicon steel Cut Laminations.

 

Model/Specification		Oil Type Transformer Core		Purchase order number
Serial number	Inspection items	Standard requirements	Sample size	Measured data
1	Seams	≤1.0mm	1	1.0mm
2	No-load loss	P0≤ 446 W	1	444w
2	Window diagonal	mutual difference≤2.0mm	1	≤2.0mm
3	Insulation resistance	Core-to-ground insulation resistance≥5MΩ	1	≥5MΩ
4	Heart column	Perpendicularity: ≤ (2/1000) mm	1	≤ (2/1000) mm
		Curvature:≤ (1.5/1000) mm	1	≤ (1/1000) mm
5	Stacking thickness	Main level:92±1mm	1	92
		Total stack thickness: 273±1mm	1	273
6	Window height and width	Window High: 470±1mm	1	470
		Window Width: 189±1mm	1	189
7	Clamp size	Strictly in accordance with the technical agreement, not standard in accordance with the national standard size tolerance (C rough);
8	Foot insulation	Laminated wood: 29±0.5mm	1	29
		Cardboard: 6±0.5mm	1	6
9	Standard part size	Strictly in accordance with the technical agreement,not standardized in accordance with the national standard dimensional tolerances (C rough) implementation.
10	Clamp insulation board thickness	Paperboard thickness: 3±0.5mm		3
11	Overall appearance	No bump damage to the iron chip, no breakage of the tip of the metal structure parts of the paint without loss of loss,tied firmly and reliably

 

Transformer Winding

 

The windings constitute the circuit of the transformer and are divided into two types: primary windings and secondary windings.

The primary winding is connected to the power supply, and the secondary winding is connected to the load. GNEE transformer windings are made of copper or aluminum wires wrapped with high-strength insulating paper.

 

The first and second windings of each phase of the three-phase transformer are made into a cylindrical shape and sleeved on the same iron core column. This placement is because it is easier for the low-voltage winding to insulate the core. A sleeve made of insulating material is used to isolate the low-voltage winding and the iron core and between the high-voltage winding and the low-voltage winding to insulate them reliably. In order to facilitate heat dissipation, a certain gap is left between the high and low windings as an oil passage, so that the transformer oil can flow.

 

Transformer oil tank

 

1. What is transformer oil tank?

The transformer oil tank is the outer casing of the transformer. The oil tank is filled with transformer oil, and the iron core and windings are installed in it. For transformers with larger capacity,GNEE ElECTRIC will be equipped with a radiator outside the transformer oil tank. The transformer tank of GNEE ElECTRIC has the characteristics of good sealing and corrosion resistance, and there will be no leakage of the oil tank.

 

2. Transformer oil

There are two main types of transformer oil used by GNEE ElECTRIC: it is mineral oil with good insulating properties. There are two types of mineral oil: No. 25 and No. 45. It has excellent electrical and thermal properties and is cheap;

The other is environmentally friendly vegetable oil, which has the advantages of high flash point, good electrical properties, renewable and biodegradable, etc., but its price is high, 3-4 times that of mineral oil.

You can choose the transformer oil that suits your needs.

 

3. What is transformer oil used for?

Transformer oil is insulating. The insulation performance of transformer oil is better than that of air. Immersion of windings in oil can improve insulation performance everywhere, and avoid contact with air to prevent windings from getting wet;

 

On the other hand, it is the heat dissipation effect, which uses the convection of the oil to dissipate the heat generated by the iron core and the winding to the outside through the transformer tank wall and the heat dissipation pipe.

 

Oil conservator (oil pillow)

 

The transformer oil conservator looks like a cylindrical pillow, so it is also called oil pillow. It is placed horizontally above the oil tank and is connected to the oil tank of the transformer with a pipeline. The volume of the oil conservator is generally about 10% of the volume of the oil tank.

The oil conservators provided by GNEE ELECTRIC are Corrugated type, Capsule type, and Diaphragm type. Among them, the corrugated oil conservator will be more expensive, and you can choose according to your needs.

 

When the transformer oil is heated and expanded, transformer oil flows into the oil conservator from the oil tank; when the transformer oil contracts when cold, the transformer oil is replenished from the oil conservator to the oil tank. The oil conservator has two functions: one is that when the volume of transformer oil expands or shrinks with the change of oil temperature, the oil pillow acts as oil storage and replenishment to ensure that the oil tank is filled with oil so that the iron core and winding are completely It is immersed in oil; second, the transformer oil is only in contact with the air in the oil pillow, which can reduce the contact area between the oil surface and the air, and reduce the chance of the transformer oil being damp and oxidized.

 

3.How does an oil-immersed transformer work?

 

The working principle of oil-immersed transformer is based on electromagnetic induction and transformer principles.

 

When AC current from the input power supply passes through the main winding, the resulting magnetic field creates magnetic flux in the iron core. This flux passes through the adjacent secondary winding, causing another voltage to be induced in the secondary winding.

 

Specifically, when the current in the main winding changes, it creates an alternating magnetic field. This alternating magnetic field causes the ferromagnetic material in the core to undergo magnetization and demagnetization processes. This process creates a potential difference in the secondary winding, causing the current in the secondary winding to change accordingly.

 

According to the principle of a transformer, the transformation ratio between the primary and secondary windings is determined by the turns ratio of the windings. If the number of turns of the main winding is larger than that of the auxiliary winding, the output voltage will decrease; conversely, if the number of turns of the main winding is smaller than that of the auxiliary winding, the output voltage will increase.

 

In oil-immersed transformers, insulating oil plays an important role. First, the insulating oil cools the internal components of the transformer and keeps its operating temperature within a safe range. Secondly, insulating oil has good insulation properties and can prevent arcs and discharges.

 

In summary, the working principle of an oil-immersed transformer can be attributed to converting the voltage of the input power supply into the required output voltage through electromagnetic induction between the primary and secondary windings under the cooling and insulation protection of insulating oil.

 

4. Types of Oil-immersed transformer

 

The Oil-immersed transformers have two main types as 1-phase transformer and 3-phase transformer.

a. One-phase oil-filled transformer

One-phase Oil-immersed transformer 50KVA-25KVA-15KVA

b. Three-phase Oil Immersed Transformer

Open-type 3-phase oil-mmersed transformer (left) and Closed-type 3-phase oil-immersed transformer(right)

 

1. Specifications (Technical Data are subjected to change without notice.)

 

1-1. 22kV - 400/230V & 24kV - 416/240V  oil-filled transformer

Item	Capacity	No load	Load loss (75oC)	Impedance	Dimensions(mm)			Total weight	Oil
	kVA	Watt	Watt	%	Height	Length	Width	kg	Liter
1	50	160	950	4	1,100	1,000	700	500	135
2	100	250	1,550	4	1,250	1,050	750	750	200
3	160	360	2,100	4	1,300	1,150	750	990	250
4	250	500	2,950	4	1,350	1,200	750	1300	300
5	315	800	3,900	4	1,400	1,400	800	1300	350
6	400	960	4,600	4	1,400	1,500	850	1550	380
7	500	1,150	5,500	4	1,500	1,550	900	1750	430
8	630	1,350	6,500	4	1,550	1,600	850	2,150	450
9	800	1,600	11,000	6	1,600	1,800	1,100	2,500	650
10	1,000	1,950	13,500	6	1,750	1,900	1,100	3,200	700
11	1,250	2,300	16,400	6	1,850	2,000	1,150	4,000	850
12	1,500	2,800	19,800	6	1,950	2,100	1,250	4,150	1,150
13	2,000	3,250	24,000	6	2,050	2,250	1,350	5,650	1,450
14	2,500	3,500	28,500	6	2,150	2,450	1,450	6,450	1,750

 

1-2. 33kV - 400/230V oil-filled transformer

Item	Capacity	No load	Load loss (75oC)	Impedance	Dimensions(mm)			Total weight	Oil
	kVA	Watt	Watt	%	Height	Length	Width	kg	Liter
1	50	170	950	4	1,300	1,000	700	550	165
2	100	260	1,550	4	1,400	1,050	750	800	230
3	160	370	2,100	4	1,450	1,150	750	990	280
4	250	520	2,950	4	1,500	1,200	750	1450	350
5	315	850	3,900	4	1,550	1,350	800	1450	400
6	400	1000	4,600	4	1,550	1,450	850	1700	450
7	500	1,200	5,500	4	1,650	1,500	900	1900	500
8	630	1,400	6,500	4	1,700	1,650	850	2,300	550
9	800	1,700	11,000	6	1,750	1,850	1,100	2,650	700
10	1,000	2,000	13,500	6	1,900	1,950	1,100	3,350	750
11	1,250	2,350	16,400	6	2,000	2,000	1,150	4,150	900
12	1,500	2,850	19,800	6	2,100	2,100	1,250	4,300	1,200
13	2,000	3,300	24,000	6	2,200	2,250	1,350	5,800	1,450
14	2,500	3,800	28,500	6	2,350	2,450	1,450	6,600	1,750

 

Distribution Transformer Outline

 

2. Accessories (Standard & Option)

Item		kVA	50	100	160	250	315	400	500	630	800	1000	1250	1500	2000	2500
1	Bushings		●	●	●	●	●	●	●	●	●	●	●	●	●	●
2	Arcing horn		●	●	●	●	●	●	●	●	●	●	●	●	●	●
3	Off load tap changer		●	●	●	●	●	●	●	●	●	●	●	●	●	●
4	Earth terminal		●	●	●	●	●	●	●	●	●	●	●	●	●	●
5	Lifting lug		●	●	●	●	●	●	●	●	●	●	●	●	●	●
6	Lifting eye		●	●	●	●	●	●	●	●	●	●	●	●	●	●
7	Wheel		○	○	○	○	○	○	○	○	○	●	●	●	●	●
8	Nameplate		●	●	●	●	●	●	●	●	●	●	●	●	●	●
9	Oil drain		●	●	●	●	●	●	●	●	●	●	●	●	●	●
10	Thermometer pocket		●	●	●	●	●	●	●	●	●	●	●	●	●	●
11	Marshaling box		○	○	○	○	○	○	○	○	○	●	●	●	●	●
12	Cable box		○	○	○	○	○	○	○	○	○	○	○	○	○	○
13	P'ry terminal connector	Pad type	○	○	○	○	○	○	○	○	○	○	○	○	○	○
		Clamp type	●	●	●	●	●	●	●	●	●	●	●	●	●	●
14	S'ry terminal connector	Pad type	●	●	●	●	●	●	○	○	○	○	○	○	○	○
		Clamp type	○	○	○	○	○	○	●	●	●	●	●	●	●	●
15	Oil level gauge	W/O contact	●	●	●	●	●	●	●	●	●	●	●	●	●	●
16	Thermometer	W/O contact	○	○	○	○	○	○	○	○	○	○	○	○	○	○
		2 contact	○	○	○	○	○	○	○	○	○	●	●	●	●	●
17	WDG Temp.indicator	2 contact	○	○	○	○	○	○	○	○	○	○	○	○	○	○
18	Pressure relief device	W/O contact	●	●	●	●	●	●	●	●	●	●	●	●	●	●
		1 contact	○	○	○	○	○	○	○	○	○	○	○	○	○	○

Accessaries List
● Standard Accessaries
○ Option Accessaries

 

3. Remarks

GNEE ELECTRIC reserve the right to any changes of these information, herein.

Distribution transformers are designed for general application uses at ambient temperature maximum 40℃ at temperature raised 60℃ (top oil) / 65℃ (winding), which will be manufactured and tested in accordance with the latest IEC standard.

 

Oil-immersed transformer Open Type with Conservator Tank (Mineral Oil)

 

1. Specifications (Technical Data are subjected to change without notice.)

 

1-1. Oil-immersed transformer Open Type with Conservator Tank 22kV – 400/230V & 24kV - 416/240V

Item	Capacity	No load	Load loss (75oC)	Impedance	Dimensions(mm)			Total weight	Oil
	kVA	Watt	Watt	%	Height	Length	Width	kg	Liter
1	50	160	950	4	1,250	1,300	850	650	150
2	100	250	1,550	4	1,350	1,300	850	750	200
3	160	360	2,100	4	1,450	1,400	850	950	250
4	250	500	2,950	4	1,550	1,500	850	1200	320
5	315	800	3,900	4	1,600	1,550	850	1250	350
6	400	960	4,600	4	1,650	1,600	900	1550	380
7	500	1,150	5,500	4	1,700	1,700	950	1800	450
8	630	1,350	6,500	4	1,750	1,800	950	2,100	600
9	800	1,600	11,000	6	1,850	1,900	1,050	2,650	650
10	1,000	1,950	13,500	6	2,050	2,050	1,150	3,200	700
11	1,250	2,300	16,400	6	2,100	2,250	1,200	4,000	900
12	1,500	2,800	19,800	6	2,250	2,250	1,350	4,200	1,100
13	2,000	3,250	24,000	6	2,350	2,300	1,400	5,500	1,200
14	2,500	3,500	28,500	6	2,500	2,500	1,550	6,500	1,800

 

1-2. Oil-immersed transformer Open Type with Conservator Tank 33kV – 400/230V

Item	Capacity	No load	Load loss (75oC)	Impedance	Dimensions(mm)			Total weight	Oil
	kVA	Watt	Watt	%	Height	Length	Width	kg	Liter
1	50	170	950	4	1,450	1,400	900	700	200
2	100	260	1,550	4	1,550	1,400	900	800	250
3	160	370	2,100	4	1,650	1,500	900	1,000	300
4	250	520	2,950	4	1,750	1,600	900	1250	350
5	315	850	3,900	4	1,750	1,650	900	1350	400
6	400	1000	4,600	4	1,800	1,700	950	1650	450
7	500	1,200	5,500	4	1,850	1,800	1000	1900	500
8	630	1,400	6,500	4	1,900	1,900	1,000	2,200	650
9	800	1,700	11,000	6	2,000	2,000	1,100	2,750	700
10	1,000	2,000	13,500	6	2,200	2,150	1,200	3,500	750
11	1,250	2,350	16,400	6	2,250	2,350	1,250	4,500	950
12	1,500	2,850	19,800	6	2,400	2,350	1,400	4,800	1,150
13	2,000	3,300	24,000	6	2,500	2,400	1,450	6,200	1,250
14	2,500	3,800	28,500	6	2,650	2,600	1,600	7,200	1,850

Distribution Transformer Outline

 

 

2. Accessories (Standard & Option)

Item		kVA	50	100	160	250	315	400	500	630	800	1000	1250	1500	2000	2500
1	Bushings		●	●	●	●	●	●	●	●	●	●	●	●	●	●
2	Arcing horn		●	●	●	●	●	●	●	●	●	●	●	●	●	●
3	Off load tap changer		●	●	●	●	●	●	●	●	●	●	●	●	●	●
4	Dehydrating breather filled with silica gel		●	●	●	●	●	●	●	●	●	●	●	●	●	●
5	Earth terminal		●	●	●	●	●	●	●	●	●	●	●	●	●	●
6	Lifting lug		●	●	●	●	●	●	●	●	●	●	●	●	●	●
7	Lifting eye		●	●	●	●	●	●	●	●	●	●	●	●	●	●
8	Wheel		○	○	○	○	○	○	○	○	○	●	●	●	●	●
9	Nameplate		●	●	●	●	●	●	●	●	●	●	●	●	●	●
10	Oil drain		●	●	●	●	●	●	●	●	●	●	●	●	●	●
11	Thermometer pocket		●	●	●	●	●	●	●	●	●	●	●	●	●	●
12	Marshaling box		○	○	○	○	○	○	○	○	○	●	●	●	●	●
13	Cable box		○	○	○	○	○	○	○	○	○	○	○	○	○	○
14	P'ry terminal connector	Pad type	○	○	○	○	○	○	○	○	○	○	○	○	○	○
		Clamp type	●	●	●	●	●	●	●	●	●	●	●	●	●	●
15	S'ry terminal connector	Pad type	●	●	●	●	●	●	○	○	○	○	○	○	○	○
		Clamp type	○	○	○	○	○	○	●	●	●	●	●	●	●	●
16	Oil level gauge	W/O contact	●	●	●	●	●	●	●	●	●	●	●	●	●	●
17	Thermometer	W/O contact	○	○	○	○	○	○	○	○	○	○	○	○	○	○
		2 contact	○	○	○	○	○	○	○	○	○	●	●	●	●	●
18	WDG Temp.indicator	2 contact	○	○	○	○	○	○	○	○	○	○	○	○	○	○
19	Buchholz relay	2 contact	○	○	○	○	○	○	○	○	○	●	●	●	●	●
19	Pressure relief device	W/O contact	●	●	●	●	●	●	●	●	●	●	●	●	●	●
		1 contact	○	○	○	○	○	○	○	○	○	○	○	○	○	○

Accessaries List
● Standard Accessaries
○ Option Accessaries

 

3. Remarks

GNEE ELECTRIC reserve the right to any changes of these information, herein.

Distribution transformers are designed for general application uses at ambient temperature maximum 40℃ at temperature raised 60℃ (top oil) / 65℃ (winding), which will be manufactured and tested in accordance with the latest IEC standard.

 

5.Purpose of using Oil Immersed Transformer

Oil-type transformers can be ground-, pad- or pole-mounted for use outdoors. They deliver efficient performance in diverse applications, including transmission and distribution networks, renewable energy generation, and small industries.

The oil transformer has a huge capacity, so it will save a lot of electrical energy, minimize power loss, save energy sources, and reduce costs for users. More than that, the Oil in the machine cools the internal wire cores to contribute to the durability and electrical properties of the transformer equipment.

 

Are Oil Filled Transformer Safe Nowadays?

Yes, oil filled transformer are safer nowadays.

Some of the non-combustible liquids that oil filled transformer use are the following.

• silicone
• elevated temperature hydrocarbons
• gas-perchloroethylene
• oil-based HMWH blends

These fluids are both safe for the environment and resistant to fire.

Biodegradable oil filled transformer apply environmentally preferable materials like animal fats and vegetable oils in place of petroleum oils, and the liquids oil with ul certificate.

Because of their lesser combustibility, they contain the dielectric substances mentioned above.

Since oil filled transformer started as a non-toxic substances, they can absorb more of their surroundings.

Overall, oil filled transformer features a high absorption rate in the environment and are less likely to catch fire.

 

How Does An Oil Immersed Transformer Differ From A Dry Type One?

Let's identify the differences between oil immersed transformer

and dry type transformer.

Cooling Source

The cooling source of the dry transformer relies mainly upon the air.

At the same time, an oil filled transformer cooling source is mainly oil.

Dry transformers come from the fact that there is no oil inside of them.

Oil is necessary for oil cooled distribution transformers because it acts as an insulator for power current.

Efficiency

Dry-type transformers are inefficient due to space and voltage limitations.

Therefore, oil immersed transformer are more efficient in terms of electrical losses and maintenance operation.

Maintenance

Oil immersed transformer necessitate regular oil quality checks, which are unnecessary for dry types.

Dry transformers are smaller in size because there is no need for a tank.

Oil is also susceptible to environmental and climatic changes, but dry transformers are not.

Application

When oil leakage poses a significant concern in an outdoor setting or inside a building, dry-type transformers are the safest option.

They're also common wherever transformer servicing or replacement is going to be easy.

Oil-immersed transformers excel in power transmission and circulation.

Because of its magnitude to keep power, an oil cooled distribution transformers is the equipment of choice when it comes to accomplishing the process of power transmission.

Investment Costs

Dry transformer is more expensive than oil immersed transformer.

Because of their typical energy efficiency, oil immersed transformer

are dependable, durable, and cheap.

The cost of running a dry transformer is higher than that of an oil-immersed one, and they also use more energy.

Recyclable Properties

The core of a dry transformer is more difficult to recycle than the coil of an oil immersed transformer when it approaches the end of its useful life.

Location

Oil cooled distribution transformers are best suitable for outdoor applications.

Meanwhile, a dry type transformer is widely used indoors because of its small carbon impact.

You can find dry transformers in a wide variety of public places since they are completely safe to use.

They are a common feature of workplaces, medical facilities, and recreational areas.