110 kv Oil Filled Power Transformer - DAELIM BELEFIC
This is article is about 110kv oil filled power transformer， as an example to talk about the oil filled of the power transformer
how the oil filled power transformer work, and the test for the oil filled power transformer.
According to these introduce, you can know more about the oil filled power transformer.
We, Daelim Belefic is a professional power transformer manufacturer in China, we have more than 16 years experience in this electric industry. We have professional engineer team, provide the best solution for you, our sales team can provide the best service for you!
Pad-mounted Transformer
Dry-type Transformer
Oil immersed transformer
Table of Content
What is oil filled transformer?
This is article is about 110kv oil filled power transformer， as an example to talk about the oil filled of the power transformer
how the oil filled power transformer work, and the test for the oil filled power transformer.
According to these introduce, you can know more about the oil filled power transformer.
We, Daelim Belefic is a professional power transformer manufacturer in China, we have more than 16 years experience in this electric industry. We have professional engineer team, provide the best solution for you, our sales team can provide the best service for you!
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Why are power transformers filled with oil?
To enhance insulation and cooling conditions, the transformer core and windings are immersed in a tank containing transformer oil. In special cases, such as street lamps, miner’s lamp lighting, and dry-type transformers.
The oil in the transformer mainly plays the role of heat dissipation and cooling during the operation of the transformer.
Insulates the inside of the transformer, so that the transformer maintains a good insulation state.
Transformer oil is used to suppress arcs at the high voltage lead and tap changer contact points to prevent corona and arc discharge.
Transformer oil is widely used for liquid seals in hydraulic safety valves
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Which oil is used in power transformers?
Transformer Oil: A product of petroleum distillation. Its main components are alkanes, naphthe-saturated hydrocarbons, aromatic unsaturated hydrocarbons and other compounds.
ONAN: mineral oil or synthetic insuating with a fire point less than or equal to 300℃.
KNAN: Insulating liquid with a fire point greater than 300℃. Like the FR3 oil, we alos have a brand in China RAPO oil, both of them are vegetable oil.
LNAN: Insulating liquid with no measurable fire point
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The main function of power transformer oil
(1) Insulation: The dielectric strength of transformer oil is much higher than that of air. Soaking insulation in oil not only increases its dielectric strength, it also protects it from moisture.
(2) Heat dissipation: Transformer oil has a large specific heat and is often used as a refrigerant. The heat generated during the operation of the transformer causes the oil near the core and windings to expand due to thermal expansion. The upper and lower convection of the oil dissipates heat through the radiator to ensure the normal operation of the transformer.
(3) Arc suppression function: In transformer oil circuit breakers and load regulator switches, arcs are generated when the contacts are changed. Transformer oil has high thermal conductivity, can contact with a large amount of high-temperature gas in the arc, generate a large pressure, improve the arc extinguishing performance of the medium, and quickly extinguish the arc.
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How does 110KV oil filled power transformer work?
1. The effect of power transformer oil pillow
Since the volume of transformer oil will expand and contract as the oil temperature increases and decreases, the oil pillow will play the role of oil storage and oil replenishment.. Some oil pillows are also equipped with diaphragms or capsules or metal expansion boxes to prevent oil and air from being oxidized and damped. An oil gauge tube is installed on the oil pillow to observe the change of oil level. The lower part of the oil pillow is provided with a sludge collector, which is used to collect mechanical impurities, sludge and moisture deposited in the oil.
2. The oil pillow of the transformer is generally composed of an oil level gauge, a respirator, a dirt collection box, an oil filling hole, an end cover, a connecting flange, a valve, etc.
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Oil filled power Transformer Type
According to the number of windings, it can be divided into two-winding transformers and three-winding transformers. The transformer is usually a two-winding transformer, i.e. there are two windings on the core, one for the primary and one for the secondary.
Three-winding transformer Large-capacity transformers (above 5600 kVA) connect three power lines of different voltages. In special cases, more windings are also applied.
According to the structure of the classification form, it can be divided into iron core transformer and transformer steel. Compared with the winding encapsulation of iron core type transformers around the core; since the core periphery is wrapped in the winding transformer steel. But the two are slightly different in structure, and there is no essential difference in principle. Power transformers are core types.
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Protection System for the oil filled power transformer
1. Oil temperature indicator:
Tank top oil temperature indicator shall be used to indicate the hottest oil which belongs to the transformer tank and shall be installed in an oil-filled or close-fitting well, located in the hottest oil, as far as practicable. It shall include a temperature sensing bulb and indicating device, equipped with a temperature-indicating pointer and a drag pointer that shows the highest temperature reached since it was last reset, two adjustable alarm contacts and at least two adjustable trip contacts.
2. Oil-level indicator: Transformer oil conservator shall be furnished with a magnetic oil-level indicator having low-level oil alarm indicating contacts and at least two trip contacts. The alarm relay shall actuate on falling oil level at a point before the insulation system is compromised.
3. Oil drain valve: A drain valve shall be installed in such a manner that liquid below the valve may be drained or pumped out to within 13 mm of the tank bottom. This valve shall not be located under or above the radiators.
4. Oil sampling valve: A sampling valve shall be installed so that samples may be obtained from the location subject to the greatest contamination.
5. Oil treatment Connections: Valves or other means for connecting the oil-conditioning unit shall be provided.
The dielectric coolant shall be listed less-flammable fluid. The dielectric coolant shall be non-toxic, non-bioaccumulating and be readily and completely biodegradable. The base fluid shall be 100% derived from edible seed oils and food grade performance enhancing additives. The fluid shall not require genetically altered seeds for its base oil. The fluid shall be Factory Mutual Approved® Envirotemp™ FR3™ fluid or equivalent.
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Liquid insulating system for the oil filled power transformer
The filling liquid shall meet requirements set out in CAN/CSA C50-08 Mineral Insulating Oil, Electrical, for Transformers and Switches for Class A Type II oil. The oil shall be compatible with Shell Diala, Nynas Nytro or Voltesso 35 and shall be inhibited to 0.08% of the total oil weight.
When shipped, the dielectric strength of the oil shall not be less than 40 kV when tested in accordance with ASTM D1816 using a 2 mm electrode spacing.
Mineral oil-immersed transformers shall be tested for concentration of individual gas and total dissolved combustible gas (TDCG) in oil. The transformer shall be acceptable if the levels of the gases do not exceed the levels established in IEEE C57.130.
Mineral oil shall be certified to contain less than 1 ppm PCBs. This certificate shall be provided at site prior to oil filling the transformer.
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Insulating liquid preservation for the oil filled power transformer
The power Transformer if be of conservator tank construction.
The oil preservation system shall be designed for oil temperatures ranging from the unloaded condition at -40°C ambient to the highest oil temperature imposed by the specified overload condition at +40°C ambient.
Throughout this range, the transformer main tank will remain filled with insulating oil and no oil will be expelled.
The main tank shall be provided with a sealed flange lid, leak free, with all seams and joints welded. Welded joints shall be provided with flanges to permit repeated opening and re-welding.
To ensure leak-free performance, all gaskets shall be capable of withstanding the temperature variations and pressure requirements. The outer edges of the gasket joints shall be protected by metal-to-metal stops or fire-resistant stop-gasket material when installed in position. Glue or other adhesive shall not be used to keep gaskets in place.
Transformers for which the oil is shipped separately shall be shipped filled with dry nitrogen under pressure with a pressure gauge attached, and with a container of dehydrating material mounted temporarily inside the transformer tank. If the transformers are to be in transit for more than 14 days, a cylinder of dry nitrogen shall be connected temporarily to each transformer tank through suitable valves for maintaining pressure while the transformers are in transit.
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DELIVERY AND STORAGE for the oil filled power transformer
The equipment shall be completely assembled and tested before shipment, disassembled if required for shipment and all parts match-marked to facilitate assembly and erection. The unit shall be suitably braced and packed for shipping to prevent breakage and distortion which in transit. All crates, boxes and cartons shall be clearly marked so that equipment can be readily identified. Shipping invoices shall show the crate, box or carton identification number. The equipment shall be shipped in sections as described in the proposal or as directed by the owner.
All shipments shall be made by motor truck unless prior approval has been granted for other method of shipment.
