Transformer oil, a type of insulating and cooling oil used in transformers and other electrical typically 5 repetitions, depending on the standard. As a result the breakdown voltage is calculated as mean value of the individual measurements. Low value of BDV indicates presence of moisture content and conducting substances in the oil. For measuring BDV of transformer oil, portable. In this article, I will discuss transformer oil sample tests other than dissolved gas analysis (DGA). Lower values are indicative of damp or dirty oil. Moisture.

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More plainly, the leakage current through insulation does have two component one capacitive or reactive, and another one is resistive or active. Flash Point of Transformer Oil Flash point of transformer trahsformer is the temperature at which oil gives enough vapors to produce a flammable mixture with air. Connects Facebook Youtube Videos. This rate of degradation of oil increases.

Some of them are even battery-powered and come with accessories. Thus the temperature of the oil at the time of taking a sample for the test is critical. Mohamed Hakeem Meerashahib February That means at which voltage dielectric strength of transformer oil between the electrodes has been broken down.

Paper absorbs the maximum amount of water from oil which affects paper insulation property as well as reduced its life. Here voltage means the instantaneous voltage between live part and ground of the equipment.

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Break down voltage is measured by observing at what voltage, sparking strants between two electrods immerged in the oil, separated by specific gap. Although Paraffin-based oil has the disadvantage as mentioned earlier but still in our country, we use it because of its easy availability.

If oil becomes acidic, the water content in the oil becomes more soluble in the oil. But while in operation if The specific resistance of oil is a measure of DC resistance between two opposite sides of one cm 3 block of oil. Pour Point of Transformer Oil It is the minimum temperature at which oil starts to flow under standard test condition.

Clean oil with a low moisture content gives higher BDV results than oil with high moisture content and other conducting impurities. Hence current through the insulator will lead the voltage with an angle little bit shorter than 90 o.


As an insulating material is dielectric in nature the current through the insulation ideally leads the voltage by 90 o.

Dielectric Strength of Transformer Insulating Oil

This may be due to sludge deposition on shell winding. Operational properties of transformer oils are checked by electrical insulating and physico- chemical characteristics:.

Upvote 1 Downvote Reply 1 Report. Regular testing and sampling of insulation Oil is very important oi the maintenance progaram to prevent c Good oil should have a low viscosity so that it offers less resistance to the conventional flow of oil thereby not affecting the cooling of a transformer.

In this kit, oil is kept in a pot in which one pair of electrodes are fixed with a gap of 2. Viscosity of Transformer Oil In few words, the viscosity of transformer oil can be said that viscosity is the resistance of flow, in normal condition.

Transformer oil testing – Wikipedia

Also known as the sparking strength, the higher the voltage required to jump the spark, the higher the BDV will be in the oil. Powered by GDPR plugin. While taking sample of oil from transformer, Sample bottle should be flushed well by Transformer oil and oil in Sample bottle should be vented properly so that atmospheric moisture could not ingress in the sample oil. Dry and clean oil gives BDV results, transformeer than the oil with moisture content and other conducting impurities.

Transformer Insulating Oil and Types of Transformer Oil

BDV is an important and popular test of transformer oil, as it is the primary indicator of the health of oil and it can be easily carried out at the site. Is Synchronous check relay system for two power transformers compatible to be used to make synchronizing between transflrmer transformer and generator?

Paper is highly hygroscopic. The Dielectric Strength of transformer oil is very important since it is essential in maintaining the reliable operation of power transformers. Retrieved from ” https: Your email address will not be published. Leave a Reply Cancel reply Your email address will not be published. Paraffin-based oil has a higher value of pour point, compared to Naphtha based oil, but in India like country, it does not affect the use of Paraffin oil due to its warm climate condition.


New York, NY [u. The accurate measurement of water content at such low levels requires very sophisticated instrument like Coulometric Karl Fisher Titrator.

Acidity of Transformer Oil Acidity of transformer oilis harmful property. Dielectric strength means the maximum capacity to withstand voltage of insulating oil. Thank you for answering the question. This test shows the dielectric strength of Transformer oil. As a result, the paper releases water and increase the water content in transformer oil.

Just after charging a transformer after long shut down, the temperature of the oil will be at ambient temperature and during full load, the temperature will be very high and may go up to 90 o C at an overload condition. Breakdown Voltage is measured by observing at what voltage, sparking straits between two electrodes emerged in the oil, separated by specific gap.

But in the case of Paraffin oil although oxidation rate is lower than that of Naphtha oil the oxidation product or sludge is insoluble and precipitated at the bottom of the tank and obstruct the transformer cooling system. When a insulating materials is placed between live part and grounded part of an electrical equipment, leakage current will flow. The dielectric strength of transformer oil is mainly determined by the presence of acids, water, and other contaminates. If the resistivity of the insulating oil gets decreased, the value of tan-delta increases and vice verse.

Transformer oil serves mainly two purposes one it is liquid insulation in electrical power transformer and two it dissipates heat of the transformer e. Electrical power equipment maintenance and testing. This mixture gives momentary flash on the application of flame under standard condition. In addition to these, this oil serves other two purposes, it helps to preserve the core and winding as these are fully immersed inside oil, and another important purpose of this oil is, it prevents direct contact of atmospheric oxygen with cellulose made paper insulation of windings, which is susceptible to oxidation.