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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Electrical Standards: Transformer Oil Testing; IS for Transformer oil; Transformer BDV values

This may be due to sludge deposition on shell winding. Properties of Transformer Insulating Oil Some specific parameters of insulating oil valje be considered to determined the serviceability of that oil.

Oil oxidation contaminants lower the IFT. The specific resistance of oil is a measure of DC resistance between two opposite sides of one cm 3 block of oil. Minimum breakdown voltage of transformer oil or dielectric strength of transformer oil at which this oil can safely be used in transformer, is considered as 30 KV.


In transformer oil has mainly two purposes, first for insulation, second as cooling of Transformer core and other winding. Why do we need to do oil analysis for oil immersed power transformers? Clean oil with a low moisture content gives higher BDV results than oil with high moisture content and other conducting impurities.

Upvote 1 Downvote Reply 0 Report. You can adjust all of your cookie settings by navigating the tabs on the left hand side. 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. More plainly, the leakage current through insulation does have two component one capacitive or reactive, and another one is resistive or active.


Here voltage means the instantaneous voltage between live part and ground of the equipment. Strictly Necessary Cookies Strictly Necessary Cookie should be enabled at all times so that we can save your preferences for cookie settings. Testing sequences and procedures are defined by various international standards, many of them set by ASTM. Vallue absorbs the maximum amount of water from oil which affects paper insulation property as well as reduced its life.

Through such testing, transformers’ life can be substantially increased, thus delaying new investment of replacement transformer assets. The dielectric strength of the oil will decrease with time and based on the service conditions where the transformer is located.

Upvote 1 Downvote Reply 1 Report. Try adding a different answer. Hence it does not obstruct convection circulation of the oil, means it does not disturb the transformer cooling system. A typical way of taking oil sample in Sample Bottle is shown in figure below. Acidity of Transformer Oil Acidity of transformer oilis harmful property. Electrical power equipment maintenance and testing. Transfirmer Upvote Report Question Comments 1. If you disable this cookie, we will not be able to save your preferences.

Breakdown Voltage is measured by observing at what voltage, sparking straits between two electrodes emerged in the oil, separated by specific gap. In this kit, oil is kept in lf pot in which one pair of electrodes are fixed with a gap of 2. Acidity accelerates the oxidation process in the oil.

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Dielectric Strength of Transformer Insulating Oil

Dielectric Dissipation Factor of Tan Delta of Transformer Oil Dielectric dissipation factor is also known as loss factor or tan traneformer of transformer oil. Pour Point of Transformer Oil It is the minimum temperature at which oil starts to flow under standard test condition. Also known as the sparking strength, the higher the voltage required to tdansformer the spark, the higher the BDV will be in the oil.


Specific Resistance of Transformer Oil This is another important property tansformer transformer oil. Pour Point kf transformer oil mainly depends upon wax content in the oil. Cookie information is stored in your browser and performs functions such as recognising you when you return to our website and helping our team to understand which sections of the website you find most interesting and useful.

The Dielectric strength of transformer oil is also known as the breakdown voltage of the transformer oil. That is why specific resistance or resistivity of transformer oil should get measured at 27 o C as well as 90 o C. Subscribe to our mailing list and get interesting stuff and updates to your email inbox.

So both resistivity test and tan delta test of transformer oil are generally not required for the same piece of the insulator or insulating oil. 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 vale not ingress in the sample oil.

Articles needing additional references from September All articles needing additional references. Strictly Necessary Cookie should be enabled at all times so that we can save your preferences for cookie settings. More If Like This. With increase in temperature the resistivity of oil decreases rapidly.