The transformer oil is filled in the vessel of the testing device. Experimental study on the dielectric breakdown voltage of. In transformer oil has mainly two purposes, first for insulation, second as. Transformer oil testing sequences and procedures are defined by various international standards. Standard test method for dielectric breakdown voltage of. This test method is applicable to insulating liquids commonly used in cables, transformers, oil circuit breakers, and similar apparatus as an. The test involves applying a ac voltage at a controlled rate to two electrodes immersed in the insulating fluid. To determine dielectric strength, transformer oil is periodically tested by means of an oil punching apparatus.
How to proceed the dielectric strength test for transformer oil. The dielectric strength of an insulating oil is a measure of the oils ability to withstand electrical stress without failure. Because these generate a lot of heat that must be removed, they need to be insulated and they have to resist sparking, the physical and chemical properties of certain oils make them ideal for use in transformers and capacitors. During the transformer operation for a period, insulation oils will become dirty degradation which results in loosing function of the oil in transformer as insulation and cooling, in that case. This test is not performed for dielectric silicones. In sealed units ingress of moisture via atmosphere or seal leaks needs to be stopped. Breakdown voltage is measured by observing at what voltage, sparking strands between two electrodes immersed in the oil, separated by a specific gap. Oils that combine a high flashpoint with high dielectric strength have long been used as an insulating medium in transformers, switchgear and other electrical. Apr 29, 2018 bdv test means breakdown voltage test.
The megger guide to insulating oil dielectric breakdown testing. The oil also has the function of insulating the metal components of the transformer. W ater may be present in transformer oil in the form of free water, physically. This test method is applicable to insulating liquids commonly used in cables, transformers, oil. The main physical and chemical properties tested in transformer oil testing methods are the oils dielectric strength, dissipation factor, flashpoint, color, amount of solid particulate matter, water content, gas content and the oils acid number. Power transformer factory test using ieee standards. Under federal regulations, used oil is a solid waste managed under 40 cfr 279. The transformer oil is used in the transformer for insulation as well as for cooling purpose. The dielectric strength test is the third test required by the electrical safety testing standards. Breakdown voltage is a minimum voltage applied to an insulation, resulting in its breaking down and becoming electrically conductive.
These tests include dielectric breakdown, power factor, interfacial tension, acidity, and color. Oil dielectric ac test sets provide replicable, accurate measurement of breakdown voltage of insulating oils used in electrical equipment. The insulating material should sustain the voltage up to its dielectric strength. These lightweight, rugged units are designed for field and laboratory use the dts series provides repeatable and accurate measurements of the breakdown voltage of insulating oils used in electrical equipment. Wet insulation contaminates the oil, temperature dependent. Dielectric oil must have excellent antioxidant properties as it has to maintain its properties over long. Lastly, take approximately 1 litre of oil for dielectric strength test and other test required to ascertain health oil. A larger quantity of oil is needed for these tests. Power factor indicates the dielectric loss of oil and, thus, its dielectric heating. Insulation dielectric test of transformer electrical4u.
The lower the resulting breakdown voltage, the poorer the quality of the transformer oil. Caltran transformer oils fully meet astm d3487 specifications for type i and type ii mineral insulating oil in electrical apparatus. The most common world standards are preprogrammed into the controls. Oil used in transformer as the insulating material. Hp transformer oil i is inhibited type transformer oil meeting is. This test shows the dielectric strength of transformer oil.
The transformer oil under test is subjected to an ac electric field with continuously increasing voltage till the oil breaks down. To gather the sample, a clean, moisture free container must be used typically a plastic. The end result is that oxidation happens in the oil which leads to transformer sludging. Mineral oil is the most common insulating fluid and has been in use since the late 19th century. Astm d974 neutralization number the acid number of an oil is a measure of the amount of acidic materials present. Dielectric strength is an indicator used to assess insulation properties of transformer oil. The dielectric test of transformer is generally performed in two different steps, likewise, separate source voltage withstand test and induced voltage withstand test of transformer, which we have discussed one by one below separate source voltage withstand test of transformer. It is done for checking the dielectric strength of the oil of the transformer.
A test voltage is applied to the electrodes and is continuously. A car requires oil for lubrication while a transformer requires oil for insulation and cooling. Dielectric fluid for use in polemounted, small distribution and small power transformer units as an alternative to mineral oilbased dielectric fluids or those containing pcbs. Parts per million moisture test moisture is the most dangerous contaminant. Separate source voltage withstand test of transformer this dielectric test is intended to check the the ability. The dielectric strength of transformer oil is also known as the breakdown voltage bdv of transformer oil. Transformer oil testing for dielectric strength vessel preparation and elimination of the effects of moisture and contamination play a major role in successful oil testing. The dielectric strength test consists in measuring the current leak of a device under test, while phase and neutral are short circuited together. Power transformer testing power transformer factory test using ieee standards waldemar ziomek cg power systems canada ieee training, houston, texas, oct. If chopped wave is requested during ligthning impulse li test, the peak value of the chopped wave is 1. Testing of transformer oil is necessary for the obtain breakdown strength of oil. Use resulting in chemical or physical change or contamination may also subject it to regulation as hazardous waste. Inhibited transformer oils can extend the service life of transformer oil.
For the love of physics walter lewin may 16, 2011 duration. Transformer oil, a type of insulating and cooling oil used in transformers and other electrical. The test cell shall be of glass or plastic and transparent and nonabsorbent eg. This dielectric test is intended to check the the ability of main insulation to earth and between winding.
It is very often equated with breakdown voltage, but their numerical values are not equal. In transformer oil has mainly two purposes, first for insulation, second as cooling of. Just hit the start button and the test is performed. They come complete with optional carry bag and transport case. If no evidence of distress or insulation failure is observed by the end of the total time of voltage application during the dielectric withstand voltage test, the test specimen is considered to have passed the test. The dts60a is a fully automatic liquid dielectric test set, typically used for testing the voltage breakdown level of insulating oils. Moisture will decrease the dielectric strength of both the oil and the winding insulation systems. Sep 24, 2017 with the help of transformer oil testing kit we can test transformer oil learn the process step by step. Dielectric strength means the maximum capacity to withstand voltage of insulating oil. Transformer oil maintenance electric energy online.
Standard practices in transformer oil tangent delta. At the same time dielectric strength is aread more. To test the oil sample, transformer oil is poured into a porcelain vessel in which two disk electrodes, one of 8mm diameter and one of 25mm diameter, are mounted. Transformer oil hp transformer oil i hp lubricants. This test is suitable for use in acceptance specifications, in control of processing and in evaluating the condition of dielectric liquids in service. The measure result of a dielectric strength test is a current value, which has to be lower than the. Transformer furnished with pressure vacuum gauge, if the gauge read zero and does not change the transformer should be checked for possible leak. Two standardcompliant test electrodes with a typical clearance of 2. A test voltage is applied to the electrodes and is continuously increased up. The minimum acceptable rating is 24 for hydrocarbon or pcbs. Perhaps, the easiest way to explain the reasoning for proper transformer oil maintenance is to compare a transformer to a car. Put simply, a dielectric breakdown voltage test is a measure of the electrical stress that an insulating oil can withstand without breakdown.
Megger portable 60 kv and 80 kv oil test sets are the lightest on the market ranging from 16 kg to 23. Aug 30, 2019 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. It is a measure of the ability of an oil to withstand electrical stress. Pdf breakdown voltage of the transformer oils under certain. Insulating oil in electrical power apparatus serves two primary roles, as an insulator and a coolant. The different insulating materials have different dielectric strength. Dielectric breakdown d1816 the dielectric breakdown is the minimum voltage at which electrical flashover occurs in an oil. The measure result of a dielectric strength test is a current value, which has to be lower than the indicated limit from. Transformer oil dielectric loss and volume resistivity tester. The dissipation factor test is widely used as an acceptance and preventive maintenance test for insulating oil. We offer two series of devices for carrying out breakdown voltage tests and. The test is performed using a test vessel that has two electrodes mounted in it, with a gap between them.
Also, transformer extra heating will cause the winding. Biotemp vegetable oil based insulating dielectric fluid. While being recycled, used oil is regulated by 40 cfr 279. The screen test is a collection of physical, electrical and chemical tests for the transformer oil. Breakdown voltage bdv testing of transformer oil youtube. Breakdown voltage of the transformer oils under certain conditions. The power factor test is widely used as an acceptance and preventive maintenance test for insulating oil. The main physical and chemical properties tested in transformer oil testing methods are the oil s dielectric strength, dissipation factor, flashpoint, color, amount of solid particulate matter, water content, gas content and the oil s acid number. Iec 156 the dielectric strength of an insulating oil is a measure of the oils ability to withstand electrical stress without failure.
The dielectric strength test is the third test required by the electrical safety testing standards the dielectric strength test consists in measuring the current leak of a device under test, while phase and neutral are short circuited together. Jan 06, 2016 dielectric fluid for use in polemounted, small distribution and small power transformer units as an alternative to mineral oilbased dielectric fluids or those containing pcbs. A low value of bdv indicates presence of moisture content and conducting substances in the oil. As an insulating liquid, oils most important property is a high dielectric strength and as a cooling liquid, a low viscosity is paramount. Nov 17, 2019 the dielectric test of transformer is generally performed in two different steps, likewise, separate source voltage withstand test and induced voltage withstand test of transformer, which we have discussed one by one below.
For transformers with the high voltage winding um 72. Obtaining max operational life is vital dielectric fluid testing is primary diagnostic tool used to determine transformer condition. W ater content in transformer oil is extremely undesirable as it reduces the dielectric properties of transformer oil. Methyl methacrylate vessel with effective volume between 300 to. Transformer oil is a required addition to electrical transformers. This application note points to the precautions that need to be taken. The transparent, shielded lid is a key feature enabling users to see what is happening within the test chamber. Thus, the dielectric quality of transformer oil is essential to secure operation of a transformer. It is a measure of the ability of an oil to withstand electrical stress at power frequencies without failure.
Just as a car requires regular checks of both oil quality and oil level, a transformer requires the same proactive treatment. Power factor test the power factor of insulating oil equals the cosine of the phase angle between an ac voltage applied to oil and the resulting current. The megger guide to insulating oil dielectric breakdown. Epa and dtsc make no express or implied warranties as to the performance of the abb biotemp vegetable oilbased insulating dielectric fluid technology. That means at which voltage dielectric strength of transformer oil between the electrodes has been.
However, in california, used oil is managed as hazardous waste until. Bdv means breakdown voltage, also named as dielectric strength valve. In the experiment proper, we considered only the acidity, whose concentration in the transformer oil increases with aging if the. Basics, maintenance, and diagnostics ix contents continued page 6.
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