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