The ratio of current flowing through capacitive part to that of resistive is tan delta. Drytype transformer testing introduction the primary concern with all transformers and also the key indicator of life expectancy is the condition of the insulation system. The cable, winding, current transformer, potential transformer, transformer bushing, on which tan delta test or dissipation factor test to. Insulation diagnostic methods for transformers and bushings jill duplessis, megger. A very lowfrequency test voltage is applied across the equipment whose insulation to be tested. Mainly two types of transformer are done by manufacturer before dispatching the transformer mainly 1 type test of transformer and 2 routine test. The test methods used by the authors for presenting the results are described. Delta has the most professional technical expertise in transformers based on over 40 years experience in product design manufacturing.
In this product information, the terms tangent delta, tan. Calibration equipmenttan deltasubstation testingegyptrol. For cts with metallic bellows, the oil should be present upto the top of the bellow for proper functioning. Electrolytic capacitors fail due to leakage or vaporization of the electrolyte inside. It is used to test the level of degradation in insulation materials of electrical machines and power cables. The cable, winding, current transformer, potential transformer, transformer bushing, on which tan delta test or dissipation factor test to be conducted, is first isolated. Also know as power factor and dissipation factor testing, these state of the art instruments give the user a wide range of results for qualitative cable assessments such as degradation and lifetime estimations on mv and hv. This is done to try to predict the remaining life expectancy and in order to prioritize cable replacement andor injection.
Advantages and disadvantages of tan measurements as a function of voltage source. These tests give a wider picture of the overall quality of the insulating oil, and will indicate if there is any contamination. The m4100 is the industry standard for power apparatus and insulation testing. Hipot test is typically used for acceptance testing or after transformer repair testing. This is used when specimen do not have two specific points isolated from ground for tan delta measurement e. With regards to your statement relating to whether tan delta testing could have any adverse effect on transformer health, the following. If not indicated, the description is for a twowinding transformer. The dissipation factor of new oil should not exceed 0. There are various test required on transformer to conform performance of transformer.
The cable, winding, current transformer, potential transformer, transformer bushing, on which tan delta test or dissipation factor test to be conducted, is first isolated from the system. The paper presents in uence of external factors on results of bushing dissipation factor tan and capacity measurements performed on not energized transformer as well as with operation voltage using online method. In other words, make the current flow only in capacitance region omit inductance in the. Since temperature correction factor for tan delta depends on make, type and alsoaging conditions, the correction factors for different types makes. Tan delta is a a diagnostic test conducted on the insulation of cables and winding. The power transformer of rating 10 kva, 1 v440 v, 3phase, 50 hz, dyn11 has been specially developed inhouse for carrying out sfra testing by. Transformer bushing tan delta test is similar to the ct tan delta test and lnk to the artivle on ct tan delta test is. Dc current is allowed to flow through the insulation. The residual of this comparison is measured and resolved into inphase watt loss and quadrature current components. The power loss is also a very convenient number when checking the accuracy of measurements. Utilities should look into such issues with seriousness.
Transformer reactor winding, cts without test tap etc. Power transformer capacitance and dissipation factor test. Insulation power factor testing of power transformers. There are discussed methods and real cases of measurements, with emphasized di erences in results interpretation. Tan delta test is done in transformer to measure the insulation quality of transformer oil.
With delta s expertise and test capability in electromagnetic compatibility and international safeties, delta is able to help you design products which fully meet emi and safety requirement. Interpretation of sweep frequency response analysis sfra. Its unique combination of test capabilities and artificial intelligence analysis software makes it the power industrys most trusted power factor tan delta instrument. One of the insulation tests we performed on the power transformer is the tan delta test. In addition some other tests are also carried out by the consumer at site before commissioning and also. To get the benchmark reference reading of equipment when the equipment is new, clean, dry and free from impurities.
Special costumer standards or values are not included. Typical limiting values of sub station electrical equipments. The eltel automatic capacitance and tan delta test sets operate on the transformer ratio arm bridge principle. Tan delta test loss angle test dissipation factor test electrical4u. It is used to measure the deterioration in the cable. Predicting the remaining life expectancy of the equipment under test. Tan delta test for transformer capacitor electrical resistance. The current from the device under test is compared to the current of an internal reference capacitor. Tan delta test sets, which come as both standalone and vanmounted systems, are increasingly common components in todays test procedures. This test measures the level of insulation degradation, allowing the user to make educated decisions as to maintenance or replacement priorities. Herewith some information relating to tan delta power factor and capacitance test on transformers from our perspective. The complete procedure, from the initial cluster variable analysis to. This test may be required to be performed during the acceptance testing stage to establish a baseline reading for future test comparison.
Tan delta, capacitance, dissipation factor measurements and for exciting current test. These two tests are considers as is the perfect yard stick for failure analysis and also for aging effect of the power equipment under use. In uence of external factors on results of bushing tan. It is typically used for test specimen that have small capacitance and as a result the power factor tan delta of the test circuit is rather high. Tan delta test for transformer free download as word doc. Multiple frequency insulation test on a healthy transformer influenced by conductive losses influenced by problems that add to. This is a diagnostic test, not a passfail or gonogo test like a withstand test where the load either holds the test voltage or fails. Delta4000 series is a fully automatic 12 kv insulation power factor dissipation factor tan delta test set designed for condition assessment of electrical insulation in high voltage apparatus such as transformers, bushings, circuit breakers, cables, lightning arresters, and rotating machinery.
Functionality of the vlf tan delta basic version is accordingly, see figure 3a. The oil tan delta otd is a laboratory instrument, which measures the tan delta, resistivity and relative permittivity of insulating liquids. Test lab cast resin transformers christopher kammermeier gttp document no 02. Correlation of dielectric loss data collected at different vlf test voltages 40. Equipment test data permissible limits reference a transformer oil a bdv at the time of first charging 600 kv gap 2. Measure with ac test signal, use ohms law to calculate. Heating can be caused by either wrong connection or the use of underrated capacitors. In electrolytic capacitors heating can cause the formation of gas inside which can explode through the vent provided. Very low frequency vlf tan delta testing is a precise and nondestructive method to provide information on the extent of ageing in cable insulation. The external insulation types of the bushing are brown porcelain housing insulators and grey uv protective silicone rubber sheds. Oil is considered as practical capacitor and therefore there will be some resistance in parallel. The ac hv test value should not surpass 75% of the factory test value.
Detecting the incipient weaknesses in hv insulation. The test as it is termed, measures the capacitance and dissipation factor or loss factor of the transformer insulation system. Insulation resistance test of transformer is one of the most important transformer tests we can perform this test at factory or site this test can be classified under type test, routine test, precommissioning and commissioning tests, periodic maintenance transformer tests you can know more about transformer testing and its. Tan delta, also called loss angle or dissipation factor testing, is a diagnostic method of testing cables to determine the quality of the cable insulation. Scope this is a general test description for castresin and drytype transformers. Insulation diagnostic methods for transformers and bushings. In other words, if any one criterion indicates the system is action.
Standard practices in transformer oil tangent delta. The default test configuration is the ust ungrounded specimen test measurement, in which the transformer. Ensure that cap in the tan delta measurement point in the bushing is grounded. This test is particularly useful in showing changes. For dry type transformers, the insulation system consists of the cast resin winding and core insulation and the termination system insulation e. Tan delta tests are carried out for transformer bushing and for the transformer winding. Insulation resistance test values electrical apparatus and systems table 100. Now, neta and doble standards recommends that for new transformers the dissipation factor or insulation power factor should be 0.
Chinsun 52kv 500kv transformer bushing and wall bushing. In this article we are going to discuss in detail about transformer winding tan delta test. When ac hipot tests are used for routine maintenance, the power transformer can be examined at. New transformers should have a tan delta value of 0,5% or less. Tan delta is also known as the loss angle or dissipation factor. Tan delta test loss angle test dissipation factor test. To know the electrical properties of the insulating oil, the tan delta test and to know the chemical impurities the dissolved gas analysis dga of the oil is conducted. In this regard, this article focuses on an electrical tests called power factor or tangent delta test which is one one the the recommended and most popular diagnostic test for power transformers.