Transformer-bushing-testing, transformer bushings when bushings are new, they should be doble tested as an acceptance test. refer to the m4000 doble test set instructions, the doble bushing field test guide, and the manufacturer’s data for guidance on acceptable results.. A transformer bushing is an insulating structure that facilitates the passage of an energized, current-carrying conductor through the grounded tank of the transformer., bushings provide an insulated path for energised conductors to enter grounded electrical power apparatus. they are a critical part of the electrical system that transforms and switches ac voltages ranging from a few hundred volts to several thousand volts..
Visual inspection of high voltage bushings. porcelain bushings should be regularly checked for cracks and/or contamination. if the bushing is damaged or heavily contaminated, leakage current will become excessive, sometimes appearing as carbon tracking, or "treeing", on the bushing surface., acceptance and routine maintenance tests most often used for checking the condition of bushings are doble power factor tests.the power factor of a bushing in good condition will remain relatively stable throughout the service life. a good indication of insulation deterioration is a slowly rising power factor.. Bushings are necessary and vital elements of the electric supply system – allowing critical equipment such as breakers and transformers to operate efficiently. with the benefit of decades of bushing testing and analysis, doble provides tools, techniques, and services to identify signs of incipient bushing failure., the test is made in line with iec standards or, on request, according to relevant ieee standards. the test is made at room temperature, and for transformer bushings with the lower end submerged in oil. capacitance and tan δ are measured in steps up to the power frequency withstand voltage, which is maintained for one minute..
The transformer turns ratio test is used to make sure that the ratio between the windings of the primary and secondary coils follow the proper specifications. this test ensures that the transformer will provide the proper step-up or step down in voltage., - the power-factor test is the most effective known field test procedure for the early detection of bushing contamination and deterioration. this test also provides measurement of ac test current which is directly proportional to bushing capacitance..
Dielectric test of a transformer is one kind of insulation test. this test is performed to ensure the expected overall insulation strength of the transformer. there are several tests performed to ensure the required quality of transformer insulation; the dielectric test is one of them.