Ensure variation in secondary volts as the taps are changed and compare the results with manufactures test report or ratio mentioned on transformer nameplate. A presentation ontransformer testing using dpatt3bi 2. For the purpose of bdv test, oil sample from transformer is taken in a sample bottle. However, in specific situations where medium power transformers are. Ideally these windings would have zero resistance, but in reality, transformers experience power loss due to load resistance, which can easily be tested with an ohmmeter. This test also performed as a routine test of transformer. Transformer can increase or decrease the voltage with corresponding decrease or increase in current. Thermal withstand capability has to be demonstrated by calculation as testing. Routine tests and type tests of transformers electrical4u. Following is an approximate sequence for transformer testing. Apr 29, 2018 bdv test means breakdown voltage test.
Free online quiz test transformer theory and practice. Testing of power transformers seems like a similar experience. Losses of transformersthe transformers are made of 2 types of materials. Electrical transformer is a static electrical machine which transforms electrical power from one circuit to another circuit, without changing the frequency. We will also look at the latest developments in transformer design, construction, testing. Field testing of a power transformer before putting into service 50mva. Ltc because in order to change taps, the transformer has to be taken out of service or at least disconnected from the load. In transformer oil has mainly two purposes, first for insulation, second as cooling of.
Alok pandey assistant professor assistant professor department of electrical department of electrical engineering engineering a seminar on high voltage testing of electrical transformer presented by hari shankar singh. Oct 18, 2012 power plants and substations are the major components of the energy system. On distribution transformer this type of switch may also be used to change nameplate voltage andor configuration. A transformer has no moving parts and is a completely. As we know that there are mainly two major parts of transformers i. Current transformer testing swp check this is the latest process zone version before use. In this article, you will learn different types of transformer testing methods, test setup, and their acceptance criteria. The transformer school of electrical engineering and.
May 10, 20 so transformer ratio test is an essential type test of transformer. The procedure of the transformer ratio test is simple. Transformer calculations quiz electrician exams practice. Threephase solution to speed up and simplify power transformer testing three wires are all you need testrano 600 is connected to the highvoltage and lowvoltage side of the transformer by using specially designed multipurpose cables. The checklists are intended to help inspectors keep track of the numerous aspects of an electrical installation. If the voltmeter is showing voltage that is sum of both primary and secondary voltage, what will be marking at b choose x1 and x2. One of the common tests done is ttr or transformer turns ratio. The most effective preventive programs are oil sampling and testing, electrical testing and visual inspection. Sasidhara rao indian institute of technology madras 7 testing of transformers the structure ofthe circuit equivalent of apractical transformer is developed earlier.
It is done for checking the dielectric strength of the oil of the transformer. For categories of power transformers and reactors which have their own iec standards. All materials and relevant documentation to this testing works shall be checked by the responsible personnel prior to the commencement of testing activities. Wherever they are used, it is critical for the installation team to complete several different tests prior to installation. A test set operator connects the leads, pushes the buttons, and records the results. Minimum insulationresistance values of transformer insulation should be in accordance with manufacturers published data. Transformer testing allows this aging process to be quantified and tracked, to help predict replacement intervals and avoid failures. The methods used during tests and measurements of the power transformers, test and measurement circuits, calculations and evaluation criterias are included in this manual. It is also done at site to ensure healthiness of a transformer that is to check loose connections, broken strands of conductor, high contact resistance in tap changers, high. The transformer the principle parts of a transformer and their functions are.
Insulation levels, dielectric tests and external clearances in air. The purchase, preparation, assembly, operation and maintenance of transformers represent a large expense to the power system. Protec offers a large catalog of electrical test equipment to help you. The performance parameters of interest can be obtained by solving that circuit for any load conditions. To understand mvhv electrical components for electrical switching, testing and protection requirements. It can be designed to step up or step down voltages and works on the magnetic induction principle. This pdf contains 77 electrical inspection checklists taken from the 2014 electrical inspection manual with checklists. Additionally covered are the proper methods for drawing transformer fluid samples and basic introduction to the analysis of such samples, and hands on testing of a. In accordance with the present invention in one embodiment there is provided a new method for testing of a threephase electrical power transformer, as shown in fig.
The checklists are in pdf format and can be completed electronically or printed and used as hard copy. So for ensuring proper performance of electrical power transformer, voltage and turn ratio test of transformer one of the important tests. So testing of oil is done according to voltage rating. This book provides a comprehensive resource on technical, application and operational aspects of all types of electrical transformers and power systems, covering operation theory. Testing and diagnostics of power transformers brochure. It evolved from the simple gonogo verdict into a sophisticated segment within transformer manufacturing.
The core, which makes a path for the magnetic flux. The secondary coil, which receives energy from the primary winding and delivers it to the load. A transformer is an electrical apparatus designed to convert alternating current from one voltage to another. This test shows the dielectric strength of transformer oil.
The resistance of an alternating current ac transformer is held within the wires wound around its core. This ms excel spreadsheet is actually detailed instruction for each procedure necessary for correct testing of power transformer. Transformers that increase stepup or reduce stepdown electrical voltage are used in many industrial and public utility applications. Modern transformers are designed to closer tolerances than transformers in the past. Electrical transformers and power equipment anthony j. An introduction to electrical diagnostic testing of power transformers feature transformer. Advanced diagnostics provide a complete health check for power. However, for installed transformers, a field test can provide the baseline curves. Prior to testing, short the primary winding of the ct under test by connecting h1 and h2, then short the secondary winding of the ct under test by connecting x1 and x2x5. Most of the times it is necessary to hire a third party in order to conduct the function testing of electrical systems. Testing power transformers highvoltage transformers are some of the most important and expensive pieces of. These tests are done mainly in a prototype unit not in all manufactured units in a lot. Get access to premium hvmvlv technical articles, electrical engineering guides.
Mainly two types of transformer testing are done at manufacturer premisestype test of transformer and routine test of transformer. Potential voltage transformers testing and precommissioning check potential voltage transformers can be broadly divided in to two type. The core of a transformer is made of iron whereas thewinding which is wrapped over the iron core is made up ofcopper. In addition there are contaminations caused due to chemical interactions with windings and other solid insulations, catalyzed by high operating temperature. An electrical power transformer has to go through a number of transformer testing procedures for confirming its specifications and performances. Use megger mit1020 to measure insulation resistance. Transformer calculations quiz electrician exams practice tests. The purpose of a distribution transformer is to reduce the primary voltage of the electric. All of these factors affect the amount of testing necessary to certify that a transformer is ready to be energized and placed in service. Dielectric strength means the maximum capacity to withstand voltage of insulating oil.
Some tests are done at manufacturer premises before delivering the transformer. Transformer theory quiz questions electrician practice tests. Testing power transformers highvoltage transformers are some of the most important and expensive pieces of equipment required for operating a power system. Type test and routine test of transformer electrical mastar. Aside from power transformers, the main parts of such a plant include instrument transformers, the protection and. Medium voltage and high voltage and system components with reference to the types of cable used, circuit breakers, transformers, instrument transformers, power capacitor, surge arresters, switchgears, protection and control devices. The test setup and procedure of the frsl test is the same as for shortcircuit. Transformer oil and other insulating liquids suffer from electrical and mechanical stresses while a transformer is in operation.
The primary coil, which receives energy from the ac source. For confirming the specifications and performances of an electrical power transformer it has to go through numbers of testing procedures. Power transformers are a critical and essential part of each power transmission system. To ensure that the product is fit for its intended use standards iec standards iec 60076 part 1 part 14 specification for transformers ieee. How to use an ohmmeter to test an ac transformer sciencing. Both short circuit and open circuit tests are conducted to measure the core and winding losses of transformers. Heres a summary of the current transformer testing paper. Back to the basics current testing valence electrical. In the absence of manufacturers published data, use table 100. By brandon dupuis an introduction to electrical diagnostic.
Insulation tests on current transformers rated 600v or less are usually performed at vdc. The cables, which support a 4wire kelvin connection, only. Basics, maintenance, and diagnostics xi contents continued page 9. Testing will commence only after the equipment is completely installed as per approved method statement for the installation of the transformer and released for testing commissioning. In this book we have laid down important aspects on transformer. For this purpose, power transformers are widely used in the industry. To prove that the transformer meets customers specifications and design expectations, the transformer has to go through different testing procedures in manufacturer premises. Page 3 of 9 standard work practice sp0507 ver 5 ergon energy corporation limited abn 50 087 646 062 ergon energy queensland pty ltd abn 11 121 177 802 rated knee point voltage 950 volts, maximum secondary winding resistance 3 ohms. Shortcircuit withstand capability of power transformers. It is equivalent to the procedure used for performing a shortcircuit impedance test on an autotransformer. Testing a transformer electrical engineering stack exchange. Power transformer testing and commissioning guidelinesoil.
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 could not ingress in the. The objective of testing is to ensure quality to ensure that the products manufactured have met the requirements of customer specificationstandard to prevent accidents which may occur if a failed product is put into service. Sweep frequency response analysis sfra has become a powerful tool in advanced power transformer assessments and probably one of the main and first tools used to diagnose troubled transformers or as a regular maintenance test. It is carried out as a type test as well as routine test. You have reached 0 of 0 points, 0 not categorized 0% question 1 of 15. Diligent testing ensures the electrical, thermal, and mechanical suitability of the. Historical test data is valuable for determining damage to the transformer after a fault or failure has occurred elsewhere in the circuit. Sep 26, 2017 for confirming the specifications and performances of an electrical power transformer it has to go through numbers of testing procedures. Apply 3 ph, 415v to high voltage winding of the transformer and,ensure the induced voltage on the low voltage terminals at all taps. Sfra testing should be performed periodically during the service life of the. Electrical transformer basic construction, working and.
A 3phase transformer, like any transformer is more naturally inclined to be an isolation transformer therefore, measuring the secondary voltages with respect to neutral may be totally meaningless because the secondaries will not normally be galvanically connected to neutral. The voltage ratio of a transformer is the ratio of the rms terminal voltage of a. Remove the neutral ground and isolate the ct from any associated burden. The core of a transformer is made of iron whereas thewinding which is wrapped over. There are a multitude of checks and tests performed as a transformer is being assembled at a substation.
Primary winding secondary winding apply 500v for 1 minute. Working principle, construction and types of transformer. These can be of electromagnetic of capacitive voltage transformer type cvt. Power plants and substations are the major components of the energy system. Secondary winding secondary winding apply 500v for 1 minute. Electrical switchgear and power transformer testing. To understand the nature of ratio testing it is important to understand the applicable definitions.