FAT or Factory Acceptance Testing is perhaps the last step the transformer goes before leaving the factory to ensure each of them adheres to the set design and operational limits. In this piece we are going to detail the FAT concepts, including its rationale and in the broader context the role it plays in confirming the performance of the transformer. To that end, we will elaborate on some of the important testing measures including examination, functional testing and check, and the involvement of quality assurance requirements. This paper articulates how FAT reduces the chances of failure occurrence, maintains adherence to the set industry level, and improves the whole transformer life span. In short in this article, the reader will be able to comprehend the significance of FAT in the quality of the finished product in the transformer production process.
What is Factory Acceptance Testing (FAT) for transformers?
СIТ or Сertification of IT is the process of practice with the durability of stress on all aspects of the manufacturing process in ways where all premises within are put to a thorough test before the product is dispersed to the market. This testing includes many tasks – inspection, evaluation, and verification – to prove that the transformer works and has all the required features from the specification of the customer, and other requirements and standards. FAT are some tests in the last stages of the production that help to fix any mistakes; that help to minimize the use of resources while working on the transformer. The set of tests has shown that manufacturers as well as end users trust the full casing of the transformer.
Definition and purpose of FAT in transformer manufacturing
Factory Acceptance Testing (FAT) is a crucial step when commissioning new, replacement, or refurbished equipment; however, this is an element that, in many cases, is omitted altogether or neglected to the point that there is essentially no testing carried out at the manufacturer’s works. To prevent such negligence from occurring it is paramount that both the supplier and recipient take this process seriously, a positive relationship is further contributing towards achieving the final goal of successful commissioning and testing. FAT is the practice of ensuring that the manufacturer’s documentation is complete, final assembly testing of the equipment has been performed, and that the equipment meets the specified requirements and can be used within the buyer’s scope of work. FAT can be said to be following international standards more or less like IEC 60076 but the idea here is the vendor or manufacturer should provide evidence that the equipment will be reliable and function properly in its intended application. what FAT provides is quality assurance in that both manufacturers and end users have to be involved thereby encouraging trust among end users concerning the entire lifetime performance of the transformer.
Key components of a transformer FAT
Visual and Dimensional Inspection
This step checks whether the transformer constructions are by the designs and construction drawings. It is important to check labeling, dimensions and any physical damage. Tolerances are generally given in millimeters and are correlated to standards, e.g. IEC 60076.
Insulation Resistance and Dielectric Testing
Included in the testing are insulation resistance evaluation employing a megohm meter and dielectric tests which comprise Applied Voltage Tests and Induced Voltage Tests by IEC or IEEE standards. These could include dielectric strengths that would require an insulation resistance of more than 1 GΩ neutralized by an allowance that is recommended for the transformer’s rated voltage.
Ratio, Polarity and Phase Relation Tests
The ratio of the transformer winding turns must meet the specifications outlined in the design as it affects the transformer’s performance. Usually, such variances are not more than ±0.5%. Correct internal connections are verified by polarity and phase relation checks.
Winding Resistance Measurement
This type of test assists both in evaluating the condition of the windings and detecting possible defects, for instance, loose connections. The value of the resistance, expressed in milliohm should be the same in different phases with a difference of not more than 2%.
Temperature Rise Test
In this case, It examines whether the transformer does not operate above the thermal limits permissible under normal operating abuse conditions. For instance, there is a requirement under the IEC standard that the rise in temperature in the top oil makes a ceiling of 65 °C.
Loss Testing
This practice focuses on evaluating the efficiency of a transformer by measuring losses at rated voltage and current. Mostly acceptable levels of no-load loss should be around ±10% of the design value while load loss levels should meet the set contract specifications.
Functional Tests of Auxiliary Equipment
Auxiliary systems including protection relay, cooling fan, and oil pump have to be tested to ascertain their actual performance. For instance, relay trip timing (typically ≤50ms) and the general performance of the cooling system need to be within the set requirements.
Oil Quality Analysis
Tests performed on oil-filled transformers include a minimum 30 kV dielectric breakdown voltage based on IEC 60156, water seal content of not more than 10 ppm according to IEC titles, and how acid the oil was to meet insulation plus cooling needs.
These outlined components were collected to validate the design, construction, and transformer operation not only from the customer requirements perspective but also from the regulatory perspective.
How FAT ensures quality and meets customer specifications
Covering all bases ensures quality and conforms to the customer’s request during the Factory Acceptance Testing (FAT) as a result of a rigorous focused process. Using advanced diagnostic tools, extensive evaluations of the equipment performance are performed, and verification of compliance with functional design specifications as well as safety tests are performed following international standards such as IEC, and IEEE among other standards. Further, enhanced proportions ensure a thorough examination of electrical and mechanical integrity whilst all outcomes can be traced back for record purposes. This stepped approach allows the obtaining of power generation equipment that is dependable, efficient in service and meets the expectations of the client and the regulations set.
What are the essential tests performed during transformer FAT?
FAT or Factory Acceptance Testing for transformers involves several checking procedures to confirm that the specifications requirements and expected performance operational requirements are satisfied. In most instances the following tests are crucial:
Visual and Dimensional Inspection: Validates physical integrity, dimensions, and assembly of the transformer as built in comparison to the design drawings.
Winding Resistance Measurement: It checks whether a transformer has its windings intact and also in uniformity.
Ratio and Vector Group Check: Check if the rated transformation ratio and the phase windows are all correctly aligned.
Insulation Resistance (IR) and Polarization Index (PI): This test evaluates the quality of the insulation and its current state.
Dielectric Tests: These include applied and induced voltage tests for dielectric strength mechanization under wa orking environment.
No-Load Loss and Load Loss Measurement: Indicates the energy efficient rating of the total operation along with load losses.
Impedance Test: Indicative measurement of short circuit impedance to the stated values.
Temperature Rise Test: This substantiates thermal performance benchmarks for transformer operation under designated load.
Oil Testing: If applicable, this checks the purity and dielectric strength of insulating oil.
Individually and together the tests above substantiate the stated operational thermal and electrical characteristics of the transformer in its final form and the requirements of the respective projects.
No-load and load loss tests
The crystal assessment test examines the core losses sustained by the transformer in magnetized conditions but without any load attached to it. This phenomenon is mostly induced by hysteresis and eddy currents in the core material. In this case, the primary coil is provided with voltage while the secondary coil is left open, and the power consumed in this case is recorded.
Now Talk about the Transformer Efficiency Test or Transformer Load Loss Test including copper losses occurring due to resistance of the windings at the full load condition. This involved passing a current through the windings equal to the rated load and recording the power lost as heat instead. These tests all measure the efficiency and energy performance of a transformer and compliance with the operational requirements and industrial standards.
Insulation resistance and voltage withstand tests
The Insulation Resistance Test determines whether the insulation of a transformer can sufficiently hold back the current flow under normal operating conditions and whether it is in good condition. This test is performed with a megohmmeter, which passes a direct current through insulation and takes resistance readings, usually in megohms. The tolerable values of insulation resistance depend upon ratings of the transformer but again some guidelines suggest that the minimum value can be given by the formula \(R \geq \frac{(kV+1) \times 1,000}{\text{M}\Omega}\), where \(kV\) is the rated voltage of the transformer.
The Voltage Withstand Test is also known as the high potential or hipot test in this case, which determines whether the insulation layer of the transformer can withstand abnormally high voltages for nonsustaining periods. Through this test, an AC or DC test voltage 2 to 3 times the rated voltage, or more as per the standards such as IEC 60076, is employed on the transformer for a set time, usually 1 minute. Good test results will mean that no insulation failure or breakdown, even measurable, occurred throughout the test. These tests aim to evaluate and prove the transformer’s performance and safety in heavy-load operations.
Ratio and phase displacement tests
The purpose of ratio and phase displacement tests is to confirm that the right transformation ratio and phase displacement exist between the transformer’s primary and secondary windings. During these tests, we measure the voltage ratio across the windings and the phase angle displacement between them under specified conditions. The results are obtained using measuring instruments and are checked against the manufacturer’s data as well as the industry codes, for instance, IEC 60076. These tests are imperative for the appropriate operation of the transformer itself and its integration into the power system.
How does FAT differ for single-phase and three-phase transformers?
According to HACOMAT, the Factory Acceptance Test does vary slightly between the three-phase and single-phase transformers. In terms of functionality testing, the transformers are tested on their core functionality, their ratio of voltages, their insulation resistance, their single-phase no load and single-phase full load efficiencies and vice versa. The tests conducted on three-phase transformers during the FAT become a bit more troublesome as there are tests for phase-angle, balance between the three active phases, denoting interconnection of the triad and the performance of the transformer’s vector group. It is also essential to conduct the phase sequence test and the harmonic distortion test, as three-phase transformers have more operational complexity to be evaluated. Although the test aim remains the same, in testing, operational procedures and calibrations are influenced by the configuration of the individual transformer.
Specific tests for single-phase transformers
To test single-phase transformers, a specialized sequence of functions is formulated to operate, withstand and perform efficiently. Some of the major tests are:
Transformer Turns Ratio (TTR) Test
The TTR test is meant to check the ratio of the primary and secondary winding as it was designed. These ratios can have a tolerable deviation of approximately ±0.5% but anything more substantial may point towards tan issues with the winding housing the two components.
Winding Resistance Test
Micro-ohmmeters are used to measure the resistance of the transformer’s primary and secondary windings through a micro-ohmmeter. The manufacturer specifies a typical resistance value which must not be too far off the range determined by the transformer rating. Furthermore, any drastic difference between phases is a cause for concern and warrants an investigation into loose connections or degraded conductors.
Insulation Resistance Test ( IR Test )
A megohmmeter which has a rating of 5 kV for units that have a rating above 1 MVA is utilized to take IR measures which are primarily the strength a dielectric material has against both ground and windings. If an IR value below one GΩ is achieved, then that is a cause for concern as that would indicate insulation concerns. A lower IR reading would further indicate the risk of insulation burst.
Excitation Current Test
To confirm whether the excitation current aligns with the expectations of the design or not, the primary winding gets rated voltage applied with a secondary circuit that is subsequently opened so that the current can be measured. It is common for the excitation current of single-phase transformers to fall between 0.5% to roughly 2% of the rated current.
Dielectric Withstand Test (Hi-pot Test)
This high voltage ‘Hi-pot’ test determines if the transformer can be operated at overvoltages without breakdown of insulation. The usual test voltages for this purpose are 2V + 1000 V, where V is the rated voltage, and the voltage is applied for 60 seconds.
Load Loss and Impedance Test
These rating test conditions are designed to assess the copper loss and impedance voltage in the transformer secondary during the rated load. Taking into account tolerances, the impedance is usually within the +2% range of the designed value.
No-Load Loss Test
This test assesses core losses that occur when the rated voltage is applied while the second side is shorted. Acceptable core loss depends on core material and transformer design but it should not deviate from the trademark core loss which is due to the factory design.
These tests, when undertaken in a methodical approach, assist in determining the operating status of single-phase transformers and hence compliance with the performance standards dictated by IEEE, IEC and other organizations.
Additional requirements for three-phase transformer FAT
In the case of FAT for transformers which are three-phase type, a vector group verification test should be performed as an additional consideration, which validates the phase displacement and connection configuration, and in addition, this also enables the short circuit impedance measurement which also a must and must be in the designed values to ensure that the load is balanced across the phases. Moreover, under full load conditions, a temperature rise test is performed to assess the thermal performance as well as the performance of the insulation materials. These tests are mandatory for the transformers due to the reason that they assist in ensuring that the standards set by bodies such as IEC 60076 or others are fully complied with thus assisting in quality operation in real workforces.
What are the IEEE standards for transformer Factory Acceptance Testing?
According to the provided information, IEEE C57.12.90 highlights the tests that should be performed before signing an acceptance certificate. It is about the FATS, as various tests are carried out on transformers as routine, custom, or type tests. These types of tests include voltage tests, insulation resistance tests, and many more such as ‘tests which need to be completed’ for confirm justification and assurance. Temperature rise tests and some impulse voltage tests are required under type tests to ensure requirements & specifications set by the designer are met. Other specific tests such as short circuit tests or sound tests are done because of the customer mentioned or system-wise. Meeting these standards enables the transformers to meet the requirements for performance, safety, and reliability expected in the industry.
Overview of relevant IEEE guidelines
In short, IEEE C57.12.90 describes elaborate testing procedures that transform has to pass through to be in line with some vital measures of performance. Three basic types of tests are included in the standard. Such routine tests as measurement of insulation resistance and winding resistance check the quality and functionality of the transformer. Type tests, which include thermal and voltage impulse tests, validate that the product is fit for use in terms of design and performance. Routine tests for special conditions like short circuit tests cater for such needs which are situational or system-oriented. The procedures are aimed at providing evaluation of operating ability, robustness, and safety of transformers when used for various applications, and in meeting the expectations of the students with the practice of engineering in the industry.
How manufacturers apply IEEE standards in FAT
For transformers to be deployed, so that they meet operational and technical criteria, manufacturers make use of IEEE standards in Factory Acceptance Testing (FAT). Routine tests are performed to be able to support insulation resistance, winding resistance and dielectric strength tests which conform to purpose-specific IEEE standards. For instance, the insulation resistance test should oscillate around acceptable minimum values based on transformer ratings and most times not less than 10 MΩ for small distribution transformers; the higher the transformer’s voltage classes, the higher the rating. Impulse voltage withstands tests are carried out to confirm the conductivity of surrounding systems whilst type test analysis assesses thermal performance by measuring temperature rise to ranges with anticipated values over time for example oil immersed transformers employ a 65 degrees Celsius rating. Among these parameters, fault current and duration can be accurately simulated, and permitting conditions under which short circuits withstand capability framework functions, tests of mechanical strength and thermal performance are validated. By carefully undertaking these evaluations and others based on the standards of IEEE norms, approved transformers are then manufactured to serve the needs of the industry in terms of reliability, safety and efficiency.
How do customers participate in the transformer FAT process?
Bundle up because I am about to blow your mind! During the FAT, a verification testis performed at the Supplier’s facility or test center, the clients are expected to be present at the test facility during the scheduled FAT procedures to witness and ensure conformity to the set specifications and standards. They also take a glance at the submittal planning to ascertain whether particular evaluations have been included. Such evaluations may include dielectric, thermal and mechanical ones for instance. During the procedure, clients see the tests being performed in a controlled environment, see the results as each measurement is done and even direct certain changes to be made in parameters if necessary. Their participation ensures that transparency is practiced, fundamental requirements in relations are satisfied and any issues which could be raised about the goods before they are shipped can be raised and rectified at that point.
Customer involvement and witness testing
The customer witnesses testing which drives the operational and contractual aspects of a particular transformer. In general, during the witness testing the customer is interested in confirming particular parameters that cover the following aspects:
Dielectric Testing
Lightning Impulse: In other words, this validates the withstand voltage levels to 250 kV for instance for a 72.5 kV transformer.
Power Frequency Voltage: Aims to prevent destruction of the insulation which is for example the case of 140 kV applied for 60 seconds.
Thermal Testing
Winding Temperature Rise: Aims at ensuring that the temperature under oil does not exceed for example 65°C for oil-immersed transformers.
Cooling Performance: Refers to the verification that the cooling systems fitted on the transformer allow it to remain thermally stable while under load.
Mechanical Testing
Short-Circuit Withstand: Generally speaking this is meant to test the mechanical depth of the windings by exposing them to short-circuit conditions, generally limit tested to rated short-circuit currents.
In these cases during the defects if any, the customers thoroughly verify these parameters with the specifications. Whenever the readings obtained from the calibrated instruments are outside the acceptable range, immediate corrective action is undertaken in the field. Such active involvement increases the trust in the working of the equipment and minimizes the chances of problems arising after the installation.
Addressing customer feedback during the FAT
At the stage of the Factory Acceptance Test (FAT), there is a need for a well-defined approach and objective criteria to address customer issues and requests. It starts with comprehensive written records of everything that was said during the consultation. Every concern raised is addressed in terms of electrical, thermal, or mechanical design criteria. Emphasis is directed towards those comments which relate to the requirements of international standards or contract obligations. Then, in the absence of satisfactory information, we provide immediate evidence through on-site measurements or testing for the agreed figures. Communication was precise and straightforward so that the customers knew what actions or validations were undertaken. Finally, all relevant comments are identified and incorporated in the post-FAT reports or other documentation signed by the parties, so that all reasonable measures needed to be taken have been implemented and therefore trust in the equipment reliability is enhanced.
References
Frequently Asked Questions (FAQ)
Q: What is a fat transformer and how does it differ from a regular transformer?
A: A fat transformer is an adaptive vision transformer model that can simultaneously process local and global contexts. It differs from regular transformers by using a wider architecture to extract local features and global information more effectively, leading to improved accuracy and state-of-the-art performance in various computer vision tasks.
Q: How does the view segmentation work in a fat transformer?
A: View segmentation in a fat transformer involves dividing the input image into multiple views or segments. This approach allows the model to analyze and explore different parts of the image simultaneously, enabling it to extract local features and global context more effectively. The segmentation process helps the transformer to adapt to diverse input types and improve overall performance.
Q: What is the short-circuit impedance of a fat transformer?
A: The short-circuit impedance of a fat transformer refers to the total impedance (resistance and reactance) measured when the secondary winding is short-circuited. This parameter is crucial for determining the transformer’s behavior during fault conditions and its ability to limit fault currents. It’s typically expressed as a percentage and is an important consideration in industrial applications.
Q: How is the DC resistance test performed on a fat transformer?
A: The DC resistance test on a fat transformer is performed by applying a DC voltage to each winding and measuring the resulting current. This test helps determine the winding resistance and can identify issues such as poor connections or damaged windings. The test is typically conducted as part of routine maintenance and during the manufacturing process to ensure the transformer meets specifications.
Q: What is the significance of the voltage test in fat transformers?
A: The voltage test, also known as the dielectric strength test, is crucial for fat transformers to ensure insulation integrity. It involves applying a voltage higher than the rated voltage to verify that the transformer can withstand electrical stress without breakdown. This test helps identify potential insulation weaknesses and ensures the transformer’s safe operation in various industrial environments.
Q: How does the output of a fat transformer differ from traditional transformers?
A: The output of a fat transformer in the context of vision transformers is typically more adaptable and comprehensive compared to traditional transformers. Fat transformers can produce outputs that correspond to both local and global features of the input, allowing for more accurate and diverse predictions. In industrial applications, the output characteristics may vary depending on the specific design and intended use of the fat transformer.
Q: What are the industrial applications of fat transformers?
A: Fat transformers have a wide range of industrial applications. In the context of power distribution, they are used in situations requiring high capacity and efficiency. For computer vision applications, fat transformers are employed in tasks such as image classification, object detection, and segmentation. They are widely installed in various industries including manufacturing, transportation, and energy sectors, where they help improve accuracy and performance in visual analysis tasks.
Q: Can you provide an abstract of the fat transformer concept?
A: An abstract of the fat transformer concept would highlight its innovative approach to vision transformers. Fat transformers utilize a wider architecture to process both local and global contexts simultaneously. They employ adaptive mechanisms to alternate between different modes of operation, allowing them to extract relevant features more effectively. Through extensive experiments, fat transformers have demonstrated state-of-the-art performance in various computer vision tasks, showcasing their ability to adapt to diverse input types and improve overall accuracy.
Q: What should I know about the warranty for fat transformers?
A: Warranty terms for fat transformers can vary depending on the manufacturer and specific application. Generally, warranties cover defects in materials and workmanship for a specified period. It’s important to review the warranty agreement carefully, as it may include conditions related to installation, maintenance, and operation. Some warranties may offer extended coverage for critical components or provide options for on-site service. Always consult with the supplier or manufacturer for detailed warranty information specific to your fat transformer.