Type and routine tests are two essential procedures carried out in the electrical field to ensure the quality, compliance, and performance of equipment. Although both aim to ensure the functionality of specific devices, there are significant differences between them in terms of scope, frequency, and objectives.
Transformer Tests: Performance, Efficiency, and Safety
Crucial for the efficient and safe operation of modern electrical systems, transformers, In brazil popularly known as "trafos", enable the transmission and distribution of energy with minimal loss and maximum reliability.
These devices are responsible for voltage adaptation, isolation between circuits, and grids coupling, ensuring the proper operation of various electrical equipment and systems.
To ensure the efficient operation of these assets, specific electrical tests are performed, which are tests intended to evaluate the performance, efficiency, safety, and general condition of transformers in operation. Conducted at different stages, from manufacturing to installation and maintenance of transformers, these tests can be classified in various ways, according to the needs of the manufacturer and/or equipment owner.
And in this post, we'll cover two main types of tests: type tests and routine tests. Check it out!
Types of Tests Conducted for Transformer Efficiency Testing:
1. Type Tests
Also known as acceptance tests or laboratory tests, these tests are conducted on a prototype representative of the transformer to verify if it meets the established specifications and standards.
Type tests include short-circuit tests, open-circuit tests, temperature rise tests, lightning impulse tests, winding resistance tests, transformation ratio tests, iron loss tests, dielectric strength tests, water content in insulating oil, dielectric loss factor, interfacial voltage, among others.
Electrical Tests - Electrical tests conducted during type tests involve evaluating the temperature rise and the transformer's resistance to lightning impulses, especially in equipment with a nominal voltage below 300 kV. These tests verify the transformer's ability to operate within safe temperature limits and withstand sudden electrical overloads.
Mechanical Tests - On the other hand, mechanical tests are not specifically conducted during type tests on transformers. However, during equipment manufacturing and assembly, quality control procedures are applied to ensure structural integrity, correct assembly, and proper functionality of the transformer.
Chemical Tests - Chemical tests on insulating oil are important for equipment with a nominal voltage below 72.5 kV. These tests include measuring dielectric strength, which assesses the insulating oil's ability to withstand high voltages without experiencing dielectric failures. Additionally, the water content in the insulating oil is checked to ensure that moisture does not compromise the transformer's efficiency. The dielectric loss factor is measured to assess energy losses in the transformer's insulation, while interfacial voltage is measured to evaluate the quality of the insulating oil and its ability to insulate and protect the transformer's internal components.
2. Routine Tests
Routine tests are conducted on each individual transformer manufactured to verify its quality and compliance. Routine tests include insulation resistance tests, transformation ratio tests, copper losses tests, applied voltage tests, overload tests, among others.
In the electrical aspect, tests are conducted to measure the electrical resistance of windings, the transformation ratio, polarity and angular displacement, insulation resistance (using a megger), load losses and impedance voltage (also known as short-circuit test and voltage drop in windings), no-load losses and excitation current (known as open-circuit test), applied voltage to windings at industrial frequency, and induced voltage at a minimum frequency of 120 Hz. Tests are also conducted on auxiliary circuits, on current transformers (CTs) of bushings, on the switch when applicable, switching surge for equipment with voltage equal to or greater than 230 kV, and lightning impulse for equipment with voltage equal to or greater than 300 kV.
Regarding mechanical tests, checks for tightness and pressure resistance are performed, as well as evaluating painting schemes for equipment with voltage equal to or greater than 230 kV. Visual and dimensional tests are also conducted to ensure equipment compliance.
Chemical tests are performed on the transformer's insulating oil, especially on equipment with voltage equal to or greater than 72.5 kV or power equal to or greater than 5.0 MVA. These tests include measuring dielectric strength, water content, dielectric loss factor, and interfacial voltage. These chemical analyses provide information on the quality and insulating capacity of the oil used in the transformer.
These routine tests are essential to ensure the quality, safety, and continuous performance of electrical transformers, ensuring that they comply with established standards and specifications. By regularly conducting these tests, it is possible to identify potential problems and take corrective or preventive measures, ensuring reliable and efficient operation of transformers over time.
Electrical Tests - In the electrical aspect, tests are conducted to measure the electrical resistance of windings, the transformation ratio, polarity and angular displacement, insulation resistance (using a megger), load losses and impedance voltage (also known as short-circuit test and voltage drop in windings), no-load losses and excitation current (known as open-circuit test), the applied voltage to windings at industrial frequency, and the induced voltage at a minimum frequency of 120 Hz. Tests are also conducted on auxiliary circuits, on current transformers (CTs) of bushings, on the switch when applicable, switching surge for equipment with voltage equal to or greater than 230 kV, and lightning impulse for equipment with voltage equal to or greater than 300 kV.
Mechanical Tests - Regarding mechanical tests, checks for tightness and pressure resistance are performed, as well as evaluating painting schemes for equipment with voltage equal to or greater than 230 kV. Visual and dimensional tests are also conducted to ensure equipment compliance.
Chemical Tests - Chemical tests are performed on the transformer's insulating oil, especially on equipment with voltage equal to or greater than 72.5 kV or power equal to or greater than 5.0 MVA. These tests include measuring dielectric strength, water content, dielectric loss factor, and interfacial voltage. These chemical analyses provide information on the quality and insulating capacity of the oil used in the transformer.
Type and Routine Tests: Differences and Processes
Transformer tests are conducted based on international standards, such as those of the International Electrotechnical Commission (IEC), and may also be regulated by national standards.
They are conducted by specialized laboratories, transformer manufacturers, power companies, and inspection and certification organizations to ensure that transformers meet performance and safety requirements. Test results provide important information for the selection, installation, and proper operation of transformers.
Type Tests:
Type Tests are conducted during the product development phase. Their purpose is to verify if the equipment meets the established requirements and specifications.
These tests are performed on a single unit of the batch, representing the entire set of equipment. Normative grounding is fundamental in this process, as standards establish the criteria and methods to be followed.
Type Tests assess the performance and capacity of the tested unit, including aspects such as dielectric withstand, operating temperature, and other essential equipment characteristics. Additionally, detailed documentation of procedures, results, and conclusions is prepared to obtain approvals and certifications before the product is launched in the market.
– Objective: meet design requirements, such as dielectric withstand and operating temperature.
– Conducted on a single unit of the batch, representing the entire batch.
– Normative grounding.
– Assess the performance and capacity of the tested unit.
– Product development phase, verifying if it meets requirements and specifications.
– Conducted once during the development process.
– Broad scope, covering different conditions and scenarios.
– May involve destructive and non-destructive tests.
– Detailed documentation of procedures, results, and conclusions.
– Obtain approvals and certifications before market launch.
Routine Tests:
On the other hand, Routine Tests are conducted during the product operation phase. They aim to monitor the continuous performance of the equipment.
Unlike Type Tests, Routine Tests are conducted regularly at defined intervals, ensuring that the equipment meets operational requirements over time. These tests are conducted on all units of the batch, checking the quality and uniformity of the equipment set.
Routine Test procedures are well-grounded in current standards, although they may be less formal and more oriented towards monitoring. Standardized and repetitive tests are used to verify the regular performance of the equipment, maintaining the reliability of the electrical system.
The documentation generated in these tests may be less detailed than in Type Tests, but it is still important for control and continuous monitoring purposes.
– Objective: ensure the quality and uniformity of the batch.
– Conducted on all units of the batch.
– Procedures grounded in current standards.
– Attest to manufacturing and assembly processes.
– Verify the level of compliance between parts of the same design.
– Product operation phase, monitoring continuous performance.
– Conducted regularly at defined intervals.
– Specific focus on verifying regular performance.
– Standardized and repetitive tests.
– Documentation oriented towards monitoring, may be less formal.
– Ensure compliance with operational requirements over time.
HVEX: Elevating Industry Standards with Custom Solutions for Transformer Testing
At HVEX, we have an extensive portfolio of solutions designed to enhance both the safety and performance of type and routine tests. We specialize in the development of Testing Laboratories.
Furthermore, we provide state-of-the-art equipment for transformer testing laboratories, allowing our clients to perform various tests to ensure quality and compliance in the production process.
We are committed to offering customized and high-quality solutions, empowering our clients to achieve exceptional performance, increase efficiency, and elevate safety standards in their operations. Experience our performance-leading solutions. Get in touch with us and discover how HVEX can drive the success of your business!