Electrical tests play a fundamental role in determining the behavior of insulating and conducting materials present in various electrical equipment. These procedures are essential to optimize performance and ensure the safe operation of electrical devices.
Transformer Tests and Their Characteristics
The variety of electrical tests is crucial for identifying possible problems in electrical components, and for this, diversified tests with different voltage levels, including high, medium, and low voltage, are employed. Through these tests, it is possible to obtain precise information about the integrity of materials and the need for preventive maintenance.
Among the specific electrical tests, the importance of transformer tests stands out, being especially applied to classify, test, and reaffirm this classification, evaluate its operation, and determine the need for corrective or preventive interventions.
The main types of transformer tests and their specific characteristics:
1. Applied Voltage Test:
The applied voltage test serves to assess the dielectric withstand of the structural elements that make up the transformer. It consists of applying a voltage to these elements, usually high voltage, and evaluating the dielectric strength of these test objects when subjected to this voltage.
2. Impulse Tests:
Impulse tests are designed to test the insulation resistance of transformers to short-duration, high-intensity voltage surges. They are crucial to ensure that the transformer can withstand overload conditions and voltage spikes, maintaining its operational integrity.
3. Induced Voltage:
The induced voltage test is carried out to measure the behavior of the transformer under induced alternating voltages in one winding when the other is energized. This type of test is important to verify the transformer's response to different voltage levels and ensure its proper operation.
4. Partial Discharge Test:
The partial discharge test can identify premature failures, deterioration, and internal defects in transformers.
Partial discharges are internal failures of a transformer, they consist of the occurrence of the conduction of a portion of the current through a path other than the one it should follow. These discharges can be caused or have their frequency and intensity increased by dirt, moisture, construction defects, and permanent degradation of the dielectric of insulating materials.
It helps predict possible problems before they become critical, allowing corrective maintenance to be carried out more efficiently.
5. Transformation Ratio Test (TTR):
The transformation ratio test is carried out to determine the relationship between the number of turns of the primary winding and the secondary winding of the transformer. It is essential to verify if the transformer is operating within the appropriate parameters and if it is correctly adjusted for the desired voltage.
6. No-Load Losses:
The no-load loss test is designed to measure power losses and parameters of the magnetizing branch of the transformer consisting of a shunt branch that has the magnetization resistance in parallel with the magnetization reactance. In this test, the transformer is energized on the high-voltage side, and the low-voltage side remains open, measuring the voltage between the terminals. It is important to verify the efficiency of the transformer and ensure that the losses are within acceptable limits.
7. Short-Circuit Losses:
This test is performed to measure the short-circuit impedance and power losses that occur when the transformer is energized on the low-voltage side and the high-voltage terminals are short-circuited while measuring the current circulating through this winding. This test is fundamental to evaluate the transformer's performance under real load conditions.
8. Temperature Rise:
The temperature rise test is performed to verify the transformer's ability to withstand and dissipate the heat generated during normal operation, and during atypical cases when the temperature may be abnormally elevated, relatively higher than the operating temperature in steady-state. It is important to ensure that the transformer does not overheat and operates within safe temperature limits, and that all components withstand such temperature properly, without jeopardizing the operation and integrity of the transformer.
9. Insulation Resistance Test:
This test for transformers can diagnose possible failures in the insulating materials of electrical equipment. This prevents transformers from having their insulating components compromised.
10. Measurement of Insulation Power Factor:
One of the most comprehensive types of transformer tests, the measurement of insulation power factor tests all the insulating properties present in a transformer. This electrical test ensures greater prevention of problems and much lower maintenance costs for the equipment.
11. Winding Resistance Test:
This test is quite important, as its purpose is to accurately detect short circuits, continuity failures, or aging in transformer coils. This prevents problems that could compromise the equipment's operation.
Observations:
It is important to highlight that each electrical test mentioned above has specific procedures and technical requirements that must be followed rigorously to ensure the accuracy and reliability of the results. Qualified professionals and adequate equipment are essential for the proper conduct of these tests on transformers.