Transformer Testing Procedures: A Key to Ensuring Safety and Efficiency of Power Equipment

In the power system, transformers are core devices for power transmission and voltage transformation, and their performance and reliability are directly related to the stable operation of the power grid. To ensure that transformers remain in good condition throughout their life cycle, transformer testing procedures have emerged. These procedures test key indicators such as insulation, electrical performance, and oil quality of transformers from multiple dimensions, serving as a key link to ensure the safety and efficiency of power equipment.

1. Pre-commissioning Tests: Comprehensive Inspection Before Operation

Pre-commissioning tests are a crucial inspection link before the formal operation of transformers, aiming to identify potential defects in the equipment.

Insulation Resistance Test: By measuring the insulation resistance between windings and between windings and the ground, it is determined whether the insulation performance of the insulating material is good, preventing short-circuit faults caused by poor insulation.

Winding Resistance Test: It detects the DC resistance of the winding, which can reflect the welding quality of the winding, whether the cross-sectional area of the conductor is uniform, and whether there are problems such as inter-turn short circuits.

Polarity Test: It determines the polarity relationship of the transformer windings to ensure that when the transformer is operating in parallel or cooperating with other equipment, there will be no current conflict due to incorrect polarity.

Vector Group Test: It clarifies the wiring group of the transformer to ensure that it matches the phase of the power grid and avoids abnormal power transmission caused by phase difference.

2. Routine Tests: Regular Verification of Daily Performance

Routine tests are routine inspections in the daily maintenance of transformers after they are put into operation, used to continuously monitor the status of the equipment.

Ratio Test (Turns Ratio Test): It verifies whether the turns ratio of the primary and secondary windings of the transformer meets the design requirements to ensure the accuracy of voltage transformation.

Magnetic Balance Test: By detecting the balance state of the magnetic circuit, it is determined whether there are problems such as magnetic saturation and excessive local loss in the iron core.

Megger Test: Similar in principle to the insulation resistance test, it is a regular review of insulation performance to detect signs of insulation aging in a timely manner.

Continuity Test: It checks whether the connections of conductive components such as windings and leads are reliable, preventing increased resistance and severe heating caused by poor contact.

3. High Voltage Tests: Withstanding Challenges Under Extreme Conditions

High voltage tests simulate the operating state of transformers under extreme voltage environments to test their insulation and anti-interference capabilities.

Applied High Voltage Test: A power frequency voltage higher than the rated voltage is applied to the main insulation of the transformer to assess its insulation withstand capability under normal operating voltage.

Induced Overvoltage Test: Overvoltage is applied by induction to simulate working conditions such as lightning and switching overvoltage, testing the insulation performance between turns and layers of the winding.

Partial Discharge Test: It detects partial discharge phenomena inside the transformer. Partial discharge is an early signal of insulation degradation, and timely detection can avoid major faults such as insulation breakdown.

4. Oil Tests: Health Monitoring of Insulating Oil

For oil-immersed transformers, insulating oil is a key medium for insulation and heat dissipation, and oil tests can reflect its performance status.

Dielectric Strength (BDV) Test: It measures the breakdown voltage of insulating oil to determine whether there are impurities and moisture in the oil, ensuring its insulation performance.

Moisture Content Test: It detects the moisture content in the oil. Moisture will reduce the insulation performance of the oil and accelerate the aging of insulating materials.

Dissolved Gas Analysis (DGA): It analyzes the characteristic gases (such as methane, acetylene, etc.) dissolved in the oil. The composition and content of the gas are used to determine whether there are faults such as overheating and discharge inside the transformer.

5. On-site Tests: Efficiency Verification in Actual Operation

On-site tests are carried out at the transformer installation site to verify its operating efficiency under actual load and environment.

Load Test: The loss, temperature rise and other indicators of the transformer are measured under load conditions to test its operating stability under rated load.

No-load Loss Measurement: It measures the loss of the transformer when it is no-load, reflecting the hysteresis and eddy current loss of the iron core, which can be used to judge the quality and design rationality of the iron core.

Temperature Rise Test: It monitors the temperature change of the transformer during operation to ensure that its temperature rise does not exceed the standard limit, preventing insulation aging and shortened service life due to overheating.

Transformer testing procedures are like a complete "health management system". From comprehensive screening before operation to regular monitoring during operation, and then to special inspections of extreme working conditions and medium performance, they ensure the safe and efficient operation of transformers from multiple dimensions. By strictly implementing these testing procedures, the power system can minimize the risk of transformer failures and lay a solid foundation for the stable power supply of the power grid.