The withstand pressure strength test of vacuum pressure switches

The withstand pressure strength test of vacuum pressure switches is an important link to ensure their safe and reliable operation. The following is a detailed analysis of this test:

Test purpose

The withstand voltage strength test aims to verify the insulation performance and structural strength of vacuum pressure switches under high-pressure environments, ensuring that they do not experience breakdown, flashover or mechanical damage during normal operation or abnormal conditions, thereby safeguarding the safety of equipment and personnel.

Preparation before the test

Environmental confirmation: The humidity of the test environment should be ≤85%, and the temperature should be within the range of -25℃ to 40℃ to avoid condensation or contamination that may affect the results. The equipment should be in a clean state, free of dust or oil stains. The oxide layer on the surface of the contacts needs to be treated in advance.

Equipment inspection: Conduct a strict inspection of the components of the vacuum pressure switch, including the condition of the outer part of the vacuum interrupter and its main dimensions, to ensure that the glass parts are bright and transparent, the internal parts are not oxidized, the surface is free of scratches, and the main geometric dimensions comply with the factory regulations.

Wiring preparation: Connect the high-voltage lead wire to the static contact end of the main circuit of the switch, and reliably connect the grounding wire to the grounding bolt of the casing to ensure the circuit is closed. Measure the insulation resistance with a 2500V megohmmeter, and the resistance value should be ≥1000MΩ.

Test steps

Voltage increase operation: The test voltage is uniformly increased from zero, with the rate controlled within 1kV/s to avoid misjudgment caused by sudden voltage changes. After rising to the target voltage, maintain it for 60 seconds and observe whether there is any breakdown, flashover or abnormal discharge sound.

Voltage reduction and recheck: Gradually reduce the voltage to zero. After disconnecting the power supply, immediately discharge the equipment to prevent residual charges from causing danger. If no breakdown occurs during the test and the leakage current is ≤5mA, it is judged as qualified.

Handling of abnormal situations

Partial discharge: If intermittent discharge sounds occur during the voltage increase process but no breakdown occurs, it may be caused by levitation potential or contamination on the insulator surface. It is necessary to clean and remeasure.

Excessive leakage current: The current suddenly increases but does not reach the breakdown value. It is necessary to check whether it is due to excessive environmental humidity or moisture inside the equipment. If necessary, drying treatment should be carried out.

Abnormal equipment after testing: After the test, measure the resistance of the main circuit. If the resistance value increases by more than 20% compared to before the test, it is necessary to check for problems such as contact ablation or loose mechanical structure.

Test records and reports

The test report should include environmental parameters, equipment model, test voltage, duration, leakage current value and description of abnormal phenomena.

Retention period: The retention period of records should be no less than the life cycle of the equipment. It is recommended to adopt a dual-track system of electronic archiving and paper backup.

Nonconforming handling: For nonconforming equipment, the defect location and possible causes should be clearly stated in the report, such as "Surface discharge of C-phase pillar insulator", to facilitate subsequent maintenance tracking.

Safety Precautions

Warning Settings: Warning fences should be set up in the test area, and non-operating personnel should maintain a safe distance of more than 3 meters.

Personal protection: Wear insulating gloves and boots, and use a high-voltage test device with a locking function to prevent electric shock from accidental operation.

Residual voltage treatment: After the test is completed, wait for 5 minutes before touching the equipment to avoid injury caused by residual voltage due to capacitive effect.