After a vacuum circuit breaker has been used for a long time, if one of the following situations occurs, it means that the vacuum interrupter may have reached the end of its life and should be replaced.
(1) The storage period or use period of the vacuum interrupter exceeds the validity period specified in the product (calculated from the date of manufacture of the vacuum interrupter). The validity period of domestic vacuum interrupters is generally about 20 years.
(2) The vacuum degree of the vacuum interrupter drops to 1.33×10-2Pa (if conditions permit, it can be measured with a magnetron vacuum gauge). If it is a glass shell type vacuum interrupter, if the color of the metal shielding cover changes significantly, its vacuum degree should be checked immediately.
(3) The cumulative wear of the contacts of the vacuum interrupter exceeds the specified value in the product instructions. Domestic products are generally 3mm. Most products have a warning mark (dot or line) on the moving contact rod to allow wear. When the cumulative wear exceeds 3mm, the warning mark will not be visible after closing the circuit breaker.
(4) The cumulative number of rated short-circuit current interruptions exceeds the product's electrical life.
(5) The number of mechanical closing and opening operations exceeds the value specified in the product manual.
Vacuum interrupter replacement steps and precautions
After the vacuum circuit breaker has interrupted the short-circuit current for the specified number of times, or when leakage is found during regular inspection, the vacuum interrupter should be replaced.
(1) Remove the old vacuum interrupter in the specified order.
(2) Before installing the new vacuum interrupter, its conductive contact surface must be wiped clean or sanded, and no oil is allowed on the contact surface.
(3) After the vacuum interrupter is assembled, its moving conductive rod must be carefully adjusted to keep it in the middle position of the interrupter to ensure that it does not rub against the interrupter during the closing and opening process.
(4) After installation, it should be subjected to a power frequency withstand voltage test (applying voltage between the moving and static contacts in the open state). Then close the circuit breaker and measure the resistance value of its main circuit.
(5) Measure the overtravel and circuit breaker stroke and adjust them to the specified value.
(6) After the installation test is passed, the closing and opening operations must be performed dozens of times without load. Only after confirmation can it be put into operation.