Replacement and precautions of vacuum interrupter of vacuum circuit breaker
How to judge that the vacuum interrupter of the vacuum circuit breaker needs to be replaced？
After the vacuum circuit breaker has been used for a long time, once one of the following conditions occurs, it means that the vacuum interrupter may have reached the end of its life and should be considered for replacement.
(1) The storage period or service period of the vacuum interrupter exceeds the validity period specified by the product (calculated from the date of delivery of the vacuum interrupter), and the validity period of the domestic vacuum interrupter is generally about 20 years.
(2) The vacuum degree of the vacuum interrupter drops to 1.33×10-2Pa (the conditions can be measured by a magnetron vacuum gauge). If it is a glass-shell type vacuum interrupter, if the color of the metal shield is observed to change significantly , its vacuum degree should be checked immediately
(3) The cumulative wear of the contacts of the vacuum interrupter exceeds the specified value of the product instructions for use. The domestic product is generally 3mm. Most products have a warning mark (point or line) for the allowable wear on the movable contact rod. When the wear When the accumulated value exceeds 3mm, the warning sign cannot be seen after closing.
(4) The cumulative number of cut-off times of rated short-circuit current exceeds the electrical life of the product
(5) The number of mechanical closing and opening operations exceeds the specified value in the product manual.
Replacement steps and matters needing attention
The vacuum interrupter should be replaced after the vacuum circuit breaker breaks the short-circuit current for a specified number of times, or when air leakage is found during regular inspection.
(1) Remove the old vacuum interrupter in the specified order.
(2) Before installing a new vacuum interrupter, its conductive contact surface must be wiped clean or sanded, and oil should not be applied to the contact surface.
(3) After the assembly of the vacuum interrupter, the movable conductive rod must be carefully adjusted to keep it in the middle of the interrupter to ensure that the interrupter will not be rubbed during the opening and closing process.
(4) After the installation is completed, it should be subjected to a power frequency withstand voltage test (voltage is applied between the dynamic and static contacts in the case of opening). Then close the circuit breaker and measure the resistance of its main circuit.
(5) Measure over travel and circuit breaker travel and adjust them to the specified values.
(6) After the installation test is qualified, the closing and opening operations must be performed for dozens of times without load. Only after confirmation can be put into operation.
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