I. Invisibility
Vacuum interrupters are fully sealed components. Even if the internal vacuum level deteriorates severely from 10⁻⁵ Pa to 10⁻² Pa, there may be no visible abnormalities on the exterior, and they can still perform normal opening and closing operations under low load conditions. Without specialized detection instruments, operators cannot identify early fault risks of vacuum interrupters through conventional electrical tests such as visual inspection, sound recognition, or circuit resistance testing.
II. Catastrophic Nature
When the vacuum level drops to a critical value (e.g., 10⁻¹ Pa), if a fault current is interrupted, reliable arc quenching cannot be achieved inside, leading to a series of severe consequences:
Failure to open (explosion): The arc continues to burn and cannot be extinguished, causing a sharp increase in internal pressure and temperature, eventually resulting in an explosion, damaging the switch cabinet and potentially causing significant equipment damage and personal injury.
Insulation breakdown: A decrease in vacuum level directly reduces the insulation strength of the component. When subjected to system overvoltage, internal breakdown is likely to occur, causing permanent damage and system short-circuit faults.
Reduced current-carrying capacity: Oxidation increases the contact resistance, leading to overheating of the component and eventual burning of the contacts.
Vacuum switch testers are like performing regular “coronary angiography” for vacuum interrupters, enabling the early and precise detection of potential hazards before any symptoms appear.
High-voltage switch vacuum level testers – Essential tools for transitioning from “regular replacement” to “condition-based maintenance”
In the absence of effective detection methods, the power system mainly adopts two maintenance strategies for vacuum circuit breakers, both of which have obvious economic and scientific deficiencies:
Post-accident maintenance: Repair and replacement are carried out after a failure occurs, which not only incurs high fault handling costs but also leads to prolonged power outages.
Regular replacement: Vacuum interrupters are replaced at fixed intervals (e.g., 10-15 years), resulting in the premature scrapping of many high-quality components that have not reached their service life, causing severe waste of resources.
The promotion and application of vacuum switch vacuum level testers provide key support for the implementation of “condition-based maintenance” mode. Through relatively precise quantitative testing of vacuum levels, the following goals can be achieved:
Remaining life assessment: Accurately determine the current operational health of vacuum interrupters and identify their remaining service cycles.
Predictive maintenance: Capture the slow decline in vacuum levels and plan replacement times in advance to avoid unplanned outages and their impact on power supply reliability.
Verification of new equipment quality: For newly installed or overhauled vacuum circuit breakers, vacuum level testing can verify whether the performance of the interrupter meets the standard requirements.
A key guarantee for grid reliability
Vacuum circuit breakers are the most widely used protection and control components in power grids, and their operational reliability directly affects the continuity of power supply.
Through large-scale and planned use of vacuum switch vacuum level testers for general testing, vacuum circuit breakers in a “sub-healthy” state in the grid can be systematically screened out, significantly reducing the rate of power outages caused by switch body failures and comprehensively enhancing the operational reliability of the distribution network.
Summary of Necessity
In response to the unique technical challenge posed by the strong concealment and severe consequences of faults due to the sealing characteristics of vacuum interrupters, it is necessary to use non-contact, quantitative professional diagnostic instruments for detection, promoting a shift in the maintenance mode of vacuum circuit breakers from passive response to proactive prediction, ultimately achieving comprehensive safety guarantees for personnel, equipment, and the grid.
Industry Regulation Basis
DL/T 596-2021 “Preventive Test Regulations for Electrical Equipment” is a core technical regulation in the power industry. It has a dedicated chapter on preventive tests for high-voltage AC circuit breakers, which clearly stipulates vacuum level testing:
Test item: “Vacuum level measurement of vacuum interrupters” is listed as a recommended test item. Test cycle: It is recommended to conduct the test after major equipment overhauls, when necessary, or when there is suspicion of abnormal vacuum degree.
Judgment criteria: Clearly specify the qualified threshold for vacuum degree to provide a core basis for on-site detection and judgment. For example, it is stipulated that the vacuum degree should not exceed 6.6 × 10⁻² Pa (in some versions, it is 5.0 × 10⁻² Pa). If the measured value exceeds this threshold, it is judged as unqualified, and the equipment should be immediately taken out of operation and replaced.
Supplementary test method: When direct measurement of vacuum degree is not possible, the “power frequency withstand voltage test of the breaking gap” can be used as an indirect and qualitative alternative judgment method.
Post time: Jan-05-2026