The Problem with HiPot Testing
High-potential (HiPot) testing has been the traditional method for evaluating vacuum interrupter condition. The test applies a voltage across the open contacts to check for dielectric breakdown. However, HiPot testing has a significant limitation: it can only detect a complete loss of vacuum, missing interrupters that are deteriorating but haven't yet failed completely.
Magnetron Atmospheric Condition (MAC) Testing
MAC testing uses the magnetron atmospheric condition principle to measure the actual vacuum level inside the interrupter without opening it. By applying a controlled magnetic field and measuring the resulting current, MAC testing can detect vacuum degradation at much earlier stages than HiPot testing.
Benefits of MAC Testing
MAC testing can identify interrupters trending toward failure before a catastrophic in-service event. This allows planned replacement during scheduled outages rather than emergency repairs after a fault. The MAC-TS4 test unit used by Circuit Breaker Sales provides quantitative vacuum level measurements that can be trended over time.
Recommended Testing Program
We recommend MAC testing as part of every medium voltage vacuum circuit breaker maintenance cycle. Initial baseline measurements should be established during commissioning, with follow-up testing every 3-5 years or as indicated by operating conditions.