What the Test Checks
A vacuum interrupter depends on a high vacuum inside a sealed envelope. If that vacuum degrades through a leak or a seal failure, its ability to withstand voltage across open contacts falls sharply. The integrity test verifies that the open contact gap can still hold off a defined test voltage.
How It Is Usually Done
With the breaker open and isolated, a high-voltage test set applies the manufacturer specified test voltage across the open contacts of each pole in turn. A healthy interrupter withstands the voltage. A sustained breakdown or excessive leakage indicates the vacuum has degraded and the interrupter needs replacing.
Safety Notes
- Always follow the manufacturer procedure and specified test voltage and duration.
- High voltage across a vacuum gap can produce X-ray emission, so recommended safety distances and precautions apply.
- Isolate, earth, and discharge properly before and after testing.
When to Test
Typically during commissioning, periodic maintenance, and after any suspected damage or long storage. See our commissioning checklist and contact wear guide.
If a test shows a failed interrupter, browse VCB spares or request a quote with your breaker model.