Vacuum Interrupting Breakers

Hi,

The vacuum is designed never to leak. However, a simple way to check if the sf6 is still in the VI is to pull the moving contact (open the VI). This motion should not be free but some resistance should be felt. On releasing the contact, it should 'spring' back into closed position and a distinct 'click' should be heard when the contacts make.

You could use a gas leak detector to check for leaks. A 5 year period is sufficient for CBs in normal operating conditions.

Let me know if you need more info'.

Regards,

Mbalu

Hi there,

VI=Vacuum Interruptor. It's typically used in 11kV VCBs.

I don't see what is SF6 doing in a VI?

Have you mixed up those 2 types of circuit breakers?

Regards

OZ

OOpps! Sorry! Must have got mixed up. I meant the vacuum - not SF6. Have been working on 33kV 8DA10 breakers which use VIs in SF6. Sorry guys.

Nice day.

In the glass ones, you can inspect the copper surface. Any gas entering causes the copper to get very thin layers of tarnish that have varied colors.

The sealed ceramic ones cannot be seen through, so the only way to tell if they have leaked is with a flashover tester. A vaccuum does not allow current fflow, so you apply the rated voltage (with a very high series resistance) and see what current draw there is.

Breakers like this are tolerant of flashover at very low currents, and cam even take brief high current flashovers from lightning etc.

In the mining industry we use vauum interrupters extensively and will get literaly multiple thousands of cycles and up to 5/8 year of service. hope this helps! This type of interrupter is invaluable in higher voltages. Some very common voltages are : 480 olts, 575 volts, 995 volts, 2300 volts, 4160 volts, 7200 volts, 12470 volts, and 13200 volts.

The vacuum can be tested by applying a voltage test as recommended by manufacturer. With the contacts open, apply voltage across the contacts of the breaker. With a DC hipot tester the voltage can go up to 50 kV. If there is leakage in the vacuum , discharge will take place and the tester will trip showing a bad vacuum.

It is important to do this test during regular intervals such as annual maintenance. A leaking vacuum poses a serious operational hazard, as it will not be able to break the current during disconnection and may result in explosion of the vacuum bottle. However, upstream breaker will ultimately trip to remove the fault.