Maintenance; Vacuum Interrupters - ABB VM1 Installation And Service Instructions Manual

9.

Maintenance

9.1. Vacuum interrupters

To verify the integrity of the vacuum interrupters perform the
following low-frequency withstand voltage test:
1. Open the circuit-breaker (no control power supplied to the
circuit-breaker).
a. Connect the high potential lead to one terminal.
b. Ground the remaining 5 terminals and circuit-breaker
frame.
2. Start machine with output potential at 0 (zero) VAC.
3. Increase the potential to the required voltage (seeTable 3).
4. Hold for one minute.
5. Decrease potential to 0 (zero) and turn off machine.
6. Repeat for the remaining 5 terminals.
A successful withstand indicates satisfactory vacuum integrity.
Replace interrupters that fail to sustain the voltage across
the open contacts. Testing MUST be done with an AC source
only.
DC testing is not considered a valid test for vacuum
integrity. If DC is the only available option, the peak DC
voltage should not exceed the corresponding AC RMS test
voltage. Additionally, a failure during DC testing should only
be considered preliminary. Additional AC testing should be
completed before replacement of the pole is considered to be
warranted. Testing with meggers or other similar devices is
not considered valid under any circumstances.
38
dangeR
the inteRnal Shield of a
vaCuuM ineRRuPteR Can an
eleCtRiC ChaRge whiCh Can
be Retained even afteR the
voltage iS ReMoved. diSChaRge
the Mid-band Ring whith a
gRounding StiCk befoRe
woRking on any PaRt of the
CiRCuit-bReakeR.