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M E D I U M V O LTA G E P R O D U C T S
We should use stronger language than recommend
("Workers must stand back at least 1.5 meters ....")
To verify the integrity of the primary insulation,
perform the following low-frequency withstand
voltage test:
1. Close the circuit breaker (no control power
supplied)
• Connect the high potential lead to one pole.
• Ground the remaining poles and the circuit-
breaker frame.
2. Start machine with output potential at 0 (zero)
VAC.
3. Increase the potential to the required voltage
(see Table 3; note that new condition test is a
factory test only and is not valid for field
condition tests.)
4. Hold for one minute.
5. Decrease potential to 0 (zero) VAC and turn off
machine.
6. Repeat for the remaining poles.
A successful withstand indicates satisfactory
insulation strength of the primary circuit.
Rated max voltage Dielectric Test Value,
1 Minute Dry AC rms
New condition
reference c37.06
15 kV
36 kV
Table 3: Primary low-frequency withstand test voltage
8.13. 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
b. Ground the remaining 5 terminals and circuit-
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.
Dielectric Test Value,
1 Minute Dry AC rms
DC testing is not considered a valid test for vacuum
Field condition
integrity. If DC is the only available option, the peak
reference c37.20.2
DC voltage should not exceed the corresponding AC
27 kV
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.
terminal.
breaker frame.
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.
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