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Installation
01.4IB.77020
PowlVac-ND
®
and PowlVac-NDA
™
Series 4
Vacuum Circuit Breakers
The tests described above are the only tests
required to ascertain insulation integrity.
Because of the design of the PowlVac
®
insulation system, no valid data can be
obtained utilizing other types of high voltage
insulation tests.
2) Vacuum Integrity
Applying abnormally high voltage across
a pair of contacts in vacuum may produce
x-radiation. The radiation may increase with
increased voltage and/or decreased contact
spacing.
X-radiation produced during this test with
the voltage specified in
and normal
contact spacing is extremely low and well
below the maximum permitted by standards.
Do NOT apply voltage that is higher than the
recommended value. Do NOT use contact
separation that is less than the normal open
position separation of the circuit breaker
contacts.
!
CAUTION
Powell recommends AC testing for reliable
verification of vacuum integrity. All
PowlVac-ND® and PowlVac-NDA™ Series
4 circuit breakers shall be tested with
a minimum of 25kVAC applied across
fully open contacts for 10 seconds. No
dielectric breakdown during the test period
constitutes a successful test.
Note:
This test does not replace the AC
high potential testing (Hipot) used to
determine “High voltage insulation
integrity.” See
D. Placing the Circuit Breaker Into
Service, 1) High Voltage Insulation
.
Powell offers a compact and lightweight
PowlVac
®
Vacuum Integrity Tester
designed specifically for PowlVac
®
circuit
breakers. If this device is used refer to
the instruction bulletin provided with the
vacuum integrity tester.
Powell recognizes the widespread use
of DC hipot equipment in the field and
the desire to use this equipment to verify
vacuum integrity. However, the capacitive
component of the vacuum interrupter
during DC testing may yield false negative
test results, which are often misinterpreted
as vacuum interrupter failure. When DC
testing is performed, a test set providing a
full wave rectified 35kV DC hipot voltage
can be applied for 5 seconds as a
“go - no go” test.
Recording the leakage readings is not
necessary, as a dielectric breakdown will
trip all portable DC hipot test sets. If a
DC test breakdown occurs, the test must
be repeated after reversing the DC high
voltage test supply connection across the
vacuum interrupter. A vacuum interrupter
should be questioned only if it has failed
both tests.
High voltages across the open gaps of the
vacuum interrupter can produce
x-radiation. When conducting high voltage
test, personnel should stand at least one
meter (3’) away from the circuit breaker with
the covers in place. Vacuum Integrity Test
voltages should not exceed 25kVAC (35kVDC)
for circuit breaker with a rated maximum
voltage of 4.76kV.
!
CAUTION