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26
Installation
PowlVac® DHP 15kV Replacement Circuit Breaker
01.4IB.50032C
2) Vacuum Integrity
!
CAUTION
Applying abnormally high voltages across a
pair of contacts in the vacuum, may produce
x-radiation. The radiation may increase with
increased voltage and/or decreased contact
spacing.
The x-radiation, produced during this test
with the voltage specified in Table A 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.
Powell recommends AC testing for
reliable verification of vacuum integrity.
All PowlVac
®
DHP 15kV replacement
circuit breakers shall be tested with a
minimum of 25kVAC applied across fully
open contacts for 10 to 15 seconds. No
dielectric breakdown during the test period
constitutes a successful test.
Note:
The AC test does not replace the AC
high potential testing (Hipot) used to
determine “High voltage insulation
integrity.” For mor details, see
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 50kVDC 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.
!
CAUTION
When testing with DC, use a DC high potential
test (hipot) set with full wave rectification.
Many DC high potential test sets use
half-wave rectification. Do not use these
half-wave rectifiers. The capacitance of the
vacuum interrupter in combination with
the leakage currents in the rectifiers and
its DC voltage measuring equipment may
result in applying peak voltages as much as
three times the measured voltage. These
abnormally high voltages may give a false
indication of a defective vacuum interrupter,
and may produce abnormal x-radiation.
