Powered by Safety
®
25
IB-65100
Installation
The circuit breaker insulation should be
tested with the circuit breaker vacuum
interrupter contacts in the CLOSED
position. Test each pole of the circuit
breaker separately, with the other 2 poles
and the frame grounded. Perform the field
dielectric test described in ANSI Standard
C37.20.2, at the voltage level appropriate
for the equipment
(Table A Field Dielectric
Test Values)
. This test will have checked all
of the primary phase-to-ground and
phase-to-phase insulation.
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.
Table A Field Dielectric Test Values
Rated Maximum Voltage
(kV rms)
Power Frequency Withstand
(kV rms)
27.5
45
38
60
CAUTION
CAUTION
!
Applying 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.
2)
Vacuum
Integrity
Powell recommends AC testing for reliable
verification of vacuum integrity. All
PowlVac ASD 38kV circuit breakers shall be
tested with a minimum of 40kVAC applied
across fully open contacts for 10 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 more details, see
Ch 4 Installation,
D. P
LACING
THE
C
IRCUIT
B
REAKER
I
NTO
S
ERVICE
,
1) High
Voltage Insulation Integrity.
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 57kVDC hipot voltage
can be applied for 5 seconds as a
“go - no go” test.