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4.4 Primary Circuit Test
The primary circuit of the breaker has been
tested prior to shipment. Retesting prior to
energization will insure no internal
transportation damages have occurred.
Verification of vacuum can be performed by
a low-frequency AC withstand test.
Additional a contact resistance testl by
performing a contact resistance test is
recommended.
Rated Max
Voltage
Dielectric Test
Value, 1 Minute
Dry AC rms
New Condition
reference
c37.06
Dielectric Test
Value, 1 Minute
Dry AC rms
Field Condition
reference
c37.20.2
4.76kV
19kV
15kV
8.25kV
36kV
27kV
15kV
36kV
27kV
27kV
60kV
45kV
Figure 4.15 Primary low-frequency withstand test
voltages
To verify the integrity of the vacuum
interrupters perform the following low-
frequency withstand voltage test:
1. Open the breaker (no control power
supplied to breaker)
a. Connect the high potential lead to
one terminal.
b. Ground the remaining 5 terminals
and breaker frame.
2. Start machine with output potential at 0
(zero) VAC
3. Increase the potential to the required
voltage (
Figure 4.15
)
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. Remove
power from the breaker.
Contact resistance is measure at the factory
according to the ANSI 37.09 using a 200A
µohm meter. This DC resistance test should
be performed after each fault the primary
circuit, from terminal to terminal of each
pole unit, in the close position shall be
measured with at least 100 A of dc current
fl
owing in the circuit and shall not exceed
the limit set for the rating of the circuit
breaker by the manufacturer.
Remove lifting angles from breaker.
Note: Breaker will not fully rack in with lifting
angles installed.
CAUTION
High voltage applied across
an open gap in a vacuum can
produce X-radiation. When
the breaker is fully open the
contact spacing is such that
when tested with the voltages
specified, X-radiation at one
meter is below the level of
concern. A danger could
exist at voltages above the
dielectric test voltage or
reduced contact spacing
caused by a major internal
mechanical failure of the
breaker.
