40
As-found insulation and contact
resistance tests
As-found tests verify the integrity of the
circuit breaker insulation system. Megger*
or insulation resistance tests and contact-
resistance tests conducted on equipment
prior to installation provide a basis of future
comparison to detect changes in the
protection afforded by the insulation
system. A permanent record of periodic
as-found tests enables the maintenance
organization to determine when corrective
actions are required by watching for
significant deterioration in insulation
resistance, or increases in contact
resistance.
* Megger is a registered trademark of
Megger Group, Ltd.
Figure 22: Circuit breaker pole assembly/vacuum-check mechanical/contact-resistance test
Insulation and contact-resistance test
equipment
In addition to the high-potential test
equipment capable of test voltages as listed
in Table 4, the following equipment is also
required:
AC high-potential tester with test voltage
of 1,500 volts, 60 Hz
Test equipment for contact-resistance
tests.
48.6
48.0
48.6
48.0
Item Description
48.0 Insulating coupler
48.6 Lever
Step 1
Detach lever (48.6) and insulated
coupler (48.0)
Step 2
Primary contact CLOSED position and
insulated coupler disconnected
Step 3
Primary contact OPEN position (forced
open by manual pressure)
3AH vacuum circuit breaker operator 3AHc vacuum circuit breaker operator
48.0
48.6
48.0
48.0
Primary contact
resistance test
Upper connector pad
Lower connector pad
Step 1
Step 2
Step 3
Step 2
Operating
position
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