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58
2.10 The centering ring (28.1) has been loose
and floating during installation of the
vacuum interrupter. Check that the
movable contact is free to move
vertically without binding, and then
tighten the hardware that secures the
centering ring. Re-check that the
movable contact is free to move
vertically without binding.
2.11 Attach insulating coupler (48.0) and
lever (48.6) together, using pin (48.5).
Apply retaining clips. Correct pin has
ends that have been generously
chamfered.
2.12 Open and close circuit breaker several
times and then check to see that all
bolted joints and devices are tight.
3.0 Checking the contact stroke
3.1 Open the circuit breaker.
3.2 Free insulating coupler (48.0) by
removing pin (48.5). The vacuum
interrupter contacts must now close
automatically as a consequence of
atmospheric pressure.
3.3 Observe the terminal clamp (29.2)
through the openings on each side of
the lower pole support (40.0).
Using vernier calipers measure the
distance from the bottom surface of the
terminal clamp to the bottom edge of
the cutout opening. Measure carefully
and record your result.
3.4 Connect the insulating coupler (48.0)
using pin (48.5) and the retaining clips
provided.
3.5 Repeat the measurement described in
step 3.3 again with care to maximize
accuracy. Record your result.
3.6 Determine difference between the
measurements made under steps 3.3
and 3.5. Your result should fall within
the range shown in Table 3: Typical
vacuum interrupter contact life and
stroke on page 44.
3.7 If you fail to achieve the listed results,
carefully repeat the entire procedure
making certain of your measurements.
3.8 Loosen locking nut on eye bolt on
insulated coupler (48.0), and retain
position of the eye. Make adjustments in
one-half turn increments. After
adjustment is completed, tighten eye-
bolt locking nut to 26-34 ft-lb
(35 to 45 Nm).
4.0 After eye bolt is tightened to proper
torque, repeat all measurement
procedures, making certain they are in
agreement with values indicated in step
3.6.
5.0 Complete all other maintenance
procedures. Completely reassembled
circuit breaker should pass high-potential
test before it is ready for service.
Hydraulic shock absorber
The type GMSG mechanism is equipped with
hydraulic shock-absorber and a stop bar that
functions when the circuit breaker opens
(refer to Figure 15: Stored-energy operating
mechanism on page 20). The shock absorber
(61.8) should require no adjustment.
However, at maintenance checks, the shock
absorber should be examined for evidence of
leaking. If evidence of fluid leakage is found,
the shock absorber must be replaced to
prevent damage to the vacuum-interrupter
bellows.
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