Periodical Inspection; Inspection After Tripping - Mitsubishi Electric C Series Handling And Maintenance

4.2 Periodical inspection

The inspection shall be worked out once one
month after the commencement of the use and
then periodically in terms of the environmental
conditions in order that any trouble may be
avoided and that the circuit-breaker can be used
for longest possible time.
Type Inspection item
1. Is any conductor connection not loosened?
2. Are the cover and base not cracked or otherwise
damaged? Is the handle not broken?
3. Internal submersion by inundation or substantial mud
or dust not adhered?
Common
4. Is there any abnormal temperature rise?
5. Is there ON/OFF operation by handle smooth?
6. Is there TRIP operation by trip button?
ELCB
7. Test shall be conducted using the test button.

4.3 Inspection after tripping

When circuit-breaker trip accidental current, it may be either reused or should be replaced by new one
depending on the intensity of the accidental current thus trip.
Intensity of the trip current/Degree of damage on MCCB/ELCB and countermeasures to be taken
Intensity of trip current
Case where it is clear that the circuit-breaker
operated within the range of time-delay trip
Such relatively low short-circuit current as
allows the instantaneous tripping.
Large short-circuit current near to the rated
breaking capacity
Remark: The leak display button may pop out when the earth leakage breaker trip an accidental current that surpasses the instantaneous
trip current.
In case when the intensity of the accidental current cannot be inferred, remove the MCCB/ELCB and
measure the insulation resistance. If the result does not attain the prescribed value (5MΩ), proceed to
the withstand voltage test.
Though the breaker may be used for the time being if there be prescribed withstand voltage, it shall be
replaced with new one as soon as possible.
If both the insulation resistance and withstand voltage are high enough, the breaker may be recognized
as reusable. For a certain period, however, it shall be checked for any abnormal temperature rise or
any other anomalies.
(1) The measurement of insulation resistance and the withstand voltage test shall be performed ac-
cording to (1) and (2) of 5.1.
(2) For ELCB, the operation shall be confirmed by test button too.
77
Yardstick for inspection periodicity
1 Clean and dry environment
2
3
Criterion
No loosening allowed.
No crack nor damage on the cover and base. No broken
handle.
No internal submersion nor substantial mud and/or dust
adhered to.
(1) Visual inspection shall find out no discoloration, by
burning, of the stud on the reverse side of the terminal,
tightened and the molded portions of the body.
(2) No terminal shall manifest any specifically high
temperature while the currents of respective phases
are well balanced. (Max. allowable value of terminal
temperature rise: 60K).
(3) No remarkable difference between the right and left
sides on the lateral face of the base as long as the
load current is well balanced.
Operation should be done smoothly.
The circuit breaker should be able to reset after tripping.
The circuit-breaker should be able to operate and be
closed again for certain.
Degree of damage on MCCB/ELCB
No such anomaly at all as soiled vent
Black soot seen near the vent.
Soot and dust seen also on the handle, and
remarkable dirt and grime near the vent.
Molten metal adheres to the vent and its
vicinity.
Severely deformed box of box type circuit-
breaker.
Environment not exposed to severe
dust, corrosive gas vapor, salt, etc.
Other places than 1 and 2
If loosened, the connection should be retightened with
such appropriate torque as indicated in the Attached Table.
In case of internal submersion, replace the circuit-
breaker with a new one, or have it overhauled at our
service center.
(1) Note that there exists some differential temperature
between the following terminals:
• Between the terminal on line side and that on load
side.
• Between the terminal of middle pole and those on
right and left sides
Normally open or normally closed circuit-breaker can
maintain a smoother operation if it is opened and closed
periodically.
Test shall be done about once a month.
Reusable (The circuit-breaker can function 50
times (100 A or less) at the overload current 6
times higher than the rated current.)
To be replaced by new one.
Once every 2 to 3 years
Once a year
Once every six months
Remarks
Countermeasures
Reusable