E-50
22.3.2-5 Accessory devices (General accessory devices)
Inspection item
Inspection method
Criteria
Treatment
1. Shunt trip device (SHT)
The circuit breaker is ON and
the specified voltage is applied
to the terminals C1 and C2 .
The circuit breaker must be
changed from ON to OFF.
Please contact Mitsubishi
Electric if there is any breakage
or deformation.
2. Auxiliary switch (LAX)
Check continuity of LAXa
and LAXb.
Must switch in accordance with
the conditions of the circuit
breaker.
Please contact Mitsubishi
Electric if there are any
abnormalities.
3. Under voltage trip device
(UVT)
Check that the UVT operates
correctly by supplying current to
D1 and D2 of control circuit
terminal block.
Must be able to close reliably
upon application of a voltage
that is 85% of the rated voltage
and to trip and disable closing
by the time when the voltage
reaches 45% of the rated
voltage.
Please contact Mitsubishi
Electric if the measured values
deviate from the standard
values.
4. Safety shutter (SST)
Drawout/Insert operation
1. There must be no breakage
of the parts.
Please contact Mitsubishi
Electric if there are any
abnormalities.
2. Must be able to perform the
drawout/insertion operation
without any difficulty.
1. Remove any broken parts
that impair the drawout/
insertion operation.
2. Please contact Mitsubishi
Electric if the drawout/
insertion operation cannot be
performed.
5. Cell switch (CL)
Drawout/Insert operation
Must switch reliably at
the “DISCONNECT” and
“CONNECT” positions.
Please contact Mitsubishi
Electric if there are any
abnormalities.
(Note) For the accessories other than the above, check the user's manual for each accessory.
Inspect the items detailed for periodic inspection (section 22.3.2) when the circuit breaker has performed a
breaking operation as a result of an overload current or a short-circuit current.
Reuse is possible if the relevant criteria are satisfied. A circuit must never be reclosed (locally or remotely)
before the cause of the fault has been identified and cleared.
However, it is recommended that the circuit breaker be replaced as soon as possible after it has interrupted
a large fault current. The circuit breaker should be monitored for unusual temperature rises and other
abnormalities until replacement occurs. Refer to the following chart regarding the level of breaking currents
and the treatments to be performed:
(Note 1) ETR with the trip indication function, it can be determined whether the cause of the tripping lies in the LTD (long-time-delay), STD
(short-time-delay) or INST (instantaneous) level.
For the circuit breaker with a display, the fault current is estimated.
(Note 2) If the magnitude of the fault current cannot be estimated, treat according to 3 of section 22.3.3.
22.3.3 Inspections after a breaking operation
Level of breaking current
Level of the circuit breaker damage
Treatment
1. Breaking current is 6
times or less the rated
current (LTD, STD range)
1. Abnormalities of the external parts
cannot be detected visually.
2. Slight wear of contacts, soiling by
soot, etc.
Reusable.
Refer to section 22.1.2 regarding the switching operation
lifetime at the rated current.
2. Breaking current is 70%
of the rated breaking
capacity or less (STD,
INST range)
1. There is slight overall soiling of the
exhaust ports by soot.
2. There is also overall damage of the
contacts and the arc extinguishing
chamber but only to a slight degree.
Reusable.
The circuit breaker can be used if the relevant criteria in
section 22.3.2 are satisfied.
3. Breaking current near
to the rated breaking
capacity
1. There is significant overall soiling of
the exhaust ports by soot.
2. The contacts and the arc
extinguishing chamber also suffer
considerable damage.
1. Immediate replacement is desirable.
2. If immediate replacement is not possible, the circuit
breaker can be used carefully by gradually reducing the
rated current, etc., provided that the relevant criteria in
section 22.3.2 are satisfied. As an additional test, perform
the withstand voltage test to the live parts of the main
circuit of the circuit breaker at twice the rated insulation
voltage, in other words, at 2000 V.
However, replace as soon as possible.
