100
5
Maintenance inspections
5-3 Replacement recommendations
5-3-1 Recommendations for MCCB
deterioration diagnosis and replacement
Table 5-8 shows guidelines for the timing of MCCB
deterioration diagnosis and replacement.
Table 5-8 Guidelines for the timing of MCCB deterioration diagnosis and replacement
(Technical Rep. 142, Standard of Japan Electrical Manufactures)
Environment Example Guidelines for the timing
of deterioration diagnosis
Guidelines for the timing
of MCCB replacement
Normal
environment
A location with a constant supply of
clean and dry air
A dustproof, air-conditioned electrical
equipment room
10 years 15 years
An indoor location with minimal dust
and no corrosive gases
Installed in a control panel in a
separate electrical equipment
room with no dustproofing or air
conditioning, or inside an enclosure.
7 years 13 years
Poor
environment
A location with high humidity and
minimal dust containing salt or
gases like nitrous acid gas and
hydrogen sulfide gas
Geothermal power generation
equipment and sewage plants as well
as paper, steel, and pulp plants
3 years About 3 to 7 years
A location where people could not
stay for long periods, or a location
with excessive dust or corrosive gas
Chemical factories, quarries, or mines 1 year About 1 to 3 years
5-3-2 Recommended replacement guidelines
based on switching durability
The number of switching operations determines the durability
of an MCCB in frequent switching applications. MCCBs should
be replaced before they exceed the value in any column in
Table 5-9.
Table 5-9 Switching durability performance (IEC 60947-2)
Frame size Number of switching operations Number of trips by a shunt trip device or undervoltage
trip device
With current Without current Total
100A max. 1500 8500 10000 10% of the total number of switching operations
300A 1000 7000 8000
600A 1000 4000 5000
800A 500 2500 3000
1000A 500 2500 3000
Over 1000A 500 2500 3000
5-3 Replacement recommendations
An MCCB is generally thought to have exceeded its limit of
durability when any of the following occurs.
s(IGHFAILURERATESANDFREQUENTLOSSESDUETOPOWERSUPPLY
interruptions
s$ECLININGPERFORMANCETHATMAKESSAFEOPERATIONNOLONGER
sustainable
s-ARKEDLYHIGHERMAINTENANCECOSTSDUETODETERIORATING
performance
The recommended replacement period makes systems
more efficient by ensuring power supply reliability and more
economical by replacing the MCCB before it reaches one
of the three preceding conditions. This is true as long as
the selected MCCB is the optimum choice (see Chapter 3)
and is used under standard operating conditions (see 4-1,
Chapter 4). The recommended period of replacement has no
bearing on the stated durability or warranty period.
Exactly when an MCCB should be replaced cannot be defined
in mere years because the replacement period will vary with
the stress brought on by the operating environment and
operating conditions.
To Next Page
Loading...