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Maintenance of low voltage switchgear

The electrical switchboard and all its equipment continue to age whether they operate or not. This aging process is due mainly to environmental influences and operating conditions. To ensure that Low voltage switchgear and especially circuit breaker retains the operating and safety characteristics specified in the catalogue for the whole of its service life, it is recommended that:

The device is installed in optimum environmental and operating conditions

Routine inspections and regular Maintenance are carried out by qualified personnel.

Parameters influencing the ageing

A device placed in given conditions is subjected to its effects. The main factors that accelerate device ageing are:

relative humidity
salt environment
corrosive atmospheres.
percent load
current harmonics

Preventive Maintenance

Preventive Maintenance consists in carrying out, at predetermined intervals or according to prescribed criteria, checks intended to reduce the probability of a failure or deterioration in the operation of a system.

There are two types of preventive Maintenance:

Periodic Maintenance

For each type of product, Maintenance recommendations have to be formalized in a dedicated document by the technical department. These verification procedures, intended to maintain systems or their subassemblies in correct operating condition over the targeted service life, must then be carried out according to the time intervals stipulated in this document.

Conditional Maintenance

To a certain extent, conditional-Maintenance operations are a means to reduce (but not eliminate) the recommended periodic-Maintenance operations (thus limited to the strict minimum) that require an annual shutdown of the installation.

These operations are launched when programmed alarms indicate that a predefined threshold has been reached. (Number of operation > durability, aging indicators…)

Electronic trip units in power circuit breaker can propose such functions. Conditional Maintenance is the means to optimize installation Maintenance.

Example of Maintenance recommendation for Power Circuit Breaker (>630A)

Recommended periodic Maintenance operations, for normal operating conditions

1 year:  Visual inspection and functional testing, replacement of faulty accessories

2 years: + servicing operation and subassembly tests

5 years: + diagnostics and repairs (by manufacturer)

The intervals stated are for normal environmental and operating conditions.

Provided all the environmental conditions are more favourable, Maintenance intervals can be longer.

If just one of the conditions is more severe, Maintenance must be carried out more frequently.

Functions linked specifically to safety require particular intervals. For example, emergency switching and earth leakage protection.

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