3 tips to prevent your LV switchboard from overheating
The monitoring of the heat build-up, often carried out by thermography, allows early detection of anomalies that will lead to spurious tripping or even fire and the immobilisation of the installation for a long period. It is therefore a subject that deserves our full attention because it deals with the safety and availability of the installations and therefore the continuity of production.
Thermography is a solution that ensures that there is no abnormal heating of the switchboard during operation.
However, well before its operation, at the time of specification, purchase and installation of the switchboard, there are a few keys factors not to be overlooked.
In the field of high-power, withdrawable, low-voltage switchboards, it is possible to have a positive influence on the future of the installation from the moment of purchase. Similarly, the choice of equipping the switchboard with certain devices allowing easy and safe access to the components to be controlled will make its’ operation simpler and safer.
A good, original design, continuous monitoring and appropriate maintenance are key to the durability and reliability of the electrical panel over the years.
1. Design your LV switchboard according to the IEC 61439-2 standard
A well-designed electrical panel should be chosen, it should be validated in all respects according to IEC 61439-2. Indeed, this standard requires tests and checks to ensure that each component is implemented in accordance with the rules of the standard and that the temperature rise is perfectly controlled, within acceptable limits. By carrying out these tests, the original manufacturer has the data at its disposal that enables it to produce suitable, reliable and long-lasting low-voltage assemblies, in line with their operating conditions.
2. Maintain your LV switchboard regularly
During installation, care should be taken to ensure that the air vents are not obstructed or limited in their effect to ensure natural ventilation of the switchboard. The cleanliness of the air vents but more generally of the electrical panel should be periodically checked to avoid any degradation of the intrinsic qualities of the assembly. In addition, the forms of internal separation will not be removed, they are the ones which ensure the protection of the personnel during the thermography and maintenance campaigns.
3. Monitor heat build-up by thermography
Thermography campaigns require going as close as possible to, and aiming at, live components. In doing so, the operator will take more risks than during the operation of his switchboard.
In addition to periodic inspections, certain safety features can facilitate or supplement the monitoring of overheating.
Easy and secure access
Inspection of the cable terminations is a must. Easy access and the width of the cable sheath are criteria to be considered. The position and shape of the downstream power connections are elements that can bring a increased ease of this operation.
For feeders, the possibility of opening the front opening drawer allows all components and all clamping points of the drawer to be seen.
If this option was not chosen at the time of purchase, the starter may have been fitted with a sighting window, which will nevertheless allow some thermal readings to be taken, but in a much smaller sighting area.
The main busbar, which is often placed in the upper position of the switchboard, can also be examined. The main purpose is to check the temperature at the busbar joints and connections. The fewer they are, the fewer points to be monitored.
The roof of the electrical panel must meet certain safety requirements:
- Easy removal of the sheet metal
- Equipment of removable sheets with captive bolts
- Presence of forms of protection
By its’ design, the assembly must facilitate this operation, which is often uncomfortable to carry out because it is high up and close to live elements.
When choosing the LV switchboard, it is therefore important to ensure that it offers a safe and easy access solution for this type of operation.
The power connections on the incoming circuit breaker(s) are also often difficult to access. This is particularly true for switchboards with cable connections from the front. In this case, permanently readable infrared sensors can be offered.
Points of vigilance for sighting devices without dismantling
For sighting devices without dismantling (arc-proof windows, large arc-proof windows, grids), the solution must allow measurements to be taken without opening the LV switchboard casing and guarantee the protection of the operator during the inspection, thus avoiding the need for reinforced individual protection to protect against the effects of a possible internal arc.
The electrical panel can be fitted with these devices on the incoming columns, to monitor the temperature at the main busbar sides or even on the fronts of some withdrawable drawers.
Focus on viewing solutions
Polycrystalline sightglasses are the best known solution; they are relatively expensive and offer a fairly narrow viewing surface but promise good internal arc resistance.
Larger sighting solutions of various shapes and sizes are also available. They consist of a honeycomb structure firmly attached to a plastic film. They allow a much better viewing angle and an increased inspection area. Their internal arc resistance is sufficient in many cases and their plastic film does not degrade over time, unlike polycrystals which lose their transparency over part of the spectrum as they age.
In the case of withdrawable drawers, cheaper solutions can be considered, such as the use of Plexiglas or removable metal sheets that allow partial inspection of the interior but with the appropriate individual protection. The use of front opening drawer is the solution allowing a complete inspection of the inside of the drawer but it leads to an increased risk for the operator during the measurement campaign.
In short, a well-designed, well maintained low-voltage switchboard and regular monitoring of its components enable you to prevent the risk of fire resulting from abnormal heating of your installation.
It should be remembered that each intervention requiring the opening of a door or front plate exposes the operator to a greater risk of internal arcing and contact with live parts.
In fact, tests on the behaviour of the electrical panel during an internal arc are always carried out with the enclosure closed and the effects of the arc on the operator are only evaluated outside the LV switchboard during internal arc conditions. For thermography campaigns, it is necessary that the operator wears adequate individual protection and is trained to follow the appropriate methodology.
Find out more about: the individual protections to adopt