IEC 61439 norm: Digital solution facilitates thermal calculation of switchgear

Excessive heat: An absolute fear of control cabinet builders. Because only if the systems are resistant to heat are they safe and can be operated without hesitation. But calculating heat in accordance with standards is a major challenge for plant engineers. For example, different variables such as power loss, temperature resistance or cable lengths have to be taken into account, which come from different component manufacturers. However, the required values are often not found in the corresponding material databases and have to be determined manually in the end. Systematised calculation tools offer an efficient and legally secure solution here.

Clear responsibilities and increased safety: this is what the IEC 61439 norm is intended to ensure. It clarifies that the responsibility for faults lies with the system builder and prescribes which documentary evidence must be available so that the question of liability can be clarified. Overall, the norm deals with three core areas of switchgear:

  • Safety
  • Function
  • Availability

While topics such as dielectric strength, current carrying capacity and also resistance to heat and fire are regulated in the area of safety, protection against environmental influences and the installation of switchgear belong to the functional area. Availability demands the provision of specifications and components. For many planners, the requirements are associated with great effort and demand great time resources, which are rarely available. One process that poses immense challenges for many plant engineers is thermal calculation.

Norm IEC 61439: Numerous variables make life difficult for planners

To ensure the resistance of a switchgear to heat and fire, a complex calculation procedure must be applied. Different variables are set in relation to each other in order to ensure the functionality of the switchgear and to avoid faults. Three aspects are of central importance:

  • Power dissipation at the intended load for all devices and conductors
  • Power dissipation capacity of the enclosure
  • Functionality of devices and conductors at the calculated temperatures

Only if planners know these variables and can work with the corresponding values is a standard-compliant calculation possible. And this is crucial. Because: According to the norm IEC 61439, the responsibility lies with the system builder. The use of individual components within a switchgear combination extinguishes the liability and responsibility of the manufacturer. The reason for this is that a switchgear forms a self-contained black box.

Equipped for errors

Schaltschrank von innen

Should an error occur, it is clear that without the required documentary evidence for the heat calculation, the plant constructor is faced with major problems. If he cannot prove beyond doubt that he has worked in accordance with the standard and that the calculations were carried out correctly, he must assume liability. With the help of the documentary proof, however, it becomes clear that the error is not his responsibility, but that of the operator, for example. Documentary evidence includes an exact type and item record of the components used.

But the real challenge begins with this proof and the heat calculation. Because the availability of the required data is rarely given

to the plant engineers. Information on power loss and temperature resistance is sought in vain. Another problem is that in practice the cables used are only cut to length during the construction of the system. Accordingly, there are no reliable figures that can be used for calculation. As a result, the planner has to contact the manufacturer for each individual unit, ask for the values and finally record them manually. A process that could hardly be more time-consuming and error-prone. In the end, this can lead to the determination of the data being so time-consuming that the costs for the heating certificate exceed the profit margin.

Highly complex heat calculation

And that’s not all. Once the data has been determined and is available, the calculation begins, which is not possible without further variables. Part of the calculation are:

  • equipment-related data, which refers to the material properties of the components used
  • Data on loads caused by the operation of the system
  • Data on the wiring used

Only in combination does this produce a reliable result that allows conclusions to be drawn about the resistance to heat. All factors are part of an exact and highly complex calculation that can overwhelm even technically skilled and experienced planners. After all, it is difficult to predict how a system will behave under prolonged full-load operation. Likewise, load conditions that are difficult to calculate may only occur after a long period of operation or after a possible expansion of the plant. However, a test or an exact simulation that checks these scenarios would involve too much effort.

Automated tools for heat calculation according to IEC 61439

The solution to the planners’ problems is: systematic software solutions. Because with them, the calculation effort is significantly reduced. Such automated calculation tools include all relevant variables in the heat calculation and, on this basis, create exact and legally impeccable documentation proofs. This fulfils the norm IEC 61439. However, not every solution is suitable and ultimately leads to increased efficiency in heat calculation.

First of all, it is particularly important to select a system that is linked to the manufacturers’ material databases. Otherwise, the solution will not have access to the required data on the individual components and will be useless. As before, the plant engineer would be forced to collect the data and manually collate the required information. A decisive expenditure of time, which is precisely what a systemic software solution wants to prevent. Equally important is the compatibility of the solution with the CAD system used. This is a prerequisite for opening and editing a CAD project with the heat calculation tool without additional effort.

Conclusion

Compliance with the norm IEC 61439 is still a major challenge for many plant engineers. The culprits are the very complex requirements of the norm and the lack of the necessary data. The AmpereSoft TemperatureCalculator makes it possible to perform the heat calculation quickly, reliably and fully. Planners thus achieve significant time savings by simply calculating the heat development in the switch cabinet at the push of a button. In addition, the solution creates the legally required documentation verifications according to DIN EN 61439-1 completely automatically without any additional effort. This means that planners work much more efficiently and are on the legally safe side.