Preventing arc flashes in distributors
Simulations do not prevent electric arcs. However, simulations can minimise the damage of electric arcs, help identify risks and increase awareness.
As a rule, work is always carried out in a de-energised state. However, there are situations in which this is not possible or desirable. For example, when working on battery systems and PV systems. In these cases, voltage (and therefore risk) is always present. Other examples include work in the vicinity of live (preferential) fields in crucial infrastructure such as hospitals.
In these kinds of situations, good preparation and knowledge of the risks are essential.
Is your protection adequate?
Arcs must be interrupted. Every circuit breaker or fuse has a specific tripping characteristic: at a certain current, it takes a certain time for the protection to switch on.
Current too low
If the current is too low, it takes a long time for the safety device to be activated. An electric arc at the end of a long cable has a lower current than at the beginning, due to the impedance of the cable. This is very dangerous: a short circuit or an arc flash may occur that does not switch off.
Current too high
In some cases, the short-circuit current can be so high that the circuit breaker cannot switch off without damage. This is also called short-circuit resistance. In such cases, cascade or pre-fuse protection is often applied: a fuse is placed before the circuit breaker to help limit the short-circuit capacity.
Adequate protection goes hand in hand with selectivity: ensuring that correct protection is activated so that as few users as possible are disconnected.
Is your PV installation safe?
Small arc flashes are becoming more and more common, these are not explosive and occur between connectors in PV installations.
Can the distributor cope with the amount of energy?
An arc flash involves an explosive amount of energy. The distributor must be designed in such a way that this does not pose a problem. For large capacities, tried and tested standard solutions are usually implemented. However, if distributors are used outside the specification, for example due to adjustments in the installation elsewhere, the consequences can be disastrous.
Several factors affect the safety of the distributor, such as its placement (freely standing in a space or against a wall), the distance between the rails, materials used and contamination.
The construction of the cables and busbars also need to be considered: due to the high current during an arc flash, high magnetic fields are developed that repel each other. This creates significant forces on the (mechanical) mounting material.
Arc flash simulations help determine the risk of electric arcs and support implementation of risk-reducing measures. Arc flash simulations go hand in hand with selectivity and are therefore a cost-effective way of quickly assessing and optimising the entire installation.
Take a look at our arc flash cases!
