Fuses: what are they and when to use them correctly?

Layman or expert, you've certainly heard of fuses. These basic safety devices are present in most photovoltaic arrays, whether commercial or not.

However, even though fuses are present in everyday life in many installations, the understanding of them is basic.

“What are they?”, “what are they for?” and “how do they work?” These are some of the most common questions about fuses, and they will all be answered in this article.

However, the most prevalent question about these devices is: “When should we use them?”

What are fuses for?

In short, fuses are protective devices used to protect electrical circuits against overloads and short circuits. A fuse has a metallic filament that supports a certain value of current.

When a current that exceeds the limit value – called the breakdown current – passes through the fuse, the current is interrupted.

How does a fuse work?

Fuses are simple devices. These are metallic filaments, often made of lead or tin, which act as fusion elements.

The filament of a fuse is capable of withstanding a certain current limit value. In other words, as long as the current passing through it is lower than the limit value, the filament allows it to pass.

The metallic filament melts and interrupts conduction, preventing overload from causing damage to the electrical installation.

When should fuses be used in photovoltaic systems?

Normal ABNT NBR 16690, they should be used when the intention is to protect string circuits and photovoltaic arrays against reverse currents.

Typically reverse currents are a possibility when a circuit has 3 or more photovoltaic arrays in parallel.

This is because in case of a problem in one of the strings, the defective string can be fed to the chain of two other strings, which could damage the modules and even cause a fire in the photovoltaic plant.

In the photovoltaic industry, the fuses used are, as a rule, gPV fuses, which are designed especially to protect solar systems.

Furthermore, the size of the fuses to be purchased varies according to the system voltage level and also the maximum current supported by each module, a value that is specified in its data sheet. As the standard requires its use only in systems with three or more parallelized strings, its use is not common in systems with fewer parallelized strings.

The opinions and information expressed are the sole responsibility of the author and do not necessarily represent the official position of Canal Solar.