Electrical systems go into the building and then into a circuit breaker of some sort. That circuit breaker can let the electrical system make sure it doesn't overload. The circuits can also be turned off by hand for whatever reason. In large industrial uses, that circuit breaker can be very large, carry a lot of voltage, and need its own enclosure so that it doesn't cause any problems with any other system. There are a lot of things that these enclosures can be made of, one of those is fiberglass.
Fiberglass can be turned into all kinds of things, from insulation to your car. Part of what gives it that flexibility is the fact that it can be made with a lot of things. The basic ingredient of any kind of fiberglass is going to be long strands of glass. The stands of glass can then be set into some kind of plastic or resin. As the fiberglass is being made, it can be turned into sheets, fluffy mats, or several other things. There are a lot of reasons to use fiberglass for enclosures around electrical circuit breakers or in other electrical uses.
One big reason to use fiberglass around electrical systems is that it is non-conductive. That means that it won't carry electricity and can, therefore, be handled much more safely than metal electrical enclosures could be used when dealing with extremely high currents or large electrical settings.
Another reason to use fiberglass electrical enclosures for electrical systems is that it's very easy to mold into different shapes. That's why you can see it in cars, bathtubs, chairs, and other settings. That lets fiberglass enclosures be made into just about any shape and any size that is necessary to make the enclosure safe and to give plenty of room to work in.
Even though fiberglass is relatively light, it can last for a long while. If the enclosure has to be outside or somewhere where it could be exposed to temperature change and the elements, fiberglass can be a really good choice since it can handle all those things.
Without electricity, nothing is going to work. When electricity comes into the factory, it's going to need to go through a set of circuit breakers and needs to have some kind of enclosure so that it can be dealt with safely. Fiberglass can be an ideal material for this usage.