Switch cabinet fire protection

In the event of a fire, the electric system plays a double role:

• It can generate the energy required for the ignition.
• It provides the combustible material needed for the spreading of the fire.

Fires originating in the electric system account for a relatively large proportion of the total number of fires. Circa 45 percent (source: BARPI) of technological accidents have a material failure as their main cause.

Causes of an electrical fire

• A short circuit. This is a rare occurrence on an electric installation conforming to standards, since the safety devices (circuit breakers or fuses) will be immediately triggered.
• A surcharge. In this instance, the conductors heat up, without the safety devices being triggered.
• A contact resistance, with heating occurring between two elements, causing electric arcing.

With our straightforward fire protection system, you will get a starting fire in the electrical switch cabinet under control in no time.

Detecting a fire in an electrical switch cabinet

You need a special kind of detector that is especially designed to rapidly identify combustion aerosols. We use two types of detectors:

• The ionisation smoke detector. The presence of smoke particles modifies the watch current in an ionisation chamber. This makes it possible to detect smoke before it becomes visible.
• The optical smoke detector. This is based on the smoke particle reflection principle called Tyndall effect.

As a rule, a manual trigger is available.

Control and indication in an electrical switch cabinet

A control and indication panel is positioned in the vicinity of the cabinet. It manages the signals generated by the various detectors and controls the automatic extinction. It also controls the information devices (sound alarm, flashing lamp) and generates the interlocking contacts required to stop switch off the cabinet.

Extinguishing agents for an electrical switch cabinet

Virtually all available extinguishing substances can be used on this type of fire. Where automatic extinction systems are concerned, it is preferable to use physical gases which will smother the fire, making the decontamination easier after triggering.

CO2 is easy to use and comes in two forms:

• Liquid, but the equipment to be protected has to be able to take the heat shock when sprayed.
• Vapour. Here, the CO2 is expanded upstream from the switch cabinet, removing all risk of a heat shock.

Nitrogen or argon are used in their gaseous form in storage reservoirs under a 200 bar pressure.

Whatever substance you decide to use, the necessary quantity depends on the elements below:

• Volume of the cabinet.
• Ventilation systems.
• Cabinet seal.

The system is calculated to maintain a concentration for 10 minutes or so in order to smother deep fires. The extinguishing system consists of steel tubes as well as hoses and spray nozzles.

Extinguishing a fire in an electrical switch cabinet

The detectors in the upper part of the cabinet detect the smoke and send a signal to the control panel. Immediately, the following elements are triggered:

• Sound alarm and flashing light.
• The interlocking contacts in order to switch off the cabinet and, if necessary, the ventilation.
• Extinction: the cylinder opens and totally empties itself inside the cabinet.