01. All-around Fire Prevention
Over the past few years, there have been many media reports linking the PV system with fire. Nearly 200GW PV systems are now installed over the world, and an increase in incident reports is to be expected.
Fig.2: PV system with fire
Fire incidents have a marked impact on people and property, and it is important to understand the likely mechanisms of ignition in PV systems.
1.1 Potential Fire Hazard：Electrical Arcing
In the discussion about the fire hazard in the PV system, the DC side is always the focus. To be more specific, the major fault that occurs on the DC side is the DC arc fault. Arcing is less of an issue in AC systems is that arcs tend to self-extinguish as the voltage alternates, passing through 0 volts 100 times per second for standard grid supplies. This means that for an arc to be self-sustaining, the conditions for starting the arc have to be present continuously. DC, on the other hand, remains at a continuous voltage and, once an arc has been established, tends to support its continuation. Thus, any evidence of arcing found on sites, whilst not conclusive, points towards a possible, even probable, cause of the fire.
The likely causes of arcing in a PV system can sum as follows:
- Plugs not fully engaged
- Loose screw terminals within junction box or isolation switches
- Damage of the component like cable or bus bar within a PV module
- Moisture ingress degrading connections in connectors or switches.
The places in PV system where arcing is most likely to occur are shown in the figure below:
Fig.3: Where arcing is always likely to occur
Please read Part II of this article, as well as Part III.
