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92-93 Safety fire prevention - DC fault and protection measures

Author: Source: Datetime: 2017-01-09 19:45:06
4.2.6 Safety fire prevention - DC fault and protection measures

With the increasingly widespread application of photovoltaic systems, fire safety issues have become more and more attention, from the system design, component selection to the installation and operation of construction and maintenance management should pay attention to, in particular, photovoltaic systems often lead to fire building Fire (Figure 4-31, Figure 4-32).



The most common cause of fire is DC arc, followed by fire protection measures are not in place, photovoltaic components and electrical accidents, etc., foreign research shows that the proportion of PV system causes the fire is as follows:
•  DC arc
•  24% failure of fire protection measures;
•  16% of PV components per set;
 6% Electrical accidents;
•  2% Other.
Figure 4-31 Photovoltaic System Fire A building caught in fire
Figure 4-32 Fire protection and safety of PV systems
Figure 4-33 Location of PV system arc occurrence

Figure 4-33 shows the location of the arc. We note that the reverse current cut off, the arc will be extinguished. Can be non-polar circuit breakers or fuses to quickly cut off the reverse current, but also to extinguish the arc in time. The problem is that, in the case of normal forward current, if the arc, because the current value does not significantly deviate from the normal current value, it is difficult to judge and distinguish from the current value, it can not detect and extinguish the arc. In this case, both the circuit breaker and the fuse will not fail, and the circuit will not be cut off. The arc will burn until the circuit is switched off and the arc is extinguished. This is one of the main threats to photovoltaic power generation system. Due to the characteristics of the current arc, in the event of a fire, in addition to man-made discovery and rapid removal of faults, the local or global burn will often end. Here to draw special attention.

Another major hazard is the short-circuit reverse current, its value is often surprisingly large, such as can not be cut off in time, this current is sufficient to burn electrical equipment and electrical lines caused the fire. Because this reverse current is easier to distinguish, and with the non-polar circuit breakers and fuses, can be very good cut off the reverse current.

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