What safety features are typically integrated into PV wire designs?
What safety features are typically integrated into PV wire designs?
Using the wrong size of wire can prevent your PV system from delivering enough voltage to power up electrical units. It can also result in arc faults and fires.
Some existing grounded PV systems have burned down because of certain electrical faults. This article compares the design solutions provided by different International Standards to mitigate these fire hazards.
Insulation
The insulation that surrounds the conductor is what protects it from mechanical damage and environmental factors. It’s important that it’s able to withstand the conditions in which it will be exposed, especially since solar power systems are often located in remote or unattractive locations.
It is typically recommended that pv wire be run through conduit, which provides extra protection from physical damage. Conduit also helps ensure that the wires are properly sized and don’t cause overheating or other problems. When running PV wire through conduit, it’s important to follow the recommended fill ratio to prevent overcrowding and excessive friction.
Depending on the installation, PV wire may be required to meet different requirements than traditional electrical wiring. For example, some PV installations require the grounding lugs to be made of copper rather than aluminum, as the latter is more susceptible to corrosion. In addition, some best practices installation standards recommend against the use of cable ties to support cables, as they can damage or break the cable jacket. Fortunately, there are many other methods to choose from that can provide the proper cable support without compromising safety and reliability.
Corrosion
Corrosion is a natural phenomenon that causes pure metals to degrade and break down in reaction to environments like water or air. Corrosion damage can be devastating to infrastructure, buildings, and even solar PV components.
Corrosive corrosion is a serious problem for the busbars (made from copper, silver, aluminium) and metallic contacts within PV solar panels and their junction boxes. This type of corrosion is often exacerbated by the presence of salt in the environment or other chemical contaminants.
To prevent this kind of corrosion, it is important to choose the right wire size and rating for your PV system. It is also essential to install the appropriate conduit and use protective covers. Also, if possible, avoid direct flame impingement on the conduit and wires. If this is not possible, fire ground operations should be conducted with caution and proper safety procedures should be followed to protect against fire-related injuries from contact with the conduit and wires. Also, it is recommended to locate and secure DC and AC disconnect switches in visible areas. This will help to reduce downtime and avoid the need for emergency repairs.
UV Resistance
For a PV solar system to function properly, the wiring needs to be protected from direct sunlight. This protects the conductors from damage and prolongs their lifespan.
This protection is typically achieved with the use of a PV wire cable raceway. Raceways are commonly installed on ground-mounted arrays to protect the cables from direct sunlight, reducing the risk of heat generation and increasing the lifespan of the wire insulation.
A general rule to follow when choosing solar wiring is to select a wire that’s rated to handle the max generating capacity of the panel. Using a wire that’s undersized can result in excessive voltage drop and overheating. Additionally, using undersized wire is a violation of electrical codes in most jurisdictions and may lead to your building inspector failing the installation.
PV wires are available in either single or stranded constructions. Stranded wire contains multiple twisted conductors that offer more flexibility than a solid core. Regardless of which type you choose, it’s important to make sure that the wire is designed for PV systems and has passed a variety of rigorous testing and quality assurance standards. This includes being able to resist temperature extremes, water absorption, harsh abrasion and corrosion, cold bend and compression cuts.
Heat Resistance
Using the right wire is vital in any PV system. Choosing the wrong type of wire can lead to voltage drop, which reduces efficiency and may even cause the system to stop working altogether.
PV systems are typically installed in outdoor environments and must withstand extreme heat, moisture and UV exposure. PV wire and USE-2 cables have thick insulation that can handle this kind of environment.
This type of wire is also designed with stranded conductors, which allows it to better withstand movement caused by vibrations or winds. It also has a higher amp capacity than standard electrical wiring, which allows it to handle high-voltage loads more efficiently.
For the equipment grounding wire (EGC) that runs from each module to the junction or combiner box, installers typically choose a sturdy bare copper AWG 6 solid cable that can withstand rodent gnawing and weather the elements. They then use a less expensive building wire, such as THWN-2 copper, to run the rest of the PV source circuit. Specifying copper over aluminum can reduce the price and improve supply chain management since most aluminum PV wire is manufactured offshore, which can create long delivery delays.
Fire Resistance
Fire resistance is a significant aspect of PV wire design. Using PV cables with higher fire ratings ensures better safety, especially in outdoor applications where the wires may be exposed to sunlight for long periods of time. It’s also important to choose a cable that is properly sized for the PV system. If the cable is undersized, it will quickly overheat and lose energy. Additionally, using undersized cables is a violation of electrical codes in most jurisdictions.
It’s worth pointing out that it is possible to generate fires in PV plants due to various electrical faults that are closely linked with the layout of the plant and the use of specific means of protection (depending on the system architecture). In this context, we analyze two case studies involving existing grounded PV systems where the development of fires was caused by blind spots in the Ground-fault Protection Device (GFPD) that were selected according to technical Standards.
It is also possible that the presence of a transformer in ungrounded PV systems could be a factor in the development of fires. Therefore, ungrounded PV systems should be equipped with an Insulation Monitoring Device or an RCD that is capable of detecting insulation faults.