Tipos de conductores
El término conductor se utiliza para referirse tanto a alambres como a cables. Los conductores permiten el transporte seguro de electricidad entre todos los diferentes componentes de un sistema eléctrico. El cable o alambre se refiere a un solo conductor, mientras que el termino cable de cordón contiene varios cables o alambres dentro de una capa adicional de aislamiento que los protege. El material conductor de un cable puede ser cobre o aluminio y su size varía según la cantidad de corriente que deberá transportar, el voltaje y las condiciones. Con los sistemas FV, normalmente se usa el cobre, ya que puede transportar más corriente para el mismo tamaño de alambre y es más fácil de doblar y manipular. Aislamiento de cables puede ser de plástico o caucho y varía en color según la aplicación y el lugar. También variará en grosor dependiendo de la clasificación de voltaje del cable, ya que una clasificación de voltaje más alta requerirá aislamiento adicional.
Los cables para un sistema fuera de la red deben dimensionarse y seleccionarse en función de la evaluación de cargas y la evaluación física para un sitio en particular. Este proceso debe realizarse junto con el tamaño y la selección del dispositivo de protección contra sobrecorriente para el circuito - consulte Dimensionamiento y selección de cables, protección contra sobrecorrientes y medios de desconexión para obtener más información.
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Tipos de conductores
Además de su clasificación de corriente máxima, los conductores tienen otras clasificaciones adicionales.[1]
Hilos
- Trenzado: el cable trenzado estándar es el tipo de cable más utilizado, ya que es fácil de trabajar en la mayoría de circunstancias y es relativamente barato.
- Trenzado fino: se prefiere el cable trenzado fino cuando se trabaja con baterías o en espacios reducidos, ya que es más fácil de doblar y manipular.
- Sólido: normalmente solo se usa para cableado interior. Por lo general, cuesta un poquito menos que el cable trenzado, pero más difícil de doblar y manipular. No se debe utilizar con un tamaño superior a 10 AWG / 4 mm².
- Desnudo (sin aislamiento): una opción barata y duradera que se puede usar como parte de un sistema de conexión a tierra en exteriores sin un conducto si se encuentra en un lugar donde no se dañará.
Insulation and conditions of use
These classifications should be printed on the side of any wire or cable, although the exact terminology may vary based upon location. Below are some of the designations that are commonly used for wires used in off-grid PV installations.
| Classification | Common designation |
|---|---|
| Maximum insulation voltage | 600 V, 1000 V, 2000 V |
| Heat resistance | 60°C, 75°C, 90°C |
| Durable thermoplastic insulation | T |
| Synthetic polymer, flame-resistant | X |
| R | Rubber or Neoprene insulation |
| Heat resistant up to 75°C | H |
| Heat resistant up to 90°C | HH |
| Rated for use in wet locations | W |
| Nylon-coated to resist damage from oil or gasoline | N |
Common wire types used in off-grid PV installations
There are countless different types of wire, but there are only a few types that are commonly used on off-grid PV installations:
| Designation | Characteristics | Use |
|---|---|---|
| THHN/THWN | Rated for up to 90°C in wet or dry locations. 600V rating. Available in nearly any size. | Used for circuits of any kind - inside or outside - within a conduit. |
| RHH RHW, or XHHW-2 | Flexible insulation rated. Characteristics may vary. | Battery wiring |
| PV wire/USE-2/RHW-2 | Rated for up to 90° in wet or dry locations. Can be exposed to sunlight. Voltage rating 600-2000 V. Typically only found in certain sizes (12 AWG, 4 mm², 10 AWG, 6 mm²) | Wiring of PV source and from PV source to combiner box or charge controller. |
Cable types
All circuits involve more than one wire, therefore using cables that include multiple cables can save time and reduce costs on installations. Additionally, using cables of this type brings advantages that single wires do not offer.
| Type | Characteristics | Use |
|---|---|---|
| Non-metallic indoor rated | A varying number of wires of a chosen size bundled inside of a flexible plastic jacket or fused together. Cheap and easy to work with but should only be installed in locations where it is protected from damage or in a conduit if it is an appropriate type of cable to be used in a conduit. | Used for indoor circuits in protected locations. |
| Direct burial cable | A varying number of wires of a chosen size bundled inside of multiple layers of insulation that provide excellent protection against damage, water and degradation. Can be directly buried underground without conduit if at a sufficient depth. Cheap and easy to work with. | Outdoor circuits that need to be run underground. |
| Metal clad indoor rated | A varying number of wires of a chosen size bundled inside of a flexible metal jacket. More expensive than other cable options but provides superior protection. | Indoor wiring that needs to be protected. |
Securing and supporting wires and cable
Wire and cable do not always have to be run in conduit if they are not in a location where they will be exposed to damage, like an attic or under a PV module. If they are not placed in conduit, they still must be properly secured and supported appropriately. The electrical code for the location will specify the minimum distance between supports, although the appropriate distance between supports should ultimately be determined based upon what will offer the most protection from accidental contact or damage from friction. Cables and wires should be snug against the surface they are being run against rather than drooping or dangling, although they should not be so tight that they are being significantly strained between supports. It is important to offer additional support near junction boxes as strain placed near a connection can lead to its failure.
Projected life
If wire is installed under proper conditions and not damaged, it should last for decades. Sunlight, abrasion, or excessive movement will gradually destroy any type of wire.
Maintenance
All wiring should be checked at least once a year to make sure that it is not deteriorating or on the verge of failure.
Recyclability
Wire contains copper and aluminum, both of which are valuable metals. Wire can be recycled in major cities in nearly any part of the world at many different scrap facilities.
Notes/references
- ↑ Multi/Cable wire abbreviations and descriptions https://www.multicable.com/resources/reference-data/wire-abbreviations-and-descriptions/
