Seguridad electrica

El camino que toma la corriente de mano a mano pasa por el corazón.

La electricidad presenta un desafío para la seguridad ya que crea peligros que no podemos ver. La única forma de trabajar de forma segura con electricidad es seguir todas las precauciones necesarias en todo momento para evitar accidentes. Incluso las descargas eléctricas pequeñas pueden ser peligrosas para los seres humanos, ya que los ritmos de nuestro corazón y cerebro funcionan con electricidad y una descarga puede interrumpirlos. Como siempre con la electricidad, el voltaje, la corriente y la resistencia entran en juego cuando se piensa en la seguridad con la electricidad. La piel humana tiene una cierta cantidad de resistencia que debe superarse para que el voltaje pueda pasar a través de ella. Si toca los terminales positivo (+) y negativo (-) de una batería de 12 V con las manos secas, no debería recibir ninguna descarga. Si sus manos están mojadas o sudorosas, es posible que reciba un golpe, ya que esto reducirá en gran medida la resistencia de su piel y la hará más conductora. Los sistemas con voltajes nominales superiores a 24 V son capaces de dar una descarga, pero generalmente se acepta que se requiere un sistema con una tensión nominal superior a 50 V para poder producir una descarga mortal. No obstante, es una buena práctica tomar todas las precauciones posibles, incluido el EPP adecuado y restringir el acceso al personal no autorizado para evitar accidentes.

Si un voltaje puede superar la resistencia de su piel, la corriente se vuelve muy importante. Una descarga eléctrica estática entre una prenda de ropa y una persona puede ser de 3000 a 20000 V, pero causa nada más que una sacudida momentánea. Por lo tanto, la corriente se convierte en un factor importante para determinar qué tan peligrosa es una fuente eléctrica. Depende del camino que tome la corriente eléctrica, pero tan solo .1 o .2 A puede causar un paro cardíaco y mucho menos hacer que sienta dolor.

La forma más segura de trabajar con electricidad es cuando el circuito o sistema está desconectado y no tiene voltaje. Sin embargo, antes de trabajar con cualquier sistema eléctrico, es necesario conocer su voltaje y la cantidad potencial de corriente que puede suministrar. Como no podemos ver la electricidad, la única forma de estar completamente seguro de que un sistema está apagado es usando un multímetro para verificar si hay voltaje en ese momento.

Safety with PV

Even with small amounts of sunlight, a PV module will produce voltage. There is no way to stop them from functioning - if there is sunlight, then it should be assumed that a PV module or an array are producing voltage. It is therefore necessary to proceed with caution at all times. Even covering a module with a tarp or opaque covering is typically not sufficient to reduce the voltage to zero as sunlight can still enter from the back of a module. In the case of PV, it is therefore very important on new installations to leave modules disconnected until all other work is finished. On existing installs, circuits connected to PV should always be treated as if have voltage and all necessary precautions should be taken.

Safety with energy storage systems

Most batteries do not have a way to disable them - they sit at a steady voltage waiting for a path through which they can supply current. Energy storage systems with a nominal voltage above 48 volts can deliver a potentially lethal shock, but also carry an additional risk due to the tremendous amounts of energy that they store that can be released very rapidly. If an energy storage system is short-circuited it can produce sparks and destructive amounts of heat that can destroy equipment and start fires instantly - this is called an arc flash. The potential for an arc flash increases with the size of the energy storage system. A small system with one or two 12V lead acid batteries with a low Ah rating will not be able to produce an arc flash, but as the size increases beyond this point, so does the potential for an arc flash.

One of the most common accidents that happens when working with batteries is the creation of a short-circuit in the battery bank by dropping a metal tool that provides a low resistance path between the (+) and (-) terminals of a battery. When installing or maintaining batteries, it is best to buy tools that are insulated. If insulated tools are not available where you work or cost prohibitive, then tools can be made less likely to create a short by insulating them with electrical tape.

Batteries should always be handled with extreme caution and carry additional hazards that go beyond electrical hazards. When working with energy storage systems of any kind, the bare minimum amount of personal protective equipment that should be worn is eye protection. Additional PPE should be worn in accordance with the risk created by the particular type of energy storage - this is discussed in more detail in the section that is dedicated to each type of energy storage. See Lead acid battery safety for more information on safety related to lead acid batteries.

Lock out, tag out

A distribution panel that has been locked out and tagged out.

Following proper electrical safety procedures has saved many lives. One of the most important electrical safety guidelines is called Lock out, tag out. Lock out, tag out means that if someone is working on an electrical system that any potential power sources are disconnected and that the means to reconnect or energize them can only be operated by someone who is authorized to do so. In commercial and industrial environments this is done with a device that includes a lock and a tag that notifies all individuals who to contact about the locked out power source. It is often unnecessary on small projects to follow this same guideline exactly, but the principles of lock out, tag out should always be applied. In off-grid settings final connections should be left undone and marked with tape at the minimum. If the distribution panel or battery box has a lock, it should be locked if no one is working in the area to avoid any accidents.

Safety on new electrical systems

1. Identify if there are any other power sources of electrical systems.
2. Leave any connections that would connect a power source disconnected. These power source connections should be locked out and tagged out.
3. Complete all work possible before energizing the system.
4. Perform all necessary checks on the system.
5. Notify everyone in the vicinity that you are going to energize the system.
6. Energize the system and perform final performance checks.

See Commissioning for more information on energizing a newly installed off-grid system.

Safety on already existing systems

1. Communicate to anyone else that may use the system, or is in the area, that you are going to begin working.
2. Determine what the rated voltage and potential current that the electrical system you are working on can supply.
3. Disconnect the circuit or turn off the system.
4. Use a multimeter to measure to make sure that there is no voltage.
5. Perform lock out, tag out.