Medio de desconexión

'Un ejemplo de un medio de desconexión tradicional.'
La manija roja mueve el cilindro rojo en el centro para conectar y desconectar las terminales de línea (superior) y de carga (inferior).

Un medio de desconexión permite desconectar o aislar un circuito del resto de un sistema eléctrico. Los medios de desconexión son vitales para la seguridad y protección de personas, ya que permiten aislar diferentes componentes del sistema para realizar el mantenimiento o el servicio. Los medios de desconexion tradicionales, como en el gráfico, vienen en innumerables tamaños y configuraciones diferentes, incluidas configuraciones personalizadas. Aunque no se utilizan a menudo en systems FV autónomos a pequeña escala, ya que la mayoría de las necesidades de desconexión se pueden satisfacer con interruptores automáticos, portafusibles o terminales de módulos que son más baratos y sencillos. Un medio de desconexión tradicional debe estar clasificada para la corriente adecuada (CA o CC), voltaje máximo y corriente máxima del circuito. También se pueden encontrar medios de desconexión que incorporan fusibles para aplicaciones que requiere un medio de desconexión tradicional y un dispositivo de protección contra sobrecorriente.

El tipo apropiado de medio desconexión para un circuito depende del tipo de circuito; hay dos tipos diferentes de desconexiones que se requieren en un sistema FV autónomo.

Medios de desconexión en un sistema FV autónomo

Each off-grid PV system will vary in terms of the necessary disconnect needs both due to design and local requirements. The diagram at right depicts a hypothetical stand-alone system with DC lighting and an inverter for loads. It depicts disconnects that are commonly required in an off-grid system, but simpler systems will not require as many and more complex systems may require additional disconnects.

Power source disconnects

Wiring diagram of a stand-alone PV system with a charge controller with DC lighting control and an inverter for AC loads. All required OCPDs are identified.

Power source disconnects enable the isolation of any potential power source, including while under load (while current is flowing) in case of emergency. In an off-grid PV system there are three power sources that meet this requirement:

• The PV source (disconnect #2 in the diagram).
• The energy storage system (disconnect #4 in the diagram).
• The inverter (disconnect #5 in the diagram).

If a system incorporates a generator then it will also require a separate disconnect. For off-grid PV systems, breakers are typically used as power source disconnects as they can fulfill the role of an OCPD at the same time, although a properly sized (suitable for DC, correct voltage, correct current) traditional disconnect would work just fine. Any power source disconnect must be rated to disconnect a circuit with current flowing, therefore fuse holders or any type of connector cannot qualify as a power source disconnect as they cannot be opened under load.

Equipment disconnects

All major components in a PV system that may require service or maintenance should have a disconnect that enables them to be isolated from these two potential power sources or any others, although for equipment that is not a power source, it is not necessary that an equipment disconnect be able to function under load. In a typical stand-alone system, there are three pieces of equipment that meet this requirement:

• PV module equipment (disconnect #1 in the diagram).
• Charge controller equipment (disconnect #3 in the diagram).
• Inverter equipment (disconnect #5 in the diagram).

Therefore, touch safe fuse holders and equipment connectors - like MC4 connectors on PV modules - can qualify as equipment disconnects. To be able to use equipment disconnects that are not designed to function under load, it is necessary to have a power source disconnect that can be used to stop any current from flowing before use.