Dispositivo de protección contra sobrecorriente
Todos los componentes de un sistema eléctrico tienen una cantidad máxima de corriente que están clasificados para manejar de manera continua, si se excede esta clasificación, se generará un exceso de calor que puede provocar un incendio. Los dispositivos de protección contra sobrecorrientes (DPCS) se utilizan para abrir (desconectar) automáticamente un circuito si se alcanza una determinada corriente durante un cierto período de tiempo. El tamaño del dispositivo de protección contra sobrecorrientes requerido está determinado por la cantidad máxima de corriente que se anticipa que transportará un circuito y el tamaño del conductor en el circuito que está protegiendo. Los tipos más comunes de dispositivos de protección contra sobrecorrientes que se utilizan en los sistemas eléctricos son los fusibles y los interruptores automáticos.
Los dispositivos de protección contra sobrecorrientes para un sistema FV autónomo deben dimensionarse y seleccionarse junto con el tamaño del conductor de un circuito; consulte Dimensionamiento y selección de cables, protección contra sobrecorrientes y medios de desconexión para obtener más información.
Contents
DPCS en un sistema FV autónomo
Each PV system will vary in terms of its OCPD 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 many OCPDs that are commonly incorporated into an off-grid system, but simpler systems will not require as many and more complex systems will likely require additional OCPDs. Not all of the OCPDs in the diagram are completely necessary, it may be possible to omit some as they are already protected from excessive current by another OCPD. Any connections made directly to the energy storage system must be protected by an OCPD as the energy storage system can supply a tremendous amount of current in a short period of time. Many of these OCPDs depicted also serve as power source disconnects and equipment disconnects.
- PV source circuit OCPD
- PV output circuit OCPD
- Charge controller ouput circuit OCPD
- DC lighting output circuit OCPD
- DC branch circuit OCPD
- Inverter input circuit OCPD
- Inverter output circuit OCPD
- AC branch circuit OCPD
- Battery circuit OCPD
Characteristics
There are innumerable different OCPDs in the market with each one designed to fit a specific purpose. Many OCPDs are similar in appearance, therefore it is very important to revise the fine print on the side of any OCPD being considered to make sure that it is appropriate for the conditions of use.
Current type
OCPDs may be designed to work with AC, DC or both types of current. If a breaker is rated for both AC and DC, it is likely that the DC voltage rating will be lower as DC circuits are more difficult to interrupt.
Current rating
(B) (most sensitive), (C) (less sensitive), (D) (most sensitive).[1]
OCPDs will be rated for a specific continuous current rating.
- Standard international OCPD sizes: 1 A, 2 A, 4 A, 6 A, 10 A, 13 A, 16 A, 20 A, 25 A, 32 A, 40 A, 50 A, 63 A, 80 A, 100 A, 125 A, 150 A, 175 A, 200 A, 225 A, 250 A.
- Standard US OCPD sizes per US NEC: 15 A, 20 A, 25 A, 30 A, 35 A, 40 A, 45 A, 50 A, 60 A, 70 A, 80 A, 90 A, 100 A, 110 A, 125 A, 150 A, 175 A, 200 A, 225 A, 250 A, 300 A, 350 A, 400 A, 450 A, 500 A. Additional standard fuse sizes are 1, 3, 6, 10, and 601 A.
Current flow
Some circuits in an off-grid PV system carry current in both directions like the energy storage system circuit as it charges and discharges. This can be an issue for certain types of breakers that are not rated for current flow in both directions. If a breaker is marked on the side specifying a direction for current flow - typically with "line" on top and "load" on the bottom, then it should not be used in a circuit that has current flow in both directions.
Trip curve
OCPDs will have a trip curve which specifies how long the device can sustain current above its continuous duty rating. This is desirable because in electrical systems there are often surge loads that require additional current for a very brief period of time when starting. If an OCPD does not have a slight time delay, it will trip every time a surge load is connected. For all typical circuits in an off-grid PV system, an OCPD with a time delay is recommended.
Maximum voltage
AC and DC breakers will be rated for the maximum circuit voltage that they are intended to work with. It can be difficult to find OCPDs rated to work with DC at higher voltages.
Ampere interrupting capacity rating
Ampere interrupting capacity (AIC) rating is the OCPDs ability to withstand current and still open (disconnect) a circuit. This rating is typically hundreds of times the current rating of the breaker with a typical 15 A household breaker having an AIC rating of 10,0000 A. AIC ratings are typically not relevant in the case of off-grid PV systems.
Mounting type
- There are many different types of fuse holders and corresponding fuses. They must be designed to work together.
- Breakers will be designed to be mounted in a specific type of distribution panel or on DIN rail.
Projected life
- Fuses only work once and need to be replaced after tripping. For off-grid applications breakers are always preferrable for this reason as acquiring replacement fuses in remote locations can be difficult.
- Breakers can typically withstand a minimum of hundreds of faults. If a breaker fails, it will typically fail open (circuit disconnected).
Maintenance
There is no maintenance to be done in either case, other than to make sure that the connections to the OCPD remain tight over time.
Recyclability
Standard breakers and fuses typically do not contain anything hazardous, but should be recycled as E-waste as traditional waste disposal streams cannot process them.
Notes/references
- ↑ Wikimedia Commons: Standard Trip Characteristic of a Thermomagnetic Circuit Breaker https://commons.wikimedia.org/wiki/File:Standard_Trip_Characteristic_of_a_Thermomagnetic_Circuit_Breaker.svg
