Solar DC Fuses are used as an overcurrent protection device in solar PV projects. Solar DC fuses are installed on the DC side of solar PV projects and are usually housed within DCDB/AJB/SCB/SMB boxes.
In this article, we will discuss what are Solar DC Fuses or Overcurrent Devices in a rooftop solar project. We will also look at the criteria to select and size the solar DC fuse with a few solved examples.
AC Fuse v/s DC Fuse
Unlike conventional AC systems, the available short circuit current within the PV systems is limited. The working principle of DC fuse is different from AC fuse.
Hence, AC Fuses shall not be used in replacement of DC fuses.
DC Fuse – Diconnecting Device
One of the misconception in the industry is that the DC fuses are used as an disconnecting device. However, DC fuses are not disconnecting device and should never be used for disconnecting or isolating a string under load conditions.
If a fuse is used to disconnect a string while the load is connected, a huge DC arc will be developed and chances of fire will increase.
DC fuses shall only be used if the inverter is switched off and load is disconnected.
Parts of DC Fuse
There are two parts of a Solar DC Fuse:
- DC fuse holder
- DC fuse link
Based on the system configuration, Voltage and Current rating of DC Fuse Holder and DC Fuse Link should be selected.
While selecting the DC fuse link, one need to check whether the selected fuse link is a gPV Photovoltaic Fuse and is manufactured in accordance with IEC 60269 – 6.