Compared with the centralized photovoltaic power station on the ground, the distributed photovoltaic power station is relatively small, but relatively dispersed, in general, the grid-connected voltage level is 380V, in this low-voltage grid-connected case, generally in the secondary computer protection involved less, usually distributed photovoltaic power station used computer protection is anti-island protection device, the device is installed in the grid-connected cabinet. For this reason, the use of distributed grid-connected cabinets is widely used in distributed photovoltaic power stations. As shown in the picture below:
It can be seen that the composition of the photovoltaic grid-connected cabinet is composed of anti-island protection device, low-voltage circuit breaker, air switch, lightning arrester, temperature and humidity heater, stainless steel box and other equipment. The choice of circuit breaker should be based on the actual current flowing through the circuit breaker, generally about 1.2 times the rated current.
The above is routine, according to the different projects, the equipment in the distributed grid-connected cabinet is also different, and some projects need to install electricity meters or other equipment in the grid-connected cabinet, depending on the project. A friend often asks where the photovoltaic anti-island protection device is installed, which is actually very simple. The main functions of anti-island protection device are high frequency protection, low frequency protection, high voltage protection, low voltage protection, reverse power protection and so on. The anti-island protection device will switch on the grid-connected circuit breaker when it detects a fault.
Therefore, it is most appropriate to install the anti-island protection device in the grid-connected cabinet. It should be noted that the anti-island protection device is a kind of microcomputer protection, and it is also necessary to debug and do experiments during use. The minimum protection setting is the need for on-site electrical debugging personnel to set the protection setting value given by the relevant department, if there is no set value, then the protection device is useless.