In medium to large photovoltaic systems, safety and availability of the system and protection of the operating personnel is very important. Any electrical isolation and the peak performance of the system play a substantial role in the selection of suitable monitoring measures. In general, it is important to locate the fault quickly and automatically.
In small photovoltaic systems, protection of the house residents and possible operators (fire brigade, chimney sweep) is very important. The inverters are mostly factory-equipped with the appropriate safety equipment. They are only safe enough if they can also detect symmetric faults caused by moisture and dirt. At the point of transfer between the internal network and the general power grid, the voltage and frequency must be checked at a predefined range.
Before internal generation systems (photovoltaics, water power, CHP, biogas, etc.) can feed electrical energy into the public grid, an automatic switching point must be installed between the generation system and the low voltage network. This checks whether the frequency and voltage fed in are within the specified range. The three-phase voltage monitoring relay is used to pre-configure numerous standard specifications at the touch of a button.
