Grid tie inverters
Grid tie inverters are connected to the national grid and match the AC frequency with the inverter (see the inverter article) frequency. This allows them to feed power into the local and national grid.
Grid tie inverters are usually only installed by certified electricians as they require comprehensive installation, connected to the national grid. In the UK for example, this can legally only be done by electricians with MCS (Micro Certification Scheme) approval.
Unlike inverters, which usually work at a fixed battery voltage, grid tie inverters can work at a wide DC range, sometimes up to 600 volts DC. At these levels, DC is extremely dangerous and installers must be very careful when working on PV systems. It could easily be forgotten that it is live, even on a cloudy day. For this and other reasons, these installations are often more serious then a off grid stand alone system 12/24/48 volt system, as they (in theory) could generate electricity which feeds back to the grid, even when the power is believed to be of, if for example a circuit breaker has been activated.
Grid tie inverters must therefore have island protection to prevent this from happening. If the grid goes off, so does the inverter. This prevents an "island" of electricity from being live when, for example, electricians work on cables nearby.
Installations of Grid tie inverters have in some cases caused analogue electrical meters to spin backwards, however today with electronic meters this is less likely. Modern grid tie inverters such as the MasterVolt 600 can be legally used on a DIY basis in some countries such as Holland, so it is important to know what your local law is if you intend to install one your self.
Furthermore, it is also important to remember that non certified solar panels, self build panels might void the warranty when used.
In almost any case, a grid tie inverter should only be installed by professional electricians with correct certification. And it is equally important that the grid tie inverters have the correct certification such as G83. Respectable and recognised names are SunnyBoy, Danfoss and Fornius to mention a few.
For more information:
