The use of inverters in energy connection to the grid requires a standard procedure that must be followed to realize desirable results. Generally, AS/NZ 4777 standard for power inverters requires that it should support a maximum of 100kVA. It also requires balancing for systems with over 20A – making its largest installation to be 4.8kVA. Throughout its lifespan it needs liaison with electricity distributor. It also involves inclusion of micro inverters such as AC modules; and with the use of inverters with multiple modes, a new definition is added. Consideration of standards such as IEC 62109 is essential. Vitally important, it is worth noting that the word shall denotes a mandatory statement and should refers to a recommendation on the basis of industry’s best practice. Failure to comply requires a justification.
It consists of inverter(s), source(s) of energy, wiring, metering, control, and safety devices – all connected to a specific point within an installation. Household installations shall have a maximum of 600V d.c. while non-household areas shall have restrictions on the wiring and equipment and permission shall only be granted to authorized persons. Also, systems with currents in excess of 20A shall have the output balanced among its three phases. It is also recommended that the gross output be metered. The system connection of MSB or DSB is compulsory. The use of connectors as well as couplers is acceptable but not the a.c. standard type. Also, cable ties made of plastic are not acceptable. The voltage drop as well as voltage rise should be by a margin of 1 percent between the inverter and main switch of the inverter, and 1 percent between main switch of inverter and connection point. In the event that a single inverter fails to meet the requirements of a multiple inverter then there shall be need for more central protection outside the IES. Balance protection of phases is essential at the inverter supply, that is, the main switch if: The unbalance in current is higher than 20A and that in voltage higher than 2 percent. There is need for voltage protection as well as frequency protection of integrated inverter for IES greater than 30kVA. This additional safety offers a coordination level between supply point, single inverters, as well as consumer installation equipment. The protection of mechanical cable is facilitated by RCDs which must be specified by the manufacturer. There is need for special consideration of UPS or Multiple Mode. These will be critical for the operation of the inverter.