ENE/Solar/TBT-ENE-010

Inverter Installation and Commissioning

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Solar inverters convert DC electricity from photovoltaic panels into AC electricity for the grid or building.
Inverters can be string type, central type, or micro-inverters depending on the system design.
Central inverters on solar farms weigh several hundred kilograms and require crane or forklift installation.
DC input voltages to string and central inverters can exceed 1,000 volts, creating lethal shock risk.
Commissioning involves energising the inverter with live DC and AC connections for the first time.
Arc flash energy at the inverter terminals can cause severe burns and blast injuries during faults.
Inverters generate heat during operation; adequate ventilation and clearance space must be maintained.
The AC output connects to the distribution network, requiring DNO approval and G99 compliance.
The Electricity at Work Regulations 1989 apply to all inverter installation and commissioning activities.
Only qualified electrical engineers should commission inverters and connect them to the grid.

Lethal DC voltage	DC voltages exceeding 1,000V at inverter inputs cause fatal electrocution with no circuit breaker to interrupt the supply.
Arc flash	Faults at inverter terminals produce arc flash with extreme heat and blast energy, causing severe burns.
Grid connection	Incorrect inverter commissioning can backfeed the distribution network, endangering linesmen and the public.

Don't

Isolate both DC and AC supplies before working on inverter connections.
Treat all DC inputs as live during daylight; they cannot be fully de-energised.
Use DC-rated isolation switches and test equipment for all inverter DC work.
Wear arc-flash-rated PPE when working near live inverter terminals.
Ensure adequate ventilation and clearance space around the installed inverter.
Obtain DNO approval and G99 compliance before connecting to the grid.
Use a crane or forklift with a lift plan for installing heavy central inverters.
Commission inverters only with qualified electrical engineers supervising the process.
Test protection systems including anti-islanding before declaring the inverter operational.
Label all DC and AC isolators clearly at the inverter and at remote locations.

DON'T open inverter covers without isolating both DC and AC supplies first.
DON'T assume DC circuits are safe because the AC side has been isolated.
DON'T use AC-rated switches, fuses, or test equipment on DC inverter circuits.
DON'T commission the inverter without DNO approval and G99 compliance confirmed.
DON'T restrict ventilation around operating inverters; they generate significant heat.
DON'T lift heavy central inverters without a lift plan and mechanical handling.
DON'T allow unqualified persons to commission or energise inverter equipment.
DON'T touch inverter terminals without confirming isolation and proving dead.
DON'T connect to the grid without testing anti-islanding protection systems.
DON'T leave inverter isolators unlabelled; clear identification prevents errors.

See also: DC Electrical Safety (Solar) | Ground Mounted Solar Farm Safety

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