We are looking to import, install and service a range of specialised electronic devices and want to understand the our obligations around electrical compliance.

What certifications are required for the following? And what work can be carried out by qualified / non-qualified persons?:

1. Importing, selling and installing a 230v electrical device by plugging cord into mains outlet.

2. Importing, selling and installing a 110v electrical device by plugging into step-down transformer then plugging transformer into main outlet.

3. Scenario 2 but then also connecting custom earth cable from transformer to device.

4. Replacing 110v or 230v components within the device.

5. Adding new 110v or 230v components to the device by wiring into device circuit breaker (screwing on ring terminals) or plugging into internal connectors (bullet terminals etc). e.g. Adding an embedded PC to run off the one power supply.

Also what difference does it make to compliance if we get any modifications "approved" by the manufacturer of the device?