Before the relay is returned to normal service, the installed modifications have to be tested and commissioned. The recommendation is that minimum the changed functionality of both the hardware and the software be tested. The testing procedure for the modified part must be the same as when commissioning a new relay.
If the relay’s hardware is extended by additional modules, the functionality that the new modules offer the relay has to be tested. If the relay hardware setup is modified by changing an existing module type to a different one, additional checks regarding the removed functionality must be done.