I am actually dealing with a project in Maine where my German company supplies mechanical stuff but the electrical side is covered by (unfortunately too many different) US guys.
The installation is hooked on something like a 50kVA single phase transformer. I would like to understand more in detail the setup of such an installation.
The engineer that planned the enclosure with the control gear is not really an electrician, but more a programmer so he is not an expert with regard to service hook up.
The manufacturer who assembled the stuff is far away and the guys on site do their job as they have ever done it without really knowing "Why".
Okay there is
- a single phase pole mounted transformer
- three wires going to the meter
- as in conduit unknown wires from the meter to a disconnect
- as in conduit unknown wires from this disconnect to the panel
- in the panel there are 240V and 120V circuit breakers
- in the enclosure there are further motor and circuit breakers
My first basic questions form a European point of view:
1. I did not see any fuses in this setup. Are they hidden in the service disconnect, on the pole or just not present.
2. At least in Germany we are supposed to organize (full) short tripping in a way that only and exactly one breaker trips at a time. We call this "selectivity". This means that in front of a breaker in my enclosure I would have to install either a fuse or a more expensive delayed breaker. To keep fuses selective you will have to keep two steps in size apart. In how far is this standardized in a NA setup?
3. We originally wanted to have an overvoltage protection against damages by lightning. Here the client refused that. How would one integrate that into such an installation.
4. We have to test and prove calculated maximum short current to prove that in case of a hot-to-ground-fault the fuses / breakers will trip within a maximum of typically 5 s. Is there a similar obligation in the US?
5. Same for grounding. It did not look like anything was tested there. Any obligations?
That's it for the beginning. Thanks for some light in the dark.
