# Connecting a synchronous generator to the grid

1. Dec 13, 2011

### braneCRO

Hi for a project i need to connect a synchronous generator to the electrical grid, i need to use 2 curcuit breakers and . How to determine the cross section of the cables required and how to connect them to the 2 curcuit breakers.

2. Dec 13, 2011

### Staff: Mentor

Welcome to the PF.

What kind of project is this? Who is the electrical utility in your area? Any connection to the grid will be coordinated by that utility, and they have a number of rules that you need to abide by. They will inspect your installation before giving you the go-ahead to make the first connection.

3. Dec 15, 2011

### braneCRO

Itâ€™s a college project, I am connecting the generator to the college network (50 Hz, 3 phases), the generator is 400 V, 640 A and 440 kVA. My assignment is to connect it to the local grid using 2 circuit breakers (one for the automatic synchronization device and the other for the main connection to the bus. I don t know how to determine the cable diameterâ€¦

4. Dec 15, 2011

### Staff: Mentor

Did the generator not come with electrical cables attached? It's a generator, so you have something driving it--a large diesel engine, or a powerful 3-phase motor? The generator is 400 volts, 3 phase. Is the college power also 400 volts? I reckon you should be able to use the same thickness conductors as are used for the motor, if you can get hold of more of them.

I've forgotten almost all my motor theory. But I think it's probably true that just because the generator is rated for 640 amps, it does not follow that you will necessarily operate it so that it does supply that amount of current.

You say two circuit breakers. Do you mean two sets of triple circuit breakers?

5. Dec 15, 2011

### Jobrag

The size of a cable depends on the maximum current that is going to pass through it there should be copies of the relevant standards in your college library. The max current that passes through the cables will depend on the protection settings on your breakers, do not be fooled into thinking that the max current is limited by what's on the data plate if you get a high leading or lagging current you can turn a generator into a pool of mo;ten copper very quickly, Go and start researching protection settings.