Protective functions and advise on adding distributed generation on M-T-M

[budhiman]

Hello,

I need advise on what all to keep in mind when adding distributed generation/microgrid as a second source to the existing Main-Tie-Main.

One main is utility service and second main is a spare. If the second main is fed from a distributed generation like PV or fuel cell. What all to keep in mind when making this change (also would like to export power back to the grid if excess available). I understand this requires a discussion and some paperwork with the utility and ISOs (if exporting power). Want to get a general idea or a reference reading material on it. The existing main, tie and second main only has relays with 50/51 functionality.
1. What protective functions are typically needed for the utility main, tie and DG main when exporting power?
2. Does the tie need to additional protective functions as well?
3. Both sides of the tie have feeders, anything to look here?

Is there a white paper or reading material I could use to learn more on it?

 

[FreddyNurk]

Here in Australia there are a number of utilities that publish requirements for connection of distributed generation to their network, there may well be an equivalent document published by your relevant utility to refer to.

In general, the practice appears to be:
[ol 1]
[li]Over / Under Voltage at the point of coupling[/li]
[li]Over / Under Frequency at the point of coupling[/li]
[li]Anti-islanding protection of some description[/li]
[li]Depending on the size and capability, some means of detecting an earth fault if other sources of generation have been tripped[/li]
[/ol]

IEEE 1547 may describe slightly different arrangements, but is likely to be one of the governing standards for the protection that may be required. The MTM may complicate things if the generation is proposed to be able to support an islanded section without using the mains as a reference.