Active Anti-Islanding Protection

[Shotty]

A client is operating a DG within an 11kV network on three feeders from a 33/11kV sub and is currently using Forward Under Power and Reverse Power protection to detect a Loss of Mains condition. This results in the embedded network always requiring a net import from the Grid, which wouldn't change if VVS or ROCOF was used. Has anyone had any experience with active network detection devices or other Anti-Islanding protection systems that have better security and/or a smaller No Detection Zone?

 

[ScottyUK]

Posting a single line diagram showing the position of your protection CTs and VTs along with their associated relays would be a good starting point.

 

[breadboard]

Maybe you could key a DTT from the feeder breaker 52a contact to the DG and/or DG's on the feeder assuming these are radial feeds.

 

[Mike111]

We have found that Vector Shift with a setting of around 6 degrees where there are no large motive power loads (Low Inertia) to be dependable without incurring nuisance tripping. Where there are large motive power loads ROCOF seems to be the only alternative with a setting of around 0.4Hz /Second. Strathclyde University have published lot of information on ROCOF recently looking at how different Relays preformed and while not directly related to your issue the information would be useful in coming to a decision

 

[Shotty]

Thanks everyone for taking the time to give your thoughts. I've been through a few papers, but there doesn't appear to be any practical solutions other than those proposed, which makes it difficult for a DG in any scenario to move from peak lopping to export capability without passing through (or operating in) a no-detect zone. I am going to advise my client that they will just have to live with the minimum import.

I did look at the CB status option, but all scenarios rely upon 3rd parties providing critical data where they refused to be responsible for the results (whether real or perceived) of the accuracy.