Utility required 59N relay, requiring Yg-Yg PT connection?

[Andrew445]

I am working on a grid-tied project, where the utility is requiring 59N protection at the secondary of the GSU transformer. The inverter output connection is delta, stepping up to grounded-wye.

It is my understanding that the 59N relay connection is typically open delta. The relay monitors across the open delta. The utility is requiring the PT connection to be grounded-wye/grounded-wye. Can this be accomplished?

Thank you for your help!

 

[jaggedben]

I am working on a grid-tied project, where the utility is requiring 59N protection at the secondary of the GSU transformer. The inverter output connection is delta, stepping up to grounded-wye.

It is my understanding that the 59N relay connection is typically open delta. The relay monitors across the open delta. The utility is requiring the PT connection to be grounded-wye/grounded-wye. Can this be accomplished?

Thank you for your help!

I can't say much, except that I think most likely you'd have no problem connecting a delta inverter to a grounded-wye system. Consult the inverter manufacturer to be sure.

 

[ggunn]

I can't say much, except that I think most likely you'd have no problem connecting a delta inverter to a grounded-wye system. Consult the inverter manufacturer to be sure.

I believe that is true but the opposite is not.

 

[Engineer#4827502]

With the correct relay made to take a Yg-Yg PT input, this should work.

 

[Andrew445]

Thanks guys.

I think one main problem is that introducing a ground with the PT messes with the inverter. The second is that most common 59N relays use the broken delta connection (Basler BE1 for example).

I think we will need to propose something alternate to the utility.

 

[SG-1]

Thanks guys.

I think one main problem is that introducing a ground with the PT messes with the inverter. The second is that most common 59N relays use the broken delta connection (Basler BE1 for example).

I think we will need to propose something alternate to the utility.

The Basler BE1 59N manual shows three different connections, one is a broken delta for use on ungrounded systems on page 4-10. Basler could probably recommend a connection scheme if contacted. These relays existed long before PV so the manuals only show the traditional uses.