ION meter configuration for 3W-Wye

[RobGraham]

I am at a site where the wye transformers have been grounded through an HRG--no neutral is pulled back to the breakers or the meters.  When I arrived, the meters were configured as 3W-Wye, which seems to make sense. 

What caught my attention was that some meters had the nominal voltage set to the L-L nominal, and some L-N.  Those with L-L are capturing PQ events normally, while the L-L meters are not.  This seems to contradict the ION Reference:  

NOTE: Nominal refers to the primary power system RMS voltage (line-to-line
voltage for Delta systems and line-to-neutral voltage for Wye systems).

Furthermore, there are a couple of notes around the ION Reference suggesting 3W-Wye may ignore the V2 input, and FA244106 seems to state this meter should be set up as Delta:  How can the PowerLogic meters monitor a 3 wire ungrounded WYE system | Schneider Electric USA

My question is, for a meter monitoring a network through a wye transformer using an HRG and no ground bus, what should the wiring type be and what should I set the nominal voltage to?

Thanks for your help!

[Charles_Murison · Accepted solution]

Hello @RobGraham 

3W-wye is not the volts mode you should be using. This is a very special configuration that is sometimes used in Utility type applications where a single CT to stepdown 100skV to 120V is worth more than the meter. In the install guide there is an image for the one and ONLY wiring that should be used with 3W-wye.

In your system, if the load is not connected to the same ground as the transformer to have a delta load, therefore I would suggest putting the meter into Delta mode. V nominal would be VL-L. If the load does have a ground connection, you will need to connect the same ground to the Vref(VN) of the meter. Volts mode would be 4W-wye and V nominal will be VL-N. 

Regards,

Charles

[RobGraham]

Thank you very much for a comprehensive solution!  I missed the wiring in the installation guide, and now I can confidently tell customers, "Don't use this.".