PQ Meter on a delta feeder

[GOTWW]

Are there ramifications as to Power Quality metering performance on a 3-phase / 3-Wire MV line, comparing Delta connected PT's & CT's "corner" grounded, or Wye connected PT's & CT's, Star grounded, or some combination of the two. Technically this line is resistance grounded, but many miles away. There is no neutral conductor. Three instrument transformers are planned for each (6-total).

I am not to much up on the triplen harmonics and such, the meter rep, did not give me much confidence in his answer delta-delta arrangement.

 

[busbar]

 
Seems like the question of PT quantity and configuration cannot be addressed without knowing capabilities of the ”meter.”

If the meter is intended to measure phase-to-ground quantities, consider three wye-grounded PTs with primaries rated for ø-ø voltage, but running at 0.58 per-unit voltage under normal conditions, similar to IEEE C57.13 §7 group 2 VT application.

 

[scottf]

Have you considered how well the instrument transformers will pass through harmonics? Up to what harmonic are you interested in measuring?

 

[GOTWW]

The meter is a name brand 4-voltage channels and 5 current channels meter. It can be "enabled" wye or delta mode.

The customer said put the meter here (at this particular location). Since all of the downstream transformers are delta-wye (secondary distribution MV level) w/neutral resistance or transformer grounding), which in turn feed the utilization level delta-wye transformers i.e. 208-480v. My thought is that the odd harmonics generated at the utilization level will not even make it to the PQ meter. What will make it back to the meter? or is this going to be in essence a voltage and current recorder? An advantage to the star connections is the PT's will have sqrt3 less voltage across them and may be more reliable.

 

[scottf]

GOTWW-

I don't believe there is any reliability issues associated with using the VTs with L-L connection (2-bushing) or L-G connection (1 bushing). Each is designed for its application.