Working on a grocery store in San Antonio served by CPS Energy. Three-phase 480V service. The meter has two CTs — 400:5 on two phases. Bill shows a multiplier of 80. But if the CT ratio is 400:5 that is an 80:1 ratio on each phase, and with two CTs I would expect either 80 or 160 depending on how the meter is wired. The utility says 80 is correct because it is a 2-element meter. Can someone explain the 2-element vs 3-element metering and how the multiplier works in each case? I do not want to file a claim if I am wrong.
Three-phase multiplier confusion — am I reading this right?
You are running into Blondel theorem territory. Short version: a balanced 3-phase 4-wire system can be accurately measured with 2 CTs (2-element metering) because the third phase can be mathematically derived. The multiplier of 80 is correct for that configuration — each element measures one phase and the meter internally calculates total power. You do NOT multiply by 2. If they had 3 CTs (3-element metering) on the same system, the multiplier would still be 80. The number of elements does not change the multiplier — it changes how the meter calculates total power. Common source of confusion.
Appreciate the explanation Amir. So the multiplier just reflects the CT ratio regardless of how many elements the meter has. That makes sense. Glad I asked before filing anything.