Dale R. in Corpus Christi. Working on a large industrial account served at 14.4kV primary voltage on AEP Texas Rate Schedule LPS. Meter shows VT ratio of 120:1 but nameplate on the voltage transformers shows 14400:120, which should be 120:1 ratio. However, bills seem too high when compared to similar facilities. Could there be an error in how they're applying the VT multiplier along with the CT multiplier? CTs are 1200:5 so total multiplier should be 240 times 120 equals 28,800 but not sure if that's right.
VT Ratio Error on Primary Metered Account - 14.4kV Service
Dale, Randy Dawson here. Primary metering with both CT and VT transformers can be tricky. Your calculation is correct - CT ratio (240) times VT ratio (120) gives you total multiplier of 28,800. But double-check that the VTs are actually 14400:120 and not 14400:100 which would be more common. Also verify the meter programming shows both multipliers correctly. On primary metered accounts, errors in either the CT or VT ratio can create massive billing discrepancies. Have you requested copies of the metering installation records from AEP?
Randy, checked the VT nameplate again with binoculars and you're right - it's 14400:100, not 120. So VT ratio should be 144:1, making total multiplier 34,560 instead of 28,800. That would explain why the bills seemed low, not high like I originally thought. Going to call AEP and request a meter test and programming verification.