1-Phase Padmounted Transformer Loading Analysis using Smart Meters

1. 1-Phase PadmountedTransformer Loading Analysisusing Smart Meters Michael L. Dyer P.E. Executive Engineer SRP

6. What we did • Twenty-five (25) REX 2 AGI nodes were installed in single phase padmountedtransformers recording (kWh & kVAh) at fifteen (15) minute intervals • Selected transformers served single family houses • Variability: • Initial installation dates ranged from 1978 to 2006 • Number of connected loads ranged from 2 to 14 • Each of the load meters were also REX meters • The kWh & kVAh data also allowed determination of the load power factor • Thermal models using IEEE std. C57.91 were conducted using the interval meter data for system peak day • County assessor’s office records determined the house size • The maximum and minimum house size was used in our single phase sizing program to determine the recommended transformer size • If the sizing program indicated a different size than existed a thermal model was created for the recommended design size • Certified loss data was used for existing transformers, if not available, data from like vintage was used • Loss data for a recommended unit based on present purchase

8. Our Single Phase Sizing Program Assumed House Size to be Served= 0.8[(Max.Size+Min.Size)/2)] + 0.2(Max.Size) Where Size is 1000Ft2 Assumed Load= 4.5(Assumed Size) For assumed sizes <4000Ft2 5.85(Assumed Size) For assumed sizes >=4000Ft2 Recommended Transformer Size <= (Assumed Load*Number of Loads*Coincident Factor)/1.19

26. 7 July 2012

28. 7 July 2012