Updated Appendix E (from wd21)

To put the terms "Power" and "Energy" into the proper context for this specification, the following definitions will be used: • Apparent Energy: the production or consumption of Apparent Power over time; unit: volt-ampere hours, VAh • Apparent Power (S): mathematical product of root-mean-square voltage and root-mean-square current, vector sum of Real Power and Reactive Power, square root of sum of squares of Real Power and Reactive Power; unit: volt-ampere, VA • Current: flow of electric charge, or rate of flow of electric charge; unit: ampere, A • Energy: the production or consumption of Power over time. • Power Factor (p.f.): ratio of Real Power to Complex Power, cosine of the phase angle between Current and Voltage, expressed as a number between 0 and 1, expressed as a percentage (i.e., 50% = 0.5); unit: dimensionless • Reactive Energy: the production or consumption of Reactive Power over time; unit: volt-ampere-reactive hours, VARh, VA-rh, varh • Reactive Power (Q): mathematical product of the root-mean-square voltage and root-mean-square current multiplied by the sine of the angle between the voltage and current; unit: volt-amperes reactive, VAR, VA-r, var • Real Energy: the production or consumption of Real Power over time; unit: Watt-hour, Wh • Real Power (P): rate at which electricity is produced or consumed, mathematical product of Voltage and Current; unit: Watt, W • Voltage: difference in electric potential between two points; unit: volt, V Generically, the use of the term "Power" refers to "Real Power" and is expressed in Watts. Otherwise, one talks of Apparent Power in VA, or Reactive Power in VARs. Generically, the use of the term "Energy" refers to "Real Energy" and is expressed in Watt-hours. Otherwise, on talks of Apparent Energy in VAh, or Reactive Energy in VARh.