With the popularization of new types of electrical equipment

the load of the power system has become increasingly complex

and the nonlinear characteristics have become more prominent. However

the traditional definition of three-phase apparent power is not unified and cannot truly reflect the energy utilization rate

which cannot meet the requirements of most power consumption conditions. Based on the core essence of apparent power

this paper starts from the equivalent process and engineering approximation of apparent power in a single-phase power system

elaborates on the equivalent principle

calculation method and practical significance of effective apparent power

and extends it to a three-phase power system. At the same time

a three-phase intelligent apparent power meter supporting arithmetic

vector and equivalent algorithms has been developed based on the effective apparent power theory. Its measurement accuracy and engineering applicability have been verified through a verification device

a traceability circuit and an LED nonlinear load test. The results show that the measurement uncertainty of the apparent energy of this electricity meter does not exceed 0.08%

which can provide a reliable basis for energy efficiency assessment and power quality management in smart grids.