Study On The Problem Of Electric Energy Metering Principle In Engineering Steady-state Environment

As the theoretical basis of power metering methods, electric energy metering principle is the premise of realizing the accurate and reasonable electric energy measurement, and ensuring the authentic metering results. Classic electric energy metering principle is based on the theory of sinusoidal power. The voltage and current signals under ideal sinusoidal steady-state condition are analyzed and calculated to obtain the cumulative energy, and the electric energy metering principle is an nonerror metering theory under ideal sinusoidal steady-state condition. However, in the actual operations, power system is constantly affected by disturbances, so the power system is in the engineering transient process for a long term. Therefore, this paper puts forward that the application premise should be broaden from ideal steady-state to engineering steady-state, by this way, the error behavior of the existing metering principle can be tested.In this paper, through the theoretical analyses and formula deductions of the first-order and second-order dynamic circuits, it can be verified that the instantaneous power of circuit elements have attenuation component in the engineering steady-state environment, and the attenuation component of reactive component’s instantaneous power would lead to a non-zero value for the integral result. It demonstrates that the reactive elements also consume energy, and the power integral result of reactive element show the properties of active element. Therefore, the electric energy metering principle which based on the theory of sinusoidal power becomes erroneous when it is applied in the engineering steady-state environment, but the metering error is limited.Analytic derivation and analysis of the electric energy metering method in actual measurement which accumulates average power for whole cycles shows that, in the engineering steady-state environment, when the energy consumed by reactive element is measured by the electric energy metering method which accumulates average power for whole cycles, then the electric energy metering principle presented erroneous characteristics, and the active power derived from the average power method contains reactive component. Therefore, the active power and reactive power defined in steady state are no longer orthogonal, and this is the reason why the classic electric energy metering principle becomes erroneous when it is applied in engineering steady-state environment. But when the system is no longer fluctuate and the measuring time is long enough, this metering error will be shared into metering periods, and the existing energy metering principle can still fulfill the engineering demand.The simulations are performed in Matlab/Simulink software platform, which take dynamic circuits as examples, simulating the engineering steady-state environment by the fluctuation processes of power supply and load. Through the analyses of the examples and data, it shows the error condition of the energy metering principle in engineering steady-state environment, and the simulation results verify the correctness and effectiveness of the theory. The impact of the engineering steady-state environment on the energy metering principle is deeply analyzed in the paper, it intends to explore a more reasonable energy metering theory, and it brings up a metering method that shares the error into multi-periods equally, so that the metering results can meet the accuracy requirements under different conditions.