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Errors may creep in when measuring power by conventional methods due to the inductance and capacitance of the coils and the induced eddy current in the metal parts of the instruments through the alternating magnetic field of the current coil. Apart from these, if a fault occurs in any of the potential transformer secondary circuits or the potential coil of the measuring equipment, a conventional meter cannot detect it, which results in underregistration. In this paper, a microprocessor-based three-phase real, reactive, and apparent power measurement system is developed, which displays the power being fed to a load under both normal and faulty conditions. The microprocessor provides a simple, accurate, reliable, and economical solution to these problems. A framework of the hardware circuitry and the assembly language program for the evaluation of power values is given, and the problems to which attention should be paid to execute the proposed algorithm using the microprocessor are discussed. Illustrative laboratory test results confirm the validity and accurate performance of the proposed method in real-time. [ABSTRACT FROM AUTHOR]

Power components definitions contained in the IEEE Standard 1459-2000 for unbalanced three-phase systems with nonsinusoidal situations are represented in the frequency domain based on Fourier transform (FT). However, FT suffers from the high computational effort especially when the number of phases increases and it is unable to provide information concerning time content because it provides only an amplitude-frequency spectrum. On the other hand, the discrete wavelet transform (DWT) preserves both time and frequency information while reducing the computational effort through dividing the frequency spectrum into bands and thus overcomes the limitations of FT. In this paper the three-phase power components definitions contained in the IEEE Standard 1459-2000 are reformulated using the DWT and thus redefined in the time-frequency domain. Also in order to study system unbalance, the concept of symmetrical components is defined in the wavelet domain. The results obtained from applying the IEEE Standard definitions and the DWT-based definitions to balanced and unbalanced three-phase systems under nonsinusoidal operating conditions, indicate that the DWT-based definitions are very accurate and the problem of spectral leakages can be reduced by suitable choice of the mother wavelet and the wavelet family. The DWT-based definitions are useful in studying nonstationary waveforms. [ABSTRACT FROM AUTHOR]

This paper rigorously considers the concept of apparent power in unbalanced three-phase situations. The analysis shows that there are various related but different concepts that can be associated with the apparent power. In particular two approaches are covered, the one relating to the literature on the single-phase sinusoidal case, the other relating to the recent IEEE Standard 1459-2000. The underlying ideas for each concept are given; the relationship and the differences between them are thoroughly discussed. [ABSTRACT FROM PUBLISHER]

In this paper it is shown that it is not possible to generalize the classical concepts of apparent power and power factor to the general polyphase nonsinusoidal case by unique concepts if one wants to retain the meaning with respect to efficiency of the electrical energy transfer as well as with respect to power oscillations. Separate generalizations are proposed and discussed. [ABSTRACT FROM AUTHOR]