Supply of rectifier equipment from emergency sets-harmonic distortion and other problems

This paper describes the well-known problem of disturbances, which often arise when a diesel-generator emergency set supplies a rectifier installation. The physical background of the phenomenon is explained. Analysis of current and voltage distortion is given, which permits calculations of harmonics and total harmonic distortion. A simplified theory of the synchronous machine reactances is presented, as this knowledge is necessary for the determination of voltage distortion. Experimental results are presented in order to evaluate the analytical method. The disturbances in the operation of equipment are analysed on the examples of thyristor rectifiers and phase compensation capacitors. Measures to reduce voltage distortion in the system are reviewed. The most important measures are suitable design of the emergency plant generator and resonant harmonic filters. The application of switch-mode rectifiers changes the described problem and the paper discusses to what extent the problem is alleviated. Finally, the author discusses whether or not an emergency set installation can meet the requirements of power quality standards IEC 552 and IEEE 519