Abstract
M.Tech. (Electrical and Electronic Engineering)
With the increasing use of nonlinear loads in power systems, harmonic pollution becomes more
frequent with disastrous consequences on the electrical network and other loads. Harmonic
currents cause problems such as system resonance, protective relays and switchgear malfunction,
communication interference, incorrect meter, equipment and process failure, over heating of
transmission and distribution systems, insulation degradation and power transformer failure. It
appears therefore absolutely essential to determine the current profile of the loads connected to
the same Point of Common Coupling (PCC). This study aims to assess a distorted power system
in order to determine the characteristics components of distorted waveforms (DC components,
fundamental and harmonics components), and to quantify the respective distortion contributions
in the power network. The numerical method is applied to analyse the current waveforms
captured with the aid of the digital scope meter (DSO) 1200 series at different sections of the
network. The power network under study is designed, constructed and analysed with the
MatLab/Simulink 7.0 package. In both methods, the Individual Harmonic Distortion (IHD) and
the current total harmonic distortion (ITHD) for the line, the non-linear and linear loads are
computed for the harmonic components 5th, 7th, 11th and 13th. The results showed that for the
analysis of the power system, numerical analysis based on the resultant harmonic curve method
and the MatLab/Simulink as applied to the network all converged to highlight that harmonic
components appear both on the line, the PCC and the linear load. This is due to the fact that the
converter characteristic harmonics (5th, 7th, 11th, 13th…) are found in the network components
(line, PCC, linear load…). The resultant harmonic curve method indicated a randomly distributed
percentage IHD in different sections of the network for harmonic orders higher than 7th, whereas
the Matlab/Simulink results normally show a non-uniform decay pattern of the IHD as the
harmonic order increases within the respective section of the network.