Characteristic of Triplen Harmonics in Low Voltage Network

Triplen harmonics study for harmonics produced by non-linear loads and
salient pole synchronous generator is very important because their presence have
caused communication line interference, damage to neutral earthing resistor etc.
The purpose of this project is to study the characteristics of triplen harmonics
under balanced/unbalanced resistive/inductive/capacitive loads, different
generator neutral earthing resistor values and various transformer winding
configurations. Lab scale non-linear load and salient pole synchronous generator
is used for the experiment and third harmonic currents are recorded for analysis to
represent triplen harmonics currents characteristics. Results from the under
balanced load experiment shows that third harmonic current is inversely
proportional to load impedance and neutral current is three times the phase
current. During unbalanced load condition, the magnitude current is different for
each phase and the neutral current is lower than arithmetic sum of phase current
due to different phase current magnitude and angle. The phase and neutral third
harmonic currents magnitude is inversely proportional to generator NER
resistance under balanced load. Transformer winding configurations under
balanced load permit third harmonic current flowing through them in accordance
to zero sequence network for the transformer apart from higher transformer
reactive impedance at third harmonic.