Saturday, September 13, 2014

Engr. Aneel Kumar

EFFECTS OF HARMONICS ON POWER SYSTEM COMPONENTS

Following is the summary of how harmonics affect on power system components.

GENERATOR: Production of pulsating or oscillating torques which involve torsional oscillations of rotor elements of TG set and rotor heating

MOTOR: Stator and rotor copper losses increase due to harmonic current flow, leakage flux created by harmonic currents causes additional stator and rotor losses, core loss increases due to harmonic voltages and positive sequence harmonics develop shaft torques that aid shaft rotations whereas negative sequence opposes it

TRANSFORMER: Stray losses increase due tom harmonic current flow, hysteresis losses increase, due to presence of high frequency harmonics resonance may occur between winding inductance and line capacitance

RELAYING: Mal-tripping may occur due to presence of harmonics which affects the time delay characteristics

SWITCHGEAR: Due to predominance of skin and proximity effects at higher frequencies, bus-bars behave like cables and transient recovery voltage changes which affect the operation of blow-out coils

CAPACITOR: Due to presence of harmonics, reactive power increases, dielectric losses increase causing additional heating and resonance and over-voltage may occur, resulting in reduced life

CABLES: Due to increased skin and proximity effects at higher frequencies, additional heating occurs, Rac increases and ac copper loss increases

CONSUMER EQUIPMENT: Life and efficiency reduce drastically

COMMUNICATION CIRCUITS: Noise creeps in transmitted signals

Engr. Aneel Kumar -

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