HARMONICS EFFECTS ON POWER SYSTEM COMPONENTS

There are many bad effects of harmonics on the power system components. These bad effects can derated the power system component or it may destroy some devices in severe cases. The following is the harmonic effects on power system components.

IN TRANSFORMERS AND REACTORS

• The eddy current losses increase in proportion to the square of the load current and square harmonics frequency,
• The hysterics losses will increase,
• The loading capability is derated by harmonic currents,
• Possible resonance may occur between transformer inductance and line capacitor.

IN CAPACITORS

• The life expectancy decreases due to increased dielectric losses that cause additional heating, reactive power increases due to harmonic voltages, and,
• Over voltage can occur and resonance may occur resulting in harmonic magnification.

IN CABLES

• Additional heating occurs in cables due to harmonic currents because of skin and proximity effects which are function of frequency, and,
• The I²R losses increase.

IN SWITCHGEAR

• Changing the rate of rise of transient recovery voltage, and,
• Affects the operation of the blowout.

IN RELAYS

• Affects the time delay characteristics,
• False tripping may occurs.

IN MOTORS

• Stator and rotor I²R losses increase due to the flow of harmonic currents,
• In the case of induction motors with skewed rotors the flux changes in both the stator and rotor and high frequency can produce substantial iron losses, and,
• Positive sequence harmonics develop shaft torque that aid shaft rotation; negative sequence harmonics have opposite effect.

IN GENERATORS

• Rotor and stator heating,
• Production of pulsating or oscillating torques, and,
• Acoustic noise.

IN ELECTRONIC EQUIPMENT

• Unstable operation of firing circuits based on zero voltage crossing,
• Erroneous operation in measuring equipment,
• Malfunction of computers allied equipment due to the presence of ac supply harmonics.

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