Distribution System Training

The objective of this module is to introduce the subject of power quality and look at the different means of mitigating the effects of poor power quality. The different attributes of power quality are discussed, including both their causes and effects.

After completion of this module, the participant should be able to understand the following concepts, and apply them in day-to-day activities.

• The attributes (components) of power quality
• Steady state voltage control
• The causes and effects of voltage sag, swell and surges
• Voltage flicker
• Voltage noise
• Complete loss of voltage due to an interruption
• Distorted current and voltage waveform due to harmonics
• Harmonic distortion due to specific customer loads
• Harmonic distortion due to static rectifiers that are installed in household appliances
• Harmonic distortion due to static converters that are employed to provide variable speed motor drives
• Static converters used in UPS systems
• Harmonic distortion due to over excitation of iron core equipment (transformers, motors, generators) under saturated conditions
• Harmonic distortion due to arcing loads such as arc furnaces, arc welding and fluorescent lighting
• The effect of harmonic waveforms on equipment performance
• Increased iron losses due to high frequency harmonic components
• Metering errors on the low side due to high frequency components
• False tripping of ground relays due to high magnitude third harmonic current flow in the neutral
• Blocking the transfer of third harmonic currents by the delta winding connection (third harmonic currents circulate around the delta connected windings)
• The application of harmonic filters to block or divert harmonic currents from flowing into the power system
• Susceptibility of microprocessor based equipment to voltage deviations
• Protection against voltage surges by the surge suppresser
• Application of the isolation transformer to prevent disturbances being transferred from line to the load
• Application of a motor generator set to provide complete isolation of a load from the system
• The need for correct grounding of the customers’ installations