UEEEL0062 - Provide engineering solutions to problems in complex polyphase power circuits

Students will also be expected to demonstrate the following knowledge:

• polyphase power circuit analysis, including:

• polyphase supply system encompassing:

  advantage of three phase system compared to single phase systems
  double subscript notation
  phase sequence
  120 degree operator
  given circuit component parameters, solve practically-based problems using:
  < equivalent circuits of transformers, lines and loads
  < component values using rectangular and polar notation
  < current divider and potential divider rules using complex impedances
  < the "per unit" values of voltage, current and impedance to a common VA base

• types of three phase system connections encompassing:

  supply to balanced star, three and four wire loads
  supply to delta connected loads
  effects of phase reversal
  representation of currents and voltages as complex phasors for three phase, and three phase and neutral quantities
  calculation of the values of, and drawing labelled phasor diagrams, not to scale, to represent complex values of current and voltage for balanced and > unbalanced loads for star and delta systems
  calculation of values of P, Q and S for balanced and unbalanced systems
  draw and label single phase diagrams to represent one phase of a complex three phase system
  represent unbalanced voltages or currents as symmetrical components
  phase-to-phase currents
  phase-to-neutral/earth currents

• balanced three phase loads encompassing:

  calculations of balanced loads connected in star
  calculations of balanced loads connected in delta
  calculation of steady state values of fault current for various configurations
  evaluation of the symmetrical component impedances for the various distribution system components, transformers (earthed neutral case) and > generators (high impedance earth)
  calculation of fault currents using the per unit approach
  calculation using the "worst case" values based on transformer impedance only (i.e. a short circuit fault)
  estimation of peak values using accepted multipliers
  effects of the direct current (d.c.) component on the instantaneous magnitudes of fault currents in transformers and generators

• unbalanced three phase loads encompassing:

  star – four wire systems
  delta systems
  star – three wire systems
  star - four wire with neutral impedance

• power in three phase circuits encompassing:

  summation of phase powers and power in balanced loads
  measurement of power in balanced loads – two Wattmeter methods

• reactive three phase power encompassing:

  power triangle calculation
  measurement of VAR
  power factor correction

• fault currents encompassing:

  symmetrical components
  positive, negative and zero sequence impedance
  fault current breaking and let-through energy capacities of circuit breakers and fuses
  importance of fault/arc impedance
  calculation of fault currents - phase-to-earth faults
  calculation of fault currents - phase-to-phase faults
  analysis of asymmetrical fault currents

• harmonics in three phase systems encompassing:

  presence of triple in harmonics in three phase systems
  effects of three phase harmonics for different star and delta connections
  methods for reducing harmonics in three phase systems

• problem-solving techniques
• relevant checks and isolation of circuits
• relevant manufacturer specifications and operating instructions
• relevant materials, tools, equipment and testing devices
• relevant job safety assessments or risk mitigation processes
• relevant WHS/OHS legislated requirements
• relevant workplace documentation
• relevant workplace instructions, policies and procedures.