Characterizing PQ values Power Quality Incidents

Published by Terry Chandler, Director of Engineering, Power Quality Thailand LTD/Power Quality Inc., USA.
E-mail: terryc@powerquality.org, terryc@powerquality.co.th

PQIncidents^TM

• A PQIncidenst^TM occurs when one or more of the PQ parameters exceeds a specification or causes a problem for a load
  
• A PQIncidenst^TM is comprised of one or more events
  
• A PQIncidents^TM is a definable point in time and power quality characteristic
  
• Most PQIncidents^TM are associated with significant changes in the voltage at the utility level
  

Sources of PQIncidents^TM

• Lightning
  
• Equipment failure
  
• Wind
  
• Phase to ground short circuits
  
• Fuses clearing/breakers tripping
  
• Loads switching
  

Power Reliability

• Is the presence of voltage at the meter point. (measured to approx. 1 to 2 sec)
  
• Depends on the utility
  
• Depends on the contract for power reliability and Power Quality
  

Power Quality

• The values of the various PQ parameters at the meter point. ( less than 1 to 2 sec)
  
• The effect on the operation of the factory or a piece of equipment. IE elevator, computer, process controller etc
  
• The effect on the electrical system of power polluting loads
  

What are the various PQ parameters?

• Voltage sags (dips) low line voltage (brown outs) RMS values
  
• Voltage waveform events (subcycle)
  
• Voltage transients (fast spikes)
  
• Harmonics
  
• Voltage imbalance
  
• Flicker
  
• Interruptions planned or unplanned
  
• Other Wiring and Construction (design)
  

Identify PQIncidents^TM

• Review the customer input and form.
  
• Review RMS graphs of the values of all PQ parameters.
  
• Review the PQ event data
  
• Identify time of day and date of occurrence
  

Characterize the PQIncidents^TM

• Determine the duration and magnitude
  
• Determine the source (load caused?)
  
• Determine if the source can be prevented
  
• Determine if an auxiliary power source is needed to “fill in the energy loss”
  
• Document the PQIncidents^TM, the source and solution
  

Why use PQIncidents^TM?

• Reduce data to manageable sizes
  
• Clear the fog on events
  
• Focus on the major issues first.
  
• Solve the major problems and the minor ones may not matter
  

General ITIC curve (1997)

 

11 kVA CBEMA PQIncidents^TM

Summary

• PQIncidents^TM summarizes the data
  
• Provides a simple model for economic analysis
  

Please feel free to leave a question in the comments section or contact Terry Chandler, terryc@powerquality.org, terryc@powerquality.co.th