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.orgterryc@powerquality.co.th

PQIncidentsTM

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

Sources of PQIncidentsTM

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

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 PQIncidentsTM

• 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 PQIncidentsTM

• 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 PQIncidentsTM, the source and solution

Why use PQIncidentsTM?

• 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 PQIncidentsTM

Summary

• PQIncidentsTM summarizes the data
• Provides a simple model for economic analysis

Please feel free to leave a question in the comments section or contact Terry