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LEONARDO Power Quality Initiative Efficiency and Quality the effect on you! . Stephanie Horton BEng Hons CEng MIEE ERA Technology. ERA Technology, Leatherhead.

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leonardo power quality initiative efficiency and quality the effect on you

LEONARDO Power Quality InitiativeEfficiency and Quality the effect on you!

Stephanie Horton BEng Hons CEng MIEE

ERA Technology

era technology leatherhead
ERA Technology, Leatherhead

Power Quality investigationsForensic and failure analysisPower SystemsProtection and earthing studiesElectrical testingMaterialsCondition assessment

introduction to pq
Introduction to PQ
  • Expectations and Drivers
  • Obstacles
  • Types of problems
  • The ‘unseen’ costs
  • Typical disturbances
    • causes
    • Effects
  • What you can do

The supply should allow business processes and equipment to operate normally.

IT Systems always work and data is available

The lights

stay on

No interruptions

Voltage and frequency should remain within the defined PQ limits

Industrial processes remain reliable

bs en 50160
BS EN 50160
  • Defines the typical voltage disturbances found on the system
  • Defines the disturbance characteristics
    • i.e. how long they last,
    • what percentage they reduce the voltage by
  • Assessed during 95% of a week
    • recommended monitoring period
    • 5% Equivalent to 8hrs/week acceptable disturbances
  • Provide guidance on the number of disturbances expected on a system - 1 to 10,000 in any year
  • Used by the DNO’s to monitor the quality of power supplied to end users
new drivers
New Drivers
  • Equipment operates efficiently
  • We operate our systems efficiency
  • We reduce costs to operate the system
  • We manage our power consumption
  • We deliver quality products & Services

So what stops us achieving all of these aims?

  • People & resource?
  • Equipment operation & age?
  • System operation and issues?
  • Process issues?
  • Power supply problems?
  • Management buy in & commitment?

All of the above…

what problems occur
What problems occur?

Typical disturbances found on the system.

  • Sags and Dips
  • Over voltages
  • Transient voltages
  • Interruptions
  • Voltage imbalance
  • Harmonics
  • Notching & Noise
where can faults occur
Where can faults occur?
  • The customer network
  • The DNO system
  • NGT transmission systems
how do they affect you
How do they affect you
  • Motors stall
  • Computers crash
  • Production is affected
  • Equipment damaged
  • Product spoilage
  • ‘The lights go out’
the effects you don t see
The effects you don’t see

Some of these problems result in:

  • Higher power consumption due to peak demands for power
  • Penalties incurred for exceeding tariffs
  • Impact on the quality of your product
  • Financial losses due to stoppages
  • Increases in reactive power consumption

A Voltage Dip

Dips/sags can cause equipment to fail

Depends on susceptibility, duration and magnitude



what happens
What happens?
  • Voltage dips vary considerably
    • do not have a consistent effect
    • Depth, duration, phases affected, equipment in service
  • Only part of the process may be affected
    • control is lost.
  • Common consequences
    • breakage, contamination, melting, burning and corruption of data
  • Occur many thousands of times in the lifetime of an installation
what causes voltage dips
What causes voltage dips
  • A fault on the system
    • causes equipment to mal-operate
    • potential increases in consumption due to restart
    • Impacts on time and efficiency
  • Large loads starting
    • Multiple loads even greater impact
    • Large demand for power
  • Lightning & some types of loads
    • Welding furnaces
  • 400kV Transformer Suspect Voltage transients Caused widespread voltage disturbances
voltage surges
Voltage Surges
  • Over voltages and Surges
    • Rarely effect operation
    • Equipment degrades over time, & can cause eventual failure

V Rms

a swell starts above 1.1 pu

X % above nominal

User defined setpoints



PQ Standards


cause effect
Cause & Effect
  • Lightening
    • Surges can damage equipment… most have protection installed
  • Large loads coming off line
  • Potentially reduce life of equipment and therefore impact on life time cost
  • Typical examples - light bulbs




  • Only affect very sensitive equipment or processes.
  • Typically >20ms
cause effect22
Cause & Effect
  • Operational / Capacitor switching
  • Faults – clearing (auto re-close operations)
  • Can damage electronic equipment
  • Can cause additional damage if initialises a fault
  • Can cause PLC to ‘lose’ control and result in significant down time, or Quality issues











cause effects
Cause & Effects
  • Single phase faults
  • Unbalanced loading
  • Can damage motors and generators
  • Can increase consumption
  • Can overload protection and cause nuisance tripping as a result

Harmonics explained

G5/4 Recommends max value of 5% THD

Note the effect of the 5th harmonic on a standard waveform

Measured according IEC 61000-4-71 FFT every 200 ms

V Rms


10 min average of RMS values should not exceed the limits





cause effects27
Cause & Effects
  • None linear loads
    • UPS
    • Servers and PC’s
    • Florescent lights
  • Causes overheating of neutrals and joints
  • Can cause spurious operation of protection
  • Resonant conditions can arise and cause catastrophic failure
so what can you do
So what can you do?
  • Monitor your supply and understand your susceptibility
  • Regularly review your start up procedures – can starting be staggered
  • Review your electricity consumption and the tariff your on
  • Review your equipment turn over and compare with expected life
a fact of life
A fact of life?
  • Utility faults will occur many hundreds or even thousands of times in the life time of every installation
  • On-site faults can be even more severe
  • Disturbances place all businesses at risk both in terms of financial losses and energy efficiency so they should be taken seriously.