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Home / Technical Articles / Detailed Overview of Power System Disturbances (Causes and Impacts)

Power Quality problems

To make the study of Power Quality problems useful, the various types of disturbances need to be classified by magnitude and duration.

Detailed Overview of Power System Disturbances (Causes and Impacts)
Detailed Overview of Power System Disturbances – Causes and Impacts (on photo: Fluke Three-Phase Power Quality and Energy Analyzer; credit:

This is especially important for manufacturers and users of equipment that may be at risk. Manufacturers need to know what is expected of their equipment, and users, through monitoring, can determine if an equipment malfunction is due to a disturbance or problems within the equipment itself.

Not surprisingly, standards have been introduced to cover this field. They define the types and sizes of disturbance, and the tolerance of various types of equipment to the possible disturbances that may be encountered. The principal standards in this field are IEC 61000, EN50160, and IEEE 1159.

Standards are essential for manufacturers and users alike, to define what is reasonable in terms of disturbances that might occur and what equipment should withstand.

Table 1 provides a broad classification of the disturbances that may occur on a power system, some typical causes of them and the potential impact on equipment. From this Table, it will be evident that the electricity supply waveform, often thought of as composed of pure sinusoidal quantities, can suffer a wide variety of disturbances.

Table 1 – Power Quality issues

Voltage dips
  • Local and remote faults
  • Inductive loading
  • Switch on of large loads
  • Tripping of sensitive equipment
  • Resetting of control system
  • Motor stalling/tripping
Voltage surges
  • Capacitor switching
  • Switch off of large loads
  • Phase faults
  • Tripping of sensitive equipment
  • Damage to insulation and windings
  • Damage to power supplies for electronic equipment
  • Load switching
  • Capacitor switching
  • System voltage regulation
  • Problems with equipment that requires constant steady-state voltage
  • Industrial furnaces
  • Non-linear loads
  • Transformers/generators
  • Rectifier equipment
  • Mal-operation of sensitive equipment and relays
  • Capacitor fuse or capacitor failures
  • Telephone interference
Power frequency
  • Loss of generation
  • Extreme loading conditions
  • Negligible most of time
  • Motors run slower
  • De-tuning of harmonic filters
Voltage fluctuation
  • AC motor drives
  • Inter-harmonic current components
  • Welding and arc furnaces
  • Flicker in Fluorescent lamps
  • Flicker in Incandescent lamps
Rapid voltage change
  • Motor starting
  • Transformer tap changing
  • Light flicker
  • Tripping of equipment
  • Unbalanced loads
  • Unbalanced impedances
  • Overheating in motors/generators
  • Interruption of 3-phase operation
Short and long voltage
  • Power system faults
  • Equipment failures
  • Control malfunctions
  • CB tripping
  • Loss of supply to customer equipment
  • Computer shutdowns
  • Motor tripping
  • Heavy network loading
  • Loss of generation
  • Poor power factor
  • Lack of var support
  • All equipment without backup supply facilities
  • Lightning
  • Capacitive switching
  • Non –linear switching loads
  • System voltage regulation
  • Control system resetting
  • Damage to sensitive electronic components
  • Damage to insulation

Table 2 lists the limits given in Standard EN 50160 and notes where other standards have similar limits.

Table 2 – Power system disturbance classification to EN 50160

Type of disturbanceVoltage levelLimits from EN50160Measurement periodTypical durationOther applicable standards
Voltage Variation230V+/- 10%95% of 1 week
Voltage Dips230V10-1000/year10ms –1secIEEE 1159
Rapid voltage changes230V5% to 10%Several per dayShort duration
1kV-35kV<6%Per dayShort durationIEEE 1159
Short Interruptions230V>99%20-200 per dayUp to 3 minsEN61000-4-11
Long Interruptions230V>99%10-50 per day>3 minsIEEE 1159
Transient Overvoltage230VGenerally <6kVNot specified<1msIEEE 1159
Voltage unbalance230V
Undervoltage230V<-10%Not specified>1 minIEEE 1159
Voltage surge230V<150% of nominal voltageNot specified>200msIEEE 1159
Voltage fluctuations230V3%10 min<200msIEC 60827
Frequency variation+/- 1%95% of 1 weekNot specifiedMeasured over 10s
+4%, -6%100% of 1 weekNot specifiedMeasured over 10s
HarmonicsTHD<8% up to 40th95% of 1 weekNot specified

For computer equipment, a common standard that manufacturers use is the ITI (Information Technology Industry) curve, illustrated in Figure 1.

ITI (Information Technology Industry) curve for equipment susceptibility
Figure 1 – ITI (Information Technology Industry) curve for equipment susceptibility

Voltage disturbances that lie in the area indicated as ‘safe’ should not cause a malfunction in any way. However, some disturbances at LV levels that lie within the boundaries defined by EN50160 might cause a malfunction because they do not lie in the safe area of the ITI curve.

It may be necessary to check carefully which standards are applicable when considering equipment susceptibility.

What is Power Quality and Why It’s Important (Webinar)

Reference // Network Protection and automation Guide – Areva

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Edvard Csanyi

Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV/MV switchgears and LV high power busbar trunking (<6300A) in power substations, commercial buildings and industry facilities. Professional in AutoCAD programming.


  1. lumor philemon
    Nov 13, 2022

    Powerful update

  2. vivek pandey
    Sep 05, 2015

    Good article

  3. nitin
    May 04, 2015

    Power quality ..need to create more third world countries…

  4. Mohamed H. shwehdi
    Apr 18, 2015

    Need such power quality review and u tube for demonstrating to electrical engineering studentd

    Apr 18, 2015

    need more downloads

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