Power Quality

Brown Out Voltage Sag or Dip

Reason: A decrease of the normal voltage levels.

Consequences: Malfunction of IT equipment (PCs etc) Tripping of relays.
Disconnection and loss of efficiency in electrical items.

Likely Cause: Faults on the transmission or distribution network. Faults in consumer installation. Connection of heavy loads and start-up of large motors.

Solution:

• Voltage Stabiliser
• Uninterruptible Power Supply (UPS)

 

Brief Black Out or Very Short Interruptions

Reason: Total interruption of electrical supply from few milliseconds to 1 or 2 seconds.

Consequences: Tripping of protection devices. Loss of information. Malfunction or stoppage of sensitive and IT equipment (PCs etc).

Likely Cause: Opening and automatic reclosure of protection devices to decommission a faulty section of the network. Fault causes are insulation failure, lightening and insulator flashover.

Solution:

• Uninterruptible Power Supply (UPS)
• Uninterruptible Power Quality (UPQ)

 

Black Out, Long Duration, Long Interruption

Reason: Total interruption of electrical supply for duration greater than 1 to 2 seconds.

Consequences: Stoppage of all equipment.

Likely Cause: Equipment failure in the power system network, storms and objects (trees, cars, etc.) striking lines or poles, fire, human error, bad coordination or failure of protection devices.

Solution:

• Uninterruptible Power Supply (UPS)
• Uninterruptible Power Quality (UPQ)
• Back Up Generator

Surge Voltage Spike

Reason: Very fast variation of voltage from several microseconds to a few milliseconds.

Consequences: Destruction of components and insulation materials. Data processing errors,
Data Loss,  Electromagnetic interference.

Likely Cause: Lightening, Switching of lines, Power Factor Correction Capacitators, Disconnection of heavy loads.

Solution:

• Surge Protection Device

Voltage Swell

Reason: Momentary increase of the voltage, at the power frequency, outside the normal tolerances with duration of more than one cycle and typically less than a few seconds.

Consequences: Data loss, Flickering of lighting and screens, Stoppage or damage of sensitive equipment.

Likely Cause: Start/Stop of heavy loads, Badly dimensioned power sources, Badly regulated transformers (mainly in off-peak time).

Solution:

• Voltage Optimiser
• Voltage Stabiliser

Intermittent Tripping Harmonic Distortion

Reason: Voltage or current waveforms assume non-sinusoidal shape. The waveform corresponds to the sum of different sine-waves with different magnitude and phase, having frequencies that are multiples of power-system frequency.

Consequences:

• Increased probability in occurrence of resonance
• Neutral overload in 3 phase systems
• Overheating of all cables and equipment
• Loss of efficiency in electric machines
• Electromagnetic interference with communication systems
• Errors in measures when using average reading meters
• Nuisance tripping of thermal protections.

Likely Cause:

Classic sources: Electric machines working above the knee of the magnetization curve (magnetic
saturation), arc furnaces, welding machines, rectifiers, and DC brush motors.

Modern sources: all non-linear loads, such as power electronics equipment including ASDs, switched mode power supplies, data processing equipment, high efficiency lighting.

Solution:

• Active Harmonic Filters
• Static VAR Generator (SVG)

Electro Magnetic Fields Noise

Reason: Superimposing of high frequency signals on the waveform of the power system frequency.

Consequences: Disturbances on sensitive electronic equipment (usually not destructive). Data loss. Data processing errors.

Likely Cause: Electromagnetic interference provoked by Hertzian waves such as microwaves, television diffusion, radiation due to welders, arc furnaces and electronic equipment. Improper grounding.

Solution:

• EMI filter, TVSS

Unbalanced Voltage

Reason: A voltage variation in a three-phase system in which the three voltage magnitudes or the phase-angle differences between them are not equal.

Consequences: Unbalanced systems imply the existence of a negative sequence that is harmful to all three-phase loads. The most affected loads are three-phase induction machines.

Likely Cause: Large single-phase loads (induction furnaces, traction loads), incorrect distribution of all single-phase loads by the three phases of the system (this may be also due to a fault).

Solution:

• Static VAR Generator (SVG)
• Voltage Optimiser
• Voltage Stabiliser