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Power Quality

Power quality refers to the ability of electrical equipment to consume the energy being supplied to it in an efficient and effective manner. A number of power quality issues including electrical harmonics, poor power factor, voltage instability and imbalance impact on the efficiency of electrical equipment.

This has a number of consequences including:

  • Higher energy usage and costs
  • Higher maintenance and repair costs
  • Equipment instability and failure resulting in process or business disruption

How is your Power Quality?

Power Quality – the efficiency and effectiveness of power supply.

Good power quality is critical in efficient and uninterrupted industrial processes.

Poor power quality can result in unstable equipment operation or failure, inefficiencies and reduced equipment lifespan, interruption of supply and plant down-time.

Captech specialise in evaluating, auditing and addressing a wide range of power quality issues to increase plant, motor and equipment efficiencies and the bottom line.

What solution is right for me?

Power consumption can be influenced by an intricate and complex set of variables. Our deep knowledge of power supply and electrical systems allow us to pinpoint your requirements as a power user and design or assign a solution that addresses your needs.

This is generally done in 2 ways:

  1. By understanding your power usage and any problems that may be occurring, our experienced people will recommend the right solution.
  2. Captech can perform a full power audit including data logging over a set period of time. This can allow an intimate knowledge of your power profile allowing us to develop a cost benefit analysis against a range of technologies of combination of technologies.

Our Technologies and Solutions are Varied

Power Quality products can be sorted in five general categories.

1. Power Filters

Active power filters (APF) are devices connected in parallel with the load to be compensated. They can be understood as controlled current sources that provide any kind of current waveform (in terms of phase, amplitude and frequency) in real time (response time <100μs).

APFs are flexible, high performance and cost-effective solutions used to mitigate all the power quality problems generated by the equipment installed in electric power systems, enhancing equipment operating life time, and improving power system capacity.

Power Filter products include:

2. Power Factor

Power Factor Correction (PFC) aims to improve power factor and hence power quality, switching in capacitors to offset usually inductive loads, for example electric motors. PFC systems increase the efficiency of power supply, delivering immediate cost savings on electricity.

Technologies in this group include:

3. Static Compensators

STATCOM and SVC use power electronics for regulating voltage, power factor, harmonics and stabilising voltage of medium and high voltage systems. They are called Static as they have no moving parts (other than internal switchgear).

The speed of response of a STATCOM is faster than that of an SVC and the harmonic emission is lower, however STATCOMs typically exhibit higher losses and may be more expensive than SVC. Selecting which is best depends on your system characteristics and need for compensation of either or both reactive power or voltage stability.

Prior to the invention of the SVC, power factor compensation was the preserve of large rotating machines such as synchronous condensers or switched capacitor banks.

Types:

4. Voltage Management

Voltage Management is a process by which the incoming voltage from a power source such as the grid or solar array, is optimised or stabilised to alleviate low, high, or changing voltages.

Voltage optimisation specifically aims to reduce the voltage received by electrical equipment to improve operating efficiency as well as reduce energy costs and power demand. It can improve power quality by eliminating or minimising transient voltages as well as balancing phase voltages.

STATCOM and SVC are used to stabilise medium and high voltage as well as to filter harmonic distortion and control reactive power.

Products available are:

Load side:

Supply side:

5. Energy Storage Devices

These products prevent power loss by storing energy in capacitors and/or batteries to maintain constant supply. By storing power, these units can use this stored energy to either replace the existing supply where needed or to address inconsistencies or errors in the supply.

UPQ systems combine power quality improvement, UPS system and power & voltage conditioner functionalities. They protect low and high voltage electric power systems against short or long power supply interruptions, voltage sags and swells, as well as from losses caused by poor power quality in the system.

Products include:

 

What Problems Can They Solve?

 

Typical Outcomes Of Poor 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)
  • Uninterruptible Power Quality (UPQ)

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)

Voltage Flicker Voltage Fluctuation

Reason: Oscillation of voltage value. Amplitude modulated by a signal with frequency of 0 to 30 Hz.

Consequences: Most consequences are common to under-voltages. Flickering of lighting and screens giving the impression of unsteady vision.

Likely Cause: Arc furnaces. Frequent start/stop of electric motors (e.g. elevators/lifts) oscillating loads.

Solution:

  • Static VAR Compensator (SVC)
  • STATCOM

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:

  • TBC

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

LEADERS IN POWER QUALITY SOLUTIONS

Our aim is to improve power quality issues, optimise power usage, reduce power costs and increase safety and compliance – outcomes critical to energy intensive sectors such as mining, industrial, commercial and power utilities.
Our team of highly qualified and skilled engineers can assist in providing a power quality solution to suit specific applications. Comprehensive system support and analysis ensure your installation is performing at its best.
Captech has helped many well recognised organisations to solve their power quality issues and are well respected in the industry for providing comprehensive and customised solutions.

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