Power Quality

Power Quality Solutions

Power quality refers to the ability of electrical equipment to utilise the energy being supplied. Poor power quality problems occurred when the perfect sinusoidal voltage waveform is changed to a distorted voltage waveform. It can result in several drawbacks such as equipment instability, reduced equipment lifespan, equipment failure, higher energy consumption and higher maintenance cost.

Low Power Factor

Every factory or household consist of resistive and inductive loads. Resistive loads consume useful power (real power) that does the work, while inductive loads consume reactive power. Reactive power is needed to produce magnetic field but it does not perform any real work. Higher reactive power results in a lower power factor. That means more current is required to complete the same amount of work.

Effects of Low Power Factor

  1. Power Factor Penalties.
  2. Overheating of equipment due to high current flow to load.
  3. Large copper losses and poor efficiency.

When is Power Factor Correction appropriate for you?

Use of equipment that operates at low lagging power factor:

  1. Three Phase Induction Motor.
  2. Transformers.
  3. Arc Lamps.
  4. Welding Equipment.
  5. Heating Furnaces.

Harmonic Problem

Harmonics is distortion of AC current waveform due to the use of non-linear loads. Non-linear loads generate a distorted current waveform that can be broken down into different harmonics order, considering up to 50th order. Different order of harmonics can bring various problems to the electrical and electronics system.

Effects of Harmonics

  1. Capacitor failure.
  2. Mechanical oscillations and overheating of motor/generator.
  3. Motor run slower/stop.
  4. Overheating of transformer, cable, switchgear.
  5. Misoperation of electronic devices.
  6. Tripping of fuse/circuit breaker.

When is harmonics mitigation appropriate for you?

Use of non-linear loads such as:

  1. Arc Furnaces.
  2. Variable speed drive.
  3. Switch-mode power supply (SMPS).
  4. Uninterruptible power supply (UPS).
  5. Solar Inverter.
  6. Static power converters.
  7. Rectifier.

Voltage Sagging

Voltage sag occurs when there is a reduction of RMS voltage (10% to 90% of nominal voltage) in half cycle of the voltage to 0.5s due to short circuits or machine drawings large inrush currents.

Effects of Voltage Sagging

  1. Lighting loads will be off or twinkle.
  2. Tripping of adjustable speed drive (ASD), which is sensitive voltage change.
  3. Relays and contactors drop out.
  4. Tripping of inverters.
  5. Induction motor speed loss, overcurrent and torque oscillations.
  6. Synchronous motor will loss synchronisation.

When will you experience voltage sagging?

  1. Motor starting.
  2. Transformers energizing.
  3. Faults on the utility system or substations.
  4. Equipment not suitable for local supply.

Voltage Surge

Voltage surge is described as the short-term increase (sudden spike) in voltage which is destructive to electrical equipment. Voltage surge can occur in two ways, voltage spike between both phases or between phase and ground.

Effects of Voltage Surge

  1. Frequently tripped circuit breakers.
  2. Disruption of devices equipped with microprocessors.
  3. Cause heating and burn marks.
  4. Devices resetting or broken.
  5. Gradually degrading internal circuitry, decreasing lifespan of equipment.

When will you experience voltage surge?

  1. Lightning strikes.
  2. Power restoration after blackout.
  3. Power switching.
  4. Electromagnetic interference.

Voltage Flickering

Voltage flicker occurs when voltage magnitude and frequencies change rapidly, large enough to cause variation in lighting level and bring annoyance to human beings. The voltage variations are due to the time variability of the reactive power components of fluctuating loads.

Effects of Voltage Flickering

  1. Visual discomfort on people.
  2. Disrupt sensitive electronic equipment that requires constant voltage.
  3. Unintended triggering of UPS.
  4. Misoperations of relays and contactors.

When will you experience voltage flickering?

Use of motors and arcing equipment with changing load current such as:

  1. Gas compressors.
  2. Liquid or gas pumps.
  3. Cutting equipment.
  4. Hard material crushing equipment.
  5. Arc-furnaces and welders.
  6. Elevators.
  7. Use of cycloconverters or static frequency converters.

Unbalanced Voltage

Unbalanced voltage occurs due to unequal voltage magnitudes and phase angle on three-phase circuits in a distribution system. This can bring damaging effects to three-phase loads that required a balance three-phase voltage to operate.

Effects of Unbalanced Voltage

  1. Damage the three-phase induction machines such as heating effect and vibration on motors.
  2. Damage the three-phase transformers, generators.
  3. Tripping of voltage-sensitive devices (e.g. variable speed drive)

When will you experience unbalanced voltage?

  1. Unbalanced incoming from the utility.
  2. Unbalanced distribution of single-phase loads.
  3. Use of single-phase load with high reactive power (furnaces, welders)