Power Quality

What is Power Quality?

Power quality as a term is often defined as the electrical networks (grids) ability to supply a clean and stable power flow acting as a perfect power supply that is always available, has a pure noise-free sinusoidal wave shape, and is always within voltage and frequency tolerances. However, deviations from these ideal conditions are frequent in most networks as the number of loads imposing disturbances is increasing rapidly.

The Problem: Poor Power Quality

Poor power quality is a problem for a wide number of business sectors and its cost is high and rising as the number of disturbances is increasing and modern production equipment is becoming more sensitive to these disturbances. Ironically, it is often the equipment itself that generates the disturbances.

Behaviors that Cause Losses and Disturbances

Loss creating behaviour and disturbance creating behaviour are simplified terms for technical related phenomenon that are a growing problem in the electrical environment and which we like to define as follows:

Loss creating behaviors constitutes reactive behaviour (phase displacement due to electric or magnetic fields), harmonics (unwanted frequency components) and unbalance in terms of uneven power distribution between the phases in the electrical network.

Disturbance creating behaviors constitutes of transients (fast disturbances), voltage variations, flicker and resonance (Oscillations causing instability and overloading).

The most commonly occurring behaviours that cause excessive losses and disturbances can be summed up as follows, to give an idea of where poor power quality arises:

		Reactive power: The phase angle between the current and voltage waveforms in an AC system. Used to develop magnetic field in motors, causes low power factor.			Voltage variations (dips, sags, swells, brown-outs): The line voltage is higher or lower than the nominal voltage for a shorter period. Caused by e.g. network faults, switching of capacitive loads and excessive loading.

		Harmonics: Multiples of the supply frequency, i.e. the fifth harmonic would be 250 Hz if the supply frequency is 50 Hz. Caused by e.g. power electronic loads such as variable speed drives and UPS systems.			Flicker: Random or repetitive variations in the voltage. Caused by e.g. mills, EAF operation (arc furnaces), welding equipment and shredders.

		Network unbalance: Different line voltages. Caused by single-phase loads, phase to phase loads and unbalanced three-phase loads like welding equipment.			Oscillations (resonances): The flow of electrical energy, e.g. between the magnetic field of an inductor and the electric field of a capacitor, changes direction periodically.

		Transients (fast disturbances): Rapid change in the sine wave that occurs in both voltage and current waveforms. Caused by switching devices, start- and stop of high power equipment.

The Consequences of Poor Power Quality

Power and power quality are often overlooked issues when companies optimize their processes to mitigate production interruptions and quality problems. Some common direct impacts of poor power quality are:

Reduced production speed
Increased energy consumption
Charges for reactive power consumption
Lost production
Equipment damage

Idling personnel
Premature equipment aging
Data loss
Rework
Start up costs

In addition to the direct impacts above, poor power quality often induces consequential business costs like:

Postponed revenues
Negative impact on cash flow
Loss of goodwill from customers
Loss of market share

The Solution: ADF

Traditionally fixed, electro-mechanical and semiconductor controlled filters and/or compensators has been used to limit loss creating behaviours. They operate mainly on a fixed or stepped basis using passive elements. All these solutions suffer from the same drawbacks - they add losses, are installation specific and have no ability to adapt to or follow dynamic load changes.

Active conditioners such as ADF eliminates loss creating behaviours such as harmonics, flicker, voltage variations and reactive energy using a highly dynamic, stepless digital controlled compensation and filtering approach.This approach enables the current waveform to be restored instantaneously, the current consumption to be lowered and changes in load or installation conditions to be fully compensated at all times. Read more about how this is done in the article about ADF Technology.

Assess Your Costs of Poor Power Quality

Improvement in power quality reduces risk, raises throughput, decreases the cost of doing business, and hence improves the business bottom line. Order an energy analysis to start to assess your hidden costs and potential savings.