Active Harmonic Conditioners

This Application Note discusses the use of active filters to reduce harmonic currents in installations. Active filters work by providing the harmonic current required by the load instead of it being drawn from the supply.

The major advantage of an active filter is that, because it responds only to downstream current harmonics, they can be distributed around an installation without cross interference. They can be programmed to respond to selected or all harmonic frequencies and quickly adapt to changes in load profile.

Capacitors in Harmonic-Rich Environments

Capacitor banks have been used for many years to compensate the fundamental reactive power required by resistive-inductive loads. They are essential for an economic operation of the electrical system. However, non-linear loads are becoming predominant in today’s electricity system. Capacitor banks now have to be designed to cope with two basic challenges those non-linear loads bring about.

Fundamentals of Electromagnetic Compatibility (EMC)

Electromagnetic interference, EMI, has become very important in the last few decades as the amount of electronic equipment in use has increased enormously.  This has led to an increase in the sources of interference, e.g. digital equipment and switching power supplies, and an increase in the sensitivity of equipment to interference, due to higher data rates.

Earthing & EMC

Earthing of electrical systems is very important.  Its primary purpose is to ensure safety by providing protection for buildings and occupants against direct damage and electrical shock due to lightning or short circuit events.  Its secondary purpose is to provide a noise free equipotential environment to enable electrical and electronic equipment to function correctly and reliably.

Predictive Maintenance - The Key to Power Quality

When PQ problems become apparent – usually in the form of a disruption – they are usually referred to as ‘events’. This terminology is misleading because it hides the fact that the causes of many ‘event’ could have been identified in advance by the use of predictive maintenance techniques. This Application Note proposes that, rather than simply responding to problems, PQ should be continuously monitored as part of a planned maintenance activity.

Introduction to Unbalance

Unbalance can be caused by the presence of single-phase generators, such as photovoltaic units, unbalanced impedance of the distribution system, due to geometric effects, and unequal loading of the phases. Unbalance can have a serious effect on the performance and energy efficiency of three-phase equipment such as induction motors, transformers and electronic converters. In most circumstances, serious unbalance can be avoided by good installation practice, but some loads, such as railways, require special attention.

Interharmonics

Interharmonics are voltages or currents with a frequency that is a non-integral multiple of the fundamental supply frequency, while each harmonic frequency is an integral multiple of the supply frequency.  Interharmonics, always present in the power system, have recently become of more importance since the widespread use of power electronic systems results in an increase of their magnitude.