Both national and international standards for the conductor sizing of cables do not adequately take into account the additional heat load arising from harmonic currents. Some standards prescribe the maximum current values for four-conductor and five-conductor cables under the assumption that only two or three conductors are loaded. However, today’s harmonic situations may give rise to the fourth conductor (neutral) being fully loaded or even overloaded simultaneously with a balanced load on the three phase conductors.Read full article
This application note discusses the compatibility, with respect to harmonic voltage levels, of load devices with the electricity supply system. Consumers' equipment operating on the network causes disturbances which affect the proper operation of other equipment on the network.
To ensure compatibility it is necessary both to control the maximum level of disturbance that may be present at any point on the network and to establish a level of disturbance to which every item of equipment will be immune.Read full article
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.
Read full article
Nuisance tripping of circuit breakers is a common problem in many commercial and industrial installations. This Application Note explains the need to use true RMS measurement instruments when troubleshooting and analyzing the performance of a power system.Read full article
This Application Note discusses practical design of earthing electrodes, including the calculation of earthing resistance for various electrode configurations, the materials used for electrodes and their corrosion performance. Equations are given for many common electrode geometries, including horizontal strips, rods, meshes, cable screens and foundations. Read full article
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.Read full article
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.Read full article
This Application Note describes an industrial case study in a nylon extrusion plant. Investigation revealed a history disruptive dips at the plant with significant loss of production. Examination of the records showed that the plant was affected by faults in a wide area of the network; the objective of the study was to decide how to limit the exposure of the plant to these faults. The options for improvement include measures at the equipment, installation and network level.Read full article
This Application Note discusses power electronic solutions. These devices may include energy stores, such as flywheels, batteries or super-capacitors, so that they can provide corrected power even when there is no retained voltage. Some newer power electronic solutions are also discussed, together with a methodology for selecting the most appropriate and cost-effective solution.
Read full article
This Application Note discusses some of the established techniques for voltage stabilisation, many of which are fast enough to protect some equipment against dips. Electro-mechanical, electromagnetic and electronic methods are described. These techniques, all of which require a significant retained voltage, are still relevant, providing a good degree of protection without the negative side effects, such as harmonic distortion, that may accompany other solutions.Read full article