December 3rd

Understanding Compatibility Levels

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.

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Nuisance tripping of circuit breakers (true RMS measurements)

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.

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Earthing Systems - Basic Constructional Aspects

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. 

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Voltage dips in continuous processes: case study

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.

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Considerations for choosing the appropriate voltage sag mitigation device

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.

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Voltage Dip Mitigation

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.

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Flicker Measurement

Flicker is one of the more difficult PQ parameters to measure because it is defined not by its electrical parameters, but by its effect on human vision. This Application Note describes the background to the perception of flicker and the research and modelling work which lead to the standardisation of flicker measurement.

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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.

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Flicker

Flicker is the impression of unsteadiness of visual sensation induced by cyclic variation in the intensity or spectral content of a light source due to fluctuation of the supply voltage. It does not have any important effect on equipment, but it affects the concentration and productivity of people.

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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.

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