ANALYSING POWER QUALITY
Improving energy efficiency
Geoff Kempster looks at the advances being made in the monitoring and analysing of power quality
The analysis of power quality has an increasingly important role to play in improving energy efficiency, as politicians, environmental bodies and the public at large remain fearful of the effect that CO2 emissions are having on the environment. In order to comply with stringent international legislation, utility companies must ensure the quality of the electricity passing through their distribution networks is constantly kept at an acceptable level. Likewise, industrial processing plants, manufacturing facilities, residential complexes, university campuses and hospitals all have to accurately monitor how effective their electrical systems are - so that energy wastage is minimised and operational costs are always kept under control. Electrical systems are made up of many
different elements - generators, transformers, cabling, switchgear, etc. The performance of each of these elements needs to be thoroughly scrutinized so that power quality problems can be revealed and steps taken to resolve them. A company or organisation can be exposed to serious financial harm through poor power quality - this can be in the form of loss of output from a manufacturing site due to production lines being shut down, the costs associated with replacing electrical hardware that’s working lifespan has been shortened, or simply increased running costs of a system operating at less than maximum levels of efficiency. To combat these problems a large number of parameters will need to be looked into and adequate information compiled on each.
Key power quality issues There are various different sources of power quality problems that engineers involved in energy auditing or electrical maintenance work must to be aware of. These include: Voltage imbalance – this is due to uneven loading of each phase in three-phase electrical systems. It can cause motor overheating and thus shorten the lifespan of equipment. Imbalance can, after being discovered, often be corrected by redistribution of loads on different phases so that the workload is better shared. Harmonic distortion – where the current signals are distorted by non-linear loads. This can lead to overheating of transformers, motors and conductors, as well as the tripping of circuit
breakers and protection relays, not to mention contributing to various kinds of system failure. If a system displays signs of having harmonic issues, then a harmonic filter should be installed to counteract them.
Load switching – this can be a major cause of power quality problems within an electrical system. The current draw sometimes brings about a drop in the voltage level when a load is switched on. This can lead to acute malfunctions elsewhere in the system. Voltage transients – these can be highly detrimental to electrical systems. They can take the form of a sudden signal spike initiated by an electrostatic discharge (ESD) strike, or they can be oscillatory in nature due to a change in the steady-state condition of the current/voltage signal. Such phenomena, if uncovered, can be tackled through use of surge protector and choke devices within the system.
Resultant energy losses
Keeping electrical energy losses derived from the power quality issues just catalogued as low as possible is clearly of prime importance in the generation or the distribution of electricity. As well as reducing the size of the bills for a home
conditions are not met, as efficiency levels will be lower than what is achievable. Losses can be due to resistance of the wiring system, imbalances in a three-phase system impinging on its efficiency, current flowing in neutral conductors and the influence of reactive power.
Specifying power analysis equipment The large amounts of data now being acquired and processed by engineers involved in power quality analysis is resulting in industry-wide demand for more sophisticated, high performance test equipment with an extensive array of functionality, as well as adherence to the latest industry standards. By possessing the ability to capture data from the voltage, current and frequency signals at a high speed and deal with longer waveforms, a thorough examination of the electrical system in question can be undertaken. The high degree of functionality such items of equipment can now support enables comprehensive power analysis without excessive time or human resources having to be allocated.
or larger facility, it will minimise the level of on- going maintenance work and the period over which repairs are carried out, while also avoiding the unwanted expense of replacing vital components. Three-phase systems should have voltage and
current signals that closely approximate mathematically idealised sine wave functions. Furthermore there should be no phase shift between voltage and current. Serious losses will negatively impact on the system, if optimum
16 CIE Power Supplement May 2013
The technology that lies behind analysis of electrical infrastructure’s power quality is progressing at a staggering pace, as our society becomes increasingly dependent on the consumption of ever larger amounts of electricity. By using the various advanced analysis tools now available on the market, sources of energy loss can be accurately pinpointed and dealt with. Any system concerned with the generation, conversion or transportation of electricity can thus be made to function more efficiently and operational costs kept in check. The sort of all-encompassing power quality analysis now being made possible means that engineers are in a position to see exactly how efficient these systems are and identify where there are indications of energy wastage. These systems can then be improved, making them better able to achieve a high degree of operational efficiency, as well ensuring the reliability is sustained in the long term. In order to offer access to the particular tools that are best suited to each set of unique power analysis criteria, Livingston partners with the leading equipment manufactures in this sector, such as Fluke, Doble and Chauvin Arnoux, so as to offer its customer base an expansive product portfolio along with expert application advice.
Livingston |
www.livingston.co.uk
Geoff Kempster is Group Inventory Manager at Livingston
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