# Disturbances Generated by Lighting Systems with LED Lamps and the Reduction in Their Impacts
## 2 The Impact of Higher Harmonics in Electrical Circuits
In the not so distant future, this type of lamp may drive all other light sources used so far out of the market. The importance of the discussed issue is intensified by provisions included in Directive 2005/32/EC of the European Parliament, which prohibit any further manufacture and marketing of incandescent light sources within the EU (excluding special applications where their use is indispensable) [48]. At the same time, the Directive orders a switch to energy-saving lighting (LED lamps or compact fluorescent lamps). The schedule for the gradual withdrawal of bulbs was included in regulation No. 244 of the European Commission from the year 2009 [49]. The limitation of the impact of higher harmonics in electrical systems in large facilities may consist of the appropriate separation of loads, that is, the application of separate power lines for loads that generate higher harmonics and for loads that are sensitive to the impact of higher harmonics. It may also involve the installation of separation transformers. In order to eliminate the impacts of higher harmonics on other electrical circuits, it is recommended, above all, to use filters. In practice, passive filters are often used for this purpose (mainly in systems where the frequency characteristics of the current drawn do not change)--solutions that are simple but at the same time cheap. In systems where there are more circuits and devices that generate higher harmonics with a different spectral distribution of the introduced harmonics, activated stochastically (not systematically), it is recommended to use active filters, which are more effective and eliminate the harmonic impacts with greater precision. However, they are more complex and much more expensive (an economic justification for their implementation is also required for them). A reduction in the impacts of higher harmonics in large systems (e.g., lighting systems) may be achieved through the use of a two-stage power supply. The mains voltage is rectified at the input of the power supply and then supplied to the inverter system via a DC line, where sinusoidal voltage with more advantageous parameters than those of the mains voltage is generated. Because of the two-stage operation (the occurrence of a DC section), disturbances generated in the circuit switched on at the output of the power supply are transferred to a limited extent to its input, i.e., the power mains. The introduction of such solutions is not planned if single LED lamps or lighting systems with a very small number of such lamps (with low total power) are implemented. Above all, in such a case, there will be no economic justification for the application of such a technical solution, and furthermore, distorted signals with extremely lower power hardly affect the power mains. Therefore, the introduction of systems to the limit the impacts of higher harmonics in systems where distorted currents will have high values (high distortion powers will be present) is more important. In such a situation, two-stage power supplies would be economically justified. In particular cases, when there is a need in the given power mains for guaranteed level of power supply, it is possible to use the two-stage power supply (UPS) system, which, in the VFI (Voltage Frequency Independent) topology, contains the two-stage power supply within its structure, and in addition to the provision of an uninterrupted power supply, will simultaneously limit the impact of higher harmonics on the remaining part of the mains. In a properly selected two-stage power supply, in addition to the elimination of the impacts of higher harmonics (distortion power), the consumption of reactive power (related to the phase shift between the basic harmonics of current and voltage) is also limited. The limitation of the reactive power consumption is also linked to a reduction in the costs of drawing energy from the mains for institutional recipients, which would be an additional justification for the introduction of such a two-stage power supply.