# Disturbances Generated by Lighting Systems with LED Lamps and the Reduction in Their Impacts
## 2 The Impact of Higher Harmonics in Electrical Circuits  
Each non-linear element incorporated into the system most frequently causes the non-linearity of that system (the distortions of currents and voltages which occur in it) and thus, the occurrence of problems connected to the impact of higher harmonics. Very frequently, the consequences of the impact of higher harmonics are severe for other devices operating in the surrounding environment, and thus also for their users [2; 3; 4; 5; 6; 7; 8; 9; 10]. A high level of distortion of the current or voltage signal is related to [4]:  
* The instability of the power supply system,
* Increased reactive power consumption,
* Increased active power losses,
* A reduction in the efficiency and durability of devices. The level of the impact of higher harmonics on electrical devices depends on the sensitivity and resistance of these devices. Loads that are similar to resistance loads in nature, and that are mainly used for heating purposes (e.g., resistance furnaces) demonstrate the highest resistance. On the other hand, small electronic devices designed to be powered by a sinusoidal signal with the mains frequency, such as the automated control equipment of an intelligent building, are characterised by the highest sensitivity to the impact of higher harmonics. The impact consequences of higher harmonics can vary depending on the group of devices [2; 3; 4; 5; 6; 9; 10; 12; 25]:  
* In motors and generators, they cause an increase in the losses in the winding and the magnetic circuits, which leads to an increase in the operating temperature of the devices and contributes to the faster ageing of winding insulations; thus, their operation time is shortened; in three-phase induction motors, negative sequence components (e.g., h5 or h11) generate a rotating field in the opposite direction to the rotation of the rotor; thus, they generate a braking torque, and as a result of this, they are an additional load for the motor;
* In transformers, the distorted current causes an increase in the losses both in the winding and the core; the higher losses mean the generation of a higher amount of heat, and in order to maintain the rated operating temperature, it is necessary to reduce the maximum transformer load in which the distorted currents and voltages occur; in three-phase four-wire systems, in the neutral wire, the zero sequence harmonics are aggregated (especially the third one and the ninth one), causing an increase in current in the neutral wire, which may, as a consequence, result in damage to the neutral wire;
* In capacitors, they are manifested in the form of current and voltage overloads; this may cause local discharges in the dielectric, which consequently lead to short circuits in the plates and permanent damage to the capacitor;
* In switches, contactors, or relays, their proper operation may be disturbed, the switch moment may be completely different from that for which they were designed (the devices may switch off in an apparently unjustified manner, and as a consequence of this, there may be downtimes in the operation of active auxiliary electrical equipment); with the THD exceeding 20%, this is a typically stochastic process;* In electronic devices, interferences in their operation may occur (due to a different total value of the supply voltage containing higher harmonics), or the devices may be subject to damage (the current higher harmonics cause additional heat losses that significantly increase the operating temperature, which, most frequently, is already extreme under normal conditions); furthermore, at high peak factors, damage to semi-conductor sub-assemblies is also possible;
* In electrical light sources, symptoms may vary depending on the type of the light source, but generally, a change in the lighting intensity is noticeable; also, the temperature of the lamps increases, which results in a speeding up of the ageing processes.