Noise

When it comes to transmission lines with a nominal voltage below 335 kV, the noise caused by the corona (ionisation of the air surrounding a conductor) is generally not disturbing. In contrast, transmission lines with higher voltages (400 kV) are constantly emitting a certain level of noise, even in good weather, which is usually in the form of a typical buzzing sound.

The reasons for increased level of noise surrounding the transmission lines may include:

• damage to  conductors (unravelling of wires in a wire cable due to damage caused by firearms, lightening or similar);
• damage to other electric equipment;
• the intentional throwing of conductive objects onto conductors; and
• humid and rainy weather (increased 'frying' sound).

A certain level of noise can also be caused by devices in substations though we at ELES try to decrease the negative impact of our devices as much as possible. We try to achieve that by additionally insulating switchyards and/or by introducing new technologies and devices (new conductors, shielded switchyards, transformers that do not need forced cooling with quieter ventilators up to a certain load, and others). By implementing these measures, we are ensuring the fulfilment of all the requirements arising from the regulations.

The limit values of noise are determined by the Decree on limit values for environmental noise indicators (Official Gazette of the Republic of Slovenia, No. 43/2018). Electrical energy transmission facilities belong among the industrial noise sources, so the limit values indicated in table 4 of Appendix 1 of the Decree are to be considered.