Wherever energy is transmitted, noise can be generated. And different noises can have different causes. The conductor cables can sometimes give rise to vibration and wind noise – the pylons also resulting in the latter of these. What’s more, the high field strengths around the conductors can lead to electrical discharges that ionise the air. It is this “corona phenomenon” that we hear crackling and humming, especially when it’s raining or foggy.
When it comes to high-voltage direct-current transmission (HVDC), the converters are also responsible for emitting noises, the primary sources being transformers and fans. We will be tackling and limiting the noises made by technical components such as power electronics, transformers and cooling systems by means of construction measures that ensure that people living nearby will not be additionally disturbed by noise pollution.
We plan, design, build and operate our high-voltage switchgear and substations such that we prevent annoying noise levels and comply with the permissible exposure levels and standards. The noise from these installations arises primarily from the transformers and, in some isolated cases, from switchgear; in the latter case, however, this is generally not perceived as annoying thanks to the low switching frequency.
We make it a hard and fast rule to purchase transformers that are the state of the art and the quietest available.
By employing a sound-absorbing screen, it’s possible to reduce noise levels by up to 12 dB(A) (in the immediate vicinity), depending on the distance between the transformer and the place of immission, that is, the location affected by the noise pollution. A 10 dB reduction in the noise level roughly equates to halving the noise volume felt subjectively.