Case Studies

Pontefract - Acoustic Enclosure

Pontefract

Brief

Northern Power Grid were informed that a residential planning application was set to bring housing to within 22m of the two electrical transformers on Pontefract Primary Substation. 

The concern was that electrical transformer noise has the potential to disturb residents that close to a substation. Disturbance likely to be greater at night when things are quieter. 

Northern Powergrid commissioned dB Attenuation to undertake a noise survey and noise modelling exercise to determine the extent of transformer noise affecting the closest houses. 

Assessment 

In October 2018 dBA attended site to undertake a site survey. During the visit, the transformer sound powers were determined and environmental noise measurements were taken around the substation and surrounding land earmarked for residential development.

Electrical transformer noise is characterised by a hum at 100Hz. It is this hum that causes residential complaint. At proposed plot 63, 22m from the transformers, the noise model predicted a level of 60dB at 100Hz. In our experience, this level is almost certain to be audible within a house and result in complaint. 

This information was passed to the developer who agreed to assist Northern Powergrid in introducing noise mitigation measures to reduce transformer noise to a level where future complaints were unlikely.   

Solution

dBA recommended that 100Hz noise should be reduced by a minimum of 25dB.

The only practical way to achieve this level of reduction is by full enclosure of the two transformers. So, dBA undertook a full design and build of two hi-specification enclosures and in July 2020 completed the installation. 

dBA re-visited site in October 2020 to undertake a compliance check to determine the 100Hz reduction provided by the enclosures. 

Despite difficult measurement conditions dBA determined a 100Hz insertion loss of between 25 and 31dB around both enclosures.

The solution will ensure the prospect of complaint will be reduced to a minimum within the residential development.