Working Group Reports
Load sound power levels for specification purposes of three-phase 50 Hz and 60 Hz liquid-filled power transformers
In the industry there is an increasing awareness observed that load sound, depending on transformer parameters and loading, contributes to, and may even dominate the total sound level of a transformer in service. This results in a growing tendency to specify the permissible sound level not only for no-load operation, but also for the loaded transformer when purchasing new transformers.
Specifying a realistic load sound level for power transformers is often challenging due to limited availability of reliable and validated information. This easily leads to physically unrealistic load sound level specifications, either unnecessary high, e.g. NEMA TR 1 standard, or, as has been a trend in recent years, unachievable low without using external sound mitigation measures.
To provide guidance towards more realistic load sound level specifications, an improved model, based on the physics behind load noise and on the Reiplinger load sound equation is developed for three-phase 50 Hz and 60 Hz transformers.
The results are presented in the form of easy to use curves, giving the typical load sound levels. The load sound model is defined in such a way that with the information available during the transformer procurement process, it is possible to estimate the load sound level.
The parameters of the developed load sound model are based on statistical analysis on an in the industry unique large database, containing 1359 carefully selected datasets, collected by 14 independent transformer manufacturers World-wide.
The presented work about load sound is part of the scope of CIGRE WG A2.54 task to study “Power Transformer audible sound requirements”. The intention of Study Committee A2 in establishing this Working Group was to provide support information and guidance for the industry for sound level specification of new power transformer purchases. This article, written on behalf of CIGRE WG A2.54 is meant to be complementary to the CIGRE paper “No-load sound power levels for specification purposes derived from more than 1000 measurements – a representative figure for three-phase transformers” as well as to the first interim report of WG A2.54 published in ELECTRA 302, February 2019.
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