BS EN 60076-10:2016 pdf free.Power transformers Determination of sound levels.
BS EN 60076-10 The representation of the sound power level of a transformer at a certain service condition isgiven by the logarithmic sum of the three sound power components at this service condition.For details see Clause 13.
Sound power due to no-load excitation has to be regarded for all types of transformer. Theexcitation voltage shall be of sinusoidal or practically of sinusoidal waveform and ratedfrequency.The voltage shall be in accordance with 11.5 of lEC 60076-1:2011. In the case ofreactors a no-load condition does not exist since rated current will flow as soon as ratedvoltage is applied.For more information on reactor sound testing see lEC 60076-6.
The usual condition for sound power level determination of transformers at no-load excitationrefers to rated voltage at an untapped winding. Other excitation conditions may occur inservice leading to lower or higher sound power levels and might also be the condition for aguarantee and if so shall be specified by the purchaser. For transformers designed to operatewith variable flux,the sound power at no-load excitation is strongly impacted by the tappingposition.The tapping position for the sound measurement has therefore to be agreed betweenmanufacturer and purchaser during tender stage.
lf a transformer is fitted with reactor-type on-load tap-changer equipment where the reactormay on certain tap-changer positions be permanently energized, the measurements shall bemade with the transformer on a tapping which involves this condition and which is also asnear to the principal tapping as possible.
The selected test conditions shall be clearly indicated in the test report.
NOTE DC bias magnetization of the core can cause a significant increase in the measured sound levels. ltspresence is indicated by the existence of odd harmonics of the excitation frequency in the sound spectrum and thiscan be identified by a narrow band analysis. The DC bias impact on no-load sound level measurements duringfactory testing can be practically eliminated by an over excitation run for some minutes.When over excitation is nota practical option， as in on-site measurements，DC bias elimination after a transformer inrush event can takeseveral hours or even days.
The usual condition for sound power level determination is to have all cooling devicesnecessary to operate the transformer at its rated power running.
In case of a water cooling device, the water flow need not be maintained during sound leveltesting.
In case of variable speed cooling devices (usually fans) the speed during sound level testinghas a significant effect on the sound power level.The speed of the cooling device selected forthe sound level measurement shall be the speed necessary to operate the transformer at itsrated power under the most onerous external cooling medium conditions.BS EN 60076-10 pdf download.