Abstract
The directivity and lateral profile of corona-generated audible noise (AN) from a single corona source are measured through experiments carried out in the semi-anechoic laboratory. The experimental results show that the waveform of corona-generated AN consists of a series of random sound pressure pulses whose pulse amplitudes decrease with the increase of measurement distance. A single corona source can be regarded as a non-directional AN source, and the A-weighted SPL (sound pressure level) decreases 6 dB(A) as doubling the measurement distance. Then, qualitative explanations for the rationality of treating the single corona source as a point source are given on the basis of the Ingard’s theory for sound generation in corona discharge. Furthermore, we take into consideration of the ground reflection and the air attenuation to reconstruct the propagation features of AN from the single corona source. The calculated results agree with the measurement well, which validates the propagation model. Finally, the influence of the ground reflection on the SPL is presented in the paper.
Highlights
When the high voltage direct current (HVDC) transmission line is in operation, the high electric field in the vicinity of the conductors may induce corona discharge which may can generate space charges and other corona effects[1,2,3] The electromagnetic environment due to the increase of corona-generated audible noise (AN) has promoted the AN being one of the vital aspects during the design and the operation of the HVDC transmission lines
The corona discharge on the on the conductors of transmission lines is usually caused by defects or contaminations which are the main corona sources due to the high electric filed on their surface
It should be the superposition of the corona-generated sound pressure pulses, background noise and reflection sound from the ground,[22] which can be expressed as n(t) = p(t) + r(t) + b(t) where n(t) is the measured AN, p(t) is the corona-generated sound pressure pulses, r(t) and b(t) are the reflection noise from the ground and the background noise, respectively
Summary
When the high voltage direct current (HVDC) transmission line is in operation, the high electric field in the vicinity of the conductors may induce corona discharge which may can generate space charges and other corona effects[1,2,3] The electromagnetic environment due to the increase of corona-generated audible noise (AN) has promoted the AN being one of the vital aspects during the design and the operation of the HVDC transmission lines. 1972, Fitaire and Mantei published three papers to investigate the sound waves generation, amplification and propagation in a weakly ionized gas.[13,14] Their results showed contributions of electrons and applied electric field on the generation of sound source. In 2011, Ueli Strauman employed the model proposed by Ingard to simulate the total sound generated by the AC corona discharge.[21] Due to the difference of the discharge mechanism between AC and DC corona discharge, the proposed method in Ref. 21 cannot be applied in the analysis of AN from the DC corona discharge. No numerical simulation methods can be used to simulate the sound source and propagation characteristics generated by the DC corona discharge due to the complexity of the generation mechanism of corona-generated AN. After the validity of the propagation model is given, the influence of the ground reflection on the resultant SPL is discussed
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