Donglai Wang

Comparison between the audible noises generated from single corona source under DC and AC corona discharge

The corona-generated audible noise (AN) factor is an important consideration in the design and operation of ultrahigh voltage direct current (DC) and alternate current (AC) transmission lines. Due to the differences in discharge process and corona-generated space charges between the DC and AC corona discharge, the audible noise from DC and AC corona has different characteristics. This paper conducts a series of experiments by measuring the time-domain waveforms of the audible noise from a single corona source under DC and AC voltage. Sound pressure pulses are extracted from a correlation analysis, and then a detailed comparison of the basic characteristics of DC and AC corona-generated AN in time-domain and frequency spectrum is given. Results from this paper stand to contribute to an explanation of existing results in AN measurement and analysis from DC and AC transmission lines.

Statistical characteristic in time-domain of direct current corona-generated audible noise from conductor in corona cage

The corona-generated audible noise (AN) has become one of decisive factors in the design of high voltage direct current (HVDC) transmission lines. The AN from transmission lines can be attributed to sound pressure pulses which are generated by the multiple corona sources formed on the conductor, i.e., transmission lines. In this paper, a detailed time-domain characteristics of the sound pressure pulses, which are generated by the DC corona discharges formed over the surfaces of a stranded conductors, are investigated systematically in a laboratory settings using a corona cage structure. The amplitude of sound pressure pulse and its time intervals are extracted by observing a direct correlation between corona current pulses and corona-generated sound pressure pulses. Based on the statistical characteristics, a stochastic model is presented for simulating the sound pressure pulses due to DC corona discharges occurring on conductors. The proposed stochastic model is validated by comparing the calculated and ...

A Laboratory Study on the Ion-Flow Field Model of the DC Wires in Stable Wind

Although transverse wind exerts an important influence on the distribution of the ion current density under HVDC transmission lines, very few experiments involving stable wind have been used to verify the numerical model. To overcome the variability of natural wind, a low-speed wind tunnel was used to produce stable wind in this research. An experimental platform was set up in the wind tunnel, to measure the ion current density of dc wires. Based on the experiment, transverse wind exerted a significant influence over the distribution of the ion current. The numerical model was discussed and the results showed reasonable agreement with the measured values for different wind speeds.

Corona characteristics of HVDC conductors with different surface conditions obtained in a controllable accelerating contamination depositing apparatus

Suspended aerosols in the vicinity of discharged HVDC transmission lines will be charged by ions and deposit on the surface of the conductors. In order to obtain the conductors with different contamination conditions, a controllable accelerating contamination depositing method by introducing a controllable ionized field is proposed in the present paper. The conductor samples contaminated by 3 typical patterns were prepared and the morphology of the conductor surfaces was characterized by scanning electron microscopy (SEM). The photon counting rate of the conductors and the electric field strength on the ground electrode were also tested. The anticipatory contamination depositing results were obtained, specifically, the surface conditions of the conductors could be improved or deteriorated, therefore, the corona discharge could be suppressed or enhanced in corresponding patterns of the proposed contamination depositing method.

Research on surface charge characteristics of insulating film in ion-flow field

Surface charges accumulated on insulating film will change the electric field around the insulating film, and the surface charge distribution has direct relationship with the electric field around. In order to investigate the surface charge characteristics of insulating film in ion-flow field, an experimental platform was designed, which contained a charge generating apparatus, an electrometer and a control apparatus. With the charge generating apparatus, the charges accumulated on the surface of insulating film, the electric field and the ion-flow around the insulating film could be controlled. The surface potentials of insulating film were measured by a vibrated capacitor electrometer, and the surface charge distributions of insulating film were obtained by the surface charge method. In this paper, the surface charge distribution characteristics of insulating film under different conditions are compared, and the factors that influence the surface charge characteristics are discussed.

3-D Electric Field Computation of Steeple Rooftop Houses Near HVDC Transmission Lines

The existence of residential houses will distort the ion flow field under high-voltage direct current transmission lines. High efficiency electric field computational method is required during the engineering design. In this paper, the surface charge method is applied in the space-charge-free electric field computation, and a half-analytical integration strategy is presented to accelerate the computational speed. Then, ion flow field around the house is computed based on Deutsch assumption. The calculation methods are validated by the experiment in the laboratory. Electric field intensity around the top edge of steeple rooftop is larger than other areas, and the field distribution characteristics on the steeple rooftop are significantly different from flat rooftop.

Propagation characteristics of audible noise generated by single corona source under positive DC voltage

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...