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Corona discharge will occur on high-voltage direct current (HVDC) transmission lines with the increase in voltage level, accompanied by audible noise, radio interference, and other phenomena. Audible noise has a serious negative impact on the lives and health of the residents around transmission lines. Therefore, it is very important to detect and study audible noise for the optimal design of transmission lines. However, the existing audible noise detection method is the direct detection method, which is vulnerable to the background noises. It is difficult to obtain the accurate measurement values in complex outdoor environment. Based on the relationship between audible noise and corona current, this article presents a method to obtain the A sound level of audible noise indirectly by measuring the corona current, which is called the indirect detection method of audible noise. The validity and accuracy of the proposed method are verified by the experiments of outdoor corona cage and actual HVDC transmission line segment. The proposed method provides a new way to solve the problems of direct detection of audible noise and can complement the existing method. [ABSTRACT FROM AUTHOR]

It is known that the distorted electric field is generated by a high-voltage alternating current (HVac) transmission line passing through a conductor, but few studies have accurately measured and analyzed it. In this article, we analyze the distorted electric field and distortion rate (DR) using a ZigBee-based optical measurement system. First, the key parameters of the integrated optical sensor (IOS) and the wireless module are discussed, respectively. Second, the plate–plate and ball–plate characteristics of the measurement system are studied, and the results show that the measurement system can accurately measure the uniform and nonuniform electric field within 25 kV/m. Third, the measurements are compared to the calculation values, and the results show that the relative error is within 12%. Finally, the distribution law of DRs when considering the grounded shielding wire and height of the obstacle is analyzed. The findings show that the DR varies with the height of the obstacle but is not affected by the grounded shielding wire. [ABSTRACT FROM AUTHOR]

The measurement of the distorted power-frequency electric field needs to meet some special requirements such as appropriate insulation, quick response, passive measurement, and small size. In this paper, based on the Pockels effect, an integrated optical sensor is designed and used for measuring distorted power-frequency electric field for the first time. The input–output characteristic, frequency response, and temperature characteristic of the sensor are studied. The data show that the sensor has a linear measurable range from 100 V/m to 27 kV/m, a 3-dB bandwidth from 20 Hz to 10 MHz, with good temperature stability. The developed sensor is used to measure the distorted electric field and is compared with the Narda-NBM-550 sensor. The relative errors between the measured values of these two sensors and the simulation values obtained by the finite-element method are calculated. It is noted that the relative errors of the integrated optical sensor in different positions are within 12%. However, the Narda-NBM-550 sensor performs poorly at the edges of the barrier with an error of 22%. In conclusion, the findings demonstrate that the integrated optical sensor developed in this paper is more suitable for measuring distorted power-frequency electric field than the Narda-NBM-550 sensor. Further research needs to focus on the measurement of the 3-D distorted power-frequency electric field. [ABSTRACT FROM AUTHOR]

The complexity and diversity of noise in corona current measurements of high-voltage direct current (HVdc) transmission lines leads to challenges in estimating corona performance. This paper proposes an offline noise suppression method for HVdc corona current measurements. Given that the corona current and background noise processes coexist within the same frequency band, we develop a novel multifaceted filtering approach for HVdc corona currents. Specifically, a cross correlation function-based center frequency recognition method is presented to provide filter design specification for a multiple notch filter to suppress narrow-band radio interference. To then suppress the residual full-band noise, wavelet denoising techniques with hard and soft thresholds are applied and compared. The proposed noise suppression method is applied to field-measured corona current data from the HVdc Experimental Base in China. We assert that the noise suppression method has versatile implementation and can be readily applied for corona loss estimation of HVdc systems. [ABSTRACT FROM AUTHOR]

Corona current measurement is essential for research into corona discharge under ultra high-voltage direct-current (HVDC) environment. The sensor is extremely important due to the small (microampere) amplitude of the corona current and the wide (dc to tens of megahertz) range in frequency. In this paper, a high-frequency sensor is described, and its application is introduced for accurate measurement of corona current under HVDC environment. Based on the finite-element method and the charge simulation method, the structure of the sensor is determined considering a \pm1200-kV environment. The sensor is immune to the effects from the external environments such as vibration and temperature changes. Results indicate that the sensor is feasible for corona current measurement. [ABSTRACT FROM PUBLISHER]

Nonintrusive pressure measurement has the crucial role to failure diagnosis and detection of hydraulic system where the conventional measurement instruments fail to make the necessary pressure readings within the sealed pipelines. The relationship between hydraulic oil's dielectric constant, temperature, and pressure was studied, and the feasibility of pressure measurement with capacitance method was demonstrated. In order to make the capacitance method be suit for the hydraulic system where pipeline's enhancement layer was made of tinsel, a capacitive transducer device (CTD) was designed. The functional link artificial neural network (FLANN) has been applied for analyzing the input-output characteristics of the CTD. Also, the FLANN-based modeling of the CTD was built. To verify the validity of the proposed method, an experimental platform was developed. The results indicate that the capacitance method is feasible for nonintrusive pressure measurement. [ABSTRACT FROM PUBLISHER]