Partial discharge

About: Partial discharge is a research topic. Over the lifetime, 13997 publications have been published within this topic receiving 102058 citations. The topic is also known as: PD.

The use of power frequency current transformers as partial discharge sensors for underground cables

Abstract: Partial discharge (PD) diagnostics can be used to diagnose insulation defects in medium voltage cables and thereby inform required maintenance planning to extend the lifespan of ageing assets. High frequency current transformers (HFCT) installed on the earth strap at the cable termination are widely used to detect the fast varying pulses resulting from PD. Due to constructional reasons earth strap accessibility in underground cables is often limited. Furthermore in three core cables, phase angle dependency of pulses resulting from PD sometimes fails to induce pulses in the earth screen. This paper investigates an alternative method of PD detection using conventional power frequency current transformers (PFCT) principally used for protection and measurement purposes. This investigation assesses the feasibility of this approach by conducting a magnetic study of the transformer core, frequency response analysis (FRA), and finally capturing and analyzing onsite PD measurements using conventional PFCTs and the developed PD data acquisition/interpretation system. Based on the laboratory and on-site measurement results, PFCTs can be considered for detecting PD. This approach does not require retrofitting additional PD sensors and can also be applied to older switchgear design without any outage. Hence this approach can be considered as a low cost and noninvasive method of PD detection in cables.

Characteristics and Development Mechanisms of Partial Discharge in SF 6 Gas Under Impulse Voltages

Abstract: It is well known that impulse voltages strongly affect the reliability of gas-insulated switchgear (GIS) under actual operational conditions. The alternating-current (ac) withstand voltage test and its corresponding partial discharge (PD) measurement are inadequate for the detection of all the hidden flaws in GIS. Such inadequacy can be compensated by additional impulse withstand voltage test and its PD detection measurement. However, the bulkiness and inefficiency of aperiodic impulse voltage generator make it unsuitable for on-site application. Therefore, in practical tests, oscillating impulse voltage (OIV) is generally adopted instead of aperiodic impulse voltage. In this paper, we measure the PD inception voltage (PDIV) and the breakdown characteristics of a needle-plate gap in SF6 gas under four types of impulse voltages by electrical and optical methods. The 50% probability PDIV is analyzed as a function of gas pressure. The physical mechanisms of the PD under the four impulse voltages are discussed. The PD characteristics under ac voltage are investigated for comparison. Experimental results reveal that the PD development process under the two aperiodic impulse voltages was mainly dominated by the precursor mechanism which consists of streamer and leader stages, while the PD propagation under the two OIVs was affected by the displacement current produced by oscillation. The difference of the PD characteristics under the aperiodic impulse voltage and OIV, and ac voltage are also presented.

Deep-learning-based partial discharge defective image diagnosing method and system

Abstract: The invention provides a deep-learning-based partial discharge defective image diagnosing method and system, comprising the following steps: 1) detecting the partial discharge signal of a piece of power equipment; obtaining a partial discharge defective image; 2) creating a partial discharge defective image sample database; extracting the training set and the testing set; 3) creating a deep convolution neural network model; using samples to do deep learning training and testing to obtain the connection weights and bias parameters of the network model; and 4) inputting the partial discharge defective image to be diagnosed into the network model obtained from the step 3; outputting and obtaining the partial discharge defect type of the image. According to the invention, through the utilization of the learning algorithm of the deep learning theory to complete the characteristic extraction task of a partial discharge defective image, it is possible to accurately and effectively identify the defect type of the partial discharge image without the reliance on manual extraction of the characteristic parameters, providing new solutions for insulation state diagnosing of power equipment.

Influence of moisture and partial discharges on the degradation of high-voltage surge arresters

Abstract: SUMMARY This paper reports the influence of moisture and internal partial discharges on the degradation of metal oxide varistors in high-voltage surge arresters. Both factors cause an increase in the varistor current under the operating voltage. This phenomenon is dangerous and can cause a total outage of the metal oxide arrester. In the field the moisture ingress can lead to internal discharges. Owing to recovery processes the changes in the voltage–current characteristics of varistors caused by moisture or partial discharges decrease in dry and partial discharge free conditions. The interesting behaviour of some varistors which were degraded by partial discharges was observed. Copyright # 2004 John Wiley & Sons, Ltd.

On the Secondary Discharge of an Atmospheric-Pressure Pulsed DBD in He with Impurities

Abstract: The secondary discharge was induced at the end of a slow-falling voltage flank, when a semisine monopolar pulse voltage excites the dielectric-barrier discharge. Formation and properties of the secondary discharge with respect to different dielectric materials such as glass, ceramic, and polyethylene theraphtalate were studied. The tunable diode laser absorption spectrometry (at 777.194 nm) was used to analyze the time-space distribution of the density of the atomic oxygen in metastable state (35S2 rarr 35P3) in addition to both discharge voltage and discharge current versus time. The secondary discharge is always formed, and its amplitude, as well as the amplitude of the main discharge, depends on surface properties of the dielectric barrier.