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.

Radial evolution of dielectric barrier glowlike discharge in helium at atmospheric pressure

Abstract: The radial evolution of dielectric barrier discharge in helium at atmospheric pressure was studied by taking end-view photographs of the discharge during one current pulse using a fast-gated intensified charge coupled device. The photographs were transformed into three-dimensional images that make the radial evolution of the discharge more visualized. It was found that the discharge begins with a weak Townsend discharge covering the entire electrode surface, develops much more rapidly in the central part where the electric field is higher, and spreads radially outward.

Optimum acoustic sensor placement for partial discharge allocation in transformers

Abstract: Partial discharges (PDs) are a cause of degradation of insulation system and its permanent activity monitoring is used as a tool for insulation condition assessment in power transformers. Information on PD position can be used by plant monitors to diagnose the cause of PD and can help to identify type and severity of an insulation fault for maintenance strategies. The acoustic PD detection system, with great advantages relative to other methods, contains inaccuracies in PD localisation, such as the multipath interferences due to reflections within transformer tank, improper acoustic coupling between sensor and tank surface, mechanical vibrations and inherent sensor inaccuracies, which can severely limit the accuracy of the positioning system and make locating the exact positions of PD difficult. In this study, a method has been proposed for calculation of position measurement sensitivity for different PD origins within transformer tank. Different possible cases have been considered for placement of acoustic emission (AE) sensors. For each case, sensitivity of PD location to the time measurement errors has been calculated. The optimum arrangement of AE sensors has been chosen as the configuration yielding lowest error in the PD localisation. A test setup has been organised and the experimental results have justified the theoretical analysis.

Electromagnetic wave radiated from an insulating spacer in gas insulated switchgear with partial discharge detection

Abstract: As a means of diagnosing partial discharge (PD) signals propagate inside a gas insulated switchgear (GIS), a study for the leakage of electromagnetic waves (EM-waves) emitted from the insulating spacer was implemented. The EM-waves leaking out from the solid insulator have the resonance frequencies depend on the spacing between adjacent bolts in the direction of the flange circumference, because the leakage portion is the equivalent of a slot antenna. In this paper, using an electromagnetic analysis model which has a simulated spacer on a concentrically-shaped GIS tank, the output characteristics of the EM-waves that leaked out from the slit were analyzed under various conditions such as the spacing between adjacent bolts, the width of the spacer, the dielectric constant of the spacer and the form of the flange. Also the actual measurement by the experimental equipment used to simulate the model was implemented for comparison with the analytical results. Consequently, the optimal specifications of the sensor and the measurement method used to achieve highly-sensitive detection for practical use were summarized and proposed as well as evaluating the effectiveness of the electromagnetic analysis model adopted in this paper.

Effect of thermally induced bubbles on the electrical breakdown characteristics of liquid nitrogen

Abstract: In any practical large-scale superconducting magnet system, abnormal high voltage across the coil layer and thermally induced bubbles in the cryogenic liquid coolant appear, during the process of quenching, with the spread of the normal zone. The voltage has a rise time of at least several milliseconds, which cannot be met with the apparatus operated at the normal temperature. In the paper, the electrical breakdown characteristics of liquid nitrogen are investigated under a simulated quenching condition, i.e. in the presence of thermally induced bubbles and an electrical field with a rise time of 1–30 ms. It is found that the application of an electrical field will promote the formation of bubbles fixed on an electrode and the production of vapour locking between the electrodes, and the time required for the vapour locking is at least about 1 ms. Furthermore, to analyse quantitatively the deformation of a bubble in the presence of a time-varying electric field, a simplified theory is proposed to explain the motion of the bubble. In the theory, the existence of a thermal layer around the bubble and the use of the Clausius-Clapeyron equation, as the relationship between vapour pressure in the bubble and ambient temperature, are assumed. The theory suggests that a partial discharge inside the bubble occurs, although the light pulse from the discharge was not detected in the experiments. A bubble breakdown mechanism in the absence of thermally induced bubbles is also discussed, on the basis of the bubble deformation process under a time-varying electric field.