Pressboard

About: Pressboard is a research topic. Over the lifetime, 1123 publications have been published within this topic receiving 9089 citations.

Assessment of Partial Discharge Phenomenon in AC and Fast-rising Square Voltage Using Optical Detection Technique in Needle-Plane Configuration With Pressboard in Mineral Oil

Abstract: The benefits offered by silicon carbide (SiC) switches in terms of repetition rate (> 100 kHz) and switching speed (up to 100 kV/µs) make them a popular choice for the converters of future grid projects. However, the impact of the fast repetitive pulses generated by these devices on the insulator discharge mechanism is yet unknown. This could be a significant obstacle in the future development of power system applications. This paper investigates the partial discharge (PD) phenomenon for pressboard/mineral oil insulation system under unipolar square voltage (USV) waveforms (dV/dt > 50 kV/µs), using a photomultiplier tube (PMT), with a high divergent field. As compared to AC, the partial discharge inception voltage (PDIV) is found to be lower under USV for tested specimens. The phase resolved partial discharge (PRPD) pattern highlights the difference in PD mechanism between AC and USV waveforms. Also, the number of PDs (NPDs) and average charge amplitude (Qavg) obtained under AC and USV waveforms are compared and discussed.

Flat hoister of hot pressed board and overturn combined hoisting tool

Abstract: The utility model relates to a hanging tool of flat plate type, particularly relates to a combined hanging tool used for flat hanging and turning over of hot pressboard. In past days, we need to drill hanging technical screw holes on two sides of hot pressboard and then hang it directly with cable wire, which sways to-and-fro, thereby it is very dangerous and apt to make damages to processed surfaces. The technical plan of the utility model has changed original hanging with soft cable wire into hanging with steel frame structure, which consists of arch board, beam, flat hanging board, hanging hook, turning board and channel steel. It makes use of frame structure, hanging hole centre of turning board which is lower to gravity center of hot pressboard, and structure of arc board to easily carry out flat hanging and turning over of hot pressboard. The utility model is characterized in that the structure of the tool is simple, it is easy to be manufactured, the versatility is good, it can be used smoothly, safely and reliably, it can prevent hot pressboard from distortion because of being pressed, and from damaging processed working surface.

Increase of Static Electrification in an Aged Oil-Immersed Transformer

Abstract: Increase of static electrification activity and discharge generation was experienced during the service operation of an aged power transformer. The transformer oil had high sulfide and sulfoxide contents and was liable to show high ECT value after aging. However, there was no apparent increase in standard ECT (electrostatic charging tendency) measurement of the insulating oil and, therefore, deterioration of pressboard was suspected for the cause of the increase. The ECT tests with aged oil and pressboard sampled from the aged transformer were insufficient to demonstrate the increase in static electrification for the aged transformer. On the other hand, the results suggested a possibility that increase in static electrification can be caused by adsorption of some deterioration compound in the aged oil to the pressboard. In order to make more effective evaluation on the transformer insulation, potential measurement on the pressboard in the oil duct was carried out. The experimental results demonstrated strong increase of the accumulated charge by the aged pressboard, which suggested effectiveness of potential measurement for the assessment of static electrification in transformers. The device of potential measurement for practical use was designed by reducing the necessary amount of oil sampling.

Characteristics of Creepage Discharge in Oil/Pressboard Composite Insulation

Abstract: This paper deals with partial discharge characteristics in oil/pressboard composite insulation system, which is used in oil-immersed power transformer. It is found that the discharge propagates in the same route on the pressboard surface as in the previous discharge every time under repeated impulse voltage application. We also revealed that the white trace remained along the path of discharge and affected the subsequent discharge progress because of being a weak point part on insulation. This study presents an investigation of the effect of the white trace on partial discharge inception voltage (PDIV) of the composite insulation system with high-speed optical observation and electrical measurements for the discharge propagation. The discharge propagation mechanism is also discussed with comparing the discharge progress characteristics before and after the white trace formation.