Partial Discharge Current Pulse Waveform Research Articles

Rise Time Properties of Partial Discharge Current Pulse Waveforms in SF<sub>6</sub> Gas with Picosecond Order and Its Formation Mechanism

Rise Time Properties of Partial Discharge Current Pulse Waveforms in SF<sub>6</sub> Gas with Picosecond Order and Its Formation Mechanism

Current pulse characteristic analysis of typical void and point partial discharge based on PIC‐MCC method

The partial discharge (PD) in a void of epoxy solid insulation is a typical kind of PD behaviour, its occurrences may lead to complete breakdown of the insulation system. The microscopic process of particle movement is simulated here by using particle in cell-Monte–Carlo collision (PIC-MCC) method, which possesses great significance for researching typical discharge. The simulation results of void discharge and point discharge show detailed motion process and the Townsend discharge phenomenon. The PD current pulse waveform possesses similar trends of steep rising edge and gentle falling edge compared with Gaussian function. The behaviour of discharge events is influenced by many factors, such as electric field strength, void thickness, and polarity effect. Thus, the characteristics of PD are discussed and compared by adjusting these simulation parameters to find out internal connection and performance differences.

Comparative analysis of air-gap PD characteristics: Vegetable oil/pressboard and mineral oil/pressboard

Partial Discharge (PD) is considered to be one of the main reasons for aging and degradation of the oil/pressboard insulation system in power transformers. Vegetable oils which own excellent dielectric performance are introduced as potential insulation liquids substituting traditional mineral oil. In this paper, an air-gap PD model was adopted to investigate the PD characteristics of refined rapeseed oil and Karamay 25# mineral oil that are both currently employed in liquid filled power transformers. The PD current pulse waveform analysis (PD-CPWA) method was used to investigate PD mechanisms of two different insulation systems: mineral oil/pressboard and vegetable oil/pressboard. For both insulation systems, phase resolved partial discharge (PRPD) patterns throughout the accelerated deterioration experiments were compared. The extracted ϕ-q-n plots with respect to various PD times were analyzed. It is found that, the air-gap PD stage characteristics of vegetable oil/pressboard are more notable. It has fewer double-peak pulses, smaller inception phase angle, lower charge amplitude, higher repetition rate, and more remarkable ‘rabbit-ear’ patterns than mineral oil/pressboard. The PD development process of both insulation systems can be characterized by four stages: initial discharge stage, weak developing stage, discharge burst stage and pre-breakdown stage.

Technique for discriminating the type of PD in SF<sub>6</sub> gas using the UHF method and the PD current with a metallic particle

The relationship between the PD current pulse waveform at the PD source and the radiated electromagnetic (EM) waveform is investigated using a needle electrode for a metallic particle in SF6 gas at 0.2MPa. A leader discharge with a larger PD charge magnitude and a longer propagation length than for a streamer discharge can be an indicator of breakdown in the SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> gas. Simultaneous and synchronous measurement of the PD current, EM signals and light emission in the SF6 gas revealed that it is possible to discriminate between a streamer discharge and a leader discharge in both time and frequency components. Compared with a streamer discharge, a leader discharge is characterized by a longer rise/fall time of around 0.9 ns in the PD current pulse waveform, and by a lower frequency component of around 250 MHz in the EM frequency spectrum. A satisfactory correlation was obtained between the actual measured EM wave spectrum and the spectrum derived using a spectrum analyzer from the product of the actual PD current and the transfer function from the needle electrode to the UHF sensor that receives the EM wave. This new technique enables streamer and leader types of PD in SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> gas to be discriminated between by measuring the EM wave with a UHF detection system.

Measurements and Classifications of PD Pulse on HDPE Specimens during Degradation

Discharge may take place in high voltage apparatuses in the form of void discharge, corona discharge and surface discharge. Understanding of the discharge is very important to know the condition of the insulation. Partial discharge (PD) current pulse waveforms contain essentially all the available information concerning the PD generation and thus the available information concerning the physical mechanism of degradation and breakdown of insulation. In this paper, three types of discharge model for polyethelene insulation material are constructed and the PD current pulse waveforms are extracted from experiments. In order to obtain pulse waveform characteristics, the extracted pulse waveforms are pre-selected and normalized, and then a Sampling Counting Ratio (SCR) classification technique is investigated to reveal the multi-peak and oscillation information about the PD current pulse waveforms. Results show that the classification would enable us to estimate the progress and degree of the degradation.

Development of procedures for partial discharge measurements at low pressures in air, argon and helium

Partial discharge (PD) characteristics in air, argon and helium at pressures between 101 kPa (760 Torr) to about 0.27 kPa (2 Torr) under 60 Hz AC energization were studied with various electrode arrangements. Measurements are presented for two representative electrode configurations, (1) needle-plane, with 20 mm spacing and a dielectric barrier, and (2) a twisted pair of insulated conductors. Typical PD current pulse waveforms are presented. Difficulties in adhering to measurement guidelines defined by the IEC 60270 standard are described, and suggested modifications of the standard procedures are presented for measurement and calibration for low-pressure PD.

A novel technique for partial discharge and breakdown investigation based on current pulse waveform analysis

A novel technique for partial discharge (PD) measurement and analysis (PD-CPWA; PD current pulse waveform analysis) is developed and introduced in this paper. PD-CPWA is expected to be utilized to discuss PD mechanisms and physics in electrical insulating materials, focusing on the PD current pulse waveform and its time transition from PD inception to breakdown (BD). In this paper, the concept and principle of PD-CPWA are described, and the applications of PD-CPWA to (1) epoxy spacer samples under thermal and electric combined stresses in GIS, (2) creepage PD on epoxy spacers in SF/sub 6/ gas and (3) liquid nitrogen/polypropylene laminated paper composite insulation system for high temperature superconducting cables are introduced and discussed.

Impulse partial discharge and breakdown characteristics of rod-plane gaps in N/sub 2//SF/sub 6/ gas mixtures

Impulse partial discharge (PD) and breakdown (BD) characteristics of rod-plane gaps in N/sub 2//SF/sub 6/ gas mixtures were investigated for different gap geometry, gas pressure and SF/sub 6/ gas content. Experimental results revealed that the 50% probability breakdown voltage increased with gas pressure, which agreed with the theoretical values with consideration of discharge time lag for impulse voltage application. For the calculation of discharge inception voltage, the volume-time theory was successfully applied to the N/sub 2//SF/sub 6/ gas mixture. Furthermore, impulse PD light emission image was observed together with PD current pulse and light intensity waveforms. The long discharge with stepwise propagation and double-peak PD pulses could be observed, which corresponded to the streamer/leader transition leading to breakdown.

The relationship between partial discharge current pulse waveforms and physical mechanisms

Partial discharge (PD) measurements have long been recognised as an important tool for detecting and predicting dielectric breakdown (BD). However, as a result of their small amplitude and wide bandwidth, the relationship between the physical mechanisms of gas breakdown and PD signal generation has not been clarified fully. We have investigated the relationship between PD current pulse waveforms and physical mechanisms to provide a basis for improved PD-based diagnostics.

SF&lt;sub&gt;6&lt;/sub&gt;ガス中における部分放電電流パルス波形の電圧位相依存性とその周波数特性

SF&lt;sub&gt;6&lt;/sub&gt;ガス中における部分放電電流パルス波形の電圧位相依存性とその周波数特性