Interests on ester liquids as replacement of mineral oil in large power transformers are growing recent years. This paper presents experimental studies streamer and breakdown synthetic natural esters. Lightning impulse voltage was chosen when considering the practicality standard tests transformer industry. First, length, velocity, shape mode were analyzed based optical images obtained by a multi-channel ultra high speed camera. Under same level, both esters propagates faster further, with...

Frequency-response analysis (FRA) has been accepted as one of the most sensitive tools to detect mechanical faults power transformers. Correct interpretation FRA responses is crucial when assessing integrity a transformer. Transformer have distinctive frequency regions which are predominated by core, windings, and measuring setup. This paper addresses major factors that affect responses: winding structure itself. In terms structures single winding, they can be categorized into windings with...

Vegetable oil is one of the alternatives to replace mineral oils in transformers. This paper focuses on oxidation stability assessment a vegetable transformer under accelerated thermal aging at 110°C with various durations up 2500 hours. Oil samples were aged open condition stimulate process, as well sealed provide comparison. A number parameters including acidity, DC conductivity, dielectric dissipation factor (DDF) and viscosity measured see their responses process oil. The results showed...

In recent years, firefighter accidents and people injured by the collapse of steel structures during a fire have occurred frequently, which has attracted attention National Emergency Management Department Fire Rescue Bureau. It is urgent to carry out research on early warning systems for building fire. Existing methods mainly use characteristic parameters such as temperature, vibration, structural deformation. Due complexity an actual fire, it difficult accurately predict critical...

Ester-based transformer fluids have the same DGA fingerprints as mineral oil. However, with lower volumes of gas produced, they will demand more precise dissolved measurements and modified or new ratio criteria to allow fault detection diagnosis.

Recent decades have seen the rapid and successful deployment of ester oils as transformer dielectrics. When evaluating compatibility with existing insulation designs, it is essential to not only compare mean breakdown voltages oils, but also consider role dispersion thus withstand voltage levels (with acceptable likelihood). Insulation designers sometimes estimate mineral oil from data, assuming that follow a parametric distribution. However, there lack discussion whether this method would...

This paper presents experimental research of creepage discharge on insulation barriers in power transformers. Using point-to-plate electrode configurations under AC voltages is studied for both single flashover breakdown and partial induced failure modes. It confirmed that the dielectric strength oil gap will not be reduced with introducing dry new pressboard surface into gap, indeed voltage hardly compromised by aged up to 3% moisture. However, increased moisture content reduces inception...

This paper presents experimental studies on streamer and breakdown of synthetic natural ester liquids with the presence pressboard interface in a divergent point-plane field under lightning impulse voltage. Based current, light signals images, characteristics both positive negative streamers surface were described, which resemble features open liquid gaps. Introducing parallel does not influence stopping length thus weaken oil gap voltage, polarities at distances up to 75 mm. However,...

Aging of transformer paper insulation is commonly investigated through indirect measurements conducted in the oil, e.g. furanic compounds. In addition to conventional indicators, recent investigations showed that alcohols like methanol and ethanol oil could be used as aging indicators. This focuses on applicability these new indicators a novel, gas-to-liquid (GTL) technology based an accelerated laboratory experiment. The experiment was at 120 °C for up 280 days. A mineral also tested...

Power electronic transformers, namely solid state have aroused a widespread attention due to the integration issue of large scale renewable energy in modern power system. High frequency transformer (HFPT) is one its key components operating at several tens kHz. Under such high voltage, accelerated insulation aging and premature failure occur frequently. Partial discharge (PD) considered as main cause electrical performance deterioration HV systems or LV ones where overvoltage surge may...

Non-technical losses (NTL) caused by fault or electricity theft is greatly harmful to the power grid. Industrial customers consume most of energy, and it important reduce this part NTL. Currently, work concentrates on analyzing characteristic consumption detect NTL among residential customers. However, related feature models cannot be adapted industrial because they do not have a fixed pattern. Therefore, paper starts from principle measurement, proposes deep learning-based method extract...

The solid-state transformer (SST) was regarded as the ideal power router in energy Internet. However, partial discharge (PD) tightly packed SST is one of main causes interturn multilayer insulation premature failure. effect high-frequency (HF) electrical-thermal coupling stress on insulation's PD characteristics and failure mechanism not clarified, which investigated this article. An HF measurement system established, a comparative study polyimide (PI) at different test frequencies...

Frequency response analysis (FRA) is an effective diagnostic tool for detecting transformer winding movements. Various FRA traces can be measured from a set of terminals each which relate to different test connection scheme. Practical considerations and time dictate that only some the connections are used, currently there no standard connection. This paper presents comparison three measurement widely employed in industry today, namely: end-to-end voltage ratio, input admittance transfer...

In general, a transformer winding end-to-end frequency response analysis (FRA) response, usually measured between 10 Hz and 2 MHz, can be divided into three regions of which from low to high frequencies, are dominated by the core, windings, measurement setup correspondingly. The coupling interaction windings may originated either nontested same phase with winding-under-test or in other phases. latter is coupled through three-phase delta connection. This paper addresses issue how it affects...

As replacement of mineral oil, the application ester liquids in large power transformers has become a hot topic recent years. Understanding esters' dielectric behaviors under ac voltage is vital importance for insulation design transformers. This paper presents experimental studies on strengths synthetic and natural quasi-uniform electric field, using oil as benchmark. The results show that esters have similar breakdown voltages to when filtered dehydrated. However, their are significantly...

This paper presents breakdown and withstand strengths of a synthetic ester, natural ester mineral oil in quasi-uniform sphere-to-sphere electric field under impulse voltages. The influences waveforms (lightning switching), voltage polarities (positive negative) testing methods (rising-voltage, up-and-down multiple-level) on the behaviour were investigated. results indicated that voltages both liquids are comparable with those various test conditions. at 1% probability was also obtained based...

Experimental investigations were carried out to study the tracking process on pressboard in esters under ac voltages. The evolutions of creepage discharges analyzed by correlating visual records surface tracking, phase resolved PD patterns, discharge current signals and high speed shadowgraph images. It is found that impregnated susceptive erosion occurring inside pressboard, which characterized "tree-shaped white carbonized marks". gaseous "white mark" channels would attract subsequent...

The applicability of using 2-furfural (2-FAL) and methanol as aging markers for synthetic ester impregnated paper insulation was investigated through laboratory experiments at temperatures 80, 100 120 °C. Methanol in the increased linearly with until degree polymerisation (DP) reached 400. During this period concentration oil higher than that 2-FAL, which proved concept to indicate early ester. However, rate increase against reduction DP about three times seen mineral oil. This is due a...

ac Breakdown voltage tests are usually used for quality check of mineral oils during transformer operation. When studying ester-based oils, previous experimental research including the ones carried out at University Manchester laboratories, were based on `as-received' oil samples and particle effects not quantified. Similarly, water determined previously also ambiguous since can be combined with particles to reduce breakdown voltages. This paper i.e. 10 Gemini X as oil, Midel7131 synthetic...

Ester oils have been successfully used in distribution transformers for many years as satisfactory substitutes mineral oil. In high voltage however their application has much slower partly due to the fact that viscosity of ester oil and hence uncertainties efficient impregnation cellulose insulation. this paper characteristics insulation by are assessed compared with Studies carried out on thick laminated pressboard blocks, typical support structures transformers. The degree time at various...