Identifying harmonic attributes from online partial discharge data

Partial discharge (PD) monitoring is a key method of tracking fault progression and degradation of insulation systems. Recent research discovered that the harmonic regime experienced by the plant also affects the PD pattern, questioning the conclusions about equipment health drawn from PD data. This paper presents the design and creation of an online system for harmonic circumstance monitoring of distribution cables, using only PD data. Based on machine learning techniques, the system can assess the prevalence of the 5th and 7th harmonic orders over the monitoring period. This information is key for asset managers to draw correct conclusions about the remaining life of polymeric cable insulation, and prevent overestimation of the degradation trend

Assessing the effects of power quality on partial discharge behaviour through machine learning

Partial discharge (PD) is commonly used as an indicator of insulation health in high voltage equipment, but research has indicated that power quality, particularly harmonics, can strongly influence the discharge behaviour and the corresponding pattern observed. Unacknowledged variation in harmonics of the excitation voltage waveform can influence the insulation's degradation, leading to possible misinterpretation of diagnostic data and erroneous estimates of the insulation's ageing state, thus resulting in inappropriate asset management decisions. This paper reports on a suite of classifiers for identifying pertinent harmonic attributes from PD data, and presents results of techniques for improving their accuracy. Aspects of PD field monitoring are used to design a practical system for on-line monitoring of voltage harmonics. This system yields a report on the harmonics experienced during the monitoring period

The role of circumstance monitoring on the diagnostic interpretation of condition monitoring data

Circumstance monitoring, a recently coined termed defines the collection of data reflecting the real network working environment of in-service equipment. This ideally complete data set should reflect the elements of the electrical, mechanical, thermal, chemical and environmental stress factors present on the network. This must be distinguished from condition monitoring, which is the collection of data reflecting the status of in-service equipment. This contribution investigates the significance of considering circumstance monitoring on diagnostic interpretation of condition monitoring data. Electrical treeing partial discharge activity from various harmonic polluted waveforms have been recorded and subjected to a series of machine learning techniques. The outcome provides a platform for improved interpretation of the harmonic influenced partial discharge patterns. The main conclusion of this exercise suggests that any diagnostic interpretation is dependent on the immunity of condition monitoring measurements to the stress factors influencing the operational conditions. This enables the asset manager to have an improved holistic view of an asset's health

Interpretation of partial discharge activity in the presence of harmonics

Recent work has identified that circumstances of equipment operation can radically change condition monitoring data. This contribution investigates the significance of considering circumstance monitoring on the diagnostic interpretation of such condition monitoring data. Electrical treeing partial discharge data have been subjected to a data mining investigation, providing a platform for classification of harmonic influenced partial discharge patterns. The Total Harmonic Distortion (THD) index was varied to a maximum of 40%. The results show progressive development for interpretation of condition monitoring data, improving the asset manager's holistic view of an asset's health

Olfactory mediated interactions between Citrus aurantium, Toxoptera citricida and Lysiphlebus testaceipes

O objetivo deste estudo foi investigar se existe interação olfativa no sistema tritrófico entre Lysiphlebus testaceipes, Toxoptera citricida e Citrus aurantium. A resposta de machos e fêmeas de L. testaceipes a diferentes fontes de odor da planta hospedeira C. aurantium, o afideo parasita T. citricida e o complexo afideo-planta foram investigados com um olfatômetro do tipo tubo em Y. Os experimentos de laboratório foram conduzidos, expondo-se machos e fêmeas de L. testaceipes de diferentes idades, individualmente, a oito tratamentos com diferentes fontes de odor. A resposta do parasitóide foi tomada depois de 15 minutos de exposição aos voláteis de diferentes fontes de odor, baseando-se na orientação dos parasitóides a uma câmara particular. Setenta por cento de L. testaceipes, machos e fêmeas, exibiram maior atração ao odor das folhas infestadas pelo afídeo. Não houve diferença significativa entre idade e entre sexo do parasitóide na sua escolha do odor. Os compostos orgânicos liberados por estas combinações agiram como semioquímicos na interação tritrófica, o que indica que afídeos, ao se alimentarem das folhas, induzem atração no parasitóide L. testaceipes.The objective of this study was to establish whether there are olfactory interactions in the Lysiphlebus testaceipes, Toxoptera citricida and Citrus aurantium tritrophic system. The response of male and female L. testaceipes to different odour sources of the host plant C. aurantium, the aphid host T. citricida and aphid-plant complex were investigated using a Y-tube olfactometer. Laboratory experiments were conducted by exposing individually aged male and female L. testaceipes to eight different odour treatments. Response of the parasitoids was taken after 15 min exposure to the volatiles from the different odour sources and based on their orientation to the particular chamber. Seventy percent of both male and female L. testaceipes showed high attractivity to aphid infested leaves. There was no significant difference based on age and sex of the parasitoid on their choice of odour. The organic compounds released by these combinations acted as semiochemicals in the tritrophic interactions and it is suggested that insect feeding induced attraction of the parasitoid L. testaceipes

Comparison of nitrification activity in membrane and conventional enhanced biological phosphorus removal processes

While research is conclusive that the membrane bioreactor process performance in removing the carbonaceous and phosphorus constituents of wastewater is superior or equivalent to a conventional gravity separation process, there have been conflicting reports regarding its ability to achieve nitrification rates comparable to the conventional process. In this long-term study conducted at University of British Columbia’s (UBC’s) wastewater treatment pilot plant facility, the specific nitrification activity of a membrane enhanced biological phosphorus removal (EBPR) process was compared to that of a conventional EBPR process operating under identical conditions to identify factors that influence the relative nitrification rate of the processes. The specific nitrification rate measured from batch experiments showed a natural variation between the processes. There were periods where the specific nitrification rate of the membrane process was either consistently high or consistently low, relative to the conventional process. Average rates were nearly equal, however, the membrane process showed less variability in the individual rates. Nitrifier decay rates measured during the various performance periods conformed to the variation observed as rates for the membrane process were lower relative to the conventional process during periods where the specific nitrification rate for the membrane process was higher and vice versa. The presence of rotifers caused an increase in the decay rate of the conventional process. These organisms were absent in the membrane process. Vigorous coarse bubble aeration did not affect the decay rate. Terminal restriction fragment length polymorphisms (T-RFLP) analysis showed that ammonia-oxidizing (AOB) communities differed for the two processes, however the nitrite-oxidizing bacteria (NOB) communities as represented by the genus Nitrobacter and Nitrospira were similar for both processes. Temperature effects were significant for both AOB and NOB communities, but the effect was greater for the AOB community. Community shifts for the AOB were observed to occur during plant operation. Quantification of the nitrifiers by a real time polymerase chain reaction assay indicated similar quantities of AOB, Nitrobacter and Nitrospira in the two processes with Nitrospira being the most abundant of the nitrifiers present in the systems. AOB and Nitrobacter quantities correlated with the relative nitrification rate of the processes.Applied Science, Faculty ofCivil Engineering, Department ofGraduat

Asset management and the role of power quality on electrical treeing in epoxy resin

Power network operators in developed countries are faced with the challenge of effectively managing network performance with an ageing asset population. A significant proportion of equipment is already operating well beyond design life, testifying to the success of the many insulation systems employed. Increased production of renewable and distributed energy has resulted in changes of load flows on the network, while demand-side management schemes cause devices results in reduced power quality from disturbances including harmonics. Consequently there is a gradual change in the working environment. Hence at the plant level, insulation systems will age differently influencing electrical ageing mechanisms such as partial discharges and electrical treeing.EThOS - Electronic Theses Online ServiceGBUnited Kingdo