The electrical and spectral characteristics of a dielectric barrier discharge (DBD) are experimentally investigated in a sealed off coaxial cylinder filled with nitrogen at a pressure of 10 mbar. The discharge is a transient diffused glow at low frequency alternating voltage (60 Hz) and changes to a filamentary mode at high frequency alternating voltage (35 kHz). In case of pulsed voltage, the discharge is always transient diffused glow at any frequency. The intensity of a second positive system (SPS) of the nitrogen molecule has been also measured to characterize the discharge excitation. The effective vibrational temperature is estimated from the SPS vibrational band, Δv = -2. It is concluded that the intensity of the SPS of the nitrogen and the effective vibrational temperature depends upon the reduced electric field and the energy consumed per cycle by the device.

The present paper describes the development of an availability simulation model for Coal handling unit of a thermal plant by making the performance analysis using probabiltic approach. In the present paper, the Coal handling unit consists of five subsystems. Assuming constant failure and repair rates for all the subsystems, the mathematical formulation is based on Markov birth-death process. After drawing the transition diagram, differential equations are generated. After that, steady state probabilities are determined. One availability matrix is also developed, which provides various performance/availability levels for different combinations of failure and repair rates of all subsystems. Based upon various availability values obtained in the availability matrix and graphs of failure/repair rates of different subsystems, performance and optimum values of failure/repair rates for maximum availability of each subsystem are analyzed. Subsequently maintenance priorities are decided for all subsystems.

Die artikel beskryf die ontwikkeling van 'n beskikbaarheidsimulasiemodel vir 'n steenkoolhanteringseenheid van 'n termiese aanleg deur gebruik te maak van werkverrigtingsanalise met 'n waarskynlikheidsbenadering. In die geval bestaan die hanteringseenheid uit vyf subsisteme. Onder die aanname van konstante faling- en hersteltempo's vir al die subsisteme word die wiskundige formulering gebaseer op die Markov geboorte-sterfte-proses. Nadat die oorgangsdiagram ontwikkel is, word differensiaalvergelykings gegenereer en waarna die gestadigde toestandwaarksynlikhede vasgestel word. Een beskikbaarheidsmatriks is verder ontwikkel wat toelaat vir verskillende werkverrigting-/beskikbaarheidsvlakke teen verskillende kombinasies van faling- en hersteltempo's van alle subsisteme. Gebaseer op verskillende beskikbaarheidswaardes verkry van die beskikbaarheidsmatriks en grafieke van die falings-/hersteltempo's van die onderskeie subsisteme, word werkverrigting en optimum waardes vir faling- en hersteltempo's vir maksimum beskikbaarheid van elke subsisteem ontleed. Vervolgens word instandhoudingsprioriteite vir elke subsisteem voorgehou.

The paper aims at assessing the reliability and availability of a critical ash handling unit of a steam thermal power plant by making a performance analysis and modeling, using probability theory and the Markov Birth-Death process. After drawing a transition diagram, differential equations are generated. After that, steady state probabilities are determined. Certain decision matrices are developed, which provide various availability levels. The behaviour analysis of the reliability module reveals that the availability decreases with increasing failure rates, while operational availability improves with initial increases in repair rates for different subsystems. Based upon various availability values, the performance of each subsystem is analyzed and used to make maintenance decisions for all subsystems.

Hierdie artikel poog om die betroubaarheid en beskikbaarheid van 'n kritiese ashanteringseenheid van 'n termiese stoomkragaanleg te beoordeel deur 'n werkverrigtingsanalise en modellering te doen aan die hand van waarskynlikheidsteorie en die Markovgeboorte-sterfteproses. Nadat die oorgangsdiagram opgestel is, is differensiaalvergelykings gegenereer. Vervolgens is die gestadigde-toestandwaarskynlikhede bepaal. Sekere besluitmatrikse is ontwikkel waar verskillende beskikbaarheidsvlakke verskaf is. Die analise van die gedrag van die betroubaarheidsmodule toon dat beskikbaarheid afneem met toenemende falingstempo's, terwyl operasionele beskikbaarheid verbeter met aanvanklike toenames en hersteltempo's vir die onderskeie subsisteme. Gebaseer op die verskillende beskikbaarheidswaardes, word die werkverrigting van elke subsisteem ontleed en aangewend om instandhoudingsbesluite vir alle subsisteme te neem.

Performance evaluation and economic analysis is carried out to predict the steady state operational availability and net present value index for a thermal power plant. Mathematical formulation of the plant's reliability is carried out using probability theory following the Chapman-Kolmogorov Birth-Death process. The system of differential equations obtained is solved using the Laplace transformation technique. The behaviour analysis of performance modules reveals that availability decreases with increasing failure rates, while operational availability improves with an initial increase in repair rates for different sub-systems. From the economic evaluation module, the plant availability and power generation capacity are found to be sensitive, while increasing the redundancies of feed pump or condensate extraction pump sub-systems has less influence on the profitability index. A high-capacity plant reflects better trends. Model predictions indicate a critical condition for repair rates; beyond these rates the plant availability, net present value, and annual revenue earned are found to be insensitive.

Prestasiebepaling en teenswoordige ontleding word uitgevoer om gestadigde operasionele beskikbaarheid en 'n netto teenswoordige indekswaarde vir 'n fossielbrandstofkragstasie te bepaal. 'n Wiskundige model vir aanlegbetroubaarheid word probabilisties geskep met gebruik van die Chapman-Kolmogorov metode. Die model se differensiaalvergelykings word gemanipuleer met gebruik van Laplace-transformasie. Die resulterende sisteemprestasie toon dat beskikbaarheid afneem met toenemende mislukkingstempo's en vice versa. Die ekonomiese ontleding van die model toon sensitiwiteit by lewering van drywing en beskikbaarheid, en dat oortolligheid van sekere hulpsubsisteme nie betekenisvol tot winsgewendheid bydra nie. Die model benadeel die belangrikheid van hersteltempo's.

The present paper discusses the performance modeling and decision support system for a feed water unit of a thermal power plant using the concept of performance analysis and modeling. A feed water unit ensures a proper supply of water for the sound functioning of a thermal power plant. The decision support system for a feed water unit has been developed with the help of performance modeling using a probabilistic approach. After drawing a transition diagram, differential equations are generated. After that, steady state probabilities are determined. Some decision matrices are also developed, which provide various performance levels for different combinations of failure and repair rates of all subsystems. Based upon various availability values obtained in decision matrices and plots of failure rates / repair rates of various subsystems, the performance of each subsystem is analyzed, and maintenance decisions are made for all subsystems.

Vertoningsanalise en -modellering word gedoen w'r die toevoerwatersisteem van 'n termiese kragstasie. Toevoerwater is 'n belangrike factor vir die doeltreffende bedryf van 'n kragstasie. Die vertoningsanalise en -model is probalisties van aard. 'n Toestandoorgangsdiagram en bypassende differensiaalvergelykings word gebruik, gevolg deur bepaling van die bestandige sisteemtoestand. Bykomende aandag word gegee aan relevante subsisteme. Die vertoning van subsisteme word gebasseer op verskeie beskikbaarheidswaardes om sodoende instandhouding to optimiseer.