Grounding and ground fault protection of multiple generator installations on medium-voltage industrial and commercial power systems - Part 4: Conclusion and Bibliography Working Group Report

This paper discusses typical grounding practices and ground fault protection methods for medium-voltage generator stators, highlighting their merits and drawbacks. Particular attention is given to applications of multiple generators connected to a single bus. The paper also provides an overview of the generator damage mechanism during stator ground faults. Problem areas associated with each type of grounding are identified and solutions are discussed. The paper also provides a list of references on the topic. The paper is intended as a guide to aid engineers in selecting adequate grounding and ground fault protection schemes for medium-voltage industrial and commercial generators for new installations, for evaluating existing systems, and for future expansion of facilities, to minimize generator damage from stator ground faults. These topics are presented in four separate parts, Parts 1-4. Part 1 covers scope, introduction, user examples of stator ground failure, and theoretical basis for the problem. Part 2 discusses various grounding methods used in industrial applications. Part 3 describes protection methods for the various types of grounding and Part 4 provides a conclusion and bibliography of additional resource material.     

Yeasts isolated from three varieties of grapes cultivated in different locations of the Dolenjska vine-growing region, Slovenia

The number and diversity of yeasts on grape berry surfaces are influenced by several factors, such as grape variety, degree of grape maturity at harvest, climatological conditions, geographic location, physical damage of grapes, the intensity of pest management etc. Cvicek is a typical Slovene wine, which has obtained a special protection under the Slovene Wine Law for its geographical origin. This blended red wine is produced from different grape varieties (Vitis vinifera L.), mostly from red grapes of Zametovka and Modra frankinja and from white grapes of Kraljevina. The aim of this study was to evaluate the impact of geographical locations in the Dolenjska vine-growing region and to obtain precise information about the influence of different grape varieties on the composition of yeast community on grape berries. The restriction fragment length polymorphism of PCR-amplified fragments from the rDNA gene cluster (PCR RFLP of rDNA) has been used for the differentiation of yeast species. The standard identification procedure has been performed on representative strains that shared identical RFLP profiles. The number of yeasts and yeast species isolated varied according to different grape varieties, Zametovka, Modra frankinja and Kraljevina (V. vinifera L.) and according to different sampling location. On the surface of grape berries 13 different yeast species have been identified. Saccharomyces cerevisiae has not been found.     

Protection and commissioning of multifunction digital transformer relays at medium voltage industrial facilities

The application of multifunction digital relays to protect medium voltage power transformers has become a common industrial practice. Industrial transformers, unlike utility transformers, frequently use neutral grounding resistors to limit ground current during faults to the 200-400-A level on medium voltage systems. This paper will discuss why these types of transformers require sensitive ground differential protection. The paper will also discuss the basics of transformer protection including phasing standards, through-fault withstand capability, differential/fusing/overcurrent protection, slope, current transformer (CT) requirements, and harmonic restraint, and communicating these properly to new digital relays. The rationale for providing transformer overexcitation protection on all major transformers within mill facilities is also addressed. Advancements in digital technology have allowed relay manufacturers to include more and more relay functions within a single hardware platform as well as address increasingly more transformer winding configurations. This has resulted in digital transformer relays requiring an Einstein to set and an Edison to commission. Since there are few Einsteins or Edisons among us, the next generation of transformer relays needs to concentrate on this complexity issue in addition to technical improvements. This paper addresses these issues that the author believes are the major shortcomings of existing digital transformer protective relays.     

Interconnection protection of IPP generators atcommercial/industrial facilities

Much of the new generation capacity installed during the next millennium will be accomplished through the construction of independent power producer (IPP) generating facilities. These facilities can take the form of small dispersed generating units, or large-capacity plants owned and even operated by nonutility personnel. It is forecasted that many of these dispersed generating units will be at smaller industrial and commercial facilities and operating in parallel with the utility system to reduce energy cost through load sharing or “peak shaving.” This paper discusses the protection requirements to interconnect these generators to utility systems, as well as methods to reconnect these generators after interconnect protection tripping     

Grounding and ground fault protection of multiple generator installations on medium-voltage industrial and commercial power systems - Part 3: Protection Methods Working Group Report

This paper discusses typical grounding practices and ground fault protection methods for medium-voltage generator stators, highlighting their merits and drawbacks. Particular attention is given to applications of multiple generators connected to a single bus. The paper also provides an overview of the generator damage mechanism during stator ground faults. Problem areas associated with each type of grounding are identified and solutions are discussed. The paper also provides a list of references on the topic. The paper is intended as a guide to aid engineers in selecting adequate grounding and ground fault protection schemes for medium-voltage industrial and commercial generators for new installations, for evaluating existing systems, and for future expansion of facilities, to minimize generator damage from stator ground faults. These topics are presented in four separate parts, Parts 1-4. Part 1 covers scope, introduction, user examples of stator ground failure, and theoretical basis for the problem. Part 2 discusses various grounding methods used in industrial applications. Part 3 describes protection methods for the various types of grounding and Part 4 provides a conclusion and bibliography of additional resource material.     

Über den Zusammenhang zwischen Jahrringbreite und Raumdichte bei Douglasienholz

Zusammenfassung Die Grundlage für die vorliegende Arbeit boten 35 St?mme waldfrischen Douglasienholzes im Alter von 45 bis 70 Jahren aus 5 Versuchsfl?chen in Meeresh?hen von 300 ... 800 m. Der Zusammenhang zwischen Jahrringbreite und Raumdichte wird in der Form von Regressionskurven für die Gesamtzahl von 3376 Proben, sowie für Einzelst?mme und für die biologischen Klassen dargestellt. Aus den Darstellungen ist zu entnehmen, da? die Raumdichte des Douglasienholzes nur in einem geringen Ma?e von der Ringbreite beeinflu?t ist. Die Abh?ngigkeit der Raumdichte vom Alter, von der Ringbreite und von der Entfernung der Proben von der Stammitte ist mit Hilfe der mehrfachen—und der Teilregression berechnet. Mittels der mehrfachen Regression lassen sich von der Gesamtstreuung der Raumdichte 50% aus Unterschieden im Alter, in der Ringbreite und in der Probenlage im Stamme erkl?ren. Nach jeweiliger Ausschaltung des Einflusses der übrigen 2 Ver?nderlichen lassen sich von der Raumdichtestreuung 10,7% aus Unterschieden in der Ringbreite, beziehungsweise 12,5% aus Unterschieden in der Probenlage im Stamme linear ableiten. Das Teilbestimmtheitsma? Raumdichte-Alter ist nicht signifikant. Daraus folgt, da? die Raumdichte des Douglasienholzes weniger von der Jahrringbreite, als von der Probenlage im Stamm und von anderen, noch unbekannten Faktoren abh?ngig ist.

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On the relationship of annual ring width and density in the wood of douglas fir

Summary The present paper is based on an examination of 35 stems of Douglas fir being 45 to 70 years of age. The logs were taken from 5 test areas, 300 ... 800 m above sea level. The relationship between annual ring width and density is plotted in a diagramme with regression curves for the total of 3376 test pieces as well as for individual stems and for the biological classes. From this it can be seen that the density of Douglas fir is, to a small extent only, influenced by the width of annual rings. The dependence of density on age, annual ring width and distance from the centre was computed with the aid of multiple and partial regressions. By multiple regression, 50% of the total variance can be explained by differences in age, the annual ring widths and the location of the samples within the logs. Having excluded the influence of the remaining 2 variables, 10.7% of variance can be linearly derived from the difference between the annual ring width or 12.5%, respectively, from the difference of location of the samples within the log. The partial coefficient density: age is not significant. Thus it can be concluded that the density of Douglas fir is depending more on the location of the samples within the logs and on other, still unknown factors than on the annual ring width.

     

Benefits of upgrading: paper mill generator protection

There are a number of functional protection areas on paper mill generators 20 years or older that have significant shortcomings when compared to current IEEE recommended generator-protection practices. This article identifies these protection areas and the risks of not addressing the shortcomings. It also points out the advantages of using multifunction digital relaying to upgrade generator protection as a technology that offers many advantages over older electromechanical relays. The completed upgrade project at MeadWestvaco's Luke Mill in Maryland provided a number of examples of these benefits in uncovering mill problems that, if they had gone undetected, could have resulted in costly mill shutdowns or damage to mill generators.     

Phenolic Profile,Antioxidant Capacity,and Antimicrobial Activity of Leaf Extracts from Six Vitis vinifera L. Varieties

The phenolic composition, antioxidant activity, and antimicrobial activity of extracts from vine leaves of six grape varieties collected in May, August, and September was studied. The phenolic potential of the extracts was dependent on variety and picking-time. Extracts of leaves collected in September were the richest in total phenols, flavonoids, flavonols, and stilbenes. The antioxidant properties determined by ferric reducing antioxidant power and 2,2-diphenyl-1-picrylhydrazyl assays, and antimicrobial activity against Stapylococcus aureus, Bacillus cereus, Campylobacter jejuni, Escherichia coli, and Salmonella Infantis were good and in correlation with the chemical composition changes of the leaf extracts. The results indicated that leaves remaining on the vine in September after the grape harvest could be especially promising as an inexpensive source of effective antioxidant/antimicrobial agents.     

On the Cosmic Nuclear Cycle and the Similarity of Nuclei and Stars

Repulsive interactions between neutrons in compact stellar cores cause luminosity and a steady outflow of hydrogen from stellar surfaces. Neutron repulsion in more massive compact objects made by gravitational collapse produces violent, energetic, cosmological events (quasars, gamma ray bursts, and active galactic centers) that had been attributed to black holes before neutron repulsion was recognized. Rather than evolving in one direction by fusion, nuclear matter on the cosmological scale cycles between fusion, gravitational collapse, and dissociation (including neutron-emission). This cycle involves neither the production of matter in an initial “Big Bang” nor the disappearance of matter into black holes. The similarity Bohr noted between atomic and planetary structures extends to a similarity between nuclear and stellar structures.