Betriebsmittelbezogene Lastmodellierung in Verteilungsnetzen

Übersicht Der Betriebszustand eines Verteilungsnetzes wird durch die Strombelastung aller Betriebsmittel beschrieben. Mit Hilfe einer statischen Estimationsmethode werden aus einzelnen Messungen und der Kenntnis der Verbrauchsdaten typische Verbraucherkurven (TVK) berechnet, die das elektrische Verhalten verschiedener Verbrauchergruppen widerspiegeln. Auf dieser Basis ist eine betriebsmittelbezogene Lastmodellierung an beliebigen Betriebsmitteln in Abhängigkeit der Verbraucherzusammensetzung unter Berücksichtigung externer Einflüsse wie der Temperatur möglich. Die so gewonnenen Belastungsverläufe erlauben eine Beschreibung des Netzzustands in den Verteilungsnetzen.

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Bus load modelling in distribution systems

Contents The operating state of a distribution system is determined by the bus load current. Based on individual substation measurements and the load composition typical load curves are calculated using statistical estimation theory. These typical load curves describe the electrical behaviour of the different load types (e.g. household, storage heating, commerce etc.). As soon as the typical load curves are determined it is possible to calculate the bus load current in any substation taking external influences such as temperature into consideration. The bus load current serve as load models which completely describe the operating state of the distribution system.

     

Bounds for the solution of hyperbolic problems

This article describes a newly developed and implemented method for computing guaranteed errorbounds for the solution of hyperbolic initial value problems. The basic concepts—modified fixed point theorems and approximated operators—allow an a posteriori error-estimation automatically. Therefore, no a priori knowledge of Lipschitz constants, monotonicity properties or additional error analysis is necessary.     

Biaxiale Ermüdung reibrührgeschweißter Strukturelemente

Biaxial fatigue of friction stir welded stiffened panels Within the framework of the European WelAir project, cruciform specimens made from stiffening FSW overlap joints were fatigued in the DLR biaxial test rig. To resemble the loading situation of pressurized fuselage structures, proportional loading without any phase shift, but with different load ratios λ between the loading components in both directions was applied.Natural crack initiation and subsequent crack growth were governed by the stiffness gradient caused by introducing the stringer. Cracks initiated and propagated at run‐in and run‐out locations in a direction perpendicular to the weld seam. The shortest fatigue life was observed for uniaxial loading in welding direction (λ = 0). An additional stress component perpendicular to the joint line (λ > 0) resulted in a higher number of cycles to failure. Similar to single stringer panels, increasing the load ratio also increased the number of cycles to failure for FSW clip‐stringer structural members, but additionally gives a different location of the fatal crack.