Field breaker tripping options for generator static excitation systems with AC field circuit breakers - A case study
Short circuit contributions from synchronous generators can persist for several seconds even after the field circuit breaker is opened. Delayed tripping of an AC field circuit breaker can allow faster reduction of generator field current in some circumstances. Faster reduction of generator field current will reduce the energy in a short circuit and consequently reduce the damage caused by the short circuit. This paper describes a case study examining the issues associated with the decision to delay tripping of AC field circuit breakers.
A New Methodology for Risk Analysis for Excitation System of Alternator in SHP using FIS
Preponderance of failures in a generator is due to excitation failure, thus it is pertinent to understand these failures, their reasons and ways to mitigate these failure modes. Failure mode and effect analysis is an ingrained tool that helps in increased availability and reliability of small hydropower plants. In this research, a FIS based methodology has been proposed to identify failure modes and prioritize maintenance action by calculating the Risk priority number. This calculation facilitates the utility to take preventive measures and ensure a safer and more reliable operation of the alternator in the powerhouse. This fuzzified approach to FMEA is a de viation from the traditional approach that gives a more tolerable range of RPN values by eliminating the role of human experts in maintenance prioritization. The model is implemented on a set of failure modes and an FMEA sheet is developed. The paper will be helpful for utilities and researchers involved with the operation and maintenance of small hydropower plants.
Die Induktivität von Induktionsrinnenöfen und anderer koaxialer Wicklungsanordnungen mit zylindrischem Eisenkern
ÜbersichtFür den rotationssymmetrischen Fall werden das Magnetfeld und die magnetische Energie zweier koaxialer, mehrlagiger Zylinderspulen, welche konzentrisch um einen zylindrischen Eisenkern angeordnet und von Gleichstrom durchflossen sind, berechnet.Für den Sonderfall, daß die sekundäre Wicklung aus einer Windung besteht und axialsymmetrisch zur Induktorspule angeordnet ist, folgt aus der magnetischen Energie die Streuinduktivität von Induktionsrinnenöfen.ContentsCalculation, for the rotation-symmetrical case, of the magnetic field and the magnetic energy of two coaxial, multilayer cylindrical coils which are arranged concentrically around a cylindrical iron core, and are carring a direct current.For the special case, where the secondary winding consists of one turn, arranged axial-symmetrically to the induction winding, leakage inductivity follows from the magnetic energy.