24 research outputs found
Ătude des variations des vitesses dâhydrolyse trypsique de quelques esters acylĂ©s
Lors de lâhydrolyse trypsique de quelques esters acylĂ©s de lâarginine on observe des variations de la vitesse de rĂ©action en fonction du pH dont le caractĂšre dĂ©pend du choix particulier du substrat. Les vitesse d'hydrolyse des deux isomĂšres optiques du TAM (p-toluĂšne-sulfonylarginine mĂ©thylester) par la trypsine, en fonction du pH, correspondent Ă deux courbes diffĂ©rentes quand les mesures sont effectuĂ©es avec des concentrations en substrat constantes. Lâhydrolyse du L-BAE (benzoyl-L-arginine Ă©thylester) en fonction du pH conduit Ă une courbe encore diffĂ©rente de celles qui se rapportent Ă lâhydrolyse des deux isomĂšres optiques.
La mĂ©thode potentiomĂ©trique Ă pH constant est susceptible dâintroduire des erreurs si un groupement du substrat est ionisĂ© dâune maniĂšre apprĂ©ciable dans la zone des mesures du pH. Par consĂ©quent, lâon ne peut attribuer aux groupements de lâenzyme, les pK Ă©valuĂ©s expĂ©rimentalement
Tutorial on operating characteristics of microprocessor-based multiterminal line current differential relays
Line current differential (87L) protection schemes face extra challenges compared with other forms of differential protection, in addition to the traditional requirements of sensitivity, speed, and immunity to current transformer saturation. Some of these challenges include data communication, alignment, and security; line charging current; and limited communications bandwidth. To address these challenges, microprocessor-based 87L relays apply elaborate operating characteristics, which are often different than a traditional percentage differential characteristic used for bus or transformer protection. These sophisticated elements may include adaptive restraining terms, apply an Alpha Plane, use external fault detection logic for extra security, and so on. While these operating characteristics provide for better performance, they create the following challenges for users: x Understanding how the 87L elements make the trip decision. x Understanding the impact of 87L settings on sensitivity and security, as well as grasping the relationship between the traditional percentage differential characteristic and the various 87L operating characteristics. x Having the ability to transfer settings between different 87L operating characteristics while keeping a similar balance between security and dependability. x Testing the 87L operating characteristics. These issues become particularly significant in applications involving more than two currents in the line protection zone (multiterminal lines) and lines terminated on dual-breaker buses. This paper is a tutorial on this relatively new protection topic and offers answers to the outlined challenges