Liander (Netherlands)

BackgroundPrevious studies reported that hypo‐ and hyperthermia are associated with several atrial and ventricular electrocardiographical parameters, including corrected QT (QTc) interval. Enhanced characterization of variations in QTc interval and normothermic body temperature aids in better understanding the underlying mechanism behind drug induced QTc interval effects. The analysis’ objective was to investigate associations between body temperature and electrocardiographical parameters in normothermic healthy volunteers.MethodsData from 3023 volunteers collected at our center were retrospectively analyzed. Subjects were considered healthy after review of collected data by a physician, including a normal tympanic body temperature (35.5‐37.5°C) and in sinus rhythm. A linear multivariate model with body temperature as a continuous was performed. Another multivariate analysis was performed with only the QT subintervals as independent variables and body temperature as dependent variable.ResultsMean age was 33.8 ± 17.5 years and mean body temperature was 36.6 ± 0.4°C. Body temperature was independently associated with age (standardized coefficient [SC] = −0.255, P < .001), female gender (SC = +0.209, P < .001), heart rate (SC = +0.231, P < .001), P‐wave axis (SC = −0.051, P < .001), J‐point elevation in lead V4 (SC = −0.121, P < .001), and QTcF duration (SC = −0.061, P = .002). In contrast, other atrial and atrioventricular (AV) nodal parameters were not independently associated with body temperature. QT subinterval analysis revealed that only QRS duration (SC = −0.121, P < .001) was independently associated with body temperature.ConclusionBody temperature in normothermic healthy volunteers was associated with heart rate, P‐wave axis, J‐point amplitude in lead V4, and ventricular conductivity, the latter primarily through prolongation of the QRS duration.

Switching operations, short-circuits, and disturbances during normal operation often cause temporary overvoltages and high-frequency oscillations. The calculation and simulation of transient voltages and currents is important for the insulation coordination, correct operation, and adequate functioning of the system protection. This chapter presents examples of analytical solutions to the relevant differential equations and numerical simulation of electrical transients. It provides the derivation of the expression for TRV originating from two oscillating circuits separated by the switching device – the source-side circuit and the load-side circuit. The chapter highlights the calculation of the switching transients that occur when separating two discrete RLC circuits. Simulation of transient phenomena, based on an ideal model of the electrical network, is an important tool for the design of the system protection. The simulation of transient phenomena may require a representation of network components valid for a frequency range that varies from DC to the megahertz range.

Load-current switching is mainly characterized by currents up to the normal-load-current rating of the switching device. Switching of normal load has to be distinguished from switching of capacitive or inductive loads. Even with much smaller current than a normal-load current, switching can become critical when current zero occurs near the voltage maximum. This is the case for capacitive and inductive load-current interruption due to the reactive nature of the respective loads. Shunt-reactor switching is by far the most common practice of the inductive-load switching. Shunt reactors are installed for overhead-line capacitance compensation, and switched in or out depending on the momentary line load. Multiple re-ignitions of breakers during shunt-reactor switching can be avoided by controlled switching. Using controlled, instead of random contact separation well in advance of current zero, avoids short arcing times and interruption follows when the gap has reached sufficient spacing.