Internal arc fault simulation using CFD to predict thermal behavior in switchgear
During an event of internal arc fault in LV/MV switchgears an electrical energy of the order of several Mega-joules is released which should be dissipated in the span of few milliseconds. Major portion of this energy is utilized in the heating of the enclosure gases resulting in the significant pressure rise inside the chamber. Objective of the simulation model developed is to improve design efficiency, increased safety, and especially to minimise real-world testing. Internal arc parameters such as pressure rise in various compartment, exhaust gas temperature, indicator temperature and pressure on panel walls are investigated with CFD simulation methodology. A 3-D CFD simulation of high temperature gases in LV/MV panel is carried out with coupled interactions between flow, temperature, turbulence and radiation fields taken into account. The internal temperature and pressure rise due to internal arc at different locations in breaker, cable and busbar compartment were compared. The same is used further to analyse structural forces and stresses on the panel members. Temperature rise at different locations on indicator walls which are modelled at a distance of 300 mm from panel were estimated from simulation. Visualization of the temperature, pressure and flow field is possible with CFD model.
Designs for Mounting Reed Switches in Vicinity of AC and DC Buses
It is noted that the use of reed switches makes it possible to solve the urgent problem of building relay protection devices without current transformers. It is emphasized that for their fastening and regulation of the response parameters of these devices by changing the position of the reed switches in the vicinity of live buses, special structures are necessary. Four new designs are offered for mounting reed switches close to AC and DC buses. The first of them differs from the known ones by the availability of a clamp covering the bus, a plate on which n reed switches are fixed and a strap fastened with this clamp. The second one differs by a double ear clamp and two rotary arcs with ratchet drums with a reed switch. The third one differs by a L-shaped plate with reed switches and mounting angles. The fourth one differs by two rectangular beams with four through holes. The article describes how to control the parameters of protections tripping on the reed switches using these structures.
Brainstem Influences on the Cephalic Circulation: Experimental Data From Cat and Monkey of Relevance to the Mechanism of Migraine
SYNOPSIS