Mitigation of Capacitor Bank Energization Harmonic Transients
In the present study, an overview of the capacitor bank energizing transients is presented and the means of harmonic mitigation technique are investigated. Capacitor bank connection is essential due to reactive compensation reasons. Transients produced upon of capacitor bank energizing, reach in harmonics, may be harmful for the capacitor and become an increasing concern for both electric utilities and customers since its switching usually occurs quite frequently. We know that power factor correction capacitors are sensitive to harmonics and one factor of the failures of power capacitors indicates the prime odd harmonics like 5th, 7th, 11th, 13th harmonics. A time domain simulation using PSCAD/EMTDC was performed to predict the harmonic spectrum of the distorted voltage waveform in a real 11 kV Romanian distribution subsystem
Comparative Study and Analysis of Switching Transient Behaviour of Overhead Transmission Lines and Underground Cables
Switching transient is not a new phenomenon; it has been around for many decades. However, it has received more attention recently because of the greater number of failure of many electrical equipments like transformer, circuit breaker etc. because of the phenomena. Both energization and de-energization of transformer and shunt capacitor bank produce considerable amount of transient overvoltage which in turn can cause insulation failure of transformer and malfunctioning of protective equipments. The worst case occurs if the frequency of the transients matches the resonance frequency of the transformer causing voltage and current magnification to a level that exceeds the BIL of transformer. The switching effects will be different depending on the medium used for power transmission. The purpose of this paper is to make a comparative study and analysis of the switching transient over-voltages that occur during different switching events in both overhead transmission lines and underground cables. PSCAD simulation tool has been used for our analysis. Finally, the analyses of the output data for both cases were done and some recommendations are given to minimize the effects of transient overvoltage.
HYPERGOLIC REACTION MECHANISMS OF CATALYTICALLY PROMOTED FUELS WITH ROCKET GRADE HYDROGEN PEROXIDE
Abstract The coupling of the physical and chemical processes controlling the ignition delays (τ ign ) of hypergolic propellants complicates the direct analysis of the transient ignition processes. The transport properties of both the propellants and the ambient gas, and the heat of vaporization and reaction affect τ ign and must be considered experimentally. Furthermore, since hypergolic ignition occurs, by definition, on contact, the mechanics of initial contact and subsequent mixing can affect τ ign and must also be considered. Experimental results from a study of the hypergolic ignition of a catalytically promoted fuel with rocket grade hydrogen peroxide (RGHP) are presented. Statistical analysis of the experimental data was conducted to evaluate the relative effects of RGHP concentration, initial ambient pressure, and the ambient gas on τ ign . At RGHP concentrations of less than 92% in water, stable ignition was difficult to achieve. At sufficiently high Lewis number, an oscillatory ignition process is observed. A phenomenological model comprising mixing, RGHP decomposition, fuel heating and vaporization, and auto-ignition is presented and compared to the experimental results.