Distributed generation and its impact on power grids and microgrids protection
The National Institute of Standards and Technology, NIST, is assigned by the US Department of Energy, DoE, to drive Smart Grid developments and harmonization efforts in the power industry. Distributed Generation has been identified as one of the important areas for the Smart Grid developments. Multiple generation sources, bi-directional power flow, power flow time co-ordination and management bring significant benefits and challenges for the existing and emerging power grids and microgrids. In particular, the effect of distributed generation on protection concepts and approaches needs to be understood, and accounted for. This paper describes distributed generation concepts, applications and scenarios. Benefits and challenges are discussed and analyzed on a number of real life examples. Special considerations are provided on ensuring security and dependability, as well as on protection parameterization and coordination.
Optimal placement of DGs in a distributed power system with power system studies
Albeit possessing their benefits, introduction of extraneous power generation like Distributed Generators (DGs) may cause complications to the existing power system and affect the overall efficiency, reliability and security of the system. Therefore, it is crucial to identify the possible snags and fix them. Additionally, inappropriate placement of DGs in power system may constrain the overall performance of the system. On the other hand, placing a DG accurately would enhance the general operation of a power system tremendously. This paper presents the potential drawbacks that may occur when DGs are added into the power system. Subsequently, a proposed methodology that comprises of power system studies is utilized to determine the optimal location of DGs in a power system. A revised methodology is then suggested which only uses load flow results to determine the best location and is highly efficient compared to the latter. The revised methodology is tested on 6-bus test system which presented identical results as the first methodology but with considerably lesser effort.
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.