Study on measuring the grounding resistance of grounding grid with short lead wire
Method of measuring the grounding resistance with short lead wire is applied to test the ground resistance of some simulated grounding grid when the resistances of the grounding conductor are considered simultaneously. The position of voltage electrode is determined through the calculation when the position of current electrode is given in advance. It is showed by test result that the method of measuring the grounding resistance with short lead wire can obtain the value of ground resistance with relatively high precision. Moreover, the length of current electrode is shortened. It provides a more scientific and suitable way for the ground resistance measurement of grounding grid in field. The relation between the position of voltage electrode and the length of current electrode is also considered.
A novel measurement system for substation grounding resistance
A measurement system including a notebook PC for substation grounding resistance has been developed. The measurement method is based on short lead wire of current electrode and a frequency inverter AC source with relatively low power. Results of computation and measurement based on this novel method and the traditional method are presented to illustrate the effectiveness of the measurement system.
Experimental Study for a Double-Glazed Forced-Flow Solar Collector/Regenerator
Experimental study of a double-glazed forced-convection solar collector/regenerator for absorption solar cooling is presented. The south facing experimental solar collector/regenerator with 10 deg slope is located at Kaohsiung, Taiwan at 120{degree}19minutesE longitude and 22{degree}34minutesN latitude. The size of the collector is 1 m wide and 7 m long with an effective regeneration area of 0.9 m by 6 m. Previous study for single-glazed forced-convection solar collector/regenerator operated at the same location has shown to have a best day-average efficiency of 17%. In order to raise the system performance, a double-glazed collector/regenerator is constructed such that air can be preheated in the upper channel flow. The preheated air is then conducted into the lower channel where it contacts with the film flow of solar heated lithium-chloride solution and regenerates the solution by carrying out the evaporated water vapor. The preheated air has lower relative humidity but the same humidity ratio since it is sensibly heated. Therefore, the regeneration driving potential is increased. The present study shows that the best day-average efficiency can reach 20% which increases the feasibility of the open-cycle absorption solar cooling system. Effects of controlling parameters on the collector/regenerator performance are studied, and heat and mass transfer correlationsmore » are also presented for design purposes.« less