| Summary: | 碩士 === 國立清華大學 === 電機工程學系 === 93 === Taiwan’s Synchronon Radiation Research Center (SRRC) located at Hsinchu has been suffered with the multitrips of accelerator and the instability of electronic beam. It is doubted that the phenomenon was caused by high frequency signals which disturb the control devices for the accelerator. Because the phenomenon has connection with grounding, SRRC built a new grid whose grounding resistance was designed to be lower than 0.2 , and also rebuilt the grounding system of accelerator. All the designs for rebuilt grounding system were based on experiences without theoretical analysis or any computational simulation. To overcome this difficulty, this thesis presents the computer modeling of both the newly built grid and the newly rebuilt grounding system of accelerator’s tunnel area, and presents the comparison results between computer simulation and field measurements. The presented are thus comprised of two major works: the modeling and simulation of grid and the evaluation results for grids ground-resistance; the investigation results on the effect of rebuilt tunnel’s ground system on the mitigation of stray current flowing on the vacuum chamber containing the electronic beam.
When the new grid was completed, the SRRC has applied the fall-of potential method to measure grid’s ground-resistance. However, neither has SRRC evaluated the actual meaning for the measurement method and measurement results, nor has SRRC compared the results with those by applying the conventional ground-resistance calculation formula. As to the high-frequency interference on the electronic beam of vacuum chamber, although after completion of the rebuilt grounding system, the instability of electronic beam has not been observed, it’s however not sure that this accomplishment was due to the new grid, the new tunnel grounding system or both or even other unknown reasons. Investigation and clarification are thus highly necessitated.
This study reviewed the conventional ground-resistance calculation formula, applied a commercial software to simulate the fall-of-potential method for ground-resistance measurement, and compared the measured with the calculated by both the formula and the software. Regarding the high-frequency interference, the author also formulated a computer model foe the grounding system of tunnel area and applied the model to simulating the voltage between the originally existing and the newly built grounding grids. As well as their magnetic field, with the support of measurement results, to evaluate the effectiveness of rebuilt ground system for the tunnel area. During the evaluation, the accuracy and limitation of grid model, tunnel ground system model as well as the modeling methods have also been investigated.
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