Stability of the Electrical Supply to Grid Computing Facilities in Tower B, Brunel University in 2009

During the latter half of 2009 a monitoring programme was undertaken so as to understand the power supply issues underlying the reliability and hence external availability of a tranche of Brunel University's GridPP Grid Computing resources.The power supply voltage in room TB208 was sampled by querying one of the UPS units. The UPS (APC SmartUPS 3000XL) reports three values for each 60-second interval (defined internally by the UPS):- the maximum supply voltage during that interval- the minimum supply voltage during that interval- the "instantaneous" supply voltage at the end of that intervalThe granularity of the measurement is coarse, about 1.5 V. Voltage spikes will be seen as high values of the maximum voltage, and supply dips as low values of the minimum voltage.The values were transmitted using the standard logging mechanism which removes duplicate values, so missing data points should be assumed to be all identical to the last provided value. They were then extracted from the logs into the text files provided in the accompanying zip archive (MainsVoltage_TowerB-2009.zip).The text files have been imported into the spreadsheet (MainsVoltage_TowerB.xls) as one week per tab with accompanying chart of the values, starting about 4.00 a.m. each Sunday.Both daily and weekly variations are clearly visible. Most of the noise is due to the building lift and workshop machinery starting and stopping. An extended brown-out can be seen on the morning of 1st December (week 48).Acknowledgements:Raul Lopes wrote the UPS query and logging mechanism.Henry Nebrensky did the data extraction and import into Microsoft Excel.A similar approach was subsequently used within the MICE project at RAL, DOI: 10.17633/rd.brunel.9691628.

自2009年下半年起，为了理解支撑布鲁内尔大学GridPP网格计算资源可靠性和外部可用性的电力供应问题，开展了一项监测计划。通过查询一个不间断电源（UPS）单元，对TB208房间内的供电电压进行了采样。该UPS（APC SmartUPS 3000XL）在每个60秒的时间间隔内（由UPS内部定义）报告三个值：该时间间隔内的最大供电电压、该时间间隔内的最小供电电压以及该时间间隔结束时的“瞬时”供电电压。测量的粒度较粗，约为1.5伏。电压尖峰将表现为最大电压的高值，而供电低谷将表现为最小电压的低值。这些值通过标准的日志记录机制进行传输，该机制移除重复值，因此应假定缺失的数据点与最后提供的值完全相同。随后，这些值从日志中提取到随附的zip归档文件（MainsVoltage_TowerB-2009.zip）中的文本文件中。文本文件已导入电子表格（MainsVoltage_TowerB.xls），每个标签页代表一周的数据，并附带相应的值图表，每周的记录从每周日的凌晨4点左右开始。日间和周间的变化均清晰可见。大部分噪声是由于建筑电梯和车间机械的启动和停止造成的。12月1日（第48周）的早晨可以看到一次较长的电压下降。致谢：Raul Lopes编写了UPS查询和日志记录机制。Henry Nebrensky完成了数据提取并将其导入Microsoft Excel。随后，在RAL的MICE项目中采用了类似的方法，DOI：10.17633/rd.brunel.9691628。