| Title |
Countermeasures against Perfect Single Line-to-Ground Faults Caused by Failures of Rack-Mounted Automatic Transfer Switches |
| DOI |
http://dx.doi.org/10.5207/JIEIE.2016.30.12.039 |
| Keywords |
Rack-Mounted Automatic Transfer Switche (RM ATS) ; Single Line-To-Ground (SLG) Fault ; Electric Shok |
| Abstract |
The use of point-of-use transfer switches (PTSs) for single cored equipments (SCEs) is prohibited by Uptime Institute's tier standard including fault-tolerant power compliance specification (FTPCS) to remove single-point-of-failures (SPFs) in Tier III and IV sites. However, there are still numerous SCEs in use of mission-critical facilities. Therefore, introduction of PTSs to allow SCEs to exploit the dual power-path benefits of Tier III and IV topology is inevitable. In this paper, the sag susceptibility of SCEs was examined in order to deploy rack-mounted automatic transfer switches (RM ATSs) as the PTS. In all cases, equipments under test (EUT) were considered to be susceptible to the sag triggered by a RM ATS. Although some cases did not meet the requirments with input voltage envelope (IVE) of information technology industry council (ITI) curve, there were no data loss in all cases. These results showed that the EUT connected to the Korean 220V 60Hz network have sag immunity greater than that defined by the ITI curve. Based on the results, thirty-five RM ATSs were employed in 2010. However, perfect single line-to-ground (SLG) faults caused by contacts welding and persistent phenomenon of the rapid alternation-switching between two different power sources with repect to controller failures of the RM ATS have been occurred on the solidly grounded system of dual power paths. Risk of electric shock has been happened by flow of load current along exposed-conductive parts such as a grounded-bus. Therefore, it was found that additional earth leakage devices (ELDs) should be installed at all circuits of RM ATSs for replacement of faulty devices and removal of SLG faults more rapidly than before. |