I am having issues with one of my buildings. I have several tenants with large server rooms with large UPS systems which record power quality issues. They also have lots of individual pc units that are not on ups. There are experiencing power drops about 3-5 time a month. Some drops are severe enough to cause the non ups protected computers to reboot loosing data. All events are loged by the data center ups's Had the local power company do a power quality survey on the building for 3 weeks and we were able to identify several incidents attributable to power grid issues,faults and cap bank switching. We compaired the monitor results to the UPS logs and discovered that some incidents could not attributed to to the power grid and could indicate possiable faulting on the secondary side. Shutting down a building of this size with the various data centers will be a nightmare in order to meger the secoundarys. Any ideas ! 1200 amp 480 feed existing secoundarys are about 20 years old.
Lots of possibilities. It is very possible that there are transients caused internal to the building. Are there TVSS' installed throughout? Are the problems sags or swells or .... It is a specialty to be able to interpret disturbance type meters and see from the oscilloscope plots, where and what the problems are, and where they come from.
Re: Power Quality#68305 08/02/0602:08 PM08/02/0602:08 PM
Do you submeter power within your building? Try monitoring the subpanels to discover if power issues are being generated within the building or external.
1200 amp 480 feed existing secoundarys are about 20 years old. What shape is the grounding system in? Has anybody done a thorough review of the building system? Checking for tight connections, improper neutral ground connections, overheating conductors and panel boards, etc.
Are the HVAC loads on seperate panels than the UPS? Are there other large infrequently operated motor loads? Such as elevators, winches, fire pumps, air compressors, dumpster compactors, etc.
A customer of mine had assorted power quality problems. I worked in the building for over a year, doing other jobs, when one Thanksgiving half the surge supressors fried, and the local UPS's kicked in. (Walking into the place was like entering a cricket convention.... chirp...chirp...).
While checking the assorted panels, trying to discover the cause, my partner was smart enough to back away, relax, and look at it all from a new perspective. Something just didn't seem right. After much headscratching, he noticed the "obvious;" ther was NO neutral wire! That's right, the panel was fed from a panel next to it, and the neutral bus was bonded to the case. 20 years of rust and vibration had finally loosened a locknut.
We ran a proper neutral, and a ground wire, removed that green screw... and the building now had amazingly "clean" power!
So- the 'moral' is... before getting into all sorts of fancy theories, check your basics. Just maybe, someone got careless....
Re: Power Quality#68309 08/03/0611:00 AM08/03/0611:00 AM
No VFD in building UPS are on disconnects straight off main buss bars monitoring was done on the secondary side of the transformer at the CT's All recording UPS are 480 feed. How do I determine if I am having transient faults in my secoundary feeds to my mains without a massive shut down and meggering? Some issues we are seeing are not related to power quality from the grid. Grounding for the UPS is up to code and has been evaluated as well as building ground.
Re: Power Quality#68310 08/03/0607:13 PM08/03/0607:13 PM
"he noticed the "obvious;" ther was NO neutral wire! That's right, the panel was fed from a panel next to it, and the neutral bus was bonded to the case. 20 years of rust and vibration had finally loosened a locknut."
High rise office building, we found the obvious and changed out some of the floor transformers to copper, after that there was never a problem.