Hi,
I hope all of you would be in good state of health.
Recently a situation has been reported to me .I thought it better to put it here on this forum for root cause analysis by worthy forum fellows also.
Situation is as under.
  1. Two chillers (TRANE ERTWA model) were in operation when suddenly D-link of electric pole ( 2 out 3 )blew.Electrical personnel were called by chiller operator and they restored d-link wire and electricity was restored.
  2. Right at the time when operator observed heavy sound in compressor then he rushed to breaker of control supply to chillers and turned it off.It is further mentioned that from chiller to electrical pole there is chiller breaker then transformer and its breaker then electric pole.But in first situation only last protection( d-link of pole) actuated.
  3. On restoration of power supply in 3 phase ,operator again started chillers (02 ) again and put load on it.But after one hour again same happened as written above.
  4. Again electrical personnel came and replaced wire of d-link of electrical pole.They were of view that some thing is happening somewhere that is again again blowing it.It may be short circuiting or overloading somewhere .
  5. However they asked to operate one chiller first and see whether same happens or not.If same happens then problem may be in same chiller ,if not then start 2nd chiller and check same.They suspected chiller for possible faults.It is worthy to mention that besides chiller load there is also lighting etc load of building on transformer. Normal load of building is 100 A while chiller draw 300 A usually. But when above incident happened ,one person observed total current on transformer meter to about 1000 A that was abnormally high and caused pole link to blow.
  6. One chiller was operated and link did not blew first and on next day only 2nd chiller was operated and link blew .Then again link was installed and first chiller was operated and again link blew .I mean to say that pole link blew on both chillers .
  7. Electrical personnel were confused and inspected whole line from pole to chiller for possible fault.
  8. Electric motors of chiller compressors were meggered and insulation of 3/4 motors wer found grounded with resistance in kilo ohms. However winding to winding results were satisfactory only winding to ground resistance was too low,motors were almost grounded.Further ,cables in the lines were meggered and found ok.

I request honorable members to analyze above situation for root cause ,please.