Since long time we observe a strange phenomenon of tripping of compressor due to high vibration while starting another compressor in a separate machine building nearby. It may require some description to understand the problem.
In a big machine building-A three sets of large centrifugal compressors are installed, 4 nos 11 MW each (say X1,X2,X3 & X4), 6 nos 2.4 MW each (say Y1-Y6) and 6 nos 3.2 MW each (say Z1-Z6). Nearby in a separate machine building-B another set of 4 centrifugal compressors 5.2 MW each (say P1,P2,P3 & P4) are installed at about 150m distance. Both buildings get power from three transformers of a common LBSS. Some compressors of building A & B get supply from same section of transformers. Sets X, Z & P are 11 kV suply. All are sychronous motors. Common discharge headers of compressors 'X' and 'P' are interconnected through two pipelines of size 350NB & 450NB for evantual requirement of give or take.
Now, the problem-
When P2 in building-B is started, vibration levels of running compressors X2 & X4 in building-A momentierly go up abnormally (beyond trip limits for some bearings). To avoid tripping we temperarily bypass it. P2 sychronize in about 17 seconds. Shooting-up of viration levels in X2 & X4 is observed between 8th to 13th seconds of starting P2 which again comes back to normal. Observation is almost similar when p.f. is kept either in auto or in manual mode.
I request experts to tell about- What causes this problem.
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