Industry Type: Commercial Facility with multiple buildings housing IT data centers & other business offices
Problem: This is a big commercial building complex involving 6 multistoried buildings with ONLINE datacenters of few multinationals. Utility company has promised 24 x 7 supply using two lines on LILO arrangement for each transformer. The site faced issues of abrupt fluctuations which caused random tripping of some crucial HVAC equipment. The site faced a lot of issues during the source to DG changeover function. The set up being critical needed trouble free transfer from source to DG & back.
Solution required: Complete load flow study recommended with 48hours monitoring of main HT lines. DG set transfer trial was recommended with live monitoring of interlocks between PLC, DG controllers. Study of electrical scheme and user requirements of critical HVAC equipment was also recommended.
Activity Conducted: We extended the Load flow study was up to SCADA of utility; the records revealed that all the source fluctuations observed were synchronized with Line switching or remote tap changing which was unavoidable. None of the loads were exceeding any trip setting. DG PLC / SYNCH panel UPS was of OFFLINE type. It was also noticed that due to lack of awareness about "TRUE ONLINE PLC OPERATION", the UPS was also replaced in between, without actual shutdown. It was noticed that a dangerous interlock was inadvertently introduced which was allowing paralleling of two unsynchronized DG set groups. ATS action initiating signals were not reaching PLC every time. Origin of "Power fail" signals was traced and malfunction of auxiliary contacts was reported. Tripping of HVAC equipment was result of voltage dips during line switching.
Benefits to Client: Simpler SOPS were defined for restarting HVAC equipments after explaining about thermal inertia and time taken for temperature increase. Automatic restart scheme already provided was rechecked and started. PLC program modifications were recommended for avoiding unsafe connections. It was recommended to modify SOPs from their generic nature to include necessary functional checking. As the client was responsible to perform with multinational clients of repute, a high end power quality monitoring equipment was recommended on both the lines.