Industry Type: SEZ for IT Sector
Problem: An SEZ Facility developed for IT companies in a designated IT hub in Pune had problems involving the changeover from Utility Power to Generators. The facilities Main distribution contained 22/11KV 25MVA transformer, 600kW x 3Nos chillers working on 11KV, 11KV DG sets and 2 MVA x 2Nos of 11KV/433V building transformers. The problem was faced in the 11KV distribution system involving 15VCB’s. The VCB’s would work/ trip randomly during the change over from Utility power to Generators. This was causing power failure & unwanted downtime in spite of having redundancy in the main Electrical system.
Study Recommended: A physical inspection of the facility along with detailed Harmonic Analysis & testing of DC substation power source. A load flow analysis along with testing of HT/ LT breaker was recommended.
Observation: Physical checking revealed that breaker trip spring motors rated voltage was not uniform with all breakers and was not matching with DC supply provided. DC supply was distributed to all panels in a loop using 1.5Sq mm cable and voltage use to drop till 15V instead of required 24Vat last panel. The DG synchronization and interlock panel was relay based and few relays were misbehaving. Apart from this the HT APFC panel connected at 11KV was wrongly designed and use to cause tripping of 22KV VCB. The Harmonics were found in order & within the specified limits.
Problem Identified: The findings revealed that the basic problem was with the faulty designing of the distribution. The detailing of the requirement was not done properly causing wrong sizing of the springs & DC supply cables. The quality of relay’s used in DG synchronization panel was substandard which also caused failure. The APFC panel at 11KV was wrongly designed causing tripping of the 22KV VCB.
Solution Executed: The solution was achieved by replacing the undersized cables & sub standard parts within the distribution. The breaker Trip spring motors were replaced with proper rated motors. The DC distribution cabling was replaced using oversize cables ensuring 24VDC supply to all panels. Replaced DG Synchronization panel relays and replaced 11KV HT APFC panel.
Benefits to Client: The activity conducted & the solution implemented ensured trouble free operation of the facility. The changes implemented post the audit enhanced the uptime of the facility & also brought down the running cost of the Generators caused due to the spurious tripping of the Electrical panels. The facility now could assure better uptime guarantees to its IT tenants.