Reduction in Downtime via Interlocking Date: 3rd March 2012 A tripping occurred since the Areva panels had a tripping command system if the DC supply failed. This was removed by removing that function from the panel and a alarm using a contractor with a reset operation was made For future purposes a downtime of 60 minutes was avoided.

How did the failure happen? DC Input to the battery charger failed The auxiliary to the Panels was now supplied by Battery storage No DC failure sign was indicated The Charge at Battery tank finished after sometime There was now no DC supply to the panels The Master relay of Areva Panels Tripped since the battery voltage was reduced Incomer no. 3 and Unit 5 (south) tripped Load now concentrated only on Dhaula Bus coupler Tripped due to interlocking to avoid overloading of Dhaula power There was no supply to Unit 1, 2, 5 (south) and Gyaanpeeth While Unit 3, Unit 4 and Unit-5(North) operated normally on Dhaula How did the failure happen?

SLD of the Hooter Circuit K1 MCB Output K1 (N.C.) K2 (N.C.) e f e1 f1 Fed by UPS Power Hooter K2 (N.O.) K1 (N.C.) a1 b1 g h Push Button (N.O) Fed by UPS Power K2

Savings Calculations Now if the DC fails the Hooter will show the fault. There is also a ‘Reset Button’ to accept the fault and bring it back to normal condition. This is not a one time saving it is applicable for the future also. Load loss per hour 70,000 INR Breakdown on transmission line will create breakdown for hours: 60 minutes   Total savings 70,000.00 Now Downtime of Unit 1, 2, 5 and Gyaanpeeth from DC failure can be avoided. Hooter would run and action can be taken in time. *This is not a one time saving. For future there will be no downtime due to this reason.