1. 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.

2. 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?

3. SLD of the Hooter CircuitK1
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

4. 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.