24V DC Fail

24V DC Fail

EMERGENCY INSTRUCTIONS

Identification of the Emergency

• 1. Boiler trips on loss of 24V DC Supply protection. Turbine trips on boiler trip protection followed by generator.
• 2. All controls operating on DDC becomes inoperative

Response in Handling the Emergency
Action Responsibility Remarks

• 1 Confirm tripping of turbine. In local governing rack the trip oil pressure should be ‘0’ otherwise trip turbine from emergency trip lever in governing rack. Trip TD BFPs from local governing rack UCE & TG Engineer
• 2 Confirm tripping of generator i.e. opening of GCB. If GCB has not opened, open 952 and 852 breakers from switchyard UCE 
• 3 Confirm starting of AOP (local) on turbine trip, otherwise start EOP from local for both main and TDBFP turbines. UCE & TG Operator 
• 4 Confirm running of ACSOP(local) if no seal oil pump is running immediately start DCSOP from local UCE & TG Operator 
• 5 Confirm AC scanner fan is in service(local),else start DC scanner fan from starter panel in LT switch gear room in TG floor Boiler Engr & Operator 
• 6 As controls are in operative do the following operations 
• A Stop FD fan, ID fan and BCW pumps (from local push buttons or switch gear). Close boiler stop valves Boiler Engr & Operator 
• B Stop MD BFP (from local push buttons or switch gear), if it was in service as D/A and drum levels cannot be monitored. TG Engr. & Operator 
• C Depressurise MS, CRH and HRH lines, Kill vacuum. Open atmospheric drains of MS,CRH and HRH lines TG Engr & Operator 
• D Stop CEPs and isolate make up to hot well since hot well level indication is not there TG Engr & Operator 
• E At 540 rpm turbine speed start DC JOP from local, and at 210 rpm open turning gear valve manually UCE,TG Engr. & Operator 
• F Continue to run DMCW pumps. Monitor and maintain DMCW tank level from local Boiler Engr & Operator